Our verdict is Uncertain significance. Variant got 4 ACMG points: 4P and 0B. PM2PP3_Moderate
The NM_017739.4(POMGNT1):āc.1010T>Cā(p.Ile337Thr) variant causes a missense change involving the alteration of a conserved nucleotide. The variant allele was found at a frequency of 0.0000446 in 1,614,084 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a pathogenic outcome for this variant. Variant has been reported in ClinVar as Conflicting classifications of pathogenicity (no stars). Another variant affecting the same amino acid position, but resulting in a different missense (i.e. I337V) has been classified as Uncertain significance.
POMGNT1 (HGNC:19139): (protein O-linked mannose N-acetylglucosaminyltransferase 1 (beta 1,2-)) This gene encodes a type II transmembrane protein that resides in the Golgi apparatus. It participates in O-mannosyl glycosylation and is specific for alpha linked terminal mannose. Mutations in this gene may be associated with muscle-eye-brain disease and several congenital muscular dystrophies. Alternatively spliced transcript variants that encode different protein isoforms have been described. [provided by RefSeq, Feb 2014]
TSPAN1 (HGNC:20657): (tetraspanin 1) The protein encoded by this gene is a member of the transmembrane 4 superfamily, also known as the tetraspanin family. Most of these members are cell-surface proteins that are characterized by the presence of four hydrophobic domains. The proteins mediate signal transduction events that play a role in the regulation of cell development, activation, growth and motility. [provided by RefSeq, Jul 2008]
Uncertain significance, criteria provided, single submitter
clinical testing
GeneDx
May 05, 2022
Not observed at significant frequency in large population cohorts (gnomAD); In silico analysis supports that this missense variant has a deleterious effect on protein structure/function; Has not been previously published as pathogenic or benign to our knowledge; This variant is associated with the following publications: (PMID: 24282183, 30564623) -
Uncertain significance, criteria provided, single submitter
clinical testing
Eurofins Ntd Llc (ga)
Dec 22, 2015
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Uncertain significance, criteria provided, single submitter
clinical testing
Revvity Omics, Revvity
Sep 13, 2022
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Muscular dystrophy-dystroglycanopathy (congenital with intellectual disability), type B3;C3150417:Autosomal recessive limb-girdle muscular dystrophy type 2O;C3151519:Muscular dystrophy-dystroglycanopathy (congenital with brain and eye anomalies), type A3;C4310704:Retinitis pigmentosa 76 Pathogenic:1
Likely pathogenic, criteria provided, single submitter
clinical testing
Fulgent Genetics, Fulgent Genetics
Jun 02, 2024
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Muscular dystrophy-dystroglycanopathy (congenital with intellectual disability), type B3;C3150417:Autosomal recessive limb-girdle muscular dystrophy type 2O Pathogenic:1
Likely pathogenic, criteria provided, single submitter
clinical testing
Labcorp Genetics (formerly Invitae), Labcorp
Dec 31, 2023
This sequence change replaces isoleucine, which is neutral and non-polar, with threonine, which is neutral and polar, at codon 337 of the POMGNT1 protein (p.Ile337Thr). This variant is present in population databases (rs138745073, gnomAD 0.01%). This missense change has been observed in individual(s) with clinical features of retinitis pigmentosa (Invitae). In at least one individual the data is consistent with being in trans (on the opposite chromosome) from a pathogenic variant. It has also been observed to segregate with disease in related individuals. ClinVar contains an entry for this variant (Variation ID: 285192). Advanced modeling of protein sequence and biophysical properties (such as structural, functional, and spatial information, amino acid conservation, physicochemical variation, residue mobility, and thermodynamic stability) has been performed at Invitae for this missense variant, however the output from this modeling did not meet the statistical confidence thresholds required to predict the impact of this variant on POMGNT1 protein function. In summary, the currently available evidence indicates that the variant is pathogenic, but additional data are needed to prove that conclusively. Therefore, this variant has been classified as Likely Pathogenic. -
Inborn genetic diseases Uncertain:1
Uncertain significance, criteria provided, single submitter
clinical testing
Ambry Genetics
Apr 21, 2021
The c.1010T>C (p.I337T) alteration is located in exon 11 (coding exon 10) of the POMGNT1 gene. This alteration results from a T to C substitution at nucleotide position 1010, causing the isoleucine (I) at amino acid position 337 to be replaced by a threonine (T). The p.I337T alteration is predicted to be deleterious by in silico analysis. Based on insufficient or conflicting evidence, the clinical significance of this alteration remains unclear. -
Retinal dystrophy Uncertain:1
Uncertain significance, criteria provided, single submitter
research
Dept Of Ophthalmology, Nagoya University
Oct 01, 2023
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Muscle eye brain disease;C3150412:Muscular dystrophy-dystroglycanopathy (congenital with intellectual disability), type B3;C3150417:Autosomal recessive limb-girdle muscular dystrophy type 2O;C4310704:Retinitis pigmentosa 76 Uncertain:1
Uncertain significance, criteria provided, single submitter