NM_000371.4:c.62G>C

Variant names:

• chr18-31591964-G-C
• rs1469623969
• NM_000371.4:c.62G>C

Variant summary

Our verdict is Uncertain significance. The variant received 1 ACMG points: 5P and 4B. PM1 PM2 PP2 BP4_Strong

The NM_000371.4(TTR):​c.62G>C​(p.Gly21Ala) variant causes a missense change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.000000684 in 1,461,820 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a benign outcome for this variant. 17/22 in silico tools predict a benign outcome for this variant. Variant has been reported in ClinVar as Uncertain significance (★★).

• Frequency:
  • Genomes: not found (cov: 33)
  • Exomes 𝑓: 6.8e-7 (0 hom.)
• Consequence: TTR NM_000371.4 missense
• Clinical Significance: Uncertain significance criteria provided, multiple submitters, no conflicts U:3
• Conservation: PhyloP100: 0.975
• Publications: 2 publications found

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]

TTR Gene-Disease associations (from GenCC):

• amyloidosis, hereditary systemic 1

  Inheritance: AD Classification: DEFINITIVE Submitted by: G2P
• familial amyloid neuropathy

  Inheritance: AD Classification: DEFINITIVE, STRONG, SUPPORTIVE Submitted by: Orphanet, Ambry Genetics, Labcorp Genetics (formerly Invitae)
• hereditary ATTR amyloidosis

  Inheritance: AD Classification: DEFINITIVE Submitted by: ClinGen
• heart conduction disease

  Inheritance: AD Classification: STRONG Submitted by: Genomics England PanelApp
• ATTRV122I amyloidosis

  Inheritance: AD Classification: SUPPORTIVE Submitted by: Orphanet

ACMG classification

Our verdict: Uncertain_significance. The variant received 1 ACMG points.

• PM1: In a chain Transthyretin (size 126) in uniprot entity TTHY_HUMAN there are 134 pathogenic changes around while only 8 benign (94%) in NM_000371.4
• PM2: Very rare variant in population databases, with high coverage
• PP2: Missense variant in the gene, where a lot of missense mutations are associated with disease in ClinVar. The gene has 108 curated pathogenic missense variants (we use a threshold of 10). The gene has 3 curated benign missense variants. Gene score misZ: 1.0149 (below the threshold of 3.09). Trascript score misZ: 1.5458 (below the threshold of 3.09). GenCC associations: The gene is linked to familial amyloid neuropathy, amyloidosis, hereditary systemic 1, ATTRV122I amyloidosis, hereditary ATTR amyloidosis, heart conduction disease.
• BP4: Computational evidence support a benign effect (MetaRNN=0.05705449).

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
TTR	NM_000371.4	c.62G>C	p.Gly21Ala	missense_variant	Exon 1 of 4	ENST00000237014.8	NP_000362.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
TTR	ENST00000237014.8	c.62G>C	p.Gly21Ala	missense_variant	Exon 1 of 4	1	NM_000371.4	ENSP00000237014.4

Frequencies

GnomAD3 genomes Cov.: 33

GnomAD4 exome AF: 6.84e-7 AC: 1 AN: 1461820 Hom.: 0 Cov.: 30 AF XY: 0.00 AC XY: 0 AN XY: 727210

African (AFR) AF: 0.00 AC: 0 AN: 33472

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

Ashkenazi Jewish (ASJ) AF: 0.00 AC: 0 AN: 26136

East Asian (EAS) AF: 0.0000252 AC: 1 AN: 39698

South Asian (SAS) AF: 0.00 AC: 0 AN: 86254

European-Finnish (FIN) AF: 0.00 AC: 0 AN: 53418

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

European-Non Finnish (NFE) AF: 0.00 AC: 0 AN: 1111974

Other (OTH) AF: 0.00 AC: 0 AN: 60384

GnomAD4 genome Cov.: 33

Alfa AF: 0.00 Hom.: 0

Bravo AF: 0.00000378

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:3

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

Cardiomyopathy Uncertain:1

Aug 04, 2021

CHEO Genetics Diagnostic Laboratory, Children's Hospital of Eastern Ontario

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

- -

Cardiovascular phenotype Uncertain:1

Oct 24, 2023

Ambry Genetics

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

The p.G21A variant (also known as c.62G>C), located in coding exon 1 of the TTR gene, results from a G to C substitution at nucleotide position 62. The glycine at codon 21 is replaced by alanine, an amino acid with similar properties. This amino acid position is not well conserved in available vertebrate species. 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. -

Amyloidosis, hereditary systemic 1 Uncertain:1

Jan 28, 2025

Labcorp Genetics (formerly Invitae), Labcorp

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

This sequence change replaces glycine, which is neutral and non-polar, with alanine, which is neutral and non-polar, at codon 21 of the TTR protein (p.Gly21Ala). This variant is not present in population databases (gnomAD no frequency). This variant has not been reported in the literature in individuals affected with TTR-related conditions. ClinVar contains an entry for this variant (Variation ID: 470719). Invitae Evidence Modeling of protein sequence and biophysical properties (such as structural, functional, and spatial information, amino acid conservation, physicochemical variation, residue mobility, and thermodynamic stability) indicates that this missense variant is not expected to disrupt TTR protein function with a negative predictive value of 95%. 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. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Benign	0.072
BayesDel_addAF	Benign	-0.042	T
BayesDel_noAF	Benign	-0.30
CADD	Benign	6.8
DANN	Benign	0.55
DEOGEN2	Benign	0.16	T;T;T;.
Eigen	Benign	-1.2
Eigen_PC	Benign	-1.2
FATHMM_MKL	Benign	0.079	N
LIST_S2	Benign	0.81	.;T;T;T
M_CAP	Benign	0.052	D
MetaRNN	Benign	0.057	T;T;T;T
MetaSVM	Benign	-0.52	T
MutationAssessor	Benign	1.2	L;L;.;.
PhyloP100		0.97
PrimateAI	Benign	0.30	T
PROVEAN	Benign	-0.11	.;N;.;.
REVEL	Benign	0.094
Sift	Benign	0.56	.;T;.;.
Sift4G	Benign	1.0	.;T;T;T
Polyphen		0.0020	B;B;.;.
Vest4		0.048, 0.12, 0.089
MutPred		0.23		Loss of catalytic residue at A20 (P = 0.0554);Loss of catalytic residue at A20 (P = 0.0554);Loss of catalytic residue at A20 (P = 0.0554);Loss of catalytic residue at A20 (P = 0.0554);
MVP		0.78
MPC		0.50
ClinPred		0.065	T
GERP RS		0.87
PromoterAI		-0.058	Neutral
Varity_R		0.13
gMVP		0.85
Mutation Taster		=93/7	polymorphism

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: rs1469623969; hg19: chr18-29171927;