16-2084303-C-T

Position:

• chr16-2084303-C-T

Variant summary

Our verdict is Pathogenic. Variant got 10 ACMG points: 10P and 0B. PVS1 PM2

The NM_000548.5(TSC2):​c.4081C>T​(p.Arg1361*) variant causes a stop gained change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.000000685 in 1,460,366 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 (★★). Variant results in nonsense mediated mRNA decay.

• Frequency:
  • Genomes: not found (cov: 34)
  • Exomes 𝑓: 6.8e-7 (0 hom.)
• Consequence: TSC2 NM_000548.5 stop_gained
• Clinical Significance: Uncertain significance criteria provided, multiple submitters, no conflicts U:2
• Conservation: PhyloP100: 0.995

Genes affected

TSC2 (HGNC:12363): (TSC complex subunit 2) This gene is a tumor suppressor gene that encodes the growth inhibitory protein tuberin. Tuberin interacts with hamartin to form the TSC protein complex which functions in the control of cell growth. This TSC protein complex negatively regulates mammalian target of rapamycin complex 1 (mTORC1) signaling which is a major regulator of anabolic cell growth. Mutations in this gene have been associated with tuberous sclerosis and lymphangioleiomyomatosis. [provided by RefSeq, May 2022]

TSC2 (HGNC:):

ACMG classification

Verdict is Pathogenic. Variant got 10 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

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
TSC2	NM_000548.5	c.4081C>T	p.Arg1361*	stop_gained	34/42	ENST00000219476.9	NP_000539.2

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
TSC2	ENST00000219476.9	c.4081C>T	p.Arg1361*	stop_gained	34/42	5	NM_000548.5	ENSP00000219476.3

Frequencies

GnomAD3 genomes Cov.: 34

GnomAD4 exome AF: 6.85e-7 AC: 1 AN: 1460366 Hom.: 0 Cov.: 33 AF XY: 0.00 AC XY: 0 AN XY: 726446

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: 0.00

Gnomad4 FIN exome AF: 0.00

Gnomad4 NFE exome AF: 8.99e-7

Gnomad4 OTH exome AF: 0.00

GnomAD4 genome Cov.: 34

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:2

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

Tuberous sclerosis 2 Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Labcorp Genetics (formerly Invitae), Labcorp

Jan 05, 2024

This sequence change creates a premature translational stop signal (p.Arg1361*) in the TSC2 gene. It is expected to result in an absent or disrupted protein product. Loss-of-function variants in TSC2 are known to be pathogenic (PMID: 10205261, 17304050). This variant is not present in population databases (gnomAD no frequency). This variant has not been reported in the literature in individuals affected with TSC2-related conditions. This premature translational stop signal has been observed in at least one individual who was not affected with TSC2-related conditions (Invitae). ClinVar contains an entry for this variant (Variation ID: 571122). Algorithms developed to predict the effect of sequence changes on RNA splicing suggest that this variant may create or strengthen a splice site. 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. -

Hereditary cancer-predisposing syndrome Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Ambry Genetics

Dec 08, 2023

The p.R1361* variant (also known as c.4081C>T), located in coding exon 33 of the TSC2 gene, results from a C to T substitution at nucleotide position 4081. This changes the amino acid from an arginine to a stop codon within coding exon 33. This alteration is expected to result in loss of function by premature protein truncation or nonsense-mediated mRNA decay. However, in silico splice site analysis predicts that this alteration will result in the creation or strengthening of a novel splice donor site, and RNA studies have demonstrated that this alteration results in an incomplete splice defect. The resulting aberrantly spliced transcript is predicted to be in-frame, and the clinical impact of this abnormal splicing is unknown at this time (Ambry internal data). In addition, this variant is described in one publication as occurring in an individual without features of tuberous sclerosis (Haque B et al. Eur J Hum Genet, 2023 Nov). Since supporting evidence is limited at this time, the clinical significance of this alteration remains unclear. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
BayesDel_addAF	Pathogenic	0.38	D
BayesDel_noAF	Pathogenic	0.30
CADD	Pathogenic	44
DANN	Uncertain	0.99
Eigen	Uncertain	0.20
Eigen_PC	Benign	-0.084
FATHMM_MKL	Benign	0.73	D
Vest4		0.89
GERP RS		1.3
RBP_binding_hub_radar		0.0
RBP_regulation_power_radar		1.0

Splicing

Name	Calibrated prediction	Score	Prediction
SpliceAI score (max)		0.80		Details are displayed if max score is > 0.2
DS_DG_spliceai		0.80		Position offset: -2

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

Publications

LitVar

Other links and lift over

dbSNP: rs560831385; hg19: chr16-2134304; COSMIC: COSV105862592; COSMIC: COSV105862592;