9-132912314-G-T

Variant summary

Our verdict is Uncertain significance. Variant got 2 ACMG points: 3P and 1B. PM2 PP2 BP4

The NM_000368.5(TSC1):c.881C>A(p.Thr294Asn) variant causes a missense change. The variant allele was found at a frequency of 0.00000205 in 1,461,888 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a benign outcome for this variant. 13/21 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. T294A) has been classified as Likely benign.

• Frequency:
  • Genomes: not found (cov: 32)
  • Exomes 𝑓: 0.0000021 (0 hom.)
• Consequence: TSC1 NM_000368.5 missense
• Clinical Significance: Uncertain significance criteria provided, multiple submitters, no conflicts U:2
• Conservation: PhyloP100: 6.29

Genes affected

TSC1 (HGNC:12362): (TSC complex subunit 1) This gene is a tumor suppressor gene that encodes the growth inhibitory protein hamartin. The encoded protein interacts with and stabilizes the GTPase activating protein tuberin. This hamartin-tuberin complex negatively regulates mammalian target of rapamycin complex 1 (mTORC1) signaling which is a major regulator of anabolic cell growth. This protein also functions as a co-chaperone for Hsp90 that inhibits its ATPase activity. This protein functions as a facilitator of Hsp90-mediated folding of kinase and non-kinase clients, including TSC2 and thereby preventing their ubiquitination and proteasomal degradation. 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
• PP2: Missense variant where missense usually causes diseases, TSC1
• BP4: Computational evidence support a benign effect (MetaRNN=0.34081078).

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
TSC1	NM_000368.5	c.881C>A	p.Thr294Asn	missense_variant	9/23	ENST00000298552.9

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
TSC1	ENST00000298552.9	c.881C>A	p.Thr294Asn	missense_variant	9/23	1	NM_000368.5	P4

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome AF: 0.00000205 AC: 3 AN: 1461888 Hom.: 0 Cov.: 31 AF XY: 0.00000413 AC XY: 3 AN XY: 727242

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: 0.00000270

Gnomad4 OTH exome AF: 0.00

GnomAD4 genome Cov.: 32

EpiCase AF: 0.0000545

EpiControl AF: 0.00

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:2

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

Tuberous sclerosis 1 Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Invitae

Jul 25, 2023

This variant has not been reported in the literature in individuals affected with TSC1-related conditions. 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 TSC1 protein function. ClinVar contains an entry for this variant (Variation ID: 237731). This variant is not present in population databases (gnomAD no frequency). This sequence change replaces threonine, which is neutral and polar, with asparagine, which is neutral and polar, at codon 294 of the TSC1 protein (p.Thr294Asn). -

Hereditary cancer-predisposing syndrome Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Ambry Genetics

Jun 07, 2022

The p.T294N variant (also known as c.881C>A), located in coding exon 7 of the TSC1 gene, results from a C to A substitution at nucleotide position 881. The threonine at codon 294 is replaced by asparagine, an amino acid with similar properties. This amino acid position is conserved. In addition, this alteration is predicted to be tolerated by in silico analysis. 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	0.085
BayesDel_addAF	Benign	-0.020	T
BayesDel_noAF	Benign	-0.27
Cadd	Benign	23
Dann	Uncertain	0.98
DEOGEN2	Benign	0.42	T;.;T;.;T;.;T;.;.;.;.;.;.;.;.;.;.;T;.
Eigen	Uncertain	0.21
Eigen_PC	Uncertain	0.35
FATHMM_MKL	Pathogenic	1.0	D
M_CAP	Benign	0.033	D
MetaRNN	Benign	0.34	T;T;T;T;T;T;T;T;T;T;T;T;T;T;T;T;T;T;T
MetaSVM	Uncertain	0.44	D
MutationAssessor	Benign	1.4	L;.;L;.;L;.;L;.;.;.;.;.;.;.;.;.;.;.;.
MutationTaster	Benign	0.76	D;D;D;D;D
PrimateAI	Benign	0.27	T
PROVEAN	Benign	-0.27	N;N;N;.;.;.;.;.;.;.;.;.;.;.;.;.;.;N;.
REVEL	Benign	0.28
Sift	Benign	0.23	T;T;T;.;.;.;.;.;.;.;.;.;.;.;.;.;.;T;.
Sift4G	Benign	0.14	T;T;T;.;.;.;.;.;.;.;.;.;.;.;.;.;.;T;.
Polyphen		0.051	B;.;B;.;B;.;B;.;.;.;.;B;B;B;.;.;.;P;.
Vest4		0.26
MutPred		0.47		Loss of glycosylation at T294 (P = 0.0217);.;Loss of glycosylation at T294 (P = 0.0217);Loss of glycosylation at T294 (P = 0.0217);Loss of glycosylation at T294 (P = 0.0217);Loss of glycosylation at T294 (P = 0.0217);Loss of glycosylation at T294 (P = 0.0217);Loss of glycosylation at T294 (P = 0.0217);Loss of glycosylation at T294 (P = 0.0217);.;.;Loss of glycosylation at T294 (P = 0.0217);Loss of glycosylation at T294 (P = 0.0217);Loss of glycosylation at T294 (P = 0.0217);Loss of glycosylation at T294 (P = 0.0217);Loss of glycosylation at T294 (P = 0.0217);.;Loss of glycosylation at T294 (P = 0.0217);.;
MVP		0.69
MPC		0.65
ClinPred		0.90	D
GERP RS		4.7
Varity_R		0.080
gMVP		0.23

Splicing

Name	Calibrated prediction	Score	Prediction
SpliceAI score (max)		0.020		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: rs878853969; hg19: chr9-135787701;