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| Intellectual disability - microarray and sequencing v3.1534 | ZBTB7A |
Konstantinos Varvagiannis gene: ZBTB7A was added gene: ZBTB7A was added to Intellectual disability. Sources: Literature,Other Mode of inheritance for gene: ZBTB7A was set to MONOALLELIC, autosomal or pseudoautosomal, imprinted status unknown Publications for gene: ZBTB7A were set to 31645653; 34515416 Phenotypes for gene: ZBTB7A were set to Global developmental delay; Intellectual disability; Macrocephaly; Abnormality of the lymphatic system; Sleep apnea; Increased body weight; Autism; Persistence of hemoglobin F; Abnormal leukocyte count; Recurrent infections; Umbilical hernia Penetrance for gene: ZBTB7A were set to unknown Review for gene: ZBTB7A was set to AMBER Added comment: Monoallelic pathogenic ZBTB7A variants cause Macrocephaly, neurodevelopmental delay, lymphoid hyperplasia, and persistent fetal hemoglobin (#619769). ---- Ohishi et al (2020 - PMID: 31645653) described the phenotype of a 6y5m-old male harboring a heterozygous, de novo ZBTB7A missense variant. Features included macrocephaly, mild intellectual disability (tIQ 65) and sleep apnea. Available hemoglobin levels (in the 1st month) supported high Hb and HbF levels. Other features included PDA and an umbilical hernia. Initial investigations incl. karyotype and CMA were normal. The ZBTB7A variant (NM_015898.3:c.1152C>G / p.Cys384Tyr) was identified following trio WES with a list of additional findings (in suppl.) not explaining the phenotype. This SNV, confirmed by Sanger sequencing, was absent from public db with several in silico predictions in favor of a deleterious effect. ZBTB7A on 19p encodes zinc finger- and BTB domain-containing protein 7 (or Pokemon). The authors performed a review of 19p13.3 microdeletion cases supporting a minimum region of overlap spanning PIAS4, ZBTB7A and MAP2K2 and common features of DD and ID, macrocephaly with prominent forehead, sleep apnea. The authors argue that loss of ZBTB7A explains part of - but probably not all - features of 19p13.3 microdeletions. ZBTB7A is known to repress expression of HBG1 and HBG2 (γ-globin), with the few available HbF patient measurements in line with this role. Based on the structure of the protein, Cys384 (along with 3 other residues) forms a coordinate bond with the Zn+2 ion, this bond predicted to be disrupted by Tyr. Further they favor a dominant negative effect given that ZBTB7A protein is known to form dimer via interaction at the BTB domain [hetero (variant+wt) and homodimers (variant+variant) having compromised function]. To support this notion, 3 previously reported somatic variants within the zinc-finger domain have been shown to exert a dominant-negative effect (PMID cited: 26455326). ---- In a collaborative study, von der Lippe et al (2022 - PMID: 34515416) identified 12 additional individuals (from 10 families) harboring monoallelic ZBTB7A missense/pLoF variants most commonly as de novo events. The authors describe a consistent phenotype with motor (9/11) and speech delay (9/12), cognitive impairment/ID (12/12 - commonly mild, ranged from specific learning difficulties to severe ID), macrocephaly (>90%le in 11/12, >97% in 7/12), lymphoid hypertrophy of pharyngeal tissue/adenoid overgrowth (12/12), sleep apnea (9/12). Autistic features were observed in 7/12. Other phenotypes included frequent upper airway infections (10/11), weight above 97th percentile (7/11). HbF levels were elevated in 4/5 individuals with available measurements (range: 2.2% to 11.2% - ref. for subjects above 6m of age : <2% ). Other hematological issues were observed in few individuals (abn. monocyte/neutrophil counts in 3-4). Cardiovascular issues were reported in 4 (2 fam). 3 subjects had umbilical hernia. There was no common dysmorphic feature. Various initial investigations were normal or did not appear to explain the NDD phenotype and incl. standard karyotype, CMA, targeted testing for genes/disorders previously considered (PTEN, FMR1, NSD1, BWS and PWS methylation studies, CFTR, etc). One male had a maternally inherited chrX dup not thought to explain his complex phenotype, while another had a concurrent diagnosis of thalassemia. Individuals were investigated with singleton (or trio) WES. Of note some individuals were DDD study participants. 8 had de novo ZBTB7A variants, incl. one who harbored 2 de novo missense SNVs several residues apart. 2 sibs had inherited a fs variant from their affected parent. For the latter as well as for another subject parental samples were unavailable. There were no other variants of interest upon exome analysis. 5 different missense, 2 nonsense and 3 fs variants were identified with pLoF all predicted to lead to NMD. All variants were absent from gnomAD (pLI of 0.96, LOEUF 0.33 and missense Z-score of 4.04) which lists one individual with htz LoF, likely not an artifact. Given this individual (and the familial case) the authors discuss on the mild phenotype and/or eventual reduced penetrance or underdiagnosis of the disorder. There was no difference in severity between those with missense/truncating variants. ZBTB7A transcription factor (or pokemon or lymphoma/leukemia-related factor) is widely expressed. It is involved in several activities being among others required to block Notch signaling which in turn drives T-cell at the expense of B-cell development. Notch pathway activation has been demonstrated in Zbtba7 ko mouse models. Finally, the authors discuss the role of notch signaling in thymus and the nervous system, as well as that ZBTB7A up/down-regulation known to repress/increase respectively HbF expression (several refs in text). ---- MGI (1335091) for Zbtb7a : "Mice homozygous for a knock-out allele die around E16.5 due to anemia and exhibit a cell autonomous defect in early B cell development". (Phenotypes from nervous system not commented on). ---- Apart from OMIM (#619769), ZBTB7A is included in the DD panel of G2P (ZBTB7A-associated developmental disorder / monoallelic_autosomal / absent gene product / confidence limited) as well as among the primary ID genes in SysID. In PanelApp Australia the gene is incl. with green rating in the ID and Macrocephaly gene panels. ---- Consider inclusion with amber or green rating (several individuals/families/variants, highly consistent phenotype, overlap with 19p microdeletions || variant effect not studied, animal models supporting contribution of the gene to the phenotype though no data on associated NDD ones). Please also consider inclusion in other relevant panels (macrocephaly, lymphatic disorders, ASD, etc). Sources: Literature, Other |
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| Intellectual disability - microarray and sequencing v2.784 | BRSK2 |
Konstantinos Varvagiannis gene: BRSK2 was added gene: BRSK2 was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: BRSK2 was set to MONOALLELIC, autosomal or pseudoautosomal, imprinted status unknown Publications for gene: BRSK2 were set to https://doi.org/10.1016/j.ajhg.2019.02.002 Phenotypes for gene: BRSK2 were set to Global developmental delay; Intellectual disability; Autism; Behavioral abnormality Penetrance for gene: BRSK2 were set to unknown Review for gene: BRSK2 was set to GREEN gene: BRSK2 was marked as current diagnostic Added comment: Hiatt et al. (2019 - https://doi.org/10.1016/j.ajhg.2019.02.002) report on 9 individuals, each with private heterozygous BRSK2 variant. Features included among others speech or motor delay, ID (8/9), ASD and variable behavioral anomalies. 6 variants predicted LoF (stopgain, frameshift or affecting splice-site) while 3 additional ones were missense (2 in the protein kinase domain and 1 in the kinase-associated 1 domain). In 6 individuals the variant had occurred as a de novo event while for 3 others parental samples were unavailable. Given the unknown inheritance, a single variant did not meet sufficient ACMG criteria to be classified as P/LP. All variants had in silico predictions supporting a deleterious effect and were absent from bravo database and gnomAD, where the gene appears to be relatively intolerant to protein-altering variation. As the authors note BRSK2 encodes a serine/threonine protein kinase involved in axonogenesis and polarization of cortical neurons. Although Brsk2- (or Brsk1-) knockout mice appear to be healthy and fertile, double knockouts for these genes resulted in pups with decreased spontaneous movement, poor response to tactile stimulation that died shortly after birth. In mice Brsk2 (and Brsk1) expression is restricted to the nervous system (PMID cited by the authors: 15705853) while in humans this gene is most highly expressed in brain (PMID cited: 23715323 - GTEx project). BRSK2 has been shown to interact with other neurodevelopmental genes eg. TSC2, PTEN, WDR45. Within the cohort of individuals studied, there was statistically significant enrichment for de novo BRSK2 variants when compared to the estimated backround mutation rate. Two further BRSK2 de novo protein-altering variants were previously reported in individuals with neurodevelopmental disorders (Iossifov et al. - PMID: 25363768 and DDD study - PMID: 28135719) although the missense variant in the latter study is also present in gnomAD database. BRSK2 is not associated with any phenotype in OMIM, nor in G2P. The gene is included in gene panels for ID offered by some diagnostic laboratories (eg. among those participating in the study). As a result, this gene can be considered for inclusion in the ID panel as green (or amber). Sources: Literature |
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| Intellectual disability - microarray and sequencing v2.558 | ODC1 |
Konstantinos Varvagiannis gene: ODC1 was added gene: ODC1 was added to Intellectual disability. Sources: Literature,Expert Review Mode of inheritance for gene: ODC1 was set to MONOALLELIC, autosomal or pseudoautosomal, imprinted status unknown Publications for gene: ODC1 were set to 30239107; 30475435 Phenotypes for gene: ODC1 were set to Global developmental delay; Intellectual disability; Macrocephaly; Alopecia; Ectodermal dysplasia Penetrance for gene: ODC1 were set to unknown Review for gene: ODC1 was set to GREEN Added comment: PMIDs 30239107 and 30475435 report on 5 cases of de novo truncating ODC1 variants in unrelated families. One concerned a stillborn male. The 4 remaining individuals presented with a similar phenotype consisting of alopecia and other ectodermal anomalies, DD/ID, relative or absolute macrocephaly and common facial features. DD/ID was severe in some instances and many of these individuals had extensive prior testing for other disorders (Fragile-X, PTEN, SLC2A1, chromosomal disorders, etc). ODC1 (ornithine decarboxylase 1) converts enzymatically ornithine to putrescine. All variants reported to date are truncating but lead to gain-of-function. Specifically they affect a 37 amino acid c-terminal destabilization region critical for the degradation of ODC1 and - as a result - lead to increased levels of ODC1 as well as putrescine. A mouse model with identical phenotype has been described several years ago. The role of ODC inhibitors is extensively discussed in both publications. As a result, ODC1 can be considered for inclusion in the ID panel as green (or amber). Sources: Literature, Expert Review |
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| Intellectual disability - microarray and sequencing v2.468 | PTEN | Louise Daugherty Source Victorian Clinical Genetics Services was added to PTEN. | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing | PTEN | BRIDGE consortium edited their review of PTEN | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing | PTEN | BRIDGE consortium edited their review of PTEN | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing | PTEN | BRIDGE consortium reviewed PTEN | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||