16-2088504-A-T

Position:

• chr16-2088504-A-T

Variant summary

Our verdict is Uncertain significance. Variant got 2 ACMG points: 4P and 2B. PM2 PM5 BP4_Moderate

The NM_000548.5(TSC2):​c.5318A>T​(p.His1773Leu) variant causes a missense change involving the alteration of a non-conserved nucleotide. The variant was absent in control chromosomes in GnomAD project. In-silico tool predicts a benign outcome for this variant. 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. H1773P) has been classified as Pathogenic.

• Frequency: Genomes: not found (cov: 33)
• Consequence: TSC2 NM_000548.5 missense
• Clinical Significance: Uncertain significance criteria provided, multiple submitters, no conflicts U:2
• Conservation: PhyloP100: 1.91

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 Uncertain_significance. Variant got 2 ACMG points.

• PM2: Very rare variant in population databases, with high coverage
• PM5: Other missense variant is known to change same aminoacid residue: Variant chr16-2088504-A-C is described in Lovd as [Pathogenic].
• BP4: Computational evidence support a benign effect (MetaRNN=0.16638806).

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
TSC2	NM_000548.5	c.5318A>T	p.His1773Leu	missense_variant	42/42	ENST00000219476.9	NP_000539.2

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
TSC2	ENST00000219476.9	c.5318A>T	p.His1773Leu	missense_variant	42/42	5	NM_000548.5	ENSP00000219476.3

Frequencies

GnomAD3 genomes Cov.: 33

GnomAD4 exome Cov.: 33

GnomAD4 genome Cov.: 33

Bravo AF: 0.00000378

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

Aug 02, 2018

This sequence change replaces histidine with leucine at codon 1773 of the TSC2 protein (p.His1773Leu). The histidine residue is weakly conserved and there is a moderate physicochemical difference between histidine and leucine. This variant is not present in population databases (ExAC no frequency). This variant has not been reported in the literature in individuals with TSC2-related disease. Algorithms developed to predict the effect of missense changes on protein structure and function (SIFT, PolyPhen-2, Align-GVGD) all suggest that this variant is likely to be tolerated, but these predictions have not been confirmed by published functional studies and their clinical significance is uncertain. 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

Jan 16, 2023

The p.H1773L variant (also known as c.5318A>T), located in coding exon 41 of the TSC2 gene, results from an A to T substitution at nucleotide position 5318. The histidine at codon 1773 is replaced by leucine, an amino acid with similar properties. This amino acid position is conserved. 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. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Benign	0.072
BayesDel_addAF	Pathogenic	0.17	D
BayesDel_noAF	Uncertain	0.0
CADD	Benign	12
DANN	Benign	0.78
DEOGEN2	Uncertain	0.56	D;.;.;.;.;.;.;.;.;.;.;.;T;.;T
Eigen	Benign	-0.68
Eigen_PC	Benign	-0.65
FATHMM_MKL	Benign	0.60	D
LIST_S2	Benign	0.76	T;T;T;T;T;T;T;T;T;T;T;T;T;D;T
M_CAP	Uncertain	0.22	D
MetaRNN	Benign	0.17	T;T;T;T;T;T;T;T;T;T;T;T;T;T;T
MetaSVM	Benign	-0.51	T
MutationAssessor	Benign	1.6	L;.;.;.;.;.;.;.;.;.;.;.;.;.;.
PrimateAI	Benign	0.40	T
PROVEAN	Uncertain	-2.4	N;.;.;N;.;N;.;.;N;N;.;.;.;.;N
REVEL	Uncertain	0.46
Sift	Uncertain	0.011	D;.;.;D;.;D;.;.;D;D;.;.;.;.;D
Sift4G	Benign	0.20	T;.;.;T;.;T;.;.;T;T;.;.;.;.;T
Polyphen		0.34	B;.;.;.;B;B;.;.;B;B;.;.;.;.;.
Vest4		0.40
MutPred		0.22		Loss of glycosylation at P1771 (P = 0.1444);.;.;.;.;.;.;.;.;.;.;.;.;.;.;
MVP		0.94
ClinPred		0.17	T
GERP RS		3.4
Varity_R		0.11
gMVP		0.41

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: rs45517418; hg19: chr16-2138505;