chr18-31595145-C-A

Variant names:

• chr18-31595145-C-A
• NM_000371.4:c.226C>A

Variant summary

Our verdict is Likely pathogenic. Variant got 6 ACMG points: 6P and 0B. PM1 PM2 PM5

The NM_000371.4(TTR):​c.226C>A​(p.His76Asn) variant causes a missense change. The variant allele was found at a frequency of 0.000000684 in 1,461,868 control chromosomes in the GnomAD database, with no homozygous occurrence. No clinical diagnostic laboratories have submitted clinical-significance assessments for this variant to ClinVar. Another variant affecting the same amino acid position, but resulting in a different missense (i.e. H76R) has been classified as Pathogenic.

• Frequency:
  • Genomes: not found (cov: 32)
  • Exomes 𝑓: 6.8e-7 (0 hom.)
• Consequence: TTR NM_000371.4 missense
• Clinical Significance: Not reported in ClinVar
• Conservation: PhyloP100: 5.98

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 Likely_pathogenic. Variant got 6 ACMG points.

• PM1: In a chain Transthyretin (size 126) in uniprot entity TTHY_HUMAN there are 141 pathogenic changes around while only 6 benign (96%) 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 chr18-31595146-A-G is described in Lovd as [Pathogenic].

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
TTR	NM_000371.4	c.226C>A	p.His76Asn	missense_variant	Exon 3 of 4	ENST00000237014.8	NP_000362.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
TTR	ENST00000237014.8	c.226C>A	p.His76Asn	missense_variant	Exon 3 of 4	1	NM_000371.4	ENSP00000237014.4
TTR	ENST00000649620.1	c.226C>A	p.His76Asn	missense_variant	Exon 5 of 6			ENSP00000497927.1
TTR	ENST00000610404.5	c.130C>A	p.His44Asn	missense_variant	Exon 3 of 4	5		ENSP00000477599.2
TTR	ENST00000541025.2	n.252C>A		non_coding_transcript_exon_variant	Exon 3 of 3	2

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome AF: 6.84e-7 AC: 1 AN: 1461868 Hom.: 0 Cov.: 31 AF XY: 0.00000138 AC XY: 1 AN XY: 727234

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

Not reported in ClinVar

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Benign	0.27
BayesDel_addAF	Pathogenic	0.20	D
BayesDel_noAF	Uncertain	0.050
CADD	Uncertain	25
DANN	Uncertain	0.99
DEOGEN2	Pathogenic	0.85	D;D;T;.
Eigen	Uncertain	0.67
Eigen_PC	Uncertain	0.63
FATHMM_MKL	Uncertain	0.96	D
LIST_S2	Benign	0.85	.;D;T;D
M_CAP	Uncertain	0.26	D
MetaRNN	Uncertain	0.74	D;D;D;D
MetaSVM	Pathogenic	0.87	D
MutationAssessor	Uncertain	2.2	M;M;.;.
PrimateAI	Uncertain	0.57	T
PROVEAN	Uncertain	-3.0	.;D;.;.
REVEL	Pathogenic	0.68
Sift	Benign	0.28	.;T;.;.
Sift4G	Benign	0.30	.;T;T;T
Polyphen		0.98	D;D;.;.
Vest4		0.69, 0.66, 0.66
MutPred		0.50		Loss of disorder (P = 0.1569);Loss of disorder (P = 0.1569);Loss of disorder (P = 0.1569);Loss of disorder (P = 0.1569);
MVP		1.0
MPC		1.4
ClinPred		0.86	D
GERP RS		5.5
Varity_R		0.76
gMVP		0.92

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: chr18-29175108;