NM_000548.5:c.77C>T

Variant names:

• chr16-2048692-C-T
• rs1555494636
• NM_000548.5:c.77C>T

Variant summary

Our verdict is Uncertain significance. The variant received 0 ACMG points: 2P and 2B. PM2 BP4_Moderate

The NM_000548.5(TSC2):​c.77C>T​(p.Pro26Leu) 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. 15/22 in silico tools predict 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. P26S) has been classified as Uncertain significance.

• Frequency:
  • Genomes: not found (cov: 32)
  • Exomes 𝑓: 6.8e-7 (0 hom.)
  • Failed GnomAD Quality Control
• Consequence: TSC2 NM_000548.5 missense
• Clinical Significance: Uncertain significance criteria provided, multiple submitters, no conflicts U:5
• Conservation: PhyloP100: 1.64
• Publications: 0 publications found

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 Gene-Disease associations (from GenCC):

• tuberous sclerosis

  Inheritance: AD Classification: DEFINITIVE Submitted by: ClinGen
• tuberous sclerosis 2

  Inheritance: AD Classification: DEFINITIVE, STRONG Submitted by: PanelApp Australia, Laboratory for Molecular Medicine, Labcorp Genetics (formerly Invitae), G2P, Genomics England PanelApp, Ambry Genetics
• lymphangioleiomyomatosis

  Inheritance: AD Classification: STRONG Submitted by: Genomics England PanelApp
• tuberous sclerosis complex

  Inheritance: AD Classification: SUPPORTIVE Submitted by: Orphanet

ACMG classification

Our verdict: Uncertain_significance. The variant received 0 ACMG points.

• PM2: Very rare variant in population databases, with high coverage
• BP4: Computational evidence support a benign effect (MetaRNN=0.089488775).

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
TSC2	NM_000548.5	c.77C>T	p.Pro26Leu	missense_variant	Exon 2 of 42	ENST00000219476.9	NP_000539.2

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
TSC2	ENST00000219476.9	c.77C>T	p.Pro26Leu	missense_variant	Exon 2 of 42	5	NM_000548.5	ENSP00000219476.3

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome Data not reliable, filtered out with message: AS_VQSR AF: 6.84e-7 AC: 1 AN: 1461752 Hom.: 0 Cov.: 32 AF XY: 0.00 AC XY: 0 AN XY: 727156

African (AFR) AF: 0.00 AC: 0 AN: 33480

American (AMR) AF: 0.00 AC: 0 AN: 44722

Ashkenazi Jewish (ASJ) AF: 0.00 AC: 0 AN: 26136

East Asian (EAS) AF: 0.00 AC: 0 AN: 39700

South Asian (SAS) AF: 0.00 AC: 0 AN: 86258

European-Finnish (FIN) AF: 0.0000188 AC: 1 AN: 53292

Middle Eastern (MID) AF: 0.00 AC: 0 AN: 5768

European-Non Finnish (NFE) AF: 0.00 AC: 0 AN: 1112004

Other (OTH) AF: 0.00 AC: 0 AN: 60392

GnomAD4 genome Cov.: 32

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:5

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

Tuberous sclerosis 2 Uncertain:2

Oct 30, 2024

Labcorp Genetics (formerly Invitae), Labcorp

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

This sequence change replaces proline, which is neutral and non-polar, with leucine, which is neutral and non-polar, at codon 26 of the TSC2 protein (p.Pro26Leu). 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: 451829). Invitae Evidence Modeling of protein sequence and biophysical properties (such as structural, functional, and spatial information, amino acid conservation, physicochemical variation, residue mobility, and thermodynamic stability) 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. -

Nov 07, 2021

Genome-Nilou Lab

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

- -

Tuberous sclerosis syndrome Uncertain:1

Sep 17, 2023

All of Us Research Program, National Institutes of Health

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

This missense variant replaces proline with leucine at codon 26 of the TSC2 protein. Computational prediction suggests that this variant may not impact protein structure and function (internally defined REVEL score threshold <= 0.5, PMID: 27666373). To our knowledge, functional studies have not been reported for this variant. This variant has not been reported in individuals affected with TSC2-related disorders in the literature. 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. -

not provided Uncertain:1

Sep 08, 2017

GeneDx

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

The P26L variant has not been published as a pathogenic variant, nor has it been reported as a benign variant to our knowledge. The P26L variant is not observed in large population cohorts (Lek et al., 2016; 1000 Genomes Consortium et al., 2015; Exome Variant Server). This variant is a semi-conservative amino acid substitution, which may impact secondary protein structure as these residues differ in some properties. This substitution occurs at a position that is conserved in mammals, and in silico analysis predicts this variant is probably damaging to the protein structure/function. However, missense variants in nearby residues have not been reported in the Human Gene Mutation Database in association with TSC (Stenson et al., 2014). -

Hereditary cancer-predisposing syndrome Uncertain:1

May 02, 2024

Ambry Genetics

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

The p.P26L variant (also known as c.77C>T), located in coding exon 1 of the TSC2 gene, results from a C to T substitution at nucleotide position 77. The proline at codon 26 is replaced by leucine, an amino acid with similar properties. This amino acid position is not well conserved in available vertebrate species. In addition, this alteration is predicted to be tolerated by in silico analysis. Based on the available evidence, the clinical significance of this variant remains unclear. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Benign	0.080
BayesDel_addAF	Benign	-0.012	T
BayesDel_noAF	Benign	-0.26
CADD	Uncertain	23
DANN	Benign	0.91
DEOGEN2	Uncertain	0.69	D;.;.;.;.;.;.;.;.;.;.;.;T;.;T
Eigen	Benign	-0.19
Eigen_PC	Benign	-0.059
FATHMM_MKL	Benign	0.27	N
LIST_S2	Uncertain	0.95	D;D;D;D;D;D;D;D;D;D;D;D;D;D;D
M_CAP	Benign	0.041	D
MetaRNN	Benign	0.089	T;T;T;T;T;T;T;T;T;T;T;T;T;T;T
MetaSVM	Benign	-0.80	T
MutationAssessor	Benign	0.97	L;.;.;L;L;.;.;L;L;.;.;L;.;.;.
PhyloP100		1.6
PrimateAI	Benign	0.41	T
PROVEAN	Uncertain	-3.0	D;.;.;.;D;.;.;N;D;.;.;.;.;.;D
REVEL	Benign	0.19
Sift	Uncertain	0.010	D;.;.;.;D;.;.;D;D;.;.;.;.;.;D
Sift4G	Benign	0.10	T;.;.;.;T;.;.;T;T;.;.;.;.;.;T
Polyphen		0.67	P;.;.;.;B;.;.;B;B;.;.;.;.;.;.
Vest4		0.29
MutPred		0.18		Loss of glycosylation at P26 (P = 0.0216);Loss of glycosylation at P26 (P = 0.0216);Loss of glycosylation at P26 (P = 0.0216);Loss of glycosylation at P26 (P = 0.0216);Loss of glycosylation at P26 (P = 0.0216);Loss of glycosylation at P26 (P = 0.0216);Loss of glycosylation at P26 (P = 0.0216);Loss of glycosylation at P26 (P = 0.0216);Loss of glycosylation at P26 (P = 0.0216);Loss of glycosylation at P26 (P = 0.0216);Loss of glycosylation at P26 (P = 0.0216);Loss of glycosylation at P26 (P = 0.0216);Loss of glycosylation at P26 (P = 0.0216);Loss of glycosylation at P26 (P = 0.0216);.;
MVP		0.57
ClinPred		0.19	T
GERP RS		4.2
PromoterAI		-0.042	Neutral
RBP_binding_hub_radar		0.0
RBP_regulation_power_radar		1.1
Varity_R		0.12
gMVP		0.30
Mutation Taster		=94/6	polymorphism

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

Other links and lift over

dbSNP: rs1555494636; hg19: chr16-2098693;