16-2053345-G-T

Position:

• chr16-2053345-G-T

Variant summary

Our verdict is Uncertain significance. Variant got 2 ACMG points: 2P and 0B. PM2

The NM_000548.5(TSC2):​c.229G>T​(p.Ala77Ser) variant causes a missense change involving the alteration of a conserved nucleotide. The variant allele was found at a frequency of 0.0000007 in 1,428,980 control chromosomes in the GnomAD database, with no homozygous occurrence. Variant has been reported in ClinVar as Uncertain significance (★★). Another variant affecting the same amino acid position, but resulting in a different missense (i.e. A77T) has been classified as Uncertain significance.

• Frequency:
  • Genomes: not found (cov: 33)
  • Exomes 𝑓: 7.0e-7 (0 hom.)
• Consequence: TSC2 NM_000548.5 missense
• Clinical Significance: Uncertain significance criteria provided, multiple submitters, no conflicts U:4
• Conservation: PhyloP100: 9.61

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]

ACMG classification

Verdict is Uncertain_significance. Variant got 2 ACMG points.

• PM2: Very rare variant in population databases, with high coverage

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
TSC2	NM_000548.5	c.229G>T	p.Ala77Ser	missense_variant	4/42	ENST00000219476.9

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
TSC2	ENST00000219476.9	c.229G>T	p.Ala77Ser	missense_variant	4/42	5	NM_000548.5

Frequencies

GnomAD3 genomes Cov.: 33

GnomAD4 exome AF: 7.00e-7 AC: 1 AN: 1428980 Hom.: 0 Cov.: 31 AF XY: 0.00000141 AC XY: 1 AN XY: 707850

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: 9.12e-7

Gnomad4 OTH exome AF: 0.00

GnomAD4 genome Cov.: 33

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:4

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

Hereditary cancer-predisposing syndrome Uncertain:2

Uncertain significance, criteria provided, single submitter	curation	Sema4, Sema4	Dec 13, 2021	- -
Uncertain significance, criteria provided, single submitter	clinical testing	Ambry Genetics	Dec 22, 2021	The p.A77S variant (also known as c.229G>T), located in coding exon 3 of the TSC2 gene, results from a G to T substitution at nucleotide position 229. The alanine at codon 77 is replaced by serine, an amino acid with similar properties. 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. -

Tuberous sclerosis 2 Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Invitae

Jun 25, 2023

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. 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) performed at Invitae indicates that this missense variant is not expected to disrupt TSC2 protein function. ClinVar contains an entry for this variant (Variation ID: 968409). This variant has not been reported in the literature in individuals affected with TSC2-related conditions. This variant is not present in population databases (gnomAD no frequency). This sequence change replaces alanine, which is neutral and non-polar, with serine, which is neutral and polar, at codon 77 of the TSC2 protein (p.Ala77Ser). -

Lymphangiomyomatosis;C1846385:Isolated focal cortical dysplasia type II;C1860707:Tuberous sclerosis 2 Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Fulgent Genetics, Fulgent Genetics

May 01, 2022

- -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Benign	0.27
BayesDel_addAF	Pathogenic	0.20	D
BayesDel_noAF	Uncertain	0.050
CADD	Pathogenic	27
DANN	Uncertain	1.0
DEOGEN2	Uncertain	0.50	D;.;.;.;.;.;.;.;.;.;.;T;.;T
Eigen	Uncertain	0.60
Eigen_PC	Uncertain	0.58
FATHMM_MKL	Pathogenic	1.0	D
LIST_S2	Uncertain	0.95	D;D;D;D;D;D;D;D;D;D;D;D;D;D
M_CAP	Pathogenic	0.44	D
MetaRNN	Uncertain	0.68	D;D;D;D;D;D;D;D;D;D;D;D;D;D
MetaSVM	Uncertain	-0.024	T
MutationAssessor	Benign	1.9	L;.;.;.;L;L;.;.;L;.;L;.;.;.
MutationTaster	Benign	1.0	D;D;D;D;D;D;D
PrimateAI	Uncertain	0.75	T
PROVEAN	Benign	-1.8	N;.;.;N;.;N;.;.;N;.;.;.;.;N
REVEL	Uncertain	0.55
Sift	Uncertain	0.0080	D;.;.;D;.;D;.;.;D;.;.;.;.;D
Sift4G	Uncertain	0.017	D;.;.;D;.;D;.;.;D;.;.;.;.;D
Polyphen		1.0	D;.;.;.;.;D;.;.;D;.;.;.;.;.
Vest4		0.70
MutPred		0.39		Gain of loop (P = 0.0121);Gain of loop (P = 0.0121);Gain of loop (P = 0.0121);.;Gain of loop (P = 0.0121);Gain of loop (P = 0.0121);Gain of loop (P = 0.0121);Gain of loop (P = 0.0121);Gain of loop (P = 0.0121);Gain of loop (P = 0.0121);Gain of loop (P = 0.0121);Gain of loop (P = 0.0121);Gain of loop (P = 0.0121);.;
MVP		0.74
ClinPred		0.91	D
GERP RS		4.8
RBP_binding_hub_radar		0.0
RBP_regulation_power_radar		1.7
Varity_R		0.25
gMVP		0.42

Splicing

Name	Calibrated prediction	Score	Prediction
SpliceAI score (max)		0.010		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: rs777459404; hg19: chr16-2103346;