1-161306763-G-T

Variant names:

• chr1-161306763-G-T
• rs121913599
• NM_000530.8:c.393C>A

Variant summary

Our verdict is Pathogenic. The variant received 19 ACMG points: 19P and 0B. PM1 PM2 PM5 PP2 PP3_Strong PP5_Very_Strong

The NM_000530.8(MPZ):​c.393C>A​(p.Asn131Lys) 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 Pathogenic (★★). Another variant affecting the same amino acid position, but resulting in a different missense (i.e. N131Y) has been classified as Uncertain significance.

• Frequency: Genomes: not found (cov: 29)
• Consequence: MPZ NM_000530.8 missense
• Clinical Significance: Pathogenic criteria provided, multiple submitters, no conflicts P:3 O:1
• Conservation: PhyloP100: 5.07
• Publications: 10 publications found

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 Gene-Disease associations (from GenCC):

• Charcot-Marie-Tooth disease

  Inheritance: AD Classification: DEFINITIVE Submitted by: ClinGen
• Charcot-Marie-Tooth disease type 1B

  Inheritance: AD Classification: DEFINITIVE, STRONG, SUPPORTIVE Submitted by: Labcorp Genetics (formerly Invitae), Laboratory for Molecular Medicine, Orphanet
• neuropathy, congenital hypomyelinating, 2

  Inheritance: AD Classification: DEFINITIVE Submitted by: G2P
• autosomal dominant intermediate Charcot-Marie-Tooth disease with neuropathic pain

  Inheritance: AD Classification: SUPPORTIVE Submitted by: Orphanet
• Charcot-Marie-Tooth disease dominant intermediate D

  Inheritance: AD Classification: SUPPORTIVE Submitted by: Orphanet
• Charcot-Marie-Tooth disease type 2I

  Inheritance: AD Classification: SUPPORTIVE Submitted by: Orphanet
• Charcot-Marie-Tooth disease type 2J

  Inheritance: AD Classification: SUPPORTIVE Submitted by: Orphanet
• Charcot-Marie-Tooth disease type 3

  Inheritance: AD Classification: SUPPORTIVE Submitted by: Orphanet

ACMG classification

Our verdict: Pathogenic. The variant received 19 ACMG points.

• PM1: In a hotspot region, there are 26 aminoacids with missense pathogenic changes in the window of +-8 aminoacids around while only 0 benign, 27 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 chr1-161306764-T-C is described in ClinVar as Pathogenic. ClinVar VariationId is 637784.Status of the report is criteria_provided_single_submitter, 1 stars.
• PP2: Missense variant in the gene, where a lot of missense mutations are associated with disease in ClinVar. The gene has 84 curated pathogenic missense variants (we use a threshold of 10). The gene has 1 curated benign missense variants. Gene score misZ: 0.98749 (below the threshold of 3.09). Trascript score misZ: 1.4782 (below the threshold of 3.09). GenCC associations: The gene is linked to Charcot-Marie-Tooth disease dominant intermediate D, Charcot-Marie-Tooth disease type 1B, autosomal dominant intermediate Charcot-Marie-Tooth disease with neuropathic pain, Charcot-Marie-Tooth disease type 2J, neuropathy, congenital hypomyelinating, 2, Charcot-Marie-Tooth disease type 2I, Charcot-Marie-Tooth disease type 3, Charcot-Marie-Tooth disease.
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.962
• PP5: Variant 1-161306763-G-T is Pathogenic according to our data. Variant chr1-161306763-G-T is described in ClinVar as Pathogenic. ClinVar VariationId is 14186.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
MPZ	NM_000530.8	c.393C>A	p.Asn131Lys	missense_variant	Exon 3 of 6	ENST00000533357.5	NP_000521.2
MPZ	NM_001315491.2	c.393C>A	p.Asn131Lys	missense_variant	Exon 3 of 6		NP_001302420.1
MPZ	XM_017001321.3	c.423C>A	p.Asn141Lys	missense_variant	Exon 3 of 6		XP_016856810.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
MPZ	ENST00000533357.5	c.393C>A	p.Asn131Lys	missense_variant	Exon 3 of 6	1	NM_000530.8	ENSP00000432943.1

Frequencies

GnomAD3 genomes Cov.: 29

GnomAD4 exome Cov.: 34

GnomAD4 genome Cov.: 29

Alfa AF: 0.00 Hom.: 0

ClinVar

Significance: Pathogenic

Submissions summary: Pathogenic:3 Other:1

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

Roussy-Lévy syndrome Pathogenic:1

Nov 01, 1999

OMIM

Significance: Pathogenic

Review Status: no assertion criteria provided

Collection Method: literature only

- -

not provided Pathogenic:1

Apr 18, 2017

Athena Diagnostics

Significance: Pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

- -

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

Dec 03, 2019

Labcorp Genetics (formerly Invitae), Labcorp

Significance: Pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

This sequence change replaces asparagine with lysine at codon 131 of the MPZ protein (p.Asn131Lys). The asparagine residue is highly conserved and there is a moderate physicochemical difference between asparagine and lysine. This variant is not present in population databases (ExAC no frequency). This variant has been observed in individual(s) with Charcot-Marie-Tooth disease (PMID: 10553995, 12940837). It has also been observed to segregate with disease in related individuals. This variant is also known as 727C>A in the literature. ClinVar contains an entry for this variant (Variation ID: 14186). 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, but these predictions have not been confirmed by published functional studies and their clinical significance is uncertain. For these reasons, this variant has been classified as Pathogenic. -

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

-

GeneReviews

Significance: not provided

Review Status: no classification provided

Collection Method: literature only

- -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	1.0
BayesDel_addAF	Pathogenic	0.23	D
BayesDel_noAF	Uncertain	0.10
CADD	Pathogenic	26
DANN	Uncertain	1.0
DEOGEN2	Uncertain	0.70	D
Eigen	Uncertain	0.65
Eigen_PC	Uncertain	0.57
FATHMM_MKL	Uncertain	0.93	D
LIST_S2	Uncertain	0.88	D
M_CAP	Pathogenic	0.43	D
MetaRNN	Pathogenic	0.96	D
MetaSVM	Pathogenic	0.97	D
MutationAssessor	Uncertain	2.2	M
PhyloP100		5.1
PrimateAI	Pathogenic	0.80	T
PROVEAN	Pathogenic	-5.6	D
REVEL	Pathogenic	0.73
Sift	Pathogenic	0.0	D
Sift4G	Uncertain	0.011	D
Polyphen		1.0	D
Vest4		0.99
MutPred		0.82		Gain of ubiquitination at N131 (P = 0.0138);
MVP		0.93
MPC		1.6
ClinPred		1.0	D
GERP RS		3.9
Varity_R		0.95
gMVP		0.98
Mutation Taster		=1/99	disease causing (ClinVar)

Splicing

Name	Calibrated prediction	Score	Prediction
SpliceAI score (max)		0.030		Details are displayed if max score is > 0.2

Find out detailed SpliceAI scores and Pangolin per-transcript scores at spliceailookup.broadinstitute.org

Other links and lift over

dbSNP: rs121913599; hg19: chr1-161276553;