rs1131691057

chr1-17053948-C-CT

Variant summary

Our verdict is Pathogenic. Variant got 18 ACMG points: 18P and 0B. PVS1 PM2 PP5_Very_Strong

The NM_003000.3(SDHB):c.71_72insA(p.Ala25GlyfsTer38) variant causes a frameshift, splice region change involving the alteration of a non-conserved nucleotide. The variant was absent in control chromosomes in GnomAD project. Variant has been reported in ClinVar as Likely pathogenic (★★). Synonymous variant affecting the same amino acid position (i.e. Q24Q) has been classified as Likely benign.

• Frequency: Genomes: not found (cov: 31)
• Consequence: SDHB NM_003000.3 frameshift, splice_region
• Clinical Significance: Pathogenic/Likely pathogenic criteria provided, multiple submitters, no conflicts P:4
• Conservation: PhyloP100: 1.27

Genes affected

SDHB (HGNC:10681): (succinate dehydrogenase complex iron sulfur subunit B) This tumor suppressor gene encodes the iron-sulfur protein subunit of the succinate dehydrogenase (SDH) enzyme complex which plays a critical role in mitochondria. The SDH enzyme complex is composed of four nuclear-encoded subunits. This enzyme complex converts succinate to fumarate which releases electrons as part of the citric acid cycle, and the enzyme complex additionally provides an attachment site for released electrons to be transferred to the oxidative phosphorylation pathway. The SDH enzyme complex plays a role in oxygen-related gene regulation through its conversion of succinate, which is an oxygen sensor that stabilizes the hypoxia-inducible factor 1 (HIF1) transcription factor. Sporadic and familial mutations in this gene result in paragangliomas, pheochromocytoma, and gastrointestinal stromal tumors, supporting a link between mitochondrial dysfunction and tumorigenesis. Mutations in this gene are also implicated in nuclear type 4 mitochondrial complex II deficiency. [provided by RefSeq, Jun 2022]

ACMG classification

Verdict is Pathogenic. Variant got 18 ACMG points.

• PVS1: Loss of function variant, product does not undergo nonsense mediated mRNA decay. Variant located near the start codon (<100nt), not predicted to undergo nonsense mediated mRNA decay. There are 287 pathogenic variants in the truncated region.
• PM2: Very rare variant in population databases, with high coverage
• PP5: Variant 1-17053948-C-CT is Pathogenic according to our data. Variant chr1-17053948-C-CT is described in ClinVar as [Likely_pathogenic]. Clinvar id is 428928.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
SDHB	NM_003000.3	c.71_72insA	p.Ala25GlyfsTer38	frameshift_variant, splice_region_variant	1/8	ENST00000375499.8
SDHB	NM_001407361.1	c.71_72insA	p.Ala25GlyfsTer38	frameshift_variant, splice_region_variant	1/8

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
SDHB	ENST00000375499.8	c.71_72insA	p.Ala25GlyfsTer38	frameshift_variant, splice_region_variant	1/8	1	NM_003000.3	P1
SDHB	ENST00000466613.2	n.83_84insA		splice_region_variant, non_coding_transcript_exon_variant	1/3	2
SDHB	ENST00000485515.5	n.59_60insA		splice_region_variant, non_coding_transcript_exon_variant	1/7	5

Frequencies

GnomAD3 genomes Cov.: 31

GnomAD4 exome Cov.: 30

GnomAD4 genome Cov.: 31

ClinVar

Significance: Pathogenic/Likely pathogenic

Submissions summary: Pathogenic:4

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

SDHB-Related Disorders Pathogenic:1

Likely pathogenic, criteria provided, single submitter

research

Snyder Lab, Genetics Department, Stanford University

Jan 01, 2017

- -

Pheochromocytoma;C0238198:Gastrointestinal stromal tumor;C1861848:Paragangliomas 4 Pathogenic:1

Pathogenic, criteria provided, single submitter

clinical testing

Invitae

Jul 10, 2023

This sequence change creates a premature translational stop signal (p.Ala25Glyfs*38) in the SDHB gene. It is expected to result in an absent or disrupted protein product. Loss-of-function variants in SDHB are known to be pathogenic (PMID: 19454582, 19802898). This variant is not present in population databases (gnomAD no frequency). This premature translational stop signal has been observed in individual(s) with papillary thyroid cancer (PMID: 30487145). ClinVar contains an entry for this variant (Variation ID: 428928). For these reasons, this variant has been classified as Pathogenic. -

Paragangliomas 4 Pathogenic:1

Pathogenic, criteria provided, single submitter

clinical testing

Myriad Genetics, Inc.

Nov 29, 2023

This variant is considered pathogenic. This variant creates a frameshift predicted to result in premature protein truncation. -

Hereditary cancer-predisposing syndrome Pathogenic:1

Pathogenic, criteria provided, single submitter

clinical testing

Ambry Genetics

May 24, 2021

The c.71dupA pathogenic mutation, located in coding exon 1 of the SDHB gene, results from a duplication of A at nucleotide position 71, causing a translational frameshift with a predicted alternate stop codon (p.A25Gfs*38). This mutation was detected in an individual with a personal history of paraganglioma and pheochromocytoma that showed loss of SDHB on immunohistochemistry (Ambry internal data). This mutation was also detected in a cohort 70 healthy individuals who underwent whole exome sequencing (Rego S et al. Cold Spring Harb Mol Case Stud, 2018 12;4). This alteration is expected to result in loss of function by premature protein truncation or nonsense-mediated mRNA decay. As such, this alteration is interpreted as a disease-causing mutation. -

Computational scores

Source: dbNSFP v4.3

Splicing

Name	Calibrated prediction	Score	Prediction
SpliceAI score (max)		0.0		Details are displayed if max score is > 0.2

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

Publications

LitVar

Other links and lift over

dbSNP: rs1131691057; hg19: chr1-17380443;