rs199948437

Positions:

• chr1-17054015-G-A

Variant summary

Our verdict is Uncertain significance. Variant got 4 ACMG points: 4P and 0B. PM2 PP3_Moderate

The NM_003000.3(SDHB):​c.5C>T​(p.Ala2Val) variant causes a missense change. The variant allele was found at a frequency of 0.000011 in 1,457,280 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a pathogenic outcome for this variant. Variant has been reported in ClinVar as Uncertain significance (★★).

• Frequency:
  • Genomes: not found (cov: 33)
  • Exomes 𝑓: 0.000011 (0 hom.)
• Consequence: SDHB NM_003000.3 missense
• Clinical Significance: Uncertain significance criteria provided, multiple submitters, no conflicts U:5
• Conservation: PhyloP100: 5.26

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]

SDHB (HGNC:):

ACMG classification

Verdict is Uncertain_significance. Variant got 4 ACMG points.

• PM2: Very rare variant in population databases, with high coverage
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.885

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
SDHB	NM_003000.3	c.5C>T	p.Ala2Val	missense_variant	1/8	ENST00000375499.8	NP_002991.2
SDHB	NM_001407361.1	c.5C>T	p.Ala2Val	missense_variant	1/8		NP_001394290.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
SDHB	ENST00000375499.8	c.5C>T	p.Ala2Val	missense_variant	1/8	1	NM_003000.3	ENSP00000364649.3
SDHB	ENST00000466613.2	n.17C>T		non_coding_transcript_exon_variant	1/3	2
SDHB	ENST00000485515.5	n.-8C>T		upstream_gene_variant		5		ENSP00000519322.1

Frequencies

GnomAD3 genomes Cov.: 33

GnomAD4 exome AF: 0.0000110 AC: 16 AN: 1457280 Hom.: 0 Cov.: 31 AF XY: 0.00000276 AC XY: 2 AN XY: 724916

Gnomad4 AFR exome AF: 0.00

Gnomad4 AMR exome AF: 0.00

Gnomad4 ASJ exome AF: 0.00

Gnomad4 EAS exome AF: 0.00

Gnomad4 SAS exome AF: 0.0000117

Gnomad4 FIN exome AF: 0.00

Gnomad4 NFE exome AF: 0.0000126

Gnomad4 OTH exome AF: 0.0000166

GnomAD4 genome Cov.: 33

Bravo AF: 0.00000756

ExAC AF: 0.0000165 AC: 2

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:5

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

not specified Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Center for Genomic Medicine, Rigshospitalet, Copenhagen University Hospital

Aug 15, 2023

- -

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

Uncertain significance, criteria provided, single submitter

clinical testing

Labcorp Genetics (formerly Invitae), Labcorp

Dec 26, 2023

This sequence change replaces alanine, which is neutral and non-polar, with valine, which is neutral and non-polar, at codon 2 of the SDHB protein (p.Ala2Val). The frequency data for this variant in the population databases is considered unreliable, as metrics indicate poor data quality at this position in the gnomAD database. This variant has not been reported in the literature in individuals affected with SDHB-related conditions. ClinVar contains an entry for this variant (Variation ID: 528745). Advanced modeling of protein sequence and biophysical properties (such as structural, functional, and spatial information, amino acid conservation, physicochemical variation, residue mobility, and thermodynamic stability) has been performed at Invitae for this missense variant, however the output from this modeling did not meet the statistical confidence thresholds required to predict the impact of this variant on SDHB protein function. In summary, the available evidence is currently insufficient to determine the role of this variant in disease. Therefore, it has been classified as a Variant of Uncertain Significance. -

Gastrointestinal stromal tumor Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Baylor Genetics

Dec 19, 2023

- -

Hereditary cancer-predisposing syndrome Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Ambry Genetics

Nov 13, 2023

The p.A2V variant (also known as c.5C>T), located in coding exon 1 of the SDHB gene, results from a C to T substitution at nucleotide position 5. The alanine at codon 2 is replaced by valine, an amino acid with similar properties. This alteration was detected in a 49 year old female with a prolactin pituitary adenoma, primary hyperparathyroidism, and parathyroid tumor tissue that demonstrated preserved staining for SDHA and SDHB immunohistochemistry. The family history included an aunt with Cushing's disease; however, there was no known family history of paraganglioma or pheochromocytoma (De Sousa SMC et al. Eur J Endocrinol, 2017 May;176:635-644). This amino acid position is highly conserved in available vertebrate species. In addition, the in silico prediction for this alteration is inconclusive. Since supporting evidence is limited at this time, the clinical significance of this alteration remains unclear. -

Hereditary pheochromocytoma-paraganglioma Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

All of Us Research Program, National Institutes of Health

Jun 26, 2023

This missense variant replaces alanine with valine at codon 2 of the SDHB protein. Computational prediction is inconclusive regarding the impact of this variant on protein structure and function (internally defined REVEL score threshold 0.5 < inconclusive < 0.7, PMID: 27666373). To our knowledge, functional studies have not been reported for this variant. This variant has been reported in individuals affected with hereditary pituitary adenoma syndrome (PMID: 28220018). This variant has not been identified in the general population by the Genome Aggregation Database (gnomAD). The available evidence is insufficient to determine the role of this variant in disease conclusively. Therefore, this variant is classified as a Variant of Uncertain Significance. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Benign	0.27
BayesDel_addAF	Pathogenic	0.23	D
BayesDel_noAF	Uncertain	0.10
CADD	Pathogenic	28
DANN	Uncertain	1.0
DEOGEN2	Benign	0.32	T
Eigen	Uncertain	0.38
Eigen_PC	Uncertain	0.41
FATHMM_MKL	Benign	0.75	D
LIST_S2	Benign	0.53	T
M_CAP	Pathogenic	0.74	D
MetaRNN	Pathogenic	0.89	D
MetaSVM	Pathogenic	1.1	D
MutationAssessor	Benign	1.2	L
PrimateAI	Uncertain	0.69	T
PROVEAN	Benign	-0.80	N
REVEL	Uncertain	0.62
Sift	Uncertain	0.0040	D
Sift4G	Benign	0.080	T
Polyphen		1.0	D
Vest4		0.54
MutPred		0.39		Gain of sheet (P = 0.0149);
MVP		0.97
MPC		0.17
ClinPred		0.94	D
GERP RS		5.2
RBP_binding_hub_radar		0.0
RBP_regulation_power_radar		2.8
Varity_R		0.37
gMVP		0.60

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: rs199948437; hg19: chr1-17380510; COSMIC: COSV64965419; COSMIC: COSV64965419;