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COVID-19 research v1.43 CX3CR1 Sarah Leigh Classified gene: CX3CR1 as Amber List (moderate evidence)
COVID-19 research v1.43 CX3CR1 Sarah Leigh Gene: cx3cr1 has been classified as Amber List (Moderate Evidence).
COVID-19 research v1.42 CX3CR1 Sarah Leigh Mode of inheritance for gene: CX3CR1 was changed from to BIALLELIC, autosomal or pseudoautosomal
COVID-19 research v1.21 CX3CR1 Sarah Leigh changed review comment from: CX3CR1 was identified through an OMIM search for potential viral susceptibility genes. Initial triage by Illumina (Alison Coffey and team) was given a Tier 3 grouping (experimental evidence and association data consistent with viral susceptibility); to: CX3CR1 was identified through an OMIM search for potential viral susceptibility genes. Initial triage by Illumina (Alison Coffey and team) was given a Tier 3 grouping (experimental evidence and association data consistent with viral susceptibility). Illumina review: Receptor for the CX3C chemokine fractalkine (CX3CL1); binds to CX3CL1 and mediates both its adhesive and migratory functions. Acts as coreceptor with CD4 for HIV-1 virus envelope protein (in vitro) (PMID:9726990). Associated with rapid progression to AIDS from HIV1 infection. PMID:14607932: Garin et al. (2003) - identified two novel isoforms of the human chemokine receptor CX3CR1, produced by alternative splicing that appear to be more potent HIV coreceptors. PMID:10731151: Faure et al. (2000) - CX3CR1 is an HIV coreceptor as well as a leukocyte chemotactic/adhesion receptor for fractalkine. Faure et al. (2000) identified 2 single nucleotide polymorphisms in the CX3CR1 gene in Caucasians and demonstrated that HIV-infected patients homozygous for I249/M280 progressed to AIDS more rapidly than those with other haplotypes (relative risk = 2.13, P = 0.039). Functional CX3CR1 analysis showed that fractalkine binding is reduced among patients homozygous for this particular haplotype. Concluded that CX3CR1-I249/M280 is a recessive genetic risk factor for HIV/AIDS. PMID 28228284: Zhivaki et al. (2017) - Upregulated in RSV infection affecting severity of infection. Respiratory syncytial virus (RSV) is the major cause of lower respiratory tract infections in infants and is characterized by pulmonary infiltration of B cells in fatal cases. Identified a population of neonatal regulatory B lymphocytes (nBreg cells) that produced interleukin 10 (IL-10) in response to RSV infection. The polyreactive B cell receptor of nBreg cells interacted with RSV protein F and induced upregulation of chemokine receptor CX3CR1. CX3CR1 interacted with RSV glycoprotein G, leading to nBreg cell infection and IL-10 production that dampened T helper 1 (Th1) cytokine production. In the respiratory tract of neonates with severe RSV-induced acute bronchiolitis, RSV-infected nBreg cell frequencies correlated with increased viral load and decreased blood memory Th1 cell frequencies. Thus, the frequency of nBreg cells is predictive of the severity of acute bronchiolitis disease and nBreg cell activity may constitute an early-life host response that favors microbial pathogenesis. PMID unavailable: Strickland et al. (2020) - Pulmonary infection with C. neoformans (opportunistic fungal pathogen and leading cause of death in HIV-affected inividuals) enhanced CX3CR1 expression in the lung. Following infection, mice lacking CX3CR1 had significantly higher pulmonary fungal burdens, as well as decreased survival times compared to wild type mice. These infected CX3CR1 knockout mice also displayed higher expression of pro-inflammatory cytokines including MIP-2, MCP-1 and CCL7, but lower expression of anti-inflammatory cytokines such as IL-10. CX3CR1 deficiency resulted in mice having dramatically enhanced neutrophil accumulation in the lungs following infection.Depletion of neutrophils drastically improved lung CFU in infected knockout mice, indicating that excessive inflammation drove fungal growth. These data indicate that CX3CR1 expression is essential for host resistance to pulmonary cryptococcal infection by inhibiting excessive lung inflammation.
COVID-19 research v1.21 CX3CR1 Sarah Leigh Phenotypes for gene: CX3CR1 were changed from to {Rapid progression to AIDS from HIV1 infection} 609423
COVID-19 research v1.20 CX3CR1 Sarah Leigh Publications for gene: CX3CR1 were set to
COVID-19 research v1.11 CX3CR1 Alison Coffey reviewed gene: CX3CR1: Rating: AMBER; Mode of pathogenicity: ; Publications: 9726990, 14607932, 10731151, 28228284; Phenotypes: ; Mode of inheritance: Unknown
COVID-19 research v1.10 CX3CR1 Sarah Leigh commented on gene: CX3CR1: CX3CR1 was identified through an OMIM search for potential viral susceptibility genes. Initial triage by Illumina (Alison Coffey and team) was given a Tier 3 grouping (experimental evidence and association data consistent with viral susceptibility)
COVID-19 research v0.348 DICER1 Rebecca Foulger changed review comment from: Evidence Summary from Illumina curation team: The DICER1 gene, located on chromosome 14, position q32.13, was discovered in 2001 by Bernstein and is a member of the RNase III family, (also known as dicer 1, ribonuclease III; dicer1, Dcr-1 homolog (Drosophila); multinodular goitre 1). DICER1 is involved in the generation of double-stranded microRNAs (miRNAs), short non-coding RNAs, the cleavage of dsRNA into siRNAs, along with the biogenesis of numerous other small RNAs. There is increasing evidence DICER1 is also involved in regulating many other essential cellular processes such as those related to chromatin remodeling, inflammation, apoptosis and cell survival (Kurzynska-Kokorniak et al. 2015; Song and Rossi, 2017). DICER1 encodes a ∼220-KDa protein (RNase III endoribonuclease) which is a crucial component of the RNA Induced Silencing Complex (RISC) loading complex (RLC), comprised of dicer, Argonaute-2 (AGO-2), and trans-activation-responsive RNA binding protein 2 (TARBP2). The encoded protein is required by the RNA interference (RNAi) and small temporal RNA (stRNA) pathways to produce the active small RNA component which has a role in modulating gene expression at the post-transcriptional level. Research has shown that expression levels of cellular transcript and protein dicer are strictly controlled, with aberrant regulation contributing to carcinogenesis, neurodegenerative, rheumatic and immune system disorders. Studies have concluded that the encoded dicer ribonuclease-dependent processing of dsRNA viral replication intermediates into successive siRNAs is a conserved mammalian immune response to infection by positive-strand RNA viruses (Svobodova et al. 2016 summary & fig1; Li et al. 2013; Ding et al. 2018). Moreover, miRNAs play an important role in host-virus interactions in mammals (See Maillard et al. 2019 REVIEW; Foulkes et al. 2014 REVIEW).

IMMUNE SYSTEM
The cre-lox method for dicer1 gene knockout has been employed for studies into the role of dicer1 in immune cell development and function. Studies of dicer1 fl/fl mice have indicated short survival times along with severely impaired GMP differentiation into monocytes, neutrophils, myeloid DCs & mature macrophages. (Devasthanam et al. 2014). Results conclude that dicer1 is important in immune response and also vital for cell survival and apoptosis pathways. Muljo et al. (2005) investigated a conditional allele of dicer-1 (dcr-1) within a mouse model and showed that specific dcr-1 deletion in the T-cell lineage, resulted in impaired development of T-cells & aberrant cell differentiation of T-helper cells & cytokine production. Dcr-1 deletion in the thymus resulted in severe block in development of CD8+ T cells and resulted in defective microRNA processing in CD4+ T-cells. The results demonstrate Dicer regulates diverse aspects of T-cell biology along with cytokine production during T-cell differentiation where dicer-deficient T-cells preferentially express interferon-ƴ.

VIRUSES
Research by Galiana-Arnoux et al. (2006), of DICER in drosophila (drosophila have two dicer genes) have identified that DICER genes (Dcr1, miRNA pathway and Dcr2, RNAi pathway) control production of siRNA and a loss-of-function mutation in Dcr2 resulted in increased susceptibility to three different families of RNA viruses. Qi et al. (2012) research into RNAi gene silencing mechanism show that the B2 protein in Wuhan nodavirus (WhNV) suppresses Dcr2 in drosophila by direct interaction with the PAZ and RNAse III domains therefore blocking processing of dsRNA and siRNA. Evidence of a dicer antiviral system was also reported by Machitani et al. (2016) for mammalian human adenoviruses where DICER1 gene knockdown increased the copy number of adenovirus-encoding small RNAs (VA-RNAs) leading to the promotion of adenovirus replication; conversely, dicer overexpression significantly inhibited viral replication.
Modai et al. (2019) conclude that HIV-1 infection inhibits DICER1 by altering miRNA expression. They conclude that upon HIV-1 infection, human miR-186, 210 and 222 directly regulate DICER1 gene expression causing down-regulation of the gene contributing to impaired cell-mediated immunity (fig6). Other methods of inhibition are from viral proteins, termed viral suppressors of RNA silencing, which interact and inhibit dicer ribonuclease activity in HIV-1 and hepatitis C infections. These viral proteins may mediate proteasomal degradation of endoribonuclease dicer through CRL4DCAF1 ubiquitin ligase complex (Klockow et al. 2013), interact directly via the core protein (Chen et al. 2008) or HIV-1 transactivation of transcription (Bennasser and Jeang, 2006). Through these methods they can block dicer interactions with TRBP2 or ADAR1, boost macrophage infection, and subsequently reduce the function of short hairpin RNAs (shRNAs) which thus inhibit RNA silencing. Ultimately these viruses, though various methods, supress the ability of dicer to process dsRNAs into siRNAs boosting viral infection and pathogenesis.
Downregulation of DICER1 gene expression has additionally been found in cord blood of infants with severe respiratory syncytial virus (RSV), prior to RSV exposure, indicating this reduced expression may predispose newborns to RSV disease. Inchley et al. (2011) theorize that this occurs via disruption of leukocyte gene regulation of miRNA and direct anti-viral RNAi mechanisms. (Inchley et al. 2011 see section on “Dicer Gene Expression”).
Otsuka et al. (2007) have shown using gene-trap methods to obtain viable dicer1 fl/fl mice where dicer1 deficiency caused impairment of miR24 and miR93 production resulting in susceptibility to vesticular stomatitis virus (VSV) and herpes simplex-1 virus, but not other viruses tested.

SARS CoV & SARS CoV-2
Recently, Pasquier and Robichon, 2020 (preprint) have investigated the Dicer host immunity system regarding SARs-CoV-2 within a computational approach, concluding SARS-CoV2 may manipulate this system of immunity against its host, requiring further research. Mu et al., 2020 suggest SARs-CoV2 suppresses RNAi thus preventing recognition by the encoded ribonuclease dicer protein
Viral suppressors of RNA silencing (VSRs) suppress RNAi at pre or post-dicer level to overcome host defense and establish infection. Cui et al. (2015) from Wuhan University laboratory of virology, identified a novel VSR from coronaviruses (CoVs) including Severe acute respiratory syndrome coronavirus (SARS-CoV) and showed that the coronavirus nucelocaspid protein (N-protein), conserved and expressed in all coronaviruses, suppressed RNAi triggered by either short hairpin RNAs or small interfering RNAs in mammalian cells. They went on to show using mouse hepatitis virus A-59 (MHV-A59) which is closely linked to SARS-CoV in the family coronaviridae, that the viral replication was increased when the N proteins (novel VSR) were expressed but that knockdown of DICER1 gene or Ago2 transcripts facilitated the viral replication specifically in mammalian cells. They demonstrate that the N-protein of CoVs could efficiently inhibit dicer-mediated dsRNA cleavage and post-Dicer activities by sequestering dsRNAs and siRNAs. Kannan et al. (2020) performed clustal W analysis of N-Protein for SARS-CoV and COVID-19 demonstrating 90% sequence identity from an NCBI amino acid blast of both nucleocapsid (N) protein sequences (figure2). They suggest that the N-protein of COVID-19 may also function as a VSR for RNAi to overcome host defense. Ding et al. (2017) show that both MHV and SARS-CoV N proteins can also disrupt protein activator of protein kinase R (PACT), a cellular dsRNA-binding protein which binds to RIG-I and MDA5 to activate interferon (IFN) production to prevent antiviral host response.

Literature Review
PMID: 17181864: Bennasser and Jeang, 2006
• HIV-1 Tat Interaction With Dicer: Requirement for RNA
• Tat-Dicer interaction depends on RNA, requires the helicase domain of Dicer, and is independent of Tat's transactivation domain.

PMID: 18325616: Chen et al., 2008
• HCV Core Protein Interacts With Dicer to Antagonize RNA Silencing

PMID: 26085159: Cui et al., 2015
• The Nucleocapsid Protein of Coronaviruses Acts as a Viral Suppressor of RNA Silencing in Mammalian Cells

PMID: 24303839: Devasthanam et al, 2014
• This study investigates the role of the dicer protein in immune cell development and function using dicer1 cre-lox knockout models to conditionally ablate dicer1 in different immune cell subsets.

PMID: 28591694: Ding et al., 2017
• The nucleocapsid proteins of mouse hepatitis virus and severe acute respiratory syndrome coronavirus share the same IFN-β antagonizing mechanism: attenuation of PACT-mediated RIG-I/MDA5 activation

PMID: 30015086: Ding et al., 2018
• Antiviral RNA Interference in Mammals: Indicates infection of plants and insects with RNA and DNA viruses triggers Dicer-dependent production of virus-derived small interfering RNAs (vsiRNAs), which subsequently guide specific virus clearance by RNA interference (RNAi).

PMID: 25176334: Foulkes et al., 2012-REVIEW
• Review of DICER1: DICER1 Mutations, microRNAs and Mechanisms

PMID: 16554838: Galiana-Arnoux et al., 2006
• Essential function in vivo for Dicer-2 in host defense against RNA viruses in drosophila.
• https://pubmed.ncbi.nlm.nih.gov/16554838/ or https://www.nature.com/articles/ni1335

PMID: 21385408: Inchley et al., 2011
• Investigates ribonuclease Dicer and analyzed the gene expression of Dicer in newborns of which 37 infants had sufficient cord blood RNA with confirmed RSV disease <1yr. Demonstrates significant reduced Dicer expression in cord blood prior to severe disease in infants <1yr later. Conclude downregulation may predispose infants to RSV disease.

PMID: 32141569: Kannan et al., 2020
• COVID-19 (Novel Coronavirus 2019) - Recent Trends
• Perform W cluster analysis of COVID-19 and SARS-CoV nucleocapsid (N) protein sequences of the viruses showing 90% amino acid sequence similarity. Suggest the N-protein may be a VSR in RNAi by targeting DICER.

PMID: 23849790: Klockow et al., 2013
• The HIV-1 Protein Vpr Targets the Endoribonuclease Dicer for Proteasomal Degradation to Boost Macrophage Infection

PMID: 25883138: Kurzynska-Kokorniak et al., 2015
• Investigating the complexity of the mechanisms regulating Dicer gene expression and enzyme activities

PMID: 24115437: Li et al, 2013
• Investigates RNA interference pathways in antiviral immunity in mammals overviewing dicer processing of dsRNA viral replication intermediates into siRNAs.

PMID: 27273616: Machitani et al., 2016
• Dicer functions as an antiviral system against human adenoviruses via cleavage of adenovirus-encoded noncoding RNA

PMID: 30872283: Maillard et al., 2019- REVIEW
• Reviewing DICER1 within the anti-viral RNAi pathway in mammals

PMID: 30682089: Modai et al, 2019
• HIV-1 infection increases miRNAs which inhibit Dicer

PMID: 32291557: Mu et al, 2020
• SARS-CoV-2-encoded nucleocapsid protein acts as a viral suppressor of RNA interference in cells

PMID: 16009718: Muljo et al., 2005
• Indicates absence of dicer results in abberant T-cell differentiation.

PMID: 17613256: Otsuka, et al 2007
• Hypersusceptibility to Vesicular Stomatitis Virus Infection in Dicer1-Deficient Mice Is Due to Impaired miR24 and miR93 Expression

No PMID: Preprint : Pasquier and Rubichon, 2020
• SARS-CoV-2 might manipulate against its host the immunity RNAi/Dicer/Ago system

PMID: 22438534: Qi et al., 2012
• Targeting of Dicer-2 and RNA by a Viral RNA Silencing Suppressor in Drosophila Cells

PMID: 28473628: Song and Rossi, 2017
• Molecular Mechanisms of Dicer: Endonuclease and Enzymatic Activity; to: Evidence Summary from Illumina curation team (Alison Coffey and Julie Taylor): The DICER1 gene, located on chromosome 14, position q32.13, was discovered in 2001 by Bernstein and is a member of the RNase III family, (also known as dicer 1, ribonuclease III; dicer1, Dcr-1 homolog (Drosophila); multinodular goitre 1). DICER1 is involved in the generation of double-stranded microRNAs (miRNAs), short non-coding RNAs, the cleavage of dsRNA into siRNAs, along with the biogenesis of numerous other small RNAs. There is increasing evidence DICER1 is also involved in regulating many other essential cellular processes such as those related to chromatin remodeling, inflammation, apoptosis and cell survival (Kurzynska-Kokorniak et al. 2015; Song and Rossi, 2017). DICER1 encodes a ∼220-KDa protein (RNase III endoribonuclease) which is a crucial component of the RNA Induced Silencing Complex (RISC) loading complex (RLC), comprised of dicer, Argonaute-2 (AGO-2), and trans-activation-responsive RNA binding protein 2 (TARBP2). The encoded protein is required by the RNA interference (RNAi) and small temporal RNA (stRNA) pathways to produce the active small RNA component which has a role in modulating gene expression at the post-transcriptional level. Research has shown that expression levels of cellular transcript and protein dicer are strictly controlled, with aberrant regulation contributing to carcinogenesis, neurodegenerative, rheumatic and immune system disorders. Studies have concluded that the encoded dicer ribonuclease-dependent processing of dsRNA viral replication intermediates into successive siRNAs is a conserved mammalian immune response to infection by positive-strand RNA viruses (Svobodova et al. 2016 summary & fig1; Li et al. 2013; Ding et al. 2018). Moreover, miRNAs play an important role in host-virus interactions in mammals (See Maillard et al. 2019 REVIEW; Foulkes et al. 2014 REVIEW).

IMMUNE SYSTEM
The cre-lox method for dicer1 gene knockout has been employed for studies into the role of dicer1 in immune cell development and function. Studies of dicer1 fl/fl mice have indicated short survival times along with severely impaired GMP differentiation into monocytes, neutrophils, myeloid DCs & mature macrophages. (Devasthanam et al. 2014). Results conclude that dicer1 is important in immune response and also vital for cell survival and apoptosis pathways. Muljo et al. (2005) investigated a conditional allele of dicer-1 (dcr-1) within a mouse model and showed that specific dcr-1 deletion in the T-cell lineage, resulted in impaired development of T-cells & aberrant cell differentiation of T-helper cells & cytokine production. Dcr-1 deletion in the thymus resulted in severe block in development of CD8+ T cells and resulted in defective microRNA processing in CD4+ T-cells. The results demonstrate Dicer regulates diverse aspects of T-cell biology along with cytokine production during T-cell differentiation where dicer-deficient T-cells preferentially express interferon-ƴ.

VIRUSES
Research by Galiana-Arnoux et al. (2006), of DICER in drosophila (drosophila have two dicer genes) have identified that DICER genes (Dcr1, miRNA pathway and Dcr2, RNAi pathway) control production of siRNA and a loss-of-function mutation in Dcr2 resulted in increased susceptibility to three different families of RNA viruses. Qi et al. (2012) research into RNAi gene silencing mechanism show that the B2 protein in Wuhan nodavirus (WhNV) suppresses Dcr2 in drosophila by direct interaction with the PAZ and RNAse III domains therefore blocking processing of dsRNA and siRNA. Evidence of a dicer antiviral system was also reported by Machitani et al. (2016) for mammalian human adenoviruses where DICER1 gene knockdown increased the copy number of adenovirus-encoding small RNAs (VA-RNAs) leading to the promotion of adenovirus replication; conversely, dicer overexpression significantly inhibited viral replication.
Modai et al. (2019) conclude that HIV-1 infection inhibits DICER1 by altering miRNA expression. They conclude that upon HIV-1 infection, human miR-186, 210 and 222 directly regulate DICER1 gene expression causing down-regulation of the gene contributing to impaired cell-mediated immunity (fig6). Other methods of inhibition are from viral proteins, termed viral suppressors of RNA silencing, which interact and inhibit dicer ribonuclease activity in HIV-1 and hepatitis C infections. These viral proteins may mediate proteasomal degradation of endoribonuclease dicer through CRL4DCAF1 ubiquitin ligase complex (Klockow et al. 2013), interact directly via the core protein (Chen et al. 2008) or HIV-1 transactivation of transcription (Bennasser and Jeang, 2006). Through these methods they can block dicer interactions with TRBP2 or ADAR1, boost macrophage infection, and subsequently reduce the function of short hairpin RNAs (shRNAs) which thus inhibit RNA silencing. Ultimately these viruses, though various methods, supress the ability of dicer to process dsRNAs into siRNAs boosting viral infection and pathogenesis.
Downregulation of DICER1 gene expression has additionally been found in cord blood of infants with severe respiratory syncytial virus (RSV), prior to RSV exposure, indicating this reduced expression may predispose newborns to RSV disease. Inchley et al. (2011) theorize that this occurs via disruption of leukocyte gene regulation of miRNA and direct anti-viral RNAi mechanisms. (Inchley et al. 2011 see section on “Dicer Gene Expression”).
Otsuka et al. (2007) have shown using gene-trap methods to obtain viable dicer1 fl/fl mice where dicer1 deficiency caused impairment of miR24 and miR93 production resulting in susceptibility to vesticular stomatitis virus (VSV) and herpes simplex-1 virus, but not other viruses tested.

SARS CoV & SARS CoV-2
Recently, Pasquier and Robichon, 2020 (preprint) have investigated the Dicer host immunity system regarding SARs-CoV-2 within a computational approach, concluding SARS-CoV2 may manipulate this system of immunity against its host, requiring further research. Mu et al., 2020 suggest SARs-CoV2 suppresses RNAi thus preventing recognition by the encoded ribonuclease dicer protein
Viral suppressors of RNA silencing (VSRs) suppress RNAi at pre or post-dicer level to overcome host defense and establish infection. Cui et al. (2015) from Wuhan University laboratory of virology, identified a novel VSR from coronaviruses (CoVs) including Severe acute respiratory syndrome coronavirus (SARS-CoV) and showed that the coronavirus nucelocaspid protein (N-protein), conserved and expressed in all coronaviruses, suppressed RNAi triggered by either short hairpin RNAs or small interfering RNAs in mammalian cells. They went on to show using mouse hepatitis virus A-59 (MHV-A59) which is closely linked to SARS-CoV in the family coronaviridae, that the viral replication was increased when the N proteins (novel VSR) were expressed but that knockdown of DICER1 gene or Ago2 transcripts facilitated the viral replication specifically in mammalian cells. They demonstrate that the N-protein of CoVs could efficiently inhibit dicer-mediated dsRNA cleavage and post-Dicer activities by sequestering dsRNAs and siRNAs. Kannan et al. (2020) performed clustal W analysis of N-Protein for SARS-CoV and COVID-19 demonstrating 90% sequence identity from an NCBI amino acid blast of both nucleocapsid (N) protein sequences (figure2). They suggest that the N-protein of COVID-19 may also function as a VSR for RNAi to overcome host defense. Ding et al. (2017) show that both MHV and SARS-CoV N proteins can also disrupt protein activator of protein kinase R (PACT), a cellular dsRNA-binding protein which binds to RIG-I and MDA5 to activate interferon (IFN) production to prevent antiviral host response.

Literature Review
PMID: 17181864: Bennasser and Jeang, 2006
• HIV-1 Tat Interaction With Dicer: Requirement for RNA
• Tat-Dicer interaction depends on RNA, requires the helicase domain of Dicer, and is independent of Tat's transactivation domain.

PMID: 18325616: Chen et al., 2008
• HCV Core Protein Interacts With Dicer to Antagonize RNA Silencing

PMID: 26085159: Cui et al., 2015
• The Nucleocapsid Protein of Coronaviruses Acts as a Viral Suppressor of RNA Silencing in Mammalian Cells

PMID: 24303839: Devasthanam et al, 2014
• This study investigates the role of the dicer protein in immune cell development and function using dicer1 cre-lox knockout models to conditionally ablate dicer1 in different immune cell subsets.

PMID: 28591694: Ding et al., 2017
• The nucleocapsid proteins of mouse hepatitis virus and severe acute respiratory syndrome coronavirus share the same IFN-β antagonizing mechanism: attenuation of PACT-mediated RIG-I/MDA5 activation

PMID: 30015086: Ding et al., 2018
• Antiviral RNA Interference in Mammals: Indicates infection of plants and insects with RNA and DNA viruses triggers Dicer-dependent production of virus-derived small interfering RNAs (vsiRNAs), which subsequently guide specific virus clearance by RNA interference (RNAi).

PMID: 25176334: Foulkes et al., 2012-REVIEW
• Review of DICER1: DICER1 Mutations, microRNAs and Mechanisms

PMID: 16554838: Galiana-Arnoux et al., 2006
• Essential function in vivo for Dicer-2 in host defense against RNA viruses in drosophila.
• https://pubmed.ncbi.nlm.nih.gov/16554838/ or https://www.nature.com/articles/ni1335

PMID: 21385408: Inchley et al., 2011
• Investigates ribonuclease Dicer and analyzed the gene expression of Dicer in newborns of which 37 infants had sufficient cord blood RNA with confirmed RSV disease <1yr. Demonstrates significant reduced Dicer expression in cord blood prior to severe disease in infants <1yr later. Conclude downregulation may predispose infants to RSV disease.

PMID: 32141569: Kannan et al., 2020
• COVID-19 (Novel Coronavirus 2019) - Recent Trends
• Perform W cluster analysis of COVID-19 and SARS-CoV nucleocapsid (N) protein sequences of the viruses showing 90% amino acid sequence similarity. Suggest the N-protein may be a VSR in RNAi by targeting DICER.

PMID: 23849790: Klockow et al., 2013
• The HIV-1 Protein Vpr Targets the Endoribonuclease Dicer for Proteasomal Degradation to Boost Macrophage Infection

PMID: 25883138: Kurzynska-Kokorniak et al., 2015
• Investigating the complexity of the mechanisms regulating Dicer gene expression and enzyme activities

PMID: 24115437: Li et al, 2013
• Investigates RNA interference pathways in antiviral immunity in mammals overviewing dicer processing of dsRNA viral replication intermediates into siRNAs.

PMID: 27273616: Machitani et al., 2016
• Dicer functions as an antiviral system against human adenoviruses via cleavage of adenovirus-encoded noncoding RNA

PMID: 30872283: Maillard et al., 2019- REVIEW
• Reviewing DICER1 within the anti-viral RNAi pathway in mammals

PMID: 30682089: Modai et al, 2019
• HIV-1 infection increases miRNAs which inhibit Dicer

PMID: 32291557: Mu et al, 2020
• SARS-CoV-2-encoded nucleocapsid protein acts as a viral suppressor of RNA interference in cells

PMID: 16009718: Muljo et al., 2005
• Indicates absence of dicer results in abberant T-cell differentiation.

PMID: 17613256: Otsuka, et al 2007
• Hypersusceptibility to Vesicular Stomatitis Virus Infection in Dicer1-Deficient Mice Is Due to Impaired miR24 and miR93 Expression

No PMID: Preprint : Pasquier and Rubichon, 2020
• SARS-CoV-2 might manipulate against its host the immunity RNAi/Dicer/Ago system

PMID: 22438534: Qi et al., 2012
• Targeting of Dicer-2 and RNA by a Viral RNA Silencing Suppressor in Drosophila Cells

PMID: 28473628: Song and Rossi, 2017
• Molecular Mechanisms of Dicer: Endonuclease and Enzymatic Activity
COVID-19 research v0.348 DICER1 Rebecca Foulger commented on gene: DICER1: Evidence Summary from Illumina curation team: The DICER1 gene, located on chromosome 14, position q32.13, was discovered in 2001 by Bernstein and is a member of the RNase III family, (also known as dicer 1, ribonuclease III; dicer1, Dcr-1 homolog (Drosophila); multinodular goitre 1). DICER1 is involved in the generation of double-stranded microRNAs (miRNAs), short non-coding RNAs, the cleavage of dsRNA into siRNAs, along with the biogenesis of numerous other small RNAs. There is increasing evidence DICER1 is also involved in regulating many other essential cellular processes such as those related to chromatin remodeling, inflammation, apoptosis and cell survival (Kurzynska-Kokorniak et al. 2015; Song and Rossi, 2017). DICER1 encodes a ∼220-KDa protein (RNase III endoribonuclease) which is a crucial component of the RNA Induced Silencing Complex (RISC) loading complex (RLC), comprised of dicer, Argonaute-2 (AGO-2), and trans-activation-responsive RNA binding protein 2 (TARBP2). The encoded protein is required by the RNA interference (RNAi) and small temporal RNA (stRNA) pathways to produce the active small RNA component which has a role in modulating gene expression at the post-transcriptional level. Research has shown that expression levels of cellular transcript and protein dicer are strictly controlled, with aberrant regulation contributing to carcinogenesis, neurodegenerative, rheumatic and immune system disorders. Studies have concluded that the encoded dicer ribonuclease-dependent processing of dsRNA viral replication intermediates into successive siRNAs is a conserved mammalian immune response to infection by positive-strand RNA viruses (Svobodova et al. 2016 summary & fig1; Li et al. 2013; Ding et al. 2018). Moreover, miRNAs play an important role in host-virus interactions in mammals (See Maillard et al. 2019 REVIEW; Foulkes et al. 2014 REVIEW).

IMMUNE SYSTEM
The cre-lox method for dicer1 gene knockout has been employed for studies into the role of dicer1 in immune cell development and function. Studies of dicer1 fl/fl mice have indicated short survival times along with severely impaired GMP differentiation into monocytes, neutrophils, myeloid DCs & mature macrophages. (Devasthanam et al. 2014). Results conclude that dicer1 is important in immune response and also vital for cell survival and apoptosis pathways. Muljo et al. (2005) investigated a conditional allele of dicer-1 (dcr-1) within a mouse model and showed that specific dcr-1 deletion in the T-cell lineage, resulted in impaired development of T-cells & aberrant cell differentiation of T-helper cells & cytokine production. Dcr-1 deletion in the thymus resulted in severe block in development of CD8+ T cells and resulted in defective microRNA processing in CD4+ T-cells. The results demonstrate Dicer regulates diverse aspects of T-cell biology along with cytokine production during T-cell differentiation where dicer-deficient T-cells preferentially express interferon-ƴ.

VIRUSES
Research by Galiana-Arnoux et al. (2006), of DICER in drosophila (drosophila have two dicer genes) have identified that DICER genes (Dcr1, miRNA pathway and Dcr2, RNAi pathway) control production of siRNA and a loss-of-function mutation in Dcr2 resulted in increased susceptibility to three different families of RNA viruses. Qi et al. (2012) research into RNAi gene silencing mechanism show that the B2 protein in Wuhan nodavirus (WhNV) suppresses Dcr2 in drosophila by direct interaction with the PAZ and RNAse III domains therefore blocking processing of dsRNA and siRNA. Evidence of a dicer antiviral system was also reported by Machitani et al. (2016) for mammalian human adenoviruses where DICER1 gene knockdown increased the copy number of adenovirus-encoding small RNAs (VA-RNAs) leading to the promotion of adenovirus replication; conversely, dicer overexpression significantly inhibited viral replication.
Modai et al. (2019) conclude that HIV-1 infection inhibits DICER1 by altering miRNA expression. They conclude that upon HIV-1 infection, human miR-186, 210 and 222 directly regulate DICER1 gene expression causing down-regulation of the gene contributing to impaired cell-mediated immunity (fig6). Other methods of inhibition are from viral proteins, termed viral suppressors of RNA silencing, which interact and inhibit dicer ribonuclease activity in HIV-1 and hepatitis C infections. These viral proteins may mediate proteasomal degradation of endoribonuclease dicer through CRL4DCAF1 ubiquitin ligase complex (Klockow et al. 2013), interact directly via the core protein (Chen et al. 2008) or HIV-1 transactivation of transcription (Bennasser and Jeang, 2006). Through these methods they can block dicer interactions with TRBP2 or ADAR1, boost macrophage infection, and subsequently reduce the function of short hairpin RNAs (shRNAs) which thus inhibit RNA silencing. Ultimately these viruses, though various methods, supress the ability of dicer to process dsRNAs into siRNAs boosting viral infection and pathogenesis.
Downregulation of DICER1 gene expression has additionally been found in cord blood of infants with severe respiratory syncytial virus (RSV), prior to RSV exposure, indicating this reduced expression may predispose newborns to RSV disease. Inchley et al. (2011) theorize that this occurs via disruption of leukocyte gene regulation of miRNA and direct anti-viral RNAi mechanisms. (Inchley et al. 2011 see section on “Dicer Gene Expression”).
Otsuka et al. (2007) have shown using gene-trap methods to obtain viable dicer1 fl/fl mice where dicer1 deficiency caused impairment of miR24 and miR93 production resulting in susceptibility to vesticular stomatitis virus (VSV) and herpes simplex-1 virus, but not other viruses tested.

SARS CoV & SARS CoV-2
Recently, Pasquier and Robichon, 2020 (preprint) have investigated the Dicer host immunity system regarding SARs-CoV-2 within a computational approach, concluding SARS-CoV2 may manipulate this system of immunity against its host, requiring further research. Mu et al., 2020 suggest SARs-CoV2 suppresses RNAi thus preventing recognition by the encoded ribonuclease dicer protein
Viral suppressors of RNA silencing (VSRs) suppress RNAi at pre or post-dicer level to overcome host defense and establish infection. Cui et al. (2015) from Wuhan University laboratory of virology, identified a novel VSR from coronaviruses (CoVs) including Severe acute respiratory syndrome coronavirus (SARS-CoV) and showed that the coronavirus nucelocaspid protein (N-protein), conserved and expressed in all coronaviruses, suppressed RNAi triggered by either short hairpin RNAs or small interfering RNAs in mammalian cells. They went on to show using mouse hepatitis virus A-59 (MHV-A59) which is closely linked to SARS-CoV in the family coronaviridae, that the viral replication was increased when the N proteins (novel VSR) were expressed but that knockdown of DICER1 gene or Ago2 transcripts facilitated the viral replication specifically in mammalian cells. They demonstrate that the N-protein of CoVs could efficiently inhibit dicer-mediated dsRNA cleavage and post-Dicer activities by sequestering dsRNAs and siRNAs. Kannan et al. (2020) performed clustal W analysis of N-Protein for SARS-CoV and COVID-19 demonstrating 90% sequence identity from an NCBI amino acid blast of both nucleocapsid (N) protein sequences (figure2). They suggest that the N-protein of COVID-19 may also function as a VSR for RNAi to overcome host defense. Ding et al. (2017) show that both MHV and SARS-CoV N proteins can also disrupt protein activator of protein kinase R (PACT), a cellular dsRNA-binding protein which binds to RIG-I and MDA5 to activate interferon (IFN) production to prevent antiviral host response.

Literature Review
PMID: 17181864: Bennasser and Jeang, 2006
• HIV-1 Tat Interaction With Dicer: Requirement for RNA
• Tat-Dicer interaction depends on RNA, requires the helicase domain of Dicer, and is independent of Tat's transactivation domain.

PMID: 18325616: Chen et al., 2008
• HCV Core Protein Interacts With Dicer to Antagonize RNA Silencing

PMID: 26085159: Cui et al., 2015
• The Nucleocapsid Protein of Coronaviruses Acts as a Viral Suppressor of RNA Silencing in Mammalian Cells

PMID: 24303839: Devasthanam et al, 2014
• This study investigates the role of the dicer protein in immune cell development and function using dicer1 cre-lox knockout models to conditionally ablate dicer1 in different immune cell subsets.

PMID: 28591694: Ding et al., 2017
• The nucleocapsid proteins of mouse hepatitis virus and severe acute respiratory syndrome coronavirus share the same IFN-β antagonizing mechanism: attenuation of PACT-mediated RIG-I/MDA5 activation

PMID: 30015086: Ding et al., 2018
• Antiviral RNA Interference in Mammals: Indicates infection of plants and insects with RNA and DNA viruses triggers Dicer-dependent production of virus-derived small interfering RNAs (vsiRNAs), which subsequently guide specific virus clearance by RNA interference (RNAi).

PMID: 25176334: Foulkes et al., 2012-REVIEW
• Review of DICER1: DICER1 Mutations, microRNAs and Mechanisms

PMID: 16554838: Galiana-Arnoux et al., 2006
• Essential function in vivo for Dicer-2 in host defense against RNA viruses in drosophila.
• https://pubmed.ncbi.nlm.nih.gov/16554838/ or https://www.nature.com/articles/ni1335

PMID: 21385408: Inchley et al., 2011
• Investigates ribonuclease Dicer and analyzed the gene expression of Dicer in newborns of which 37 infants had sufficient cord blood RNA with confirmed RSV disease <1yr. Demonstrates significant reduced Dicer expression in cord blood prior to severe disease in infants <1yr later. Conclude downregulation may predispose infants to RSV disease.

PMID: 32141569: Kannan et al., 2020
• COVID-19 (Novel Coronavirus 2019) - Recent Trends
• Perform W cluster analysis of COVID-19 and SARS-CoV nucleocapsid (N) protein sequences of the viruses showing 90% amino acid sequence similarity. Suggest the N-protein may be a VSR in RNAi by targeting DICER.

PMID: 23849790: Klockow et al., 2013
• The HIV-1 Protein Vpr Targets the Endoribonuclease Dicer for Proteasomal Degradation to Boost Macrophage Infection

PMID: 25883138: Kurzynska-Kokorniak et al., 2015
• Investigating the complexity of the mechanisms regulating Dicer gene expression and enzyme activities

PMID: 24115437: Li et al, 2013
• Investigates RNA interference pathways in antiviral immunity in mammals overviewing dicer processing of dsRNA viral replication intermediates into siRNAs.

PMID: 27273616: Machitani et al., 2016
• Dicer functions as an antiviral system against human adenoviruses via cleavage of adenovirus-encoded noncoding RNA

PMID: 30872283: Maillard et al., 2019- REVIEW
• Reviewing DICER1 within the anti-viral RNAi pathway in mammals

PMID: 30682089: Modai et al, 2019
• HIV-1 infection increases miRNAs which inhibit Dicer

PMID: 32291557: Mu et al, 2020
• SARS-CoV-2-encoded nucleocapsid protein acts as a viral suppressor of RNA interference in cells

PMID: 16009718: Muljo et al., 2005
• Indicates absence of dicer results in abberant T-cell differentiation.

PMID: 17613256: Otsuka, et al 2007
• Hypersusceptibility to Vesicular Stomatitis Virus Infection in Dicer1-Deficient Mice Is Due to Impaired miR24 and miR93 Expression

No PMID: Preprint : Pasquier and Rubichon, 2020
• SARS-CoV-2 might manipulate against its host the immunity RNAi/Dicer/Ago system

PMID: 22438534: Qi et al., 2012
• Targeting of Dicer-2 and RNA by a Viral RNA Silencing Suppressor in Drosophila Cells

PMID: 28473628: Song and Rossi, 2017
• Molecular Mechanisms of Dicer: Endonuclease and Enzymatic Activity
COVID-19 research v0.347 HAVCR1 Alison Coffey commented on gene: HAVCR1: Evidence Summary from Illumina curation team: HAVCR1 encodes the human hepatitis A virus (HAV) cellular receptor 1 (CD365, TIM1, KIM1) a phospholipid receptor which is expressed in mucosal epthelium from a range of tissues including trachea, conjunctiva and cornea (Kondratowicz et al. 2011). HAVCR1 acts as a cell receptor or entry factor for a number of enveloped viruses including Hepatitis A, Ebolavirus, Marberg virus and Dengue virus (Kondratowicz et al. 2011; Costfreda et al. 2018; Meertens et al. 2012).
COVID-19 research v0.341 HAVCR1 Alison Coffey reviewed gene: HAVCR1: Rating: GREEN; Mode of pathogenicity: ; Publications: 23084921, 29321304, 29437974, 21536871, 9658108; Phenotypes: ; Mode of inheritance:
COVID-19 research v0.339 HAVCR1 Rebecca Foulger commented on gene: HAVCR1
COVID-19 research v0.339 HAVCR1 Rebecca Foulger gene: HAVCR1 was added
gene: HAVCR1 was added to COVID-19 research. Sources: Expert list,OMIM,Expert Review Green
Mode of inheritance for gene: HAVCR1 was set to Unknown
Publications for gene: HAVCR1 were set to 29321304; 21536871; 23084921; 29437974; 9658108
COVID-19 research v0.176 CX3CR1 Sarah Leigh reviewed gene: CX3CR1: Rating: AMBER; Mode of pathogenicity: ; Publications: 14607932, 10731151; Phenotypes: {Rapid progression to AIDS from HIV1 infection} 609423; Mode of inheritance: BIALLELIC, autosomal or pseudoautosomal
COVID-19 research v0.176 CR1 Sarah Leigh reviewed gene: CR1: Rating: RED; Mode of pathogenicity: ; Publications: 16517720; Phenotypes: acute myocarditis and pericardial fibrosis due to coxsackievirus B3; Mode of inheritance: Unknown
COVID-19 research v0.121 CX3CR1 Sarah Leigh gene: CX3CR1 was added
gene: CX3CR1 was added to Viral susceptibility. Sources: OMIM
Mode of inheritance for gene: CX3CR1 was set to
COVID-19 research v0.121 CR1 Sarah Leigh gene: CR1 was added
gene: CR1 was added to Viral susceptibility. Sources: OMIM
Mode of inheritance for gene: CR1 was set to