chr1-161307292-C-G

Position:

• chr1-161307292-C-G

Variant summary

Our verdict is Likely pathogenic. Variant got 8 ACMG points: 8P and 0B. PM1 PM2 PP3_Moderate PP5_Moderate

The NM_000530.8(MPZ):​c.200G>C​(p.Arg67Pro) 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. R67H) has been classified as Uncertain significance.

• Frequency: Genomes: not found (cov: 32)
• Consequence: MPZ NM_000530.8 missense
• Clinical Significance: Likely pathogenic criteria provided, single submitter P:1 U:1
• Conservation: PhyloP100: 0.608

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]

MPZ (HGNC:):

ACMG classification

Verdict is Likely_pathogenic. Variant got 8 ACMG points.

• PM1: In a hotspot region, there are 8 aminoacids with missense pathogenic changes in the window of +-8 aminoacids around while only 1 benign, 12 uncertain in NM_000530.8
• PM2: Very rare variant in population databases, with high coverage
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.858
• PP5: Variant 1-161307292-C-G is Pathogenic according to our data. Variant chr1-161307292-C-G is described in ClinVar as [Likely_pathogenic]. Clinvar id is 637325.Status of the report is criteria_provided_single_submitter, 1 stars. Variant chr1-161307292-C-G is described in Lovd as [Pathogenic].

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
MPZ	NM_000530.8	c.200G>C	p.Arg67Pro	missense_variant	2/6	ENST00000533357.5	NP_000521.2
MPZ	NM_001315491.2	c.200G>C	p.Arg67Pro	missense_variant	2/6		NP_001302420.1
MPZ	XM_017001321.3	c.230G>C	p.Arg77Pro	missense_variant	2/6		XP_016856810.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
MPZ	ENST00000533357.5	c.200G>C	p.Arg67Pro	missense_variant	2/6	1	NM_000530.8	ENSP00000432943.1

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome Cov.: 32

GnomAD4 genome Cov.: 32

ClinVar

Significance: Likely pathogenic

Submissions summary: Pathogenic:1 Uncertain:1

Revision: criteria provided, single submitter

Submissions by phenotype

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

Likely pathogenic, criteria provided, single submitter

clinical testing

Labcorp Genetics (formerly Invitae), Labcorp

Nov 15, 2022

In summary, the currently available evidence indicates that the variant is pathogenic, but additional data are needed to prove that conclusively. Therefore, this variant has been classified as Likely Pathogenic. This variant disrupts the p.Arg67 amino acid residue in MPZ. Other variant(s) that disrupt this residue have been observed in individuals with MPZ-related conditions (Invitae), which suggests that this may be a clinically significant amino acid residue. 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: 637325). This missense change has been observed in individual(s) with autosomal dominant Charcot-Marie-Tooth disease (PMID: 15642860). It has also been observed to segregate with disease in related individuals. This variant is not present in population databases (gnomAD no frequency). This sequence change replaces arginine, which is basic and polar, with proline, which is neutral and non-polar, at codon 67 of the MPZ protein (p.Arg67Pro). -

Charcot-Marie-Tooth disease Uncertain:1

Uncertain significance, no assertion criteria provided

literature only

Inherited Neuropathy Consortium

-

- -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	1.0
BayesDel_addAF	Pathogenic	0.26	D
BayesDel_noAF	Pathogenic	0.14
CADD	Pathogenic	29
DANN	Uncertain	1.0
DEOGEN2	Benign	0.35	T
Eigen	Uncertain	0.41
Eigen_PC	Uncertain	0.42
FATHMM_MKL	Benign	0.58	D
LIST_S2	Uncertain	0.86	D
M_CAP	Benign	0.047	D
MetaRNN	Pathogenic	0.86	D
MetaSVM	Benign	-0.76	T
MutationAssessor	Benign	1.5	L
PrimateAI	Uncertain	0.60	T
PROVEAN	Benign	-1.7	N
REVEL	Uncertain	0.40
Sift	Benign	0.11	T
Sift4G	Benign	0.16	T
Polyphen		0.99	D
Vest4		0.88
MutPred		0.65		Gain of loop (P = 0.1069);
MVP		0.98
MPC		1.5
ClinPred		0.89	D
GERP RS		5.2
Varity_R		0.97
gMVP		0.99

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: rs201720099; hg19: chr1-161277082;