rs864622732

chr1-161307386-T-Achr1-161307386-T-C

Variant summary

Our verdict is Pathogenic. Variant got 14 ACMG points: 14P and 0B. PM1 PM2 PM5 PP5_Very_Strong

The NM_000530.8(MPZ):c.106A>T(p.Arg36Trp) variant causes a missense change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.000000684 in 1,461,892 control chromosomes in the GnomAD database, with no homozygous occurrence. Variant has been reported in ClinVar as Pathogenic (★★). Another variant affecting the same amino acid position, but resulting in a different missense (i.e. R36G) has been classified as Likely pathogenic.

• Frequency:
  • Genomes: not found (cov: 32)
  • Exomes 𝑓: 6.8e-7 (0 hom.)
• Consequence: MPZ NM_000530.8 missense
• Clinical Significance: Pathogenic criteria provided, multiple submitters, no conflicts P:4 U:1
• Conservation: PhyloP100: 3.49

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 14 ACMG points.

• PM1: In a hotspot region, there are 6 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
• PM5: Other missense variant is known to change same aminoacid residue: Variant chr1-161307386-T-C is described in ClinVar as [Conflicting_classifications_of_pathogenicity]. Clinvar id is 420151.We mark this variant Likely_pathogenic, oryginal submissions are: {Likely_pathogenic=1, Uncertain_significance=1}.
• PP5: Variant 1-161307386-T-A is Pathogenic according to our data. Variant chr1-161307386-T-A is described in ClinVar as [Pathogenic]. Clinvar id is 221065.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars. Variant chr1-161307386-T-A is described in Lovd as [Pathogenic].

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
MPZ	NM_000530.8	c.106A>T	p.Arg36Trp	missense_variant	2/6	ENST00000533357.5
MPZ	NM_001315491.2	c.106A>T	p.Arg36Trp	missense_variant	2/6
MPZ	XM_017001321.3	c.136A>T	p.Arg46Trp	missense_variant	2/6

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
MPZ	ENST00000533357.5	c.106A>T	p.Arg36Trp	missense_variant	2/6	1	NM_000530.8	P1

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome AF: 6.84e-7 AC: 1 AN: 1461892 Hom.: 0 Cov.: 32 AF XY: 0.00 AC XY: 0 AN XY: 727246

Gnomad4 AFR exome AF: 0.00

Gnomad4 AMR exome AF: 0.00

Gnomad4 ASJ exome AF: 0.00

Gnomad4 EAS exome AF: 0.00

Gnomad4 SAS exome AF: 0.00

Gnomad4 FIN exome AF: 0.00

Gnomad4 NFE exome AF: 8.99e-7

Gnomad4 OTH exome AF: 0.00

GnomAD4 genome Cov.: 32

Bravo AF: 0.00000378

ClinVar

Significance: Pathogenic

Submissions summary: Pathogenic:4 Uncertain:1

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

not provided Pathogenic:3

Pathogenic, criteria provided, single submitter	clinical testing	Athena Diagnostics	May 19, 2021	This variant has not been reported in large, multi-ethnic general populations (http://gnomad.broadinstitute.org). This variant has been identified in at least one individual with clinical features associated with this gene. This variant occurs as the most likely explanation for disease in a significant number of internal cases, suggesting this variant is associated with disease. The variant is located in a region that is considered important for protein function and/or structure. -
Pathogenic, criteria provided, single submitter	clinical testing	Mayo Clinic Laboratories, Mayo Clinic	Dec 23, 2022	PS3, PS4, PM2, PM1, PP1 -
Pathogenic, criteria provided, single submitter	clinical testing	GeneDx	Feb 14, 2023	Reported previously in patient with acute onset painful polyneuropathy; his mother had milder symptoms and also harbored the variant (Burns et al., 2006); Published functional studies demonstrate that R36W alters the normal MPZ function (Bai et al., 2018); Missense variants in this gene are often considered pathogenic (HGMD); Not observed at significant frequency in large population cohorts (gnomAD); 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: 16616845, 26310628, 22704856, 29687021, 23279346, 18636082, 14711881, 31278453, 16616847, 20461396, 33179255, 33359733, 33386210) -

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

Pathogenic, criteria provided, single submitter

clinical testing

Invitae

Jan 27, 2024

This sequence change replaces arginine, which is basic and polar, with tryptophan, which is neutral and slightly polar, at codon 36 of the MPZ protein (p.Arg36Trp). This variant is not present in population databases (gnomAD no frequency). This missense change has been observed in individuals with clinical features of MPZ-related conditions (PMID: 16616847, 26310628). It has also been observed to segregate with disease in related individuals. ClinVar contains an entry for this variant (Variation ID: 221065). 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 with a negative predictive value of 80%. This variant disrupts the p.Arg36 amino acid residue in MPZ. Other variant(s) that disrupt this residue have been determined to be pathogenic (PMID: 14711881, 23279346). This suggests that this residue is clinically significant, and that variants that disrupt this residue are likely to be disease-causing. For these reasons, this variant has been classified as Pathogenic. -

Charcot-Marie-Tooth disease Uncertain:1

Uncertain significance, no assertion criteria provided

literature only

Inherited Neuropathy Consortium

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Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Benign	0.32
BayesDel_addAF	Pathogenic	0.23	D
BayesDel_noAF	Uncertain	0.090
Cadd	Benign	22
Dann	Uncertain	0.99
DEOGEN2	Uncertain	0.54	D
Eigen	Benign	-0.17
Eigen_PC	Benign	-0.053
FATHMM_MKL	Benign	0.56	D
LIST_S2	Uncertain	0.87	D
M_CAP	Uncertain	0.13	D
MetaRNN	Uncertain	0.48	T
MetaSVM	Uncertain	0.052	D
MutationAssessor	Benign	0.95	L
MutationTaster	Benign	0.85	D;D;D;D
PrimateAI	Benign	0.44	T
PROVEAN	Uncertain	-3.4	D
REVEL	Uncertain	0.55
Sift	Benign	0.13	T
Sift4G	Benign	0.079	T
Polyphen		0.0030	B
Vest4		0.56
MutPred		0.45		Loss of disorder (P = 0.0549);
MVP		0.99
MPC		1.4
ClinPred		0.93	D
GERP RS		2.7
RBP_binding_hub_radar		0.0
RBP_regulation_power_radar		1.6
Varity_R		0.55
gMVP		0.91

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: rs864622732; hg19: chr1-161277176;