16-2072960-A-G

Position:

• chr16-2072960-A-G

Variant summary

Our verdict is Uncertain significance. Variant got 1 ACMG points: 2P and 1B. PM2 BP4

The NM_000548.5(TSC2):​c.2332A>G​(p.Asn778Asp) variant causes a missense change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.000000684 in 1,461,198 control chromosomes in the GnomAD database, with no homozygous occurrence. 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. N778K) has been classified as Benign.

• Frequency:
  • Genomes: not found (cov: 33)
  • Exomes 𝑓: 6.8e-7 (0 hom.)
• Consequence: TSC2 NM_000548.5 missense
• Clinical Significance: Uncertain significance criteria provided, multiple submitters, no conflicts U:4
• Conservation: PhyloP100: 2.78

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 1 ACMG points.

• PM2: Very rare variant in population databases, with high coverage
• BP4: Computational evidence support a benign effect (MetaRNN=0.32963425).

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
TSC2	NM_000548.5	c.2332A>G	p.Asn778Asp	missense_variant	21/42	ENST00000219476.9

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
TSC2	ENST00000219476.9	c.2332A>G	p.Asn778Asp	missense_variant	21/42	5	NM_000548.5

Frequencies

GnomAD3 genomes Cov.: 33

GnomAD4 exome AF: 6.84e-7 AC: 1 AN: 1461198 Hom.: 0 Cov.: 31 AF XY: 0.00000138 AC XY: 1 AN XY: 726874

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: 0.00

Gnomad4 OTH exome AF: 0.0000166

GnomAD4 genome Cov.: 33

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:4

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

Tuberous sclerosis 2 Uncertain:2

Uncertain significance, criteria provided, single submitter	clinical testing	Genome-Nilou Lab	Nov 07, 2021	- -
Uncertain significance, criteria provided, single submitter	clinical testing	Invitae	Dec 23, 2023	This sequence change replaces asparagine, which is neutral and polar, with aspartic acid, which is acidic and polar, at codon 778 of the TSC2 protein (p.Asn778Asp). 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. ClinVar contains an entry for this variant (Variation ID: 406045). 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 with a negative predictive value of 95%. 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:2

Uncertain significance, criteria provided, single submitter	curation	Sema4, Sema4	Oct 22, 2021	- -
Uncertain significance, criteria provided, single submitter	clinical testing	Ambry Genetics	May 21, 2023	The p.N778D variant (also known as c.2332A>G), located in coding exon 20 of the TSC2 gene, results from an A to G substitution at nucleotide position 2332. The asparagine at codon 778 is replaced by aspartic acid, an amino acid with highly similar properties. This variant was not reported in population based cohorts in the following databases: Database of Single Nucleotide Polymorphisms (dbSNP), NHLBI Exome Sequencing Project (ESP), and 1000 Genomes Project. In the ESP, this variant was not observed in 6498 samples (12996 alleles) with coverage at this position. To date, this alteration has been detected with an allele frequency of approximately 0.006% (greater than 20000 alleles tested) in our clinical cohort. This amino acid position is not well 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. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Benign	0.10
BayesDel_addAF	Uncertain	0.054	T
BayesDel_noAF	Benign	-0.16
CADD	Benign	22
DANN	Uncertain	0.99
DEOGEN2	Uncertain	0.58	D;.;.;.;.;.;.;.;.;.;.;.;T;.;T
Eigen	Benign	0.11
Eigen_PC	Benign	0.039
FATHMM_MKL	Benign	0.64	D
LIST_S2	Uncertain	0.93	D;D;D;D;D;D;D;D;D;D;D;D;D;D;D
M_CAP	Benign	0.083	D
MetaRNN	Benign	0.33	T;T;T;T;T;T;T;T;T;T;T;T;T;T;T
MetaSVM	Uncertain	-0.10	T
MutationAssessor	Uncertain	2.1	M;.;.;.;M;M;.;.;.;M;.;M;.;.;.
MutationTaster	Benign	1.0	N;N;N;N;N;N;N
PrimateAI	Uncertain	0.49	T
PROVEAN	Benign	-1.9	N;.;.;N;.;N;.;.;N;N;.;.;.;.;N
REVEL	Uncertain	0.45
Sift	Benign	0.14	T;.;.;T;.;T;.;.;T;T;.;.;.;.;T
Sift4G	Benign	0.16	T;.;.;T;.;T;.;.;T;T;.;.;.;.;T
Polyphen		0.99	D;.;.;.;D;P;.;.;D;P;.;.;.;.;.
Vest4		0.33
MutPred		0.56		Gain of sheet (P = 0.0266);Gain of sheet (P = 0.0266);Gain of sheet (P = 0.0266);.;Gain of sheet (P = 0.0266);Gain of sheet (P = 0.0266);Gain of sheet (P = 0.0266);Gain of sheet (P = 0.0266);.;Gain of sheet (P = 0.0266);Gain of sheet (P = 0.0266);Gain of sheet (P = 0.0266);Gain of sheet (P = 0.0266);Gain of sheet (P = 0.0266);.;
MVP		0.92
ClinPred		0.40	T
GERP RS		4.5
RBP_binding_hub_radar		0.0
RBP_regulation_power_radar		1.1
Varity_R		0.18
gMVP		0.32

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: rs1060500946; hg19: chr16-2122961;