rs1057516755

Variant names:

• chr15-72348074-CTTGA-C
• rs1057516755
• NM_000520.6:c.1043_1046delTCAA

Variant summary

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

The NM_000520.6(HEXA):​c.1043_1046delTCAA​(p.Phe348CysfsTer33) variant causes a frameshift change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.000000685 in 1,460,878 control chromosomes in the GnomAD database, with no homozygous occurrence. Variant has been reported in ClinVar as Pathogenic (★★). Variant results in nonsense mediated mRNA decay.

• Frequency:
  • Genomes: not found (cov: 32)
  • Exomes 𝑓: 6.8e-7 (0 hom.)
• Consequence: HEXA NM_000520.6 frameshift
• Clinical Significance: Pathogenic criteria provided, multiple submitters, no conflicts P:4
• Conservation: PhyloP100: 3.09
• Publications: 0 publications found

Genes affected

HEXA (HGNC:4878): (hexosaminidase subunit alpha) This gene encodes a member of the glycosyl hydrolase 20 family of proteins. The encoded preproprotein is proteolytically processed to generate the alpha subunit of the lysosomal enzyme beta-hexosaminidase. This enzyme, together with the cofactor GM2 activator protein, catalyzes the degradation of the ganglioside GM2, and other molecules containing terminal N-acetyl hexosamines. Mutations in this gene lead to an accumulation of GM2 ganglioside in neurons, the underlying cause of neurodegenerative disorders termed the GM2 gangliosidoses, including Tay-Sachs disease (GM2-gangliosidosis type I). Alternative splicing results in multiple transcript variants, at least one of which encodes a preproprotein that is proteolytically processed. [provided by RefSeq, Jan 2016]

HEXA Gene-Disease associations (from GenCC):

• Tay-Sachs disease

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

ENSG00000260729 (HGNC:):

ENSG00000261460 (HGNC:58304):

ACMG classification

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

• PVS1: Loss of function variant, product undergoes nonsense mediated mRNA decay. LoF is a known mechanism of disease.
• PM2: Very rare variant in population databases, with high coverage
• PP5: Variant 15-72348074-CTTGA-C is Pathogenic according to our data. Variant chr15-72348074-CTTGA-C is described in ClinVar as Pathogenic. ClinVar VariationId is 370773.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
HEXA	NM_000520.6	c.1043_1046delTCAA	p.Phe348CysfsTer33	frameshift_variant	Exon 9 of 14	ENST00000268097.10	NP_000511.2
HEXA	NM_001318825.2	c.1076_1079delTCAA	p.Phe359CysfsTer33	frameshift_variant	Exon 9 of 14		NP_001305754.1
HEXA	NR_134869.3	n.1085_1088delTCAA		non_coding_transcript_exon_variant	Exon 9 of 11

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
HEXA	ENST00000268097.10	c.1043_1046delTCAA	p.Phe348CysfsTer33	frameshift_variant	Exon 9 of 14	1	NM_000520.6	ENSP00000268097.6
ENSG00000260729	ENST00000379915.4	n.413-1753_413-1750delTCAA		intron_variant	Intron 3 of 15	2		ENSP00000478716.1

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome AF: 6.85e-7 AC: 1 AN: 1460878 Hom.: 0 AF XY: 0.00000138 AC XY: 1 AN XY: 726806

⚠️ 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: 33452

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

Ashkenazi Jewish (ASJ) AF: 0.00 AC: 0 AN: 26126

East Asian (EAS) AF: 0.00 AC: 0 AN: 39698

South Asian (SAS) AF: 0.00 AC: 0 AN: 86246

European-Finnish (FIN) AF: 0.00 AC: 0 AN: 53404

Middle Eastern (MID) AF: 0.00 AC: 0 AN: 5764

European-Non Finnish (NFE) AF: 9.00e-7 AC: 1 AN: 1111120

Other (OTH) AF: 0.00 AC: 0 AN: 60344

⚠️ The allele balance in gnomAD4 Exomes is highly skewed from 0.5 (p-value = 0), which strongly suggests a high chance of mosaicism in these individuals.

GnomAD4 genome Cov.: 32

ClinVar

Significance: Pathogenic

Submissions summary: Pathogenic:4

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

Tay-Sachs disease Pathogenic:3

Sep 01, 2022

Women's Health and Genetics/Laboratory Corporation of America, LabCorp

Significance: Pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

Variant summary: HEXA c.1043_1046delTCAA (p.Phe348CysfsX33) results in a premature termination codon, predicted to cause a truncation of the encoded protein or absence of the protein due to nonsense mediated decay, which are commonly known mechanisms for disease. Truncations downstream of this position have been classified as pathogenic by our laboratory. The variant was absent in 251446 control chromosomes (gnomAD). c.1043_1046delTCAA has been reported in the literature in a homozygous individual affected with Tay-Sachs Disease (Montalvo_2005). These data indicate that the variant is likely to be associated with disease. To our knowledge, no experimental evidence demonstrating an impact on protein function has been reported. A ClinVar submitter (evaluation after 2014) cites the variant as likely pathogenic. Based on the evidence outlined above, the variant was classified as pathogenic. -

Apr 13, 2016

Counsyl

Significance: Likely pathogenic

Review Status: no assertion criteria provided

Collection Method: clinical testing

This submission and the accompanying classification are no longer maintained by the submitter. For more information on current observations and classification, please contact variantquestions@myriad.com. -

Mar 07, 2024

Labcorp Genetics (formerly Invitae), Labcorp

Significance: Pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

This sequence change creates a premature translational stop signal (p.Phe348Cysfs*33) in the HEXA gene. It is expected to result in an absent or disrupted protein product. Loss-of-function variants in HEXA are known to be pathogenic (PMID: 1833974, 8490625). This variant is not present in population databases (gnomAD no frequency). This premature translational stop signal has been observed in individual(s) with Tay-Sachs disease (PMID: 16088929). ClinVar contains an entry for this variant (Variation ID: 370773). Algorithms developed to predict the effect of sequence changes on RNA splicing suggest that this variant may create or strengthen a splice site. For these reasons, this variant has been classified as Pathogenic. -

not provided Pathogenic:1

Feb 07, 2024

GeneDx

Significance: Pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

Frameshift variant predicted to result in protein truncation or nonsense mediated decay in a gene for which loss of function is a known mechanism of disease; Not observed at significant frequency in large population cohorts (gnomAD); This variant is associated with the following publications: (PMID: 16088929) -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
PhyloP100		3.1
Mutation Taster		=1/199	disease causing (ClinVar)

Splicing

Name	Calibrated prediction	Score	Prediction
SpliceAI score (max)		0.26		Details are displayed if max score is > 0.2
DS_DG_spliceai		0.26		Position offset: 14

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

Other links and lift over

dbSNP: rs1057516755; hg19: chr15-72640415;