16-2050463-G-C

Variant names:

• chr16-2050463-G-C
• rs767626323
• NM_000548.5:c.202G>C

Variant summary

Our verdict is Uncertain significance. The variant received 2 ACMG points: 3P and 1B. PM2 PP3 BP6

The NM_000548.5(TSC2):​c.202G>C​(p.Ala68Pro) variant causes a missense change involving the alteration of a conserved nucleotide. The variant allele was found at a frequency of 0.000000684 in 1,461,562 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a pathogenic outcome for this variant. Variant has been reported in ClinVar as Conflicting classifications of pathogenicity (no stars). Another nucleotide change resulting in the same amino acid substitution has been previously reported as Uncertain significance in ClinVar. Another variant affecting the same amino acid position, but resulting in a different missense (i.e. A68T) has been classified as Uncertain significance.

• Frequency:
  • Genomes: not found (cov: 30)
  • Exomes 𝑓: 6.8e-7 (0 hom.)
• Consequence: TSC2 NM_000548.5 missense
• Clinical Significance: Conflicting classifications of pathogenicity criteria provided, conflicting classifications U:2 B:1
• Conservation: PhyloP100: 9.21
• Publications: 12 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 2 ACMG points.

• PM2: Very rare variant in population databases, with high coverage
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.834
• BP6: Variant 16-2050463-G-C is Benign according to our data. Variant chr16-2050463-G-C is described in ClinVar as Conflicting_classifications_of_pathogenicity. ClinVar VariationId is 570657.

Variant Effect in Transcripts

ACMG analysis was done for transcript: NM_000548.5. You can select a different transcript below to see updated ACMG assignments.

RefSeq Transcripts

Selected	Gene	Transcript	Tags	HGVSc	HGVSp	Effect	Exon Rank	Protein	UniProt
	TSC2	NM_000548.5	MANE Select	c.202G>C	p.Ala68Pro	missense	Exon 3 of 42	NP_000539.2
	TSC2	NM_001406663.1		c.202G>C	p.Ala68Pro	missense	Exon 3 of 42	NP_001393592.1
	TSC2	NM_001114382.3		c.202G>C	p.Ala68Pro	missense	Exon 3 of 41	NP_001107854.1

Ensembl Transcripts

Selected	Gene	Transcript	Tags	HGVSc	HGVSp	Effect	Exon Rank	Protein	UniProt
	TSC2	ENST00000219476.9	TSL:5 MANE Select	c.202G>C	p.Ala68Pro	missense	Exon 3 of 42	ENSP00000219476.3
	TSC2	ENST00000350773.9	TSL:1	c.202G>C	p.Ala68Pro	missense	Exon 3 of 41	ENSP00000344383.4
	TSC2	ENST00000401874.7	TSL:1	c.202G>C	p.Ala68Pro	missense	Exon 3 of 40	ENSP00000384468.2

Frequencies

GnomAD3 genomes Cov.: 30

GnomAD2 exomes AF: 0.00000398 AC: 1 AN: 251046 AF XY: 0.00000736

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: 0.00

Gnomad OTH exome AF: 0.00

GnomAD4 exome AF: 6.84e-7 AC: 1 AN: 1461562 Hom.: 0 Cov.: 32 AF XY: 0.00000138 AC XY: 1 AN XY: 727070

⚠️ The allele balance in gnomAD version 4 Exomes is significantly skewed from the expected value of 0.5.

African (AFR) AF: 0.00 AC: 0 AN: 33474

American (AMR) AF: 0.00 AC: 0 AN: 44716

Ashkenazi Jewish (ASJ) AF: 0.00 AC: 0 AN: 26130

East Asian (EAS) AF: 0.00 AC: 0 AN: 39688

South Asian (SAS) AF: 0.0000116 AC: 1 AN: 86248

European-Finnish (FIN) AF: 0.00 AC: 0 AN: 53318

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

European-Non Finnish (NFE) AF: 0.00 AC: 0 AN: 1111838

Other (OTH) AF: 0.00 AC: 0 AN: 60382

⚠️ The allele balance in gnomAD4 Exomes is highly skewed from 0.5 (p-value = 0), which strongly suggests a high chance of mosaicism in these individuals.

GnomAD4 genome Cov.: 30

ClinVar

Significance: Conflicting classifications of pathogenicity

Submissions summary: Uncertain:2 Benign:1

Revision: criteria provided, conflicting classifications

Submissions by phenotype

Tuberous sclerosis syndrome Uncertain:1

Mar 23, 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 alanine with proline at codon 68 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 tuberous sclerosis complex in the literature. This variant has been identified in 1/251046 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

Feb 25, 2024

Ambry Genetics

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

The p.A68P variant (also known as c.202G>C), located in coding exon 2 of the TSC2 gene, results from a G to C substitution at nucleotide position 202. The alanine at codon 68 is replaced by proline, an amino acid with highly similar properties. This amino acid position is conserved. In addition, this alteration is predicted to be deleterious by in silico analysis. Based on the available evidence, the clinical significance of this alteration remains unclear.

Tuberous sclerosis 2 Benign:1

Dec 31, 2023

Labcorp Genetics (formerly Invitae), Labcorp

Significance: Benign

Review Status: criteria provided, single submitter

Collection Method: clinical testing

Computational scores

Source: dbNSFP v4.9

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	0.98
BayesDel_addAF	Pathogenic	0.32	D
BayesDel_noAF	Pathogenic	0.31
CADD	Pathogenic	30
DANN	Uncertain	1.0
DEOGEN2	Uncertain	0.62	D
Eigen	Uncertain	0.64
Eigen_PC	Uncertain	0.62
FATHMM_MKL	Pathogenic	0.99	D
LIST_S2	Uncertain	0.97	D
M_CAP	Pathogenic	0.44	D
MetaRNN	Pathogenic	0.83	D
MetaSVM	Uncertain	0.14	D
MutationAssessor	Uncertain	2.2	M
PhyloP100		9.2
PrimateAI	Uncertain	0.73	T
PROVEAN	Uncertain	-2.5	N
REVEL	Pathogenic	0.68
Sift	Benign	0.17	T
Sift4G	Uncertain	0.042	D
Polyphen		1.0	D
Vest4		0.91
MutPred		0.60		Loss of helix (P = 0.0017)
MVP		0.80
ClinPred		0.97	D
GERP RS		4.8
Varity_R		0.61
gMVP		0.82
Mutation Taster		=31/69	disease causing

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: rs767626323; hg19: chr16-2100464;