rs121913587

Positions:

• chr1-161306752-A-G

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.404T>C​(p.Ile135Thr) variant causes a missense change involving the alteration of a 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. I135M) has been classified as Uncertain significance.

• Frequency: Genomes: not found (cov: 29)
• Consequence: MPZ NM_000530.8 missense
• Clinical Significance: Pathogenic/Likely pathogenic criteria provided, multiple submitters, no conflicts P:3
• Conservation: PhyloP100: 8.37

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 12 aminoacids with missense pathogenic changes in the window of +-8 aminoacids around while only 0 benign, 15 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 chr1-161306753-T-A is described in ClinVar as [Likely_pathogenic]. Clinvar id is 861910.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars.
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.849
• PP5: Variant 1-161306752-A-G is Pathogenic according to our data. Variant chr1-161306752-A-G is described in ClinVar as [Likely_pathogenic]. Clinvar id is 14172.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars. Variant chr1-161306752-A-G is described in Lovd as [Pathogenic].

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
MPZ	NM_000530.8	c.404T>C	p.Ile135Thr	missense_variant	3/6	ENST00000533357.5
MPZ	NM_001315491.2	c.404T>C	p.Ile135Thr	missense_variant	3/6
MPZ	XM_017001321.3	c.434T>C	p.Ile145Thr	missense_variant	3/6

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
MPZ	ENST00000533357.5	c.404T>C	p.Ile135Thr	missense_variant	3/6	1	NM_000530.8	P1

Frequencies

GnomAD3 genomes Cov.: 29

GnomAD4 exome Cov.: 34

GnomAD4 genome Cov.: 29

ClinVar

Significance: Pathogenic/Likely pathogenic

Submissions summary: Pathogenic:3

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

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

Pathogenic, no assertion criteria provided

literature only

OMIM

Jan 01, 1996

- -

Dejerine-Sottas disease Pathogenic:1

Likely pathogenic, criteria provided, single submitter

clinical testing

3billion

Jan 03, 2022

Same nucleotide change resulting in same amino acid change has been previously reported as pathogenic (ClinVar ID: VCV000014172, PMID:8664899, PS1). The variant has been previously reported as assumed (i.e. paternity and maternity not confirmed) de novo in at least one similarly affected unrelated individual (PMID_8664899, PM6_M). A different missense change at the same codon has been reported as pathogenic/likely pathogenic with strong evidence (ClinVar ID: VCV000861910, PMID:8797476,22018721,30340945, PM5_M). A missense variant is a common mechanism associated with Dejerine-Sottas disease (PP2_P). It is not observed in the gnomAD v2.1.1 dataset (PM2_M).Therefore, this variant is classified as pathogenic according to the recommendation of ACMG/AMP guideline. -

not provided Pathogenic:1

Pathogenic, criteria provided, single submitter

clinical testing

GeneDx

Dec 13, 2021

Not observed at significant frequency in large population cohorts (Lek et al., 2016); 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; This variant is associated with the following publications: (PMID: 29627640, 21107784, 9055797, 10737979, 29687021, 32959227, 33179255, 8664899, 26310628, 20461396) -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	0.95
BayesDel_addAF	Pathogenic	0.34	D
BayesDel_noAF	Pathogenic	0.25
CADD	Pathogenic	32
DANN	Uncertain	1.0
DEOGEN2	Uncertain	0.62	D
Eigen	Uncertain	0.42
Eigen_PC	Uncertain	0.49
FATHMM_MKL	Pathogenic	0.97	D
LIST_S2	Uncertain	0.88	D
M_CAP	Benign	0.026	D
MetaRNN	Pathogenic	0.85	D
MetaSVM	Benign	-0.86	T
MutationAssessor	Benign	2.0	M
MutationTaster	Benign	1.0	A;A;A;A
PrimateAI	Uncertain	0.75	T
PROVEAN	Uncertain	-3.8	D
REVEL	Uncertain	0.55
Sift	Uncertain	0.0010	D
Sift4G	Uncertain	0.0050	D
Polyphen		0.75	P
Vest4		0.85
MutPred		0.57		Gain of disorder (P = 0.0061);
MVP		0.82
MPC		1.1
ClinPred		1.0	D
GERP RS		4.9
RBP_binding_hub_radar		0.0
RBP_regulation_power_radar		1.7
Varity_R		0.89
gMVP		0.97

Splicing

Name	Calibrated prediction	Score	Prediction
SpliceAI score (max)		0.080		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: rs121913587; hg19: chr1-161276542;