chr1-161306759-G-T

Position:

• chr1-161306759-G-T

Variant summary

Our verdict is Pathogenic. Variant got 18 ACMG points: 18P and 0B. PM1 PM2 PM5 PP3_Strong PP5_Very_Strong

The ENST00000533357.5(MPZ):​c.397C>A​(p.Pro133Thr) 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. P133R) has been classified as Likely pathogenic.

• Frequency: Genomes: not found (cov: 29)
• Consequence: MPZ ENST00000533357.5 missense
• Clinical Significance: Pathogenic/Likely pathogenic criteria provided, multiple submitters, no conflicts P:2
• Conservation: PhyloP100: 9.01

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 18 ACMG points.

• PM1: In a hotspot region, there are 11 aminoacids with missense pathogenic changes in the window of +-8 aminoacids around while only 0 benign, 16 uncertain in ENST00000533357.5
• PM2: Very rare variant in population databases, with high coverage
• PM5: Other missense variant is known to change same aminoacid residue: Variant chr1-161306758-G-C is described in ClinVar as [Likely_pathogenic]. Clinvar id is 572034.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars.
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.966
• PP5: Variant 1-161306759-G-T is Pathogenic according to our data. Variant chr1-161306759-G-T is described in ClinVar as [Likely_pathogenic]. Clinvar id is 462797.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
MPZ	NM_000530.8	c.397C>A	p.Pro133Thr	missense_variant	3/6	ENST00000533357.5	NP_000521.2
MPZ	NM_001315491.2	c.397C>A	p.Pro133Thr	missense_variant	3/6		NP_001302420.1
MPZ	XM_017001321.3	c.427C>A	p.Pro143Thr	missense_variant	3/6		XP_016856810.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
MPZ	ENST00000533357.5	c.397C>A	p.Pro133Thr	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: Pathogenic/Likely pathogenic

Submissions summary: Pathogenic:2

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

Dejerine-Sottas disease;C0205713:Roussy-Lévy syndrome;C0270912:Charcot-Marie-Tooth disease type 1B;C1843075:Charcot-Marie-Tooth disease dominant intermediate D;C1843153:Charcot-Marie-Tooth disease type 2J;C3888087:Charcot-Marie-Tooth disease type 2I;C4721436:Charcot-Marie-Tooth disease type 4E Pathogenic:1

Likely pathogenic, criteria provided, single submitter

clinical testing

Fulgent Genetics, Fulgent Genetics

Oct 31, 2018

- -

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

Pathogenic, criteria provided, single submitter

clinical testing

Labcorp Genetics (formerly Invitae), Labcorp

Jul 05, 2022

This sequence change replaces proline, which is neutral and non-polar, with threonine, which is neutral and polar, at codon 133 of the MPZ protein (p.Pro133Thr). This variant is not present in population databases (gnomAD no frequency). For these reasons, this variant has been classified as Pathogenic. This variant disrupts the p.Pro133 amino acid residue in MPZ. Other variant(s) that disrupt this residue have been observed in individuals with MPZ-related conditions (PMID: 22433810, 26310628), which suggests that this may be a clinically significant amino acid residue. Algorithms developed to predict the effect of missense changes on protein structure and function (SIFT, PolyPhen-2, Align-GVGD) all suggest that this variant is likely to be disruptive. ClinVar contains an entry for this variant (Variation ID: 462797). This missense change has been observed in individual(s) with Charcot-Marie-Tooth disease (Invitae). In at least one individual the variant was observed to be de novo. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	0.99
BayesDel_addAF	Pathogenic	0.31	D
BayesDel_noAF	Pathogenic	0.21
CADD	Pathogenic	32
DANN	Uncertain	1.0
DEOGEN2	Uncertain	0.69	D
Eigen	Pathogenic	0.87
Eigen_PC	Pathogenic	0.81
FATHMM_MKL	Uncertain	0.96	D
LIST_S2	Uncertain	0.91	D
M_CAP	Pathogenic	0.29	D
MetaRNN	Pathogenic	0.97	D
MetaSVM	Pathogenic	1.0	D
MutationAssessor	Pathogenic	2.9	M
MutationTaster	Benign	1.0	D;D;D;D
PrimateAI	Uncertain	0.76	T
PROVEAN	Pathogenic	-7.2	D
REVEL	Pathogenic	0.75
Sift	Pathogenic	0.0	D
Sift4G	Pathogenic	0.0	D
Polyphen		0.98	D
Vest4		0.81
MutPred		0.85		Loss of catalytic residue at P132 (P = 0.0452);
MVP		0.92
MPC		1.6
ClinPred		1.0	D
GERP RS		4.8
Varity_R		0.92
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: rs1553259648; hg19: chr1-161276549;