16-2048747-A-G

Position:

• chr16-2048747-A-G

Variant summary

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

The NM_001406680.1(TSC2):​c.-685A>G variant causes a 5 prime UTR premature start codon gain change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.000000684 in 1,461,748 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 (★★).

• Frequency:
  • Genomes: not found (cov: 32)
  • Exomes 𝑓: 6.8e-7 (0 hom.)
• Consequence: TSC2 NM_001406680.1 5_prime_UTR_premature_start_codon_gain
• Clinical Significance: Uncertain significance criteria provided, multiple submitters, no conflicts U:3
• Conservation: PhyloP100: 0.760

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 (HGNC:):

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=0.2998106).

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
TSC2	NM_000548.5	c.132A>G	p.Ile44Met	missense_variant	2/42	ENST00000219476.9	NP_000539.2

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
TSC2	ENST00000219476.9	c.132A>G	p.Ile44Met	missense_variant	2/42	5	NM_000548.5	ENSP00000219476.3

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome AF: 6.84e-7 AC: 1 AN: 1461748 Hom.: 0 Cov.: 32 AF XY: 0.00000138 AC XY: 1 AN XY: 727158

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: 8.99e-7

Gnomad4 OTH exome AF: 0.00

GnomAD4 genome Cov.: 32

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:3

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	Labcorp Genetics (formerly Invitae), Labcorp	Jan 21, 2020	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. Algorithms developed to predict the effect of missense changes on protein structure and function (SIFT, PolyPhen-2, Align-GVGD) all suggest that this variant is likely to be tolerated, but these predictions have not been confirmed by published functional studies and their clinical significance is uncertain. This variant has not been reported in the literature in individuals with TSC2-related disease. ClinVar contains an entry for this variant (Variation ID: 207778). This variant is not present in population databases (ExAC no frequency). This sequence change replaces isoleucine with methionine at codon 44 of the TSC2 protein (p.Ile44Met). The isoleucine residue is moderately conserved and there is a small physicochemical difference between isoleucine and methionine. -

not provided Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

GeneDx

Jan 14, 2015

p.Ile44Met (ATA>ATG): c.132 A>G in exon 2 of the TSC2 gene (NM_000548.3) A variant of unknown significance has been identified in the TSC2 gene. The I44M variant has not been published as a mutation, nor has it been reported as a benign polymorphism to our knowledge. It was not observed in approximately 6,500 individuals of European and African American ancestry in the NHLBI Exome Sequencing Project, indicating it is not a common benign variant in these populations. This substitution occurs at a position that is conserved across species, and in silico analysis predicts this variant is probably damaging to the protein structure/function. The I44M variant occurs within a known functional domain of the tuberin protein, where many pathogenic missense mutations have been identified (Northrup et al., 2011; Au et al., 2007). However, the I44M variant is a conservative amino acid substitution, which is not likely to impact secondary protein structure as these residues share similar properties. Therefore, based on the currently available information, it is unclear whether this variant is a pathogenic mutation or a rare benign variant. The variant is found in EPILEPSYV2-1 panel(s). -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Benign	0.12
BayesDel_addAF	Benign	-0.012	T
BayesDel_noAF	Benign	-0.26
CADD	Benign	20
DANN	Uncertain	0.99
DEOGEN2	Uncertain	0.52	D;.;.;.;.;.;.;.;.;.;.;.;T;.;T
Eigen	Benign	-0.13
Eigen_PC	Benign	-0.25
FATHMM_MKL	Uncertain	0.79	D
LIST_S2	Uncertain	0.95	D;D;D;D;D;D;D;D;D;D;D;D;D;D;D
M_CAP	Uncertain	0.15	D
MetaRNN	Benign	0.30	T;T;T;T;T;T;T;T;T;T;T;T;T;T;T
MetaSVM	Benign	-0.58	T
MutationAssessor	Benign	2.0	M;.;.;M;M;.;.;M;M;.;.;M;.;.;.
PrimateAI	Uncertain	0.53	T
PROVEAN	Benign	-1.0	N;.;.;.;N;.;.;N;N;.;.;.;.;.;N
REVEL	Benign	0.29
Sift	Uncertain	0.012	D;.;.;.;D;.;.;D;D;.;.;.;.;.;D
Sift4G	Uncertain	0.023	D;.;.;.;D;.;.;D;D;.;.;.;.;.;D
Polyphen		0.99	D;.;.;.;D;.;.;D;D;.;.;.;.;.;.
Vest4		0.67
MutPred		0.56		Gain of disorder (P = 0.0565);Gain of disorder (P = 0.0565);Gain of disorder (P = 0.0565);Gain of disorder (P = 0.0565);Gain of disorder (P = 0.0565);Gain of disorder (P = 0.0565);Gain of disorder (P = 0.0565);Gain of disorder (P = 0.0565);Gain of disorder (P = 0.0565);Gain of disorder (P = 0.0565);Gain of disorder (P = 0.0565);Gain of disorder (P = 0.0565);Gain of disorder (P = 0.0565);Gain of disorder (P = 0.0565);.;
MVP		0.46
ClinPred		0.34	T
GERP RS		1.4
RBP_binding_hub_radar		0.0
RBP_regulation_power_radar		1.1
Varity_R		0.11
gMVP		0.40

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

Publications

LitVar

Other links and lift over

dbSNP: rs796053508; hg19: chr16-2098748;