1-46192307-C-G

Variant names:

• chr1-46192307-C-G
• rs587777821
• NM_017739.4:c.1413+1G>C

Variant summary

Our verdict is Uncertain significance. The variant received 5 ACMG points: 5P and 0B. PVS1_Moderate PM2 PP5

The NM_017739.4(POMGNT1):​c.1413+1G>C variant causes a splice donor, intron change involving the alteration of a conserved nucleotide. The variant allele was found at a frequency of 0.00000342 in 1,461,894 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a pathogenic outcome for this variant. 3/3 splice prediction tools predicting alterations to normal splicing. Variant has been reported in ClinVar as Conflicting classifications of pathogenicity (no stars).

• Frequency:
  • Genomes: not found (cov: 32)
  • Exomes 𝑓: 0.0000034 (0 hom.)
• Consequence: POMGNT1 NM_017739.4 splice_donor, intron
• Scores: Splicing: ADA: 1.000
• Clinical Significance: Conflicting classifications of pathogenicity criteria provided, conflicting classifications P:1 U:1
• Conservation: PhyloP100: 7.53
• Publications: 1 publications found

Genes affected

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]

ACMG classification

Our verdict: Uncertain_significance. The variant received 5 ACMG points.

• PVS1: Splicing +-2 bp (donor or acceptor) variant, product NOT destroyed by NMD, known LOF gene, truncates exone, which is 0.06505295 fraction of the gene. Cryptic splice site detected, with MaxEntScore 5.8, offset of 12, new splice context is: aggGTaggg. Cryptic site results in inframe change. If cryptic site found is not functional and variant results in exon loss, it results in inframe change.
• PM2: Very rare variant in population databases, with high coverage
• PP5: Variant 1-46192307-C-G is Pathogenic according to our data. Variant chr1-46192307-C-G is described in ClinVar as Conflicting_classifications_of_pathogenicity. ClinVar VariationId is 211939.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
POMGNT1	NM_017739.4	c.1413+1G>C		splice_donor_variant, intron_variant	Intron 16 of 21	ENST00000371984.8	NP_060209.4

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
POMGNT1	ENST00000371984.8	c.1413+1G>C		splice_donor_variant, intron_variant	Intron 16 of 21	1	NM_017739.4	ENSP00000361052.3

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD2 exomes AF: 0.0000119 AC: 3 AN: 251480 AF XY: 0.0000221

Gnomad AFR exome AF: 0.00

Gnomad AMR exome AF: 0.00

Gnomad ASJ exome AF: 0.00

Gnomad EAS exome AF: 0.00

Gnomad FIN exome AF: 0.00

Gnomad NFE exome AF: 0.00

Gnomad OTH exome AF: 0.00

GnomAD4 exome AF: 0.00000342 AC: 5 AN: 1461894 Hom.: 0 Cov.: 31 AF XY: 0.00000688 AC XY: 5 AN XY: 727248

African (AFR) AF: 0.00 AC: 0 AN: 33480

American (AMR) AF: 0.00 AC: 0 AN: 44724

Ashkenazi Jewish (ASJ) AF: 0.00 AC: 0 AN: 26136

East Asian (EAS) AF: 0.00 AC: 0 AN: 39700

South Asian (SAS) AF: 0.0000580 AC: 5 AN: 86258

European-Finnish (FIN) AF: 0.00 AC: 0 AN: 53420

Middle Eastern (MID) AF: 0.00 AC: 0 AN: 5768

European-Non Finnish (NFE) AF: 0.00 AC: 0 AN: 1112012

Other (OTH) AF: 0.00 AC: 0 AN: 60396

GnomAD4 genome Cov.: 32

ExAC AF: 0.0000165 AC: 2

ClinVar

Significance: Conflicting classifications of pathogenicity

Submissions summary: Pathogenic:1 Uncertain:1

Revision: criteria provided, conflicting classifications

Submissions by phenotype

Muscular dystrophy-dystroglycanopathy (congenital with brain and eye anomalies), type A3 Pathogenic:1

Jun 08, 2015

Genetic Services Laboratory, University of Chicago

Significance: Pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

- -

Muscular dystrophy-dystroglycanopathy Uncertain:1

Jan 24, 2023

Broad Center for Mendelian Genomics, Broad Institute of MIT and Harvard

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: curation

The c.1413+1G>C variant in POMGNT1 has not been previously reported in the literature in individuals with POMGNT1-associated muscular dystrophy-dystroglycanopathy but has been identified in 0.01% (3/30616) of South Asian chromosomes by the Genome Aggregation Database (gnomAD, http://gnomad.broadinstitute.org; dbSNP ID: rs587777821). Although this variant has been seen in the general population in a heterozygous state, its frequency is low enough to be consistent with a recessive carrier frequency. This variant has also been reported in ClinVar (Variation ID#:211939) and has been interpreted as pathogenic by the University of Chicago Genetic Services Library. This variant is located in the 5' splice region. Computational tools predict a splicing impact, though this information is not predictive enough to determine pathogenicity. This variant is adjacent to an in-frame exon and is more likely to escape nonsense mediated decay (NMD) and result in a truncated protein. Loss of function of the POMGNT1 gene is an established disease mechanism in autosomal recessive POMGNT1-associated muscular dystrophy-dystroglycanopathy. In summary, the clinical significance of the c.1413+1G>C variant is uncertain. ACMG/AMP Criteria applied: PVS1_Moderate, PM2_Supporting (Richards 2015). -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
BayesDel_addAF	Pathogenic	0.48	D
BayesDel_noAF	Pathogenic	0.31
CADD	Pathogenic	29
DANN	Uncertain	0.99
Eigen	Pathogenic	1.1
Eigen_PC	Pathogenic	0.97
FATHMM_MKL	Pathogenic	0.98	D
PhyloP100		7.5
GERP RS		6.0
RBP_binding_hub_radar		0.0
RBP_regulation_power_radar		2.9
Mutation Taster		=0/100	disease causing (ClinVar)

Splicing

Name	Calibrated prediction	Score	Prediction
dbscSNV1_ADA	Pathogenic	1.0
dbscSNV1_RF	Pathogenic	0.93
SpliceAI score (max)		1.0		Details are displayed if max score is > 0.2
DS_DG_spliceai		0.21		Position offset: -11
DS_DL_spliceai		1.0		Position offset: 1

Find out detailed SpliceAI scores and Pangolin per-transcript scores at spliceailookup.broadinstitute.org

Other links and lift over

dbSNP: rs587777821; hg19: chr1-46657979;