18-31591927-C-T

Variant summary

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

The NM_000371.4(TTR):c.25C>T(p.Leu9Phe) variant causes a missense change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.000015 in 1,461,880 control chromosomes in the GnomAD database, with no homozygous occurrence. Variant has been reported in ClinVar as Uncertain significance (★★).

• Frequency:
  • Genomes: not found (cov: 32)
  • Exomes 𝑓: 0.000015 (0 hom.)
• Consequence: TTR NM_000371.4 missense
• Clinical Significance: Uncertain significance criteria provided, multiple submitters, no conflicts U:2
• Conservation: PhyloP100: 0.572

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 0 ACMG points.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
TTR	NM_000371.4	c.25C>T	p.Leu9Phe	missense_variant	1/4	ENST00000237014.8

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
TTR	ENST00000237014.8	c.25C>T	p.Leu9Phe	missense_variant	1/4	1	NM_000371.4	P1

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD3 exomes AF: 0.0000119 AC: 3 AN: 251434 Hom.: 0 AF XY: 0.00000736 AC XY: 1 AN XY: 135882

Gnomad AFR exome AF: 0.00

Gnomad AMR exome AF: 0.0000289

Gnomad ASJ exome AF: 0.00

Gnomad EAS exome AF: 0.00

Gnomad SAS exome AF: 0.00

Gnomad FIN exome AF: 0.00

Gnomad NFE exome AF: 0.00000879

Gnomad OTH exome AF: 0.000163

GnomAD4 exome AF: 0.0000150 AC: 22 AN: 1461880 Hom.: 0 Cov.: 30 AF XY: 0.00000688 AC XY: 5 AN XY: 727240

Gnomad4 AFR exome AF: 0.00

Gnomad4 AMR exome AF: 0.0000447

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: 0.0000171

Gnomad4 OTH exome AF: 0.0000166

GnomAD4 genome Cov.: 32

Bravo AF: 0.0000113

ExAC AF: 0.00000824 AC: 1

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:2

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

not provided Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

GeneDx

Apr 21, 2015

The L9F variant has not been published as a pathogenic mutation, nor has it been reported as a benign polymorphism to our knowledge. The L9F variant 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. In silico analysis predicts this variant is probably damaging to the protein structure/function. However, the L9F variant is a conservative amino acid substitution, which is not likely to impact secondary protein structure as these residues share similar properties. Additionally, no missense mutations in nearby residues have been reported in the Human Gene Mutation Database in association with amyloidosis (Stenson et al., 2014), suggesting this region of the protein may be tolerant of change. -

Familial amyloid neuropathy Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Invitae

Dec 06, 2017

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 do not agree on the potential impact of this missense change (SIFT: "Tolerated"; PolyPhen-2: "Possibly Damaging"; Align-GVGD: "Class C0"). This variant has not been reported in the literature in individuals with TTR-related disease. ClinVar contains an entry for this variant (Variation ID: 245725). This variant is present in population databases (rs762243340, ExAC 0.001%). This sequence change replaces leucine with phenylalanine at codon 9 of the TTR protein (p.Leu9Phe). The leucine residue is moderately conserved and there is a small physicochemical difference between leucine and phenylalanine. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Benign	0.075
BayesDel_addAF	Pathogenic	0.17	D
BayesDel_noAF	Uncertain	0.010
Cadd	Benign	21
Dann	Uncertain	1.0
DEOGEN2	Uncertain	0.44	T;T;T;.
Eigen	Uncertain	0.30
Eigen_PC	Benign	0.21
FATHMM_MKL	Benign	0.63	D
M_CAP	Pathogenic	0.32	D
MetaRNN	Uncertain	0.56	D;D;D;D
MetaSVM	Pathogenic	0.94	D
MutationAssessor	Pathogenic	3.0	M;M;.;.
MutationTaster	Benign	0.98	D
PrimateAI	Benign	0.37	T
Polyphen		0.96	D;D;.;.
Vest4		0.23, 0.34, 0.32
MutPred		0.29		Loss of loop (P = 0.1242);Loss of loop (P = 0.1242);Loss of loop (P = 0.1242);Loss of loop (P = 0.1242);
MVP		0.94
MPC		1.1
ClinPred		0.92	D
GERP RS		4.0
Varity_R		0.12
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

LitVar

Other links and lift over

dbSNP: rs762243340; hg19: chr18-29171890;