18-31591937-C-T

Variant summary

Our verdict is Uncertain significance. Variant got 2 ACMG points: 2P and 0B. PM2

The NM_000371.4(TTR):c.35C>T(p.Ala12Val) variant causes a missense change. The variant was absent in control chromosomes in GnomAD project. 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. A12S) has been classified as Uncertain significance.

• Frequency: Genomes: not found (cov: 33)
• Consequence: TTR NM_000371.4 missense
• Clinical Significance: Uncertain significance criteria provided, single submitter U:1
• Conservation: PhyloP100: 4.09

Genes affected

TTR (HGNC:12405): (transthyretin) This gene encodes one of the three prealbumins, which include alpha-1-antitrypsin, transthyretin and orosomucoid. The encoded protein, transthyretin, is a homo-tetrameric carrier protein, which transports thyroid hormones in the plasma and cerebrospinal fluid. It is also involved in the transport of retinol (vitamin A) in the plasma by associating with retinol-binding protein. The protein may also be involved in other intracellular processes including proteolysis, nerve regeneration, autophagy and glucose homeostasis. Mutations in this gene are associated with amyloid deposition, predominantly affecting peripheral nerves or the heart, while a small percentage of the gene mutations are non-amyloidogenic. The mutations are implicated in the etiology of several diseases, including amyloidotic polyneuropathy, euthyroid hyperthyroxinaemia, amyloidotic vitreous opacities, cardiomyopathy, oculoleptomeningeal amyloidosis, meningocerebrovascular amyloidosis and carpal tunnel syndrome. [provided by RefSeq, Aug 2017]

ACMG classification

Verdict is Uncertain_significance. Variant got 2 ACMG points.

• PM2: Very rare variant in population databases, with high coverage

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
TTR	NM_000371.4	c.35C>T	p.Ala12Val	missense_variant	1/4	ENST00000237014.8

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
TTR	ENST00000237014.8	c.35C>T	p.Ala12Val	missense_variant	1/4	1	NM_000371.4	P1

Frequencies

GnomAD3 genomes Cov.: 33

GnomAD4 exome Cov.: 30

GnomAD4 genome Cov.: 33

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:1

Revision: criteria provided, single submitter

Submissions by phenotype

Familial amyloid neuropathy Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Invitae

Feb 06, 2022

This variant has not been reported in the literature in individuals affected with TTR-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 expected to disrupt TTR protein function. This variant is not present in population databases (gnomAD no frequency). This sequence change replaces alanine, which is neutral and non-polar, with valine, which is neutral and non-polar, at codon 12 of the TTR protein (p.Ala12Val). -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Benign	0.17
BayesDel_addAF	Pathogenic	0.26	D
BayesDel_noAF	Uncertain	0.13
Cadd	Uncertain	25
Dann	Pathogenic	1.0
DEOGEN2	Uncertain	0.45	T;T;T;.
Eigen	Pathogenic	0.69
Eigen_PC	Uncertain	0.62
FATHMM_MKL	Uncertain	0.89	D
M_CAP	Pathogenic	0.40	D
MetaRNN	Uncertain	0.70	D;D;D;D
MetaSVM	Pathogenic	1.0	D
MutationAssessor	Uncertain	2.6	M;M;.;.
MutationTaster	Benign	1.0	D
PrimateAI	Uncertain	0.50	T
Polyphen		1.0	D;D;.;.
Vest4		0.51, 0.54, 0.49
MutPred		0.47		Loss of helix (P = 0.3949);Loss of helix (P = 0.3949);Loss of helix (P = 0.3949);Loss of helix (P = 0.3949);
MVP		0.96
MPC		1.1
ClinPred		0.98	D
GERP RS		5.8
Varity_R		0.35
gMVP		0.94

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

Publications

No publications associated with this variant yet.

Other links and lift over

hg19: chr18-29171900;