rs121913600

Positions:

• chr1-161306848-C-T

Variant summary

Our verdict is Pathogenic. Variant got 11 ACMG points: 11P and 0B. PM1 PM2 PM5 PP3_Strong PP5

The NM_000530.8(MPZ):​c.308G>A​(p.Gly103Glu) variant causes a missense change. 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 Conflicting classifications of pathogenicity (no stars). Another variant affecting the same amino acid position, but resulting in a different missense (i.e. G103A) has been classified as Likely pathogenic.

• Frequency: Genomes: not found (cov: 29)
• Consequence: MPZ NM_000530.8 missense
• Clinical Significance: Conflicting classifications of pathogenicity criteria provided, conflicting classifications P:3 U:1
• Conservation: PhyloP100: 7.17

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 11 ACMG points.

• PM1: In a disulfide_bond (size 77) in uniprot entity MYP0_HUMAN there are 81 pathogenic changes around while only 1 benign (99%) 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 chr1-161306848-C-G is described in Lovd as [Likely_pathogenic].
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.989
• PP5: Variant 1-161306848-C-T is Pathogenic according to our data. Variant chr1-161306848-C-T is described in ClinVar as [Conflicting_classifications_of_pathogenicity]. Clinvar id is 14187.We mark this variant Likely_pathogenic, oryginal submissions are: {Uncertain_significance=1, Pathogenic=2}. Variant chr1-161306848-C-T is described in Lovd as [Pathogenic].

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
MPZ	NM_000530.8	c.308G>A	p.Gly103Glu	missense_variant	3/6	ENST00000533357.5	NP_000521.2
MPZ	NM_001315491.2	c.308G>A	p.Gly103Glu	missense_variant	3/6		NP_001302420.1
MPZ	XM_017001321.3	c.338G>A	p.Gly113Glu	missense_variant	3/6		XP_016856810.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
MPZ	ENST00000533357.5	c.308G>A	p.Gly103Glu	missense_variant	3/6	1	NM_000530.8	ENSP00000432943	P1

Frequencies

GnomAD3 genomes Cov.: 29

GnomAD4 exome Cov.: 34

GnomAD4 genome Cov.: 29

ClinVar

Significance: Conflicting classifications of pathogenicity

Submissions summary: Pathogenic:3 Uncertain:1

Revision: criteria provided, conflicting classifications

Submissions by phenotype

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

Pathogenic, no assertion criteria provided

literature only

OMIM

Jul 10, 2001

- -

not provided Pathogenic:1

Pathogenic, criteria provided, single submitter

clinical testing

GeneDx

Jan 04, 2022

Reported previously in two sisters with severe CMT1 neuropathy; this variant was inherited from a mother who was mosaic for the G103E variant (Fabrizi et al., 2001); Published functional studies demonstrate that the unfolded protein response (UPR) and endoplasmic reticulum (ER) retention was significantly increased in the G103E variant when compared to wild type (Bai et al., 2018); Not observed at significant frequency in large population cohorts (gnomAD); Missense variants in this gene are often considered pathogenic (HGMD); In silico analysis supports that this missense variant has a deleterious effect on protein structure/function; This variant is associated with the following publications: (PMID: 26310628, 20461396, 20456450, 28063088, 11445635, 29687021, 30076350, 24077912, 28902413) -

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

Pathogenic, criteria provided, single submitter

clinical testing

Labcorp Genetics (formerly Invitae), Labcorp

Oct 05, 2022

This missense change has been observed in individual(s) with Charcot-Marie-Tooth disease (PMID: 11445635; Invitae). In at least one individual the variant was observed to be de novo. For these reasons, this variant has been classified as Pathogenic. This variant disrupts the p.Gly103 amino acid residue in MPZ. Other variant(s) that disrupt this residue have been observed in individuals with MPZ-related conditions (PMID: 20456450), which suggests that this may be a clinically significant amino acid residue. Experimental studies have shown that this missense change affects MPZ function (PMID: 29687021). 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 expected to disrupt MPZ protein function. ClinVar contains an entry for this variant (Variation ID: 14187). This variant is not present in population databases (gnomAD no frequency). This sequence change replaces glycine, which is neutral and non-polar, with glutamic acid, which is acidic and polar, at codon 103 of the MPZ protein (p.Gly103Glu). -

Inborn genetic diseases Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Ambry Genetics

Oct 08, 2021

The p.G103E variant (also known as c.308G>A), located in coding exon 3 of the MPZ gene, results from a G to A substitution at nucleotide position 308. The glycine at codon 103 is replaced by glutamic acid, an amino acid with similar properties. This variant was detected in two siblings with Charcot-Marie-Tooth disease type 1 (CMT1), whose mother was also mosaic for the variant (Fabrizi GM et al. Neurology, 2001 Jul;57:101-5). This variant was also detected in an individual with Charcot-Marie-Tooth disease, type 1B (CMT1B); however, clinical details were limited (Sanmaneechai O et al. Brain, 2015 Nov;138:3180-92). Functional studies revealed this alteration led to abnormal accumulation in the ER and activation of the UPR (Bai Y et al. Ann Clin Transl Neurol, 2018 Apr;5:445-455). This amino acid position is highly conserved in available vertebrate species. In addition, this alteration is predicted to be deleterious by in silico analysis. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	1.0
BayesDel_addAF	Pathogenic	0.36	D
BayesDel_noAF	Pathogenic	0.27
CADD	Pathogenic	29
DANN	Uncertain	1.0
DEOGEN2	Uncertain	0.69	D
Eigen	Pathogenic	0.83
Eigen_PC	Pathogenic	0.75
FATHMM_MKL	Uncertain	0.94	D
LIST_S2	Benign	0.78	T
M_CAP	Uncertain	0.15	D
MetaRNN	Pathogenic	0.99	D
MetaSVM	Uncertain	0.0023	D
MutationAssessor	Pathogenic	3.0	M
MutationTaster	Benign	1.0	A;A;A;A
PrimateAI	Uncertain	0.63	T
PROVEAN	Pathogenic	-7.5	D
REVEL	Pathogenic	0.67
Sift	Uncertain	0.0020	D
Sift4G	Uncertain	0.015	D
Polyphen		1.0	D
Vest4		0.99
MutPred		0.92		Gain of ubiquitination at K108 (P = 0.0918);
MVP		0.96
MPC		1.7
ClinPred		1.0	D
GERP RS		4.7
RBP_binding_hub_radar		0.0
RBP_regulation_power_radar		1.7
Varity_R		0.95
gMVP		0.98

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: rs121913600; hg19: chr1-161276638;