16-2058823-C-T

Variant names:

• chr16-2058823-C-T
• rs1258567486
• NM_000548.5:c.925C>T

Variant summary

Our verdict is Likely benign. The variant received -5 ACMG points: 0P and 5B. BP6 BS2

The NM_000548.5(TSC2):​c.925C>T​(p.Leu309Phe) variant causes a missense change. The variant allele was found at a frequency of 0.00000964 in 1,452,152 control chromosomes in the GnomAD database, with no homozygous occurrence. Variant has been reported in ClinVar as Conflicting classifications of pathogenicity (no stars). Another variant affecting the same amino acid position, but resulting in a different missense (i.e. L309H) has been classified as Likely benign.

• Frequency:
  • Genomes: not found (cov: 33)
  • Exomes 𝑓: 0.0000096 (0 hom.)
• Consequence: TSC2 NM_000548.5 missense
• Clinical Significance: Conflicting classifications of pathogenicity criteria provided, conflicting classifications U:4 B:2
• Conservation: PhyloP100: 4.71
• Publications: 3 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: Likely_benign. The variant received -5 ACMG points.

• BP6: Variant 16-2058823-C-T is Benign according to our data. Variant chr16-2058823-C-T is described in ClinVar as Conflicting_classifications_of_pathogenicity. ClinVar VariationId is 468192.
• BS2: High AC in GnomAdExome4 at 14 AD gene.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
TSC2	NM_000548.5	c.925C>T	p.Leu309Phe	missense_variant	Exon 10 of 42	ENST00000219476.9	NP_000539.2

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
TSC2	ENST00000219476.9	c.925C>T	p.Leu309Phe	missense_variant	Exon 10 of 42	5	NM_000548.5	ENSP00000219476.3

Frequencies

GnomAD3 genomes Cov.: 33

GnomAD2 exomes AF: 0.00000429 AC: 1 AN: 233352 AF XY: 0.00

Gnomad AFR exome AF: 0.00

Gnomad AMR exome AF: 0.00

Gnomad ASJ exome AF: 0.00

Gnomad EAS exome AF: 0.00

Gnomad FIN exome AF: 0.00

Gnomad NFE exome AF: 0.00000958

Gnomad OTH exome AF: 0.00

GnomAD4 exome AF: 0.00000964 AC: 14 AN: 1452152 Hom.: 0 Cov.: 32 AF XY: 0.00000832 AC XY: 6 AN XY: 721254

African (AFR) AF: 0.00 AC: 0 AN: 33428

American (AMR) AF: 0.00 AC: 0 AN: 43220

Ashkenazi Jewish (ASJ) AF: 0.00 AC: 0 AN: 25836

East Asian (EAS) AF: 0.00 AC: 0 AN: 39526

South Asian (SAS) AF: 0.00 AC: 0 AN: 84168

European-Finnish (FIN) AF: 0.00 AC: 0 AN: 52696

Middle Eastern (MID) AF: 0.00 AC: 0 AN: 5738

European-Non Finnish (NFE) AF: 0.0000126 AC: 14 AN: 1107444

Other (OTH) AF: 0.00 AC: 0 AN: 60096

GnomAD4 genome Cov.: 33

Alfa AF: 0.0000624 Hom.: 0

ClinVar

Significance: Conflicting classifications of pathogenicity

Submissions summary: Uncertain:4 Benign:2

Revision: criteria provided, conflicting classifications

Submissions by phenotype

not provided Uncertain:2

-

Department of Pathology and Laboratory Medicine, Sinai Health System

Significance: Uncertain significance

Review Status: no assertion criteria provided

Collection Method: clinical testing

The TSC2 p.Leu309Phe variant was not identified in the literature nor was it identified in Cosmic. The variant was identified in dbSNP (ID: rs1258567486) and ClinVar (classified as likely benign by Invitae and uncertain significance by Ambry Genetics). The variant was identified in control databases in 1 of 221912 chromosomes at a frequency of 0.000004506 (Genome Aggregation Database March 6, 2019, v2.1.1). The variant was observed in the European (non-Finnish) population in 1 of 95764 chromosomes (freq: 0.00001), but was not observed in the African, Latino, Ashkenazi Jewish, East Asian, European (Finnish), Other, or South Asian populations. The p.Leu309 residue is conserved in mammals and computational analyses (PolyPhen-2, SIFT, AlignGVGD, BLOSUM, MutationTaster) provide inconsistent predictions regarding the impact to the protein; this information is not very predictive of pathogenicity. The variant occurs outside of the splicing consensus sequence and in silico or computational prediction software programs (SpliceSiteFinder, MaxEntScan, NNSPLICE, GeneSplicer) do not predict a difference in splicing. In summary, based on the above information the clinical significance of this variant cannot be determined with certainty at this time. This variant is classified as a variant of uncertain significance. -

Sep 12, 2023

GeneDx

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

In silico analysis supports that this missense variant has a deleterious effect on protein structure/function; Has not been previously published as pathogenic or benign to our knowledge -

Tuberous sclerosis 2 Benign:2

Nov 07, 2021

Genome-Nilou Lab

Significance: Likely benign

Review Status: criteria provided, single submitter

Collection Method: clinical testing

- -

Nov 16, 2024

Labcorp Genetics (formerly Invitae), Labcorp

Significance: Likely benign

Review Status: criteria provided, single submitter

Collection Method: clinical testing

- -

Tuberous sclerosis syndrome Uncertain:1

Aug 15, 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 leucine with phenylalanine at codon 309 of the TSC2 protein. Computational prediction is inconclusive regarding the impact of this variant on protein structure and function (internally defined REVEL score threshold 0.5 < inconclusive < 0.7, 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 been identified in 1/233352 chromosomes 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. -

Hereditary cancer-predisposing syndrome Uncertain:1

Mar 14, 2023

Ambry Genetics

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

The p.L309F variant (also known as c.925C>T), located in coding exon 9 of the TSC2 gene, results from a C to T substitution at nucleotide position 925. The leucine at codon 309 is replaced by phenylalanine, an amino acid with highly 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. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	0.70
BayesDel_addAF	Pathogenic	0.24	D
BayesDel_noAF	Uncertain	0.11
CADD	Uncertain	25
DANN	Uncertain	1.0
DEOGEN2	Uncertain	0.75	D;.;.;.;.;.;.;.;.;.;.;.;T;.;T
Eigen	Uncertain	0.49
Eigen_PC	Uncertain	0.40
FATHMM_MKL	Uncertain	0.95	D
LIST_S2	Uncertain	0.89	D;D;D;D;D;D;D;D;D;D;D;D;D;D;D
M_CAP	Pathogenic	0.35	D
MetaRNN	Uncertain	0.50	T;T;T;T;T;T;T;T;T;T;T;T;T;T;T
MetaSVM	Uncertain	0.25	D
MutationAssessor	Uncertain	2.1	M;.;.;.;M;M;.;.;.;M;.;M;.;.;.
PhyloP100		4.7
PrimateAI	Uncertain	0.71	T
PROVEAN	Uncertain	-2.4	N;.;.;N;.;N;.;.;N;N;.;.;.;.;N
REVEL	Uncertain	0.52
Sift	Uncertain	0.0080	D;.;.;D;.;D;.;.;D;D;.;.;.;.;D
Sift4G	Uncertain	0.011	D;.;.;D;.;D;.;.;D;D;.;.;.;.;D
Polyphen		1.0	D;.;.;.;D;D;.;.;D;D;.;.;.;.;.
Vest4		0.74
MutPred		0.33		Loss of helix (P = 0.0626);Loss of helix (P = 0.0626);Loss of helix (P = 0.0626);.;Loss of helix (P = 0.0626);Loss of helix (P = 0.0626);Loss of helix (P = 0.0626);Loss of helix (P = 0.0626);.;Loss of helix (P = 0.0626);Loss of helix (P = 0.0626);Loss of helix (P = 0.0626);Loss of helix (P = 0.0626);Loss of helix (P = 0.0626);.;
MVP		0.62
ClinPred		0.80	D
GERP RS		5.1
Varity_R		0.34
gMVP		0.44
Mutation Taster		=38/62	disease causing

Splicing

Name	Calibrated prediction	Score	Prediction
SpliceAI score (max)		0.030		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: rs1258567486; hg19: chr16-2108824;