8-99096433-G-T

Variant names:

• chr8-99096433-G-T
• rs1057517295
• NM_017890.5:c.412+1G>T

Variant summary

Our verdict is Pathogenic. The variant received 18 ACMG points: 18P and 0B. PVS1 PM2 PP5_Very_Strong

The NM_017890.5(VPS13B):​c.412+1G>T variant causes a splice donor, intron change involving the alteration of a conserved nucleotide. The variant allele was found at a frequency of 0.000000684 in 1,461,686 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 Likely pathogenic (★★).

• Frequency:
  • Genomes: not found (cov: 31)
  • Exomes 𝑓: 6.8e-7 (0 hom.)
• Consequence: VPS13B NM_017890.5 splice_donor, intron
• Scores: Splicing: ADA: 1.000
• Clinical Significance: Pathogenic/Likely pathogenic criteria provided, multiple submitters, no conflicts P:3
• Conservation: PhyloP100: 8.82
• Publications: 0 publications found

Genes affected

VPS13B (HGNC:2183): (vacuolar protein sorting 13 homolog B) This gene encodes a potential transmembrane protein that may function in vesicle-mediated transport and sorting of proteins within the cell. This protein may play a role in the development and the function of the eye, hematological system, and central nervous system. Mutations in this gene have been associated with Cohen syndrome. Multiple splice variants encoding distinct isoforms have been identified for this gene. [provided by RefSeq, Jul 2008]

VPS13B Gene-Disease associations (from GenCC):

• Cohen syndrome

  Inheritance: AR Classification: DEFINITIVE, STRONG, SUPPORTIVE Submitted by: Orphanet, Myriad Women’s Health, Labcorp Genetics (formerly Invitae), G2P, Genomics England PanelApp, Laboratory for Molecular Medicine, ClinGen

ACMG classification

Our verdict: Pathogenic. The variant received 18 ACMG points.

• PVS1: Splicing +-2 bp (donor or acceptor) variant, LoF is a know mechanism of disease, No cryptic splice site detected. Exon removal results in frameshift change.
• PM2: Very rare variant in population databases, with high coverage
• PP5: Variant 8-99096433-G-T is Pathogenic according to our data. Variant chr8-99096433-G-T is described in ClinVar as Pathogenic/Likely_pathogenic. ClinVar VariationId is 402219.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
VPS13B	NM_017890.5	c.412+1G>T		splice_donor_variant, intron_variant	Intron 4 of 61	ENST00000358544.7	NP_060360.3
VPS13B	NM_152564.5	c.412+1G>T		splice_donor_variant, intron_variant	Intron 4 of 61	ENST00000357162.7	NP_689777.3

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
VPS13B	ENST00000358544.7	c.412+1G>T		splice_donor_variant, intron_variant	Intron 4 of 61	1	NM_017890.5	ENSP00000351346.2
VPS13B	ENST00000357162.7	c.412+1G>T		splice_donor_variant, intron_variant	Intron 4 of 61	1	NM_152564.5	ENSP00000349685.2

Frequencies

GnomAD3 genomes Cov.: 31

GnomAD4 exome AF: 6.84e-7 AC: 1 AN: 1461686 Hom.: 0 Cov.: 31 AF XY: 0.00 AC XY: 0 AN XY: 727148

⚠️ The allele balance in gnomAD version 4 Exomes is significantly skewed from the expected value of 0.5.

African (AFR) AF: 0.00 AC: 0 AN: 33470

American (AMR) AF: 0.00 AC: 0 AN: 44704

Ashkenazi Jewish (ASJ) AF: 0.00 AC: 0 AN: 26124

East Asian (EAS) AF: 0.00 AC: 0 AN: 39684

South Asian (SAS) AF: 0.00 AC: 0 AN: 86256

European-Finnish (FIN) AF: 0.00 AC: 0 AN: 53406

Middle Eastern (MID) AF: 0.000173 AC: 1 AN: 5764

European-Non Finnish (NFE) AF: 0.00 AC: 0 AN: 1111896

Other (OTH) AF: 0.00 AC: 0 AN: 60382

⚠️ The allele balance in gnomAD4 Exomes is highly skewed from 0.5 (p-value = 0.000000), which strongly suggests a high chance of mosaicism in these individuals.

GnomAD4 genome Cov.: 31

ClinVar

Significance: Pathogenic/Likely pathogenic

Submissions summary: Pathogenic:3

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

Cohen syndrome Pathogenic:2

May 02, 2023

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

Significance: Pathogenic

Review Status: criteria provided, single submitter

Collection Method: curation

The homozygous c.412+1G>T variant in VPS13B was identified in our study in one individual with growth delay, intellectual disability, and microcephaly. The c.412+1G>T variant in VPS13B has been previously reported in one individual with Cohen syndrome (PMID: 26539891). This variant has also been reported in ClinVar (Variation ID: 402219) and has been interpreted as likely pathogenic by the Lupski Lab of the Baylor College of Medicine. The affected individual previously reported (PMID: 26539891) and the patient identified by our study were homozygotes for the variant, which increases the likelihood that the c.412+1G>T variant is pathogenic. A different nucleotide change that also results in a splice donor variant at the same site, c.412+1G>A has been reported likely pathogenic in ClinVar (Variation ID: 371467), and the variant being assessed here, c.412+1G>T, is predicted by SpliceAI to have a similar effect on splicing. This variant was absent from large population studies. 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. Loss of function of the VPS13B gene is an established disease mechanism in autosomal recessive Cohen syndrome. In summary, this variant meets criteria to be classified as pathogenic for autosomal recessive Cohen syndrome. ACMG/AMP Criteria applied: PVS1, PS1_Supporting, PM2_Supporting, PM3 (Richards 2015). -

Oct 18, 2023

3billion

Significance: Pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

The variant is not observed in the gnomAD v2.1.1 dataset. Predicted Consequence/Location: Canonical splice site: predicted to alter splicing and result in a loss or disruption of normal protein function. Multiple pathogenic loss-of-function variants are reported downstream of the variant. The variant has been reported at least twice as pathogenic without evidence for the classification (ClinVar ID: VCV000402219 /PMID: 26539891). Therefore, this variant is classified as Pathogenic according to the recommendation of ACMG/AMP guideline. -

Abnormal brain morphology Pathogenic:1

-

Lupski Lab, Baylor-Hopkins CMG, Baylor College of Medicine

Significance: Likely pathogenic

Review Status: criteria provided, single submitter

Collection Method: research

- -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
BayesDel_addAF	Pathogenic	0.63	D
BayesDel_noAF	Pathogenic	0.40
CADD	Pathogenic	34
DANN	Uncertain	0.99
Eigen	Pathogenic	1.3
Eigen_PC	Pathogenic	1.1
FATHMM_MKL	Pathogenic	0.99	D
PhyloP100		8.8
GERP RS		5.9
Mutation Taster		=0/100	disease causing (ClinVar)

Splicing

Name	Calibrated prediction	Score	Prediction
dbscSNV1_ADA	Pathogenic	1.0
dbscSNV1_RF	Pathogenic	0.94
SpliceAI score (max)		0.99		Details are displayed if max score is > 0.2
DS_DL_spliceai		0.99		Position offset: -1

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

Other links and lift over

dbSNP: rs1057517295; hg19: chr8-100108661;