rs80338851
Variant summary
Our verdict is Pathogenic. Variant got 18 ACMG points: 18P and 0B. PVS1PM2PP5_Very_Strong
The NM_194318.4(B3GLCT):c.660+1G>A variant causes a splice donor, intron change involving the alteration of a conserved nucleotide. The variant allele was found at a frequency of 0.00103 in 1,588,686 control chromosomes in the GnomAD database, with no homozygous occurrence. 3/3 splice prediction tools predicting alterations to normal splicing. Variant has been reported in ClinVar as Pathogenic (★★).
Frequency
Consequence
NM_194318.4 splice_donor, intron
Scores
Clinical Significance
Conservation
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ACMG classification
Verdict is Pathogenic. Variant got 18 ACMG points.
Transcripts
RefSeq
Ensembl
Frequencies
GnomAD3 genomes AF: 0.000802 AC: 122AN: 152076Hom.: 0 Cov.: 32
GnomAD3 exomes AF: 0.000700 AC: 175AN: 250126Hom.: 0 AF XY: 0.000688 AC XY: 93AN XY: 135206
GnomAD4 exome AF: 0.00106 AC: 1521AN: 1436492Hom.: 0 Cov.: 27 AF XY: 0.00101 AC XY: 721AN XY: 716300
GnomAD4 genome AF: 0.000802 AC: 122AN: 152194Hom.: 0 Cov.: 32 AF XY: 0.000632 AC XY: 47AN XY: 74420
ClinVar
Submissions by phenotype
Peters plus syndrome Pathogenic:15Other:1
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PVS1, PM3_strong -
This variant was classified as: Pathogenic. The following ACMG criteria were applied in classifying this variant: PVS1,PS1,PM2,PP3. -
Variant summary: B3GALTL c.660+1G>A (aka c.1020+1G>A) is located in a canonical splice-site and is predicted to affect mRNA splicing resulting in a significantly altered protein due to either exon skipping, shortening, or inclusion of intronic material. Several computational tools predict a significant impact on normal splicing: four predict the variant abolishes a 5' splicing donor site. The variant allele was found at a frequency of 0.00076 in 281510 control chromosomes (gnomAD). The variant, c.660+1G>A, has been reported in the literature in numerous homozygous- and compound heterozygous individuals affected with Peters Plus Syndrome (see e.g. Lesnik_2006, Hess_2008, Wang_2020); the variant was described as a recurrent mutation in many different ethnicities, and was reported as the most frequent disease associated allele. These data indicate that the variant is very likely to be associated with disease. Publications also reported experimental evidence and confirmed that the variant results in the skipping of exon 8, in addition, fucosylation defects were also demonstrated in patients (Lesnik_2006, Hess_2008). Nine clinical diagnostic laboratories have submitted clinical-significance assessments for this variant to ClinVar after 2014, and all of them classified the variant as pathogenic. Based on the evidence outlined above, the variant was classified as pathogenic. -
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The variant is observed at an extremely low frequency in the gnomAD v2.1.1 dataset (total allele frequency: <0.001%). Predicted Consequence/Location: The variant is located in a mutational hot spot and/or well-established functional domain in which established pathogenic variants have been reported. Missense changes are a common disease-causing mechanism. Functional studies provide strong evidence of the variant having a damaging effect on the gene or gene product (PMID: 17981815, 18413255, 23093928). In silico tool predictions suggest damaging effect of the variant on gene or gene product [REVEL: 0.98 (>=0.6, sensitivity 0.68 and specificity 0.92); 3Cnet: 0.97 (>=0.6, sensitivity 0.72 and precision 0.9)]. Same nucleotide change resulting in same amino acid change has been previously reported as pathogenic/likely pathogenic with strong evidence (ClinVar ID: VCV000013351 /PMID: 16439621 /3billion dataset). The variant has been previously reported as de novo in at least two similarly affected unrelated individuals (PMID: 16439621, 17551924, 18042262). Different missense changes at the same codon (p.Tyr130Asn, p.Tyr130His) have been reported as pathogenic/likely pathogenic with strong evidence (ClinVar ID: VCV000040747, VCV000636238 /PMID: 18413255, 19156172). Therefore, this variant is classified as Pathogenic according to the recommendation of ACMG/AMP guideline. -
ACMG classification criteria: PVS1 strong, PM3 strong -
The B3GALTL c.660+1G>A variant occurs in a canonical splice site (donor) and is therefore predicted to disrupt or distort the normal gene product. The c.660+1G>A variant is well described in the literature and is the most frequently identified variant in individuals with Peters plus syndrome (PPS) (Saskia et al. 2014). Across a selection of literature, the c.660+1G>A variant was reported in a homozygous state in 24 patients and in a compound heterozygous state in 13 patients (Lesnik Oberstein et al. 2006; Reis et al. 2008; Dassie-Ajdid et al. 2009; Schoner et al. 2013; Weh et al. 2013). Parental testing was described in at least 15 sets of parent of affected patients, and the c.660+1G>A variant was identified in unaffected parents as expected based on their child's genotype. Hess et al.(2008) demonstrated that synthesis of the disaccharide Glc-β1,3-Fuc-O- is disrupted in patients with homozygous B3GALTL variants in contrast with their heterozygous relatives. The c.660+1G>A variant was not detected in 455 control chromosomes and is reported at a frequency of is 0.00104 in the non-Finnish European population of the Exome Aggregation Consortium. Based on the collective evidence and the potential impact of splice donor variants the c.660+1G>A variant is classified as pathogenic for Peters plus syndrome. This variant was observed by ICSL as part of a predisposition screen in an ostensibly healthy population. -
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The B3GLCT c.660+1G>A variant is classified as PATHOGENIC (PS4, PVS1) The B3GLCT c.660+1G>A variant is located in a splice donor region (PVS1). This recurrent variant has been identiified in both a homozygous and comound heterozygous state in multiple individuals with Peters-plus syndrome (PMID:16909395) (PS4). This variant is in dbSNP (rs80338851) and has been reported in population databases (gnomAD 122/152076 alleles, no homozygotes). This variant has been reported in ClinVar as pathogenic by other diagnostic laboratories (Variation ID:1264) and is damaging in HGMD for Peters-plus syndrome (CS064369). -
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This sequence change affects a donor splice site in intron 8 of the B3GLCT gene. It is expected to disrupt RNA splicing. Variants that disrupt the donor or acceptor splice site typically lead to a loss of protein function (PMID: 16199547), and loss-of-function variants in B3GLCT are known to be pathogenic (PMID: 18798333, 23889335). This variant is present in population databases (rs80338851, gnomAD 0.1%), and has an allele count higher than expected for a pathogenic variant. Disruption of this splice site has been observed in individuals with Peters-Plus syndrome (PMID: 16909395, 18199743, 19796186, 23161355, 23213277, 23889335, 26684045). ClinVar contains an entry for this variant (Variation ID: 1264). Algorithms developed to predict the effect of sequence changes on RNA splicing suggest that this variant may disrupt the consensus splice site. For these reasons, this variant has been classified as Pathogenic. -
not provided Pathogenic:9
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Canonical splice site variant in a gene for which loss-of-function is a known mechanism of disease; leads to skipping of exon 8, as confirmed by RT-PCR studies (Lesnik Oberstein et al., 2006); Also known as c.1020+1G>A using alternate nomenclature; This variant is associated with the following publications: (PMID: 26684045, 25525159, 19796186, 29096039, 18798333, 16909395, 23161355, 34426522, 31589614, 30577886, 31081795, 32224865, 31795264, 32204707, 33726816, 32732226) -
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B3GLCT: PVS1, PM2 -
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B3GLCT-related disorder Pathogenic:1
The B3GLCT c.660+1G>A variant is predicted to disrupt the GT donor site and interfere with normal splicing. This variant has been reported to be a common pathogenic variant for Peters Plus syndrome in the homozygous or compound heterozygous state (described as c.1020+1 G>A, Lesnik Oberstein. 2006. PubMed ID: 16909395; Reis., 2008. PubMed ID: 18798333). This variant is reported in 0.12% of alleles in individuals of European (Non-Finnish) descent in gnomAD. Variants that disrupt the consensus splice donor site in B3GLCT are expected to be pathogenic. This variant is interpreted as pathogenic. -
Inborn genetic diseases Pathogenic:1
The c.660+1G>A intronic variant results from a G to A substitution one nucleotide after coding exon 8 of the B3GLCT gene. Alterations that disrupt the canonical splice site are expected to cause aberrant splicing, resulting in an abnormal protein or a transcript that is subject to nonsense-mediated mRNA decay. Based on data from gnomAD, the A allele has an overall frequency of 0.076% (214/281510) total alleles studied. The highest observed frequency was 0.122% (157/128666) of European (non-Finnish) alleles. This alteration is the most common mutation in this gene and has been reported in the homozygous and compound heterozygous states in association with Peters plus syndrome; this variant has also been reported as c.1020+1G>A (Lesnik Oberstein, 2006; Wang, 2020). This nucleotide position is highly conserved in available vertebrate species. Functional analysis demonstrated that this splice site variant destroys the canonical splice donor site in intron 8, and leads to skipping of exon 8 as confirmed by RT-PCR studies (Lesnik Oberstein, 2006). In silico splice site analysis predicts that this alteration will weaken the native splice donor site. Based on the available evidence, this alteration is classified as pathogenic. -
Computational scores
Source:
Splicing
Find out detailed SpliceAI scores and Pangolin per-transcript scores at