18-31593026-G-C

Variant names:

• chr18-31593026-G-C
• rs121918090
• NM_000371.4:c.200G>C

Variant summary

Our verdict is Pathogenic. The variant received 19 ACMG points: 19P and 0B. PM1 PM2 PM5 PP2 PP3_Strong PP5_Very_Strong

The NM_000371.4(TTR):​c.200G>C​(p.Gly67Ala) variant causes a missense, splice region change. The variant was absent in control chromosomes in GnomAD project. In-silico tool predicts a pathogenic outcome for this variant. 2/3 splice prediction tools predicting alterations to normal splicing. Variant has been reported in ClinVar as Pathogenic (★★). Another variant affecting the same amino acid position, but resulting in a different missense (i.e. G67R) has been classified as Pathogenic.

• Frequency: Genomes: not found (cov: 32)
• Consequence: TTR NM_000371.4 missense, splice_region
• Scores: Splicing: ADA: 1.000
• Clinical Significance: Pathogenic criteria provided, multiple submitters, no conflicts P:5
• Conservation: PhyloP100: 5.86
• Publications: 14 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: Pathogenic. The variant received 19 ACMG points.

• PM1: In a hotspot region, there are 30 aminoacids with missense pathogenic changes in the window of +-8 aminoacids around while only 0 benign, 11 uncertain in NM_000371.4
• PM2: Very rare variant in population databases, with high coverage
• PM5: Other missense variant is known to change same aminoacid residue: Variant chr18-31593025-G-A is described in ClinVar as Pathogenic. ClinVar VariationId is 13459.Status of the report is no_assertion_criteria_provided, 0 stars.
• 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.
• PP3: Splicing predictors support a deleterious effect. Scorers claiming Pathogenic: dbscSNV1_ADA, dbscSNV1_RF. No scorers claiming Uncertain. Scorers claiming Benign: max_spliceai.
• PP5: Variant 18-31593026-G-C is Pathogenic according to our data. Variant chr18-31593026-G-C is described in ClinVar as Pathogenic. ClinVar VariationId is 13451.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
TTR	NM_000371.4	c.200G>C	p.Gly67Ala	missense_variant, splice_region_variant	Exon 2 of 4	ENST00000237014.8	NP_000362.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
TTR	ENST00000237014.8	c.200G>C	p.Gly67Ala	missense_variant, splice_region_variant	Exon 2 of 4	1	NM_000371.4	ENSP00000237014.4

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome Cov.: 31

GnomAD4 genome Cov.: 32

ClinVar

Significance: Pathogenic

Submissions summary: Pathogenic:5

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

Amyloidosis, hereditary systemic 1 Pathogenic:3

Mar 20, 2024

Labcorp Genetics (formerly Invitae), Labcorp

Significance: Pathogenic

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 67 of the TTR protein (p.Gly67Ala). This variant also falls at the last nucleotide of exon 2, which is part of the consensus splice site for this exon. This variant is not present in population databases (gnomAD no frequency). This missense change has been observed in individuals with clinical features of transthyretin amyloidosis (PMID: 7951260, 10677864, 24053266, 34024775). It has also been observed to segregate with disease in related individuals. This variant is also known as p.Gly47Ala. ClinVar contains an entry for this variant (Variation ID: 13451). An algorithm developed to predict the effect of missense changes on protein structure and function (PolyPhen-2) suggests that this variant is likely to be disruptive. Variants that disrupt the consensus splice site are a relatively common cause of aberrant splicing (PMID: 17576681, 9536098). This variant disrupts the c.200G nucleotide in the TTR gene. Other variant(s) that disrupt this nucleotide have been determined to be pathogenic (PMID: 12000196, 20209591). This suggests that this nucleotide is clinically significant, and that variants that disrupt this position are likely to be disease-causing. For these reasons, this variant has been classified as Pathogenic.

Feb 15, 2017

Women's Health and Genetics/Laboratory Corporation of America, LabCorp

Significance: Pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

Variant summary: The TTR c.200G>C (p.Gly67Ala) variant involves the alteration of a conserved nucleotide. 3/4 in silico tools predict a damaging outcome for this substitution (SNPs&GO not captured due to low reliability index). This variant is absent in 121408 control chromosomes but was reported in several patients suggesting causality. Moreover, in at least two families the variant was observed to co-segregate with the disease further supporting a pathogenic outcome. Different variants affecting the same codon are listed in HGMD/ClinVar with a casual classification indicating the variant to be located in a mutational hotspot which supports the clinical relevance of the Gly67 residue. In addition, the p.Gly67Ala is found worldwide and has a high prevalence in German familial amyloid polyneuropathy patients (Niemietz_PlosOne_2016). Taken together, this variant is classified as pathogenic.

Apr 01, 2000

OMIM

Significance: Pathogenic

Review Status: no assertion criteria provided

Collection Method: literature only

not provided Pathogenic:1

Mar 31, 2016

Athena Diagnostics

Significance: Pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

Cardiovascular phenotype Pathogenic:1

Dec 29, 2021

Ambry Genetics

Significance: Pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

The p.G67A pathogenic mutation (also known as c.200G>C), located in coding exon 2 of the TTR gene, results from a G to C substitution at nucleotide position 200. The amino acid change results in glycine to alanine at codon 67, an amino acid with similar properties. This mutation, which is also known as p.G47A, was first reported in two unrelated Italian families with transthyretin (TTR) amyloidosis; both families presented with peripheral neuropathy and cardiomyopathy (Ferlini A et al. Hum. Mutat., 1994;4:61-4; Ferlini A et al. Clin. Genet., 2000 Apr;57:284-90). In a large cohort of families with TTR amyloidosis, this mutation was identified in 7 individuals from 2 unrelated families; 4 of these individuals had a mixed cardiac and neurologic phenotype and 3 of these individuals only had neurologic phenotype (Rapezzi C et al. Eur. Heart J., 2013 Feb;34:520-8). This variant is considered to be rare based on population cohorts in the Genome Aggregation Database (gnomAD). In addition, this alteration is predicted to be deleterious by BayesDel in silico analysis. Based on the supporting evidence, this alteration is interpreted as a disease-causing mutation.

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Benign	0.25
BayesDel_addAF	Pathogenic	0.46	D
BayesDel_noAF	Pathogenic	0.42
CADD	Pathogenic	32
DANN	Uncertain	1.0
DEOGEN2	Pathogenic	0.89	D;D;T;.
Eigen	Uncertain	0.61
Eigen_PC	Uncertain	0.57
FATHMM_MKL	Uncertain	0.90	D
LIST_S2	Benign	0.0	.;D;D;D
M_CAP	Pathogenic	0.50	D
MetaRNN	Pathogenic	0.97	D;D;D;D
MetaSVM	Pathogenic	0.98	D
MutationAssessor	Uncertain	2.2	M;M;.;.
PhyloP100		5.9
PrimateAI	Uncertain	0.53	T
PROVEAN	Benign	0.0	.;D;.;.
REVEL	Benign	0.0
Sift	Pathogenic	0.0	.;D;.;.
Sift4G	Pathogenic	0.0	.;T;D;D
Vest4		0.0
ClinPred		0.99	D
GERP RS		5.7
RBP_binding_hub_radar		0.0
RBP_regulation_power_radar		1.7
Varity_R		0.90
gMVP		0.95
Mutation Taster		=9/91	disease causing (ClinVar)

Splicing

Name	Calibrated prediction	Score	Prediction
dbscSNV1_ADA	Pathogenic	1.0
dbscSNV1_RF	Pathogenic	0.95
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: rs121918090; hg19: chr18-29172989;