Genetic Variant MTTP:c.-149C>A (chr4-99564190-C-A) – ACMG Classification: Likely_benign (-2 pts)

Variant summary

Our verdict is Likely benign. Variant got -2 ACMG points: 2P and 4B. PM2BP4_Strong

The NM_000253.4(MTTP):c.-149C>A variant causes a 5 prime UTR change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.00000847 in 1,535,284 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a benign outcome for this variant. Variant has been reported in ClinVar as Uncertain significance (★).

Frequency

Genomes: 𝑓 0.0000066 ( 0 hom., cov: 32)

Exomes 𝑓: 0.0000087 ( 0 hom. )

Consequence

MTTP
NM_000253.4 5_prime_UTR

Scores

Clinical Significance

Uncertain significance criteria provided, single submitter P:1U:1

Conservation

PhyloP100: 0.0400

Variant links:

Genes affected

MTTP (HGNC:7467): (microsomal triglyceride transfer protein) MTP encodes the large subunit of the heterodimeric microsomal triglyceride transfer protein. Protein disulfide isomerase (PDI) completes the heterodimeric microsomal triglyceride transfer protein, which has been shown to play a central role in lipoprotein assembly. Mutations in MTP can cause abetalipoproteinemia. [provided by RefSeq, Jul 2008]

MTTP links:

TRMT10A (HGNC:28403): (tRNA methyltransferase 10A) This gene encodes a protein that belongs to the tRNA (Guanine-1)-methyltransferase family. A similar gene in yeast modifies several different tRNA species. Mutations in this gene are associated with microcephaly, short stature, and impaired glucose metabolism. Alternative splicing results in multiple transcript variants. [provided by RefSeq, Oct 2014]

TRMT10A links:

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ACMG classification

Classification made for transcript

Verdict is Likely_benign. Variant got -2 ACMG points.

PM2

Very rare variant in population databases, with high coverage;

BP4

Computational evidence support a benign effect (BayesDel_addAF=-0.525766).

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
TRMT10A	NM_001134665.3 link	c.-301G>T		upstream_gene_variant		ENST00000394876.7	NP_001128137.1	Q8TBZ6V9HVY8

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
TRMT10A	ENST00000394876.7 link	c.-301G>T		upstream_gene_variant		1	NM_001134665.3	ENSP00000378342.2		Q8TBZ6

Frequencies

GnomAD3 genomes

AF:

0.00000658

AC:

AN:

151924

Hom.:

Cov.:

show subpopulations

Gnomad AFR

AF:

0.00

Gnomad AMI

AF:

0.00

Gnomad AMR

AF:

0.00

Gnomad ASJ

AF:

0.00

Gnomad EAS

AF:

0.00

Gnomad SAS

AF:

0.00

Gnomad FIN

AF:

0.00

Gnomad MID

AF:

0.00

Gnomad NFE

AF:

0.0000147

Gnomad OTH

AF:

0.00

GnomAD3 exomes

AF:

0.0000306

AC:

AN:

130842

Hom.:

AF XY:

0.0000280

AC XY:

AN XY:

71428

show subpopulations

Gnomad AFR exome

AF:

0.00

Gnomad AMR exome

AF:

0.000123

Gnomad ASJ exome

AF:

0.00

Gnomad EAS exome

AF:

0.00

Gnomad SAS exome

AF:

0.00

Gnomad FIN exome

AF:

0.000186

Gnomad NFE exome

AF:

0.00

Gnomad OTH exome

AF:

0.00

GnomAD4 exome

AF:

0.00000867

AC:

AN:

1383360

Hom.:

Cov.:

AF XY:

0.0000132

AC XY:

AN XY:

682586

show subpopulations

Gnomad4 AFR exome

AF:

0.0000317

Gnomad4 AMR exome

AF:

0.0000560

Gnomad4 ASJ exome

AF:

0.00

Gnomad4 EAS exome

AF:

0.00

Gnomad4 SAS exome

AF:

0.00

Gnomad4 FIN exome

AF:

0.0000299

Gnomad4 NFE exome

AF:

0.00000556

Gnomad4 OTH exome

AF:

0.0000173

GnomAD4 genome

AF:

0.00000658

AC:

AN:

151924

Hom.:

Cov.:

AF XY:

0.00

AC XY:

AN XY:

74188

show subpopulations

Gnomad4 AFR

AF:

0.00

Gnomad4 AMR

AF:

0.00

Gnomad4 ASJ

AF:

0.00

Gnomad4 EAS

AF:

0.00

Gnomad4 SAS

AF:

0.00

Gnomad4 FIN

AF:

0.00

Gnomad4 NFE

AF:

0.0000147

Gnomad4 OTH

AF:

0.00

Bravo

AF:

0.00000378

ClinVar

Significance: Uncertain significance

Submissions summary: Pathogenic:1Uncertain:1

Revision: criteria provided, single submitter

LINK: link

Submissions by phenotype

Abetalipoproteinaemia

Pathogenic:1Uncertain:1

Department of Pathology and Laboratory Medicine, Sinai Health System

Significance: Likely pathogenic

Review Status: no assertion criteria provided

Collection Method: clinical testing

The MTTP p.Ser32* variant was not identified in the literature nor was it identified in Cosmic or LOVD 3.0. The variant was identified in dbSNP (ID: rs886058955) and ClinVar (classified as a VUS by Illumina for abetalipoproteinemia). The variant was also identified in control databases in 4 of 130842 chromosomes at a frequency of 0.000031 (Genome Aggregation Database Feb 27, 2017). The variant was observed in the following populations: European (Finnish) in 1 of 5388 chromosomes (freq: 0.000186) and Latino in 3 of 24356 chromosomes (freq: 0.000123); it was not observed in the African, Ashkenazi Jewish, East Asian, European (non-Finnish), Other or South Asian populations. The p.Ser32* variant leads to a premature stop codon at position 32 which may lead to a truncated or absent protein and loss of function. Loss of function variants of the MTTP gene are an established mechanism of disease in Abetalipoproteinemia and is the type of variant expected to cause the disorder when found in the homozygous or compound heterozygous state. In summary, based on the above information the clinical significance of this variant cannot be determined with certainty at this time although we would lean towards a more pathogenic role for this variant. This variant is classified as likely pathogenic. -

Jan 13, 2018

Illumina Laboratory Services, Illumina

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

This variant was observed in the ICSL laboratory as part of a predisposition screen in an ostensibly healthy population. It had not been previously curated by ICSL or reported in the Human Gene Mutation Database (HGMD: prior to June 1st, 2018), and was therefore a candidate for classification through an automated scoring system. Utilizing variant allele frequency, disease prevalence and penetrance estimates, and inheritance mode, an automated score was calculated to assess if this variant is too frequent to cause the disease. Based on the score, this variant could not be ruled out of causing disease and therefore its association with disease required further investigation. A literature search was performed for the gene, cDNA change, and amino acid change (if applicable). No publications were found based on this search. This variant was therefore classified as a variant of unknown significance for this disease. -

Computational scores

Source: dbNSFP v4.3

Name

Calibrated prediction

Score

Prediction

BayesDel_addAF

Benign

-0.53

BayesDel_noAF

Benign

-0.80

CADD

Benign

2.2

DANN

Benign

0.90

Eigen

Benign

-0.75

Eigen_PC

Benign

-0.93

FATHMM_MKL

Benign

0.0016

Vest4

0.32

GERP RS

-0.25

Splicing

Name

Calibrated prediction

Score

Prediction

SpliceAI score (max)

0.040

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

Below is the list of publications found by LitVar. It may be empty.

Variant summary

Frequency

Consequence

Scores

Clinical Significance

Conservation

ACMG classification

Transcripts

RefSeq

Ensembl

Frequencies

ClinVar

Submissions by phenotype

Computational scores

Splicing

Publications

LitVar

Other links and lift over