1-161307389-C-A

Position:

• chr1-161307389-C-A

Variant summary

Our verdict is Pathogenic. Variant got 16 ACMG points: 16P and 0B. PM1 PM2 PM5 PP3_Moderate PP5_Very_Strong

The NM_000530.8(MPZ):​c.103G>T​(p.Asp35Tyr) variant causes a missense change involving the alteration of a non-conserved nucleotide. The variant was absent in control chromosomes in GnomAD project. In-silico tool predicts a pathogenic outcome for this variant. Variant has been reported in ClinVar as Likely pathogenic (★★). Another variant affecting the same amino acid position, but resulting in a different missense (i.e. D35E) has been classified as Uncertain significance.

• Frequency: Genomes: not found (cov: 32)
• Consequence: MPZ NM_000530.8 missense
• Clinical Significance: Pathogenic/Likely pathogenic criteria provided, multiple submitters, no conflicts P:4
• Conservation: PhyloP100: 3.36

Genes affected

MPZ (HGNC:7225): (myelin protein zero) This gene is specifically expressed in Schwann cells of the peripheral nervous system and encodes a type I transmembrane glycoprotein that is a major structural protein of the peripheral myelin sheath. The encoded protein contains a large hydrophobic extracellular domain and a smaller basic intracellular domain, which are essential for the formation and stabilization of the multilamellar structure of the compact myelin. Mutations in this gene are associated with autosomal dominant form of Charcot-Marie-Tooth disease type 1 (CMT1B) and other polyneuropathies, such as Dejerine-Sottas syndrome (DSS) and congenital hypomyelinating neuropathy (CHN). A recent study showed that two isoforms are produced from the same mRNA by use of alternative in-frame translation termination codons via a stop codon readthrough mechanism. [provided by RefSeq, Oct 2015]

ACMG classification

Verdict is Pathogenic. Variant got 16 ACMG points.

• PM1: In a hotspot region, there are 6 aminoacids with missense pathogenic changes in the window of +-8 aminoacids around while only 0 benign, 14 uncertain in NM_000530.8
• PM2: Very rare variant in population databases, with high coverage
• PM5: Other missense variant is known to change same aminoacid residue: Variant chr1-161307389-C-T is described in ClinVar as [Pathogenic]. Clinvar id is 462790.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars.
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.888
• PP5: Variant 1-161307389-C-A is Pathogenic according to our data. Variant chr1-161307389-C-A is described in ClinVar as [Likely_pathogenic]. Clinvar id is 14183.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars. Variant chr1-161307389-C-A is described in Lovd as [Pathogenic].

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
MPZ	NM_000530.8	c.103G>T	p.Asp35Tyr	missense_variant	2/6	ENST00000533357.5
MPZ	NM_001315491.2	c.103G>T	p.Asp35Tyr	missense_variant	2/6
MPZ	XM_017001321.3	c.133G>T	p.Asp45Tyr	missense_variant	2/6

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
MPZ	ENST00000533357.5	c.103G>T	p.Asp35Tyr	missense_variant	2/6	1	NM_000530.8	P1

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome Cov.: 32

GnomAD4 genome Cov.: 32

ClinVar

Significance: Pathogenic/Likely pathogenic

Submissions summary: Pathogenic:4

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

Charcot-Marie-Tooth disease Pathogenic:1

Likely pathogenic, criteria provided, single submitter

clinical testing

Molecular Genetics Laboratory, London Health Sciences Centre

-

- -

not provided Pathogenic:1

Likely pathogenic, criteria provided, single submitter

clinical testing

GeneDx

Apr 06, 2021

Reported previously in a Japanese CMT registry; however, no further information is available (Hattori et al., 2003); Missense variants in this gene are often considered pathogenic (Stenson et al., 2014); In silico analysis supports that this missense variant has a deleterious effect on protein structure/function; Not observed in large population cohorts (Lek et al., 2016); This variant is associated with the following publications: (PMID: 32376792, 33179255, 12477701, 26406915, 10406984) -

Charcot-Marie-Tooth disease dominant intermediate D Pathogenic:1

Pathogenic, no assertion criteria provided

literature only

OMIM

Aug 01, 1999

- -

Charcot-Marie-Tooth disease, type I Pathogenic:1

Pathogenic, criteria provided, single submitter

clinical testing

Labcorp Genetics (formerly Invitae), Labcorp

Apr 22, 2023

This variant is not present in population databases (gnomAD no frequency). This sequence change replaces aspartic acid, which is acidic and polar, with tyrosine, which is neutral and polar, at codon 35 of the MPZ protein (p.Asp35Tyr). This missense change has been observed in individual(s) with clinical features of Charcot-Marie-Tooth disease (PMID: 10406984, 32376792). It has also been observed to segregate with disease in related individuals. For these reasons, this variant has been classified as Pathogenic. Experimental studies have shown that this missense change affects MPZ function (PMID: 26406915). Advanced modeling of protein sequence and biophysical properties (such as structural, functional, and spatial information, amino acid conservation, physicochemical variation, residue mobility, and thermodynamic stability) performed at Invitae indicates that this missense variant is not expected to disrupt MPZ protein function. ClinVar contains an entry for this variant (Variation ID: 14183). This variant is also known as Asp6Tyr. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	0.57
BayesDel_addAF	Pathogenic	0.40	D
BayesDel_noAF	Pathogenic	0.33
CADD	Pathogenic	29
DANN	Uncertain	0.99
DEOGEN2	Uncertain	0.57	D
Eigen	Uncertain	0.59
Eigen_PC	Uncertain	0.59
FATHMM_MKL	Uncertain	0.82	D
LIST_S2	Uncertain	0.90	D
M_CAP	Uncertain	0.25	D
MetaRNN	Pathogenic	0.89	D
MetaSVM	Pathogenic	0.81	D
MutationAssessor	Uncertain	2.1	M
MutationTaster	Benign	1.0	A;A;A;A
PrimateAI	Uncertain	0.63	T
PROVEAN	Uncertain	-3.7	D
REVEL	Pathogenic	0.80
Sift	Benign	0.070	T
Sift4G	Uncertain	0.044	D
Polyphen		0.99	D
Vest4		0.85
MutPred		0.62		Loss of loop (P = 0.1242);
MVP		0.94
MPC		1.2
ClinPred		0.99	D
GERP RS		5.3
RBP_binding_hub_radar		0.0
RBP_regulation_power_radar		1.7
Varity_R		0.85
gMVP		0.92

Splicing

Name	Calibrated prediction	Score	Prediction
SpliceAI score (max)		0.060		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: rs121913596; hg19: chr1-161277179;