rs797044845

chr1-161307311-C-T

Variant summary

Our verdict is Pathogenic. Variant got 15 ACMG points: 15P and 0B. PM1 PM2 PM5 PP3 PP5_Very_Strong

The NM_000530.8(MPZ):c.181G>A(p.Asp61Asn) 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 Pathogenic (★★). Another variant affecting the same amino acid position, but resulting in a different missense (i.e. D61G) has been classified as Likely pathogenic.

• Frequency: Genomes: not found (cov: 32)
• Consequence: MPZ NM_000530.8 missense
• Clinical Significance: Pathogenic criteria provided, multiple submitters, no conflicts P:2 U:1 O:1
• Conservation: PhyloP100: 3.39

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 15 ACMG points.

• PM1: In a hotspot region, there are 10 aminoacids with missense pathogenic changes in the window of +-8 aminoacids around while only 0 benign, 11 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 chr1-161307310-T-C is described in ClinVar as [Likely_pathogenic]. Clinvar id is 188168.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars.
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.76
• PP5: Variant 1-161307311-C-T is Pathogenic according to our data. Variant chr1-161307311-C-T is described in ClinVar as [Pathogenic]. Clinvar id is 208146.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars. Variant chr1-161307311-C-T is described in Lovd as [Pathogenic].

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
MPZ	NM_000530.8	c.181G>A	p.Asp61Asn	missense_variant	2/6	ENST00000533357.5
MPZ	NM_001315491.2	c.181G>A	p.Asp61Asn	missense_variant	2/6
MPZ	XM_017001321.3	c.211G>A	p.Asp71Asn	missense_variant	2/6

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
MPZ	ENST00000533357.5	c.181G>A	p.Asp61Asn	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

Submissions summary: Pathogenic:2 Uncertain:1 Other:1

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

not provided Pathogenic:1

Pathogenic, criteria provided, single submitter

clinical testing

Athena Diagnostics

Mar 22, 2019

Not found in the total gnomAD dataset, and the data is high quality (0/282678 chr). Found in at least one symptomatic patient. Predicted to have a damaging effect on the protein. Located in potentially critical domain of the protein. Damaging to protein function(s) relevant to disease mechanism. One de novo case without parental identity confirmed. -

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

Pathogenic, criteria provided, single submitter

clinical testing

Invitae

May 10, 2019

This sequence change replaces aspartic acid with asparagine at codon 61 of the MPZ protein (p.Asp61Asn). The aspartic acid residue is highly conserved and there is a small physicochemical difference between aspartic acid and asparagine. This variant is not present in population databases (ExAC no frequency). For these reasons, this variant has been classified as Pathogenic. A different missense substitution at this codon (p.Asp61Gly) has been determined to be pathogenic (PMID: 10764043). This suggests that the aspartic acid residue is critical for MPZ protein function and that other missense substitutions at this position may also be pathogenic. Experimental studies have shown that this missense change results in increased glycosylation of the MPZ protein and impairs intracellular trafficking (PMID: 22451207). This variant has been reported to be de novo in an individual affected with congenital hypomyelinating neuropathy (PMID: 23290023). This variant has also been reported in individuals affected with Charcot-Marie-Tooth disease (PMID: 22451207, 11484669). ClinVar contains an entry for this variant (Variation ID: 208146). -

Charcot-Marie-Tooth disease Uncertain:1

Uncertain significance, no assertion criteria provided

literature only

Inherited Neuropathy Consortium

-

- -

Charcot-Marie-Tooth disease type 1B Other:1

not provided, no classification provided

literature only

GeneReviews

-

- -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	0.57
BayesDel_addAF	Benign	-0.15	T
BayesDel_noAF	Benign	-0.45
Cadd	Pathogenic	31
Dann	Uncertain	1.0
DEOGEN2	Benign	0.18	T
Eigen	Uncertain	0.48
Eigen_PC	Uncertain	0.53
FATHMM_MKL	Uncertain	0.89	D
LIST_S2	Uncertain	0.89	D
M_CAP	Benign	0.026	D
MetaRNN	Pathogenic	0.76	D
MetaSVM	Benign	-0.88	T
MutationAssessor	Benign	1.3	L
MutationTaster	Benign	1.0	D;D;D;D
PrimateAI	Uncertain	0.78	T
PROVEAN	Benign	-0.62	N
REVEL	Benign	0.20
Sift	Benign	0.099	T
Sift4G	Benign	0.44	T
Polyphen		1.0	D
Vest4		0.86
MutPred		0.34		Loss of catalytic residue at D61 (P = 0.1169);
MVP		0.83
MPC		1.0
ClinPred		0.84	D
GERP RS		5.3
Varity_R		0.42
gMVP		0.96

Splicing

Name	Calibrated prediction	Score	Prediction
SpliceAI score (max)		0.010		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: rs797044845; hg19: chr1-161277101; COSMIC: COSV60668161; COSMIC: COSV60668161;