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| Intellectual disability - microarray and sequencing v3.1558 | SLC35B2 |
Konstantinos Varvagiannis gene: SLC35B2 was added gene: SLC35B2 was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: SLC35B2 was set to BIALLELIC, autosomal or pseudoautosomal Publications for gene: SLC35B2 were set to 35325049 Phenotypes for gene: SLC35B2 were set to Abnormality of the skeletal system; Short long bone; Short stature; Abnormality of epiphysis morphology; Scoliosis; Multiple joint dislocation; Global develpmental delay; Intellectual disability; CNS hypomyelination; Abnormality of the corpus callosum; Cerebral atrophy; Abnormality of the amniotic fluid Penetrance for gene: SLC35B2 were set to Complete Review for gene: SLC35B2 was set to AMBER Added comment: 2 unrelated individuals with biallelic SLC35B2 variants have been reported. DD and ID were part of the phenotype. There is currently no associated phenotype in OMIM/G2P/SysID. The gene has amber rating in the leukodystrophies panel of PanelApp Australia. Consider inclusion in the current panel (or other possibly relevant ones eg. for skeletal disorders, short stature, white matter disorders, corpus callosum, etc) with amber rating. --- Guasto et al (2022 - PMID:35325049) report 2 unrelated individuals with biallelic SLC35B2 variants. SLC35B2 encodes solute carrier family 35 (3'-phosphoadenosine 5'-phosphosulfate (PAPS) transporter), member B2. The protein is located in the Golgi membrane and serves as transporter of the activated nucleotide sulfate PAPS from the cytosol, where it is synthesized to the Golgi lumen. Another PAPS transporter is encoded by SLC35B3. In the Golgi apparatus PAPS serves as substrate of sulfotransferases for the addition sulfate to the covalently attached GAG chains of proteoglycans (PGs). The phenotype corresponded to a chondrodysplasia manifesting as severe pre- and postnatal growth retardation (height <-4 SD and -8 SD), early scoliosis, multiple joint dislocations (in one). There was severe DD affecting motor and expressive language development with associated ID. Brain imaging was suggestive of hypomyelinating leukodystrophy with thin corpus callosum and cerebral atrophy. One individual had a cleft palate in the context of Pierre Robin sequence. Both individuals were investigated with exome sequencing. The first individual - born to consanguineous parents - was homozygous for an in-frame del (NM_178148.3:c.1218_1220del, p.Leu407del) with Sanger sequencing confirming the variants, and heterozygosity in parents and 2 unaffected sibs. There was an initially identified hmz CUL7 variant (for 3M syndrome), which was not felt sufficient to explain the severity of the phenotype and notably ID. The 2nd proband was homozygous for a fs variant (c.1224_1225delAG / p.Arg408SerfsTer18 - leading to loss of the last 8 amino acids) occurring in the context of uniparental isodisomy [iUPD(6)] spanning the complete chr6 based on the exome data. Among the evidence presented for SLC35B2 and the variants : - SLC35B2 has high mRNA expression in fetal and adult mouse brain and other tissues. - Upon qPCR analysis of mRNA expression in human brain samples, the gene had expression across the brain (frontal lobe grey matter, subcortical frontal white matter/cerebellum). - High expression was shown upon analysis of mouse brain single cell RNA data (EMBL) in oligodendrocytes and microglial cells. - RT-PCR on mRNA from skin fibroblasts (both individuals) revealed significant decrease of SCL35B2 mRNA levels compared to controls. - Transfection of C-terminal c-myc tagged wt or mutant proteins in HEK293F cells, followed by western blotting did not reveal significant difference at the protein level. Wt SLC35B2 localized at the Golgi apparatus as suggested by colocalization with GM130 marker. The 2 variants however displayed only partial colocalization (/loss of localization specificity) with diffuse signal in the cell. - Chondroitin sulfate disaccharide sulfation was decreased upon HPLC disaccharide analysis in patient fibroblasts and bikunin (a circulating proteoglycan in blood) electrophoretic pattern in patient sera. - Disorders due to variants in genes implicated in proteoglycan biogenesis (e.g. XYLT1, B3GALT6, CHSY1) are associated with skeletal/connective tissue manifestations with DD/ID. - C-elegans model lacking pst-1 (SLC35B2 ortholog) provides support that the protein is required for migration, axonal guidance, and presynaptic development in a subset of neurons. - dsm-1 - the rat ortholog - is expressed in rat brain in D-serine and NMDA receptor rich regions. When expressed in Xenopus oocytes it accelerated the efflux of D-serine (a co-agonist for NMDA receptor). - Variants in other members of SLC superfamily (e.g. SLC17A5, SLC35A3, SLC29A3, SLC35A2) have been associated with brain-bone phenotypes. Sources: Literature |
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| Intellectual disability - microarray and sequencing v2.651 | SLC35A3 | Rebecca Foulger Tag watchlist tag was added to gene: SLC35A3. | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v2.651 | SLC35A3 | Rebecca Foulger commented on gene: SLC35A3: Added watchlist tag. | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v2.651 | SLC35A3 | Rebecca Foulger Classified gene: SLC35A3 as Amber List (moderate evidence) | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v2.651 | SLC35A3 | Rebecca Foulger Added comment: Comment on list classification: Updated rating from Grey to Amber. Gene was added to panel and rated Green by Konstantinos Varvagiannis. 1 case (multiple individuals from Ashkenazi Jewish kindred) in PMID:24031089. A second case comes from PMID:28328131 (Marini et al. 2017). ID is not recorded in the SLC35A3‐related skeletal dysplasia patient from PMID:28777481 who died at 21days. ClinVar submissions weren't included as additional cases as individual phenotypes were not recorded. Therefore rated Amber awaiting further published or clinical cases. | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v2.651 | SLC35A3 | Rebecca Foulger Gene: slc35a3 has been classified as Amber List (Moderate Evidence). | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v2.649 | SLC35A3 | Rebecca Foulger commented on gene: SLC35A3: The 2013 and 2016 ClinVar submissions SCV000699337.1 and SCV000108589.2 reported in the review by Konstantinos Varvagiannis link to the same publication: Edvardson et al. (2013, PMID:24031089). | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v2.647 | SLC35A3 | Rebecca Foulger commented on gene: SLC35A3: Marini et al. 2017 (PMID: 28328131) provide a second case. They report a non-consanguineous Italian family with two siblings manifesting a severe EE. Both siblings exhibited infantile spasms associated with focal and tonic seizures from early infancy. In addition, both had quadriplegia, acquired microcephaly and severe ID. WGS identified novel compound het variants in SLC35A3 in both children. | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v2.647 | SLC35A3 | Rebecca Foulger commented on gene: SLC35A3 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v2.588 | SLC35A3 |
Konstantinos Varvagiannis gene: SLC35A3 was added gene: SLC35A3 was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: SLC35A3 was set to BIALLELIC, autosomal or pseudoautosomal Publications for gene: SLC35A3 were set to 24031089; 28328131; 28777481; 16344554 Phenotypes for gene: SLC35A3 were set to ?Arthrogryposis, mental retardation, and seizures (MIM 615553) Penetrance for gene: SLC35A3 were set to Complete Review for gene: SLC35A3 was set to GREEN gene: SLC35A3 was marked as current diagnostic Added comment: Biallelic pathogenic variants in SLC35A3 cause Arthrogryposis, mental retardation, and seizures (MIM 615553). -------- Edvardson et al. (PMID: 24031089) report on 8 affected individuals from 3 nuclear Ashkenazi Jewish families. All harbored a nonsense [NM_012243.1:c.514C>T / p.(Gln172*)] as well as a missense variant [NM_012243.1:c.886A>G / p.(Ser296Gly)] in the compound heterozygous state. Most of the parents, who were heterozygous for the one or the other variant, were distantly related. Common features included ASD (8/8), arthrogryposis (8/8), seizures (6/8) and intellectual disability (6/8 - variable degrees). Upon cDNA studies, the (predicted) missense variant led to skipping of exon 8 and there was no normal size transcript (as would be expected for a variant of this type). Introduction of a premature stop codon due to this variant as well instability of the mRNA from the Gln172Ter allele was presumed to lead to absence of functional SLC35A3 protein. Testing of 2045 Ashkenazi Jewish individuals revealed a carrier frequency of 1/205 for the missense variant in this community (with no occurrence of the nonsense variant). SLC35A3 is a nucleotide sugar transporter that transports (uniquely) UDP-N-acetylglucosamine (UDP-GlcNAc) from the cytoplasm where it is synthesized to its site of use in the Golgi. Proper function of such transporters is essential for biosynthesis of glycoproteins, glycolipids and proteoglycans. Although the transport of UDP-GlcNAc is mediated also by other less specific transporters, members of the SLC35 family, reduced transport was shown in patient fibroblasts compared to controls. In addition an abnormal N-glycan profile was shown in patient fibroblasts (but was not the case in serum). Biallelic SLC35A3 mutations in cattle were previously shown to cause a Complex Vertebral Malformation (CVM) syndrome characterized by abnormal growth, vertebral and heart malformations as well as arthrogryposis (Thomsen et al. - PMID: 16344554). Arthrogryposis as well as some skeletal features observed in patients were similar to those of the animal model. -------- Marini et al. (PMID: 28328131) report on 2 sibs compound heterozygous for a missense and a frameshift variant [NM_012243.2:c.73C>T or p.(Arg25Cys) and c.899_900delTTinsA or p.(Leu300Glnfs*6)]. Hypotonia, DD with ID, early-onset seizures and arthrogryposis were features in both. Severe scoliosis was also noted in the younger sib. --------- Edmondson et al. (PMID: 28777481) report on a neonate (follow-up till the 21st day of life) with extensive vertebral anomalies (butterfly vertebrae, hemibertebrae, sagittal clefts, scoliosis), heart defects (PFO, PDA) and arthrogryposis. Presence of hypotonia or other neurologic features (eg. seizures) is not commented on. Conventional caryotype and SNP-array analysis were normal apart from the presence of ROH regions due to parental consanguinity. Exome sequencing revealed only a homozygous missense SNV [c.74G>T or p.(Arg25Leu) - NP_036375.1] which was supported by an abnormal N-glycan profile. As proposed for the bovine model (PMID: 16344554) and discussed in this article, similarity of the skeletal/congenital heart defects with those observed in Alagille syndrome might be due to some of the Notch functions being dependent upon N-acetylglucosamine modification. --------- In ClinVar : There is a further submission of p.Ser296Gly as pathogenic (SCV000699337.1 - 2016) apart from the submission by OMIM (SCV000108589.2 - 2013). The associated condition is Arthrogryposis, mental retardation, and seizures. A frameshift variant [NM_012243.2(SLC35A3):c.680dup (p.Asp227Glufs)- SCV000826704.1 - April 2018] as well as an intragenic deletion [NC_000001.10:g.(?_100472570)_(100477109_?)del (GRCh37) - SCV000837123.1 - June 2018] have both been submitted as pathogenic, associated with Arthrogryposis, mental retardation, and seizures. (Note: due to the different submission dates, one can presume that these variants were found in different individuals). --------- SLC35A3 is not associated with any phenotype in OMIM. It is included in gene panels for ID offered by some diagnostic laboratories. --------- As a result, this gene can be considered for inclusion in the ID panel probably as green (or amber) [Consider upgrade of this gene to green in other panels (eg. CDGs, arthrogryposis, IEMs) and/or inclusion in other possibly relevant panels.] Sources: Literature |
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