1-161307386-T-C

Variant names:

• chr1-161307386-T-C
• rs864622732
• NM_000530.8:c.106A>G

Variant summary

Our verdict is Likely pathogenic. The variant received 8 ACMG points: 8P and 0B. PM1 PM2 PM5 PP2 PP5

The NM_000530.8(MPZ):​c.106A>G​(p.Arg36Gly) variant causes a missense change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.00000274 in 1,461,892 control chromosomes in the GnomAD database, with no homozygous occurrence. Variant has been reported in ClinVar as Conflicting classifications of pathogenicity (no stars). Another variant affecting the same amino acid position, but resulting in a different missense (i.e. R36W) has been classified as Likely pathogenic.

• Frequency:
  • Genomes: not found (cov: 32)
  • Exomes 𝑓: 0.0000027 (0 hom.)
• Consequence: MPZ NM_000530.8 missense
• Clinical Significance: Conflicting classifications of pathogenicity criteria provided, conflicting classifications P:1 U:2
• Conservation: PhyloP100: 3.49
• Publications: 6 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: Likely_pathogenic. The variant received 8 ACMG points.

• PM1: In a hotspot region, there are 14 aminoacids with missense pathogenic changes in the window of +-8 aminoacids around while only 0 benign, 19 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-A is described in ClinVar as Pathogenic/Likely_pathogenic. ClinVar VariationId is 221065.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 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.
• PP5: Variant 1-161307386-T-C is Pathogenic according to our data. Variant chr1-161307386-T-C is described in ClinVar as Conflicting_classifications_of_pathogenicity. ClinVar VariationId is 420151.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
MPZ	NM_000530.8	c.106A>G	p.Arg36Gly	missense_variant	Exon 2 of 6	ENST00000533357.5	NP_000521.2
MPZ	NM_001315491.2	c.106A>G	p.Arg36Gly	missense_variant	Exon 2 of 6		NP_001302420.1
MPZ	XM_017001321.3	c.136A>G	p.Arg46Gly	missense_variant	Exon 2 of 6		XP_016856810.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
MPZ	ENST00000533357.5	c.106A>G	p.Arg36Gly	missense_variant	Exon 2 of 6	1	NM_000530.8	ENSP00000432943.1

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD2 exomes AF: 0.00000398 AC: 1 AN: 251272 AF XY: 0.00000736

Gnomad AFR exome AF: 0.00

Gnomad AMR exome AF: 0.00

Gnomad ASJ exome AF: 0.00

Gnomad EAS exome AF: 0.00

Gnomad FIN exome AF: 0.00

Gnomad NFE exome AF: 0.00000880

Gnomad OTH exome AF: 0.00

GnomAD4 exome AF: 0.00000274 AC: 4 AN: 1461892 Hom.: 0 Cov.: 32 AF XY: 0.00000138 AC XY: 1 AN XY: 727246

African (AFR) AF: 0.00 AC: 0 AN: 33480

American (AMR) AF: 0.00 AC: 0 AN: 44724

Ashkenazi Jewish (ASJ) AF: 0.00 AC: 0 AN: 26136

East Asian (EAS) AF: 0.00 AC: 0 AN: 39700

South Asian (SAS) AF: 0.00 AC: 0 AN: 86258

European-Finnish (FIN) AF: 0.00 AC: 0 AN: 53418

Middle Eastern (MID) AF: 0.00 AC: 0 AN: 5768

European-Non Finnish (NFE) AF: 0.00000360 AC: 4 AN: 1112012

Other (OTH) AF: 0.00 AC: 0 AN: 60396

GnomAD4 genome Cov.: 32

ClinVar

Significance: Conflicting classifications of pathogenicity

Submissions summary: Pathogenic:1 Uncertain:2

Revision: criteria provided, conflicting classifications

Submissions by phenotype

not provided Pathogenic:1

Feb 24, 2017

GeneDx

Significance: Likely pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

The R36G variant has been reported previously in a patient and her son with progressive axonal and demyelinating sensorimotor neuropathy, respectively (Dacci et al., 2012). The R36G variant is not observed in large population cohorts (Lek et al., 2016; 1000 Genomes Consortium et al., 2015; Exome Variant Server). The R36G variant is a non-conservative amino acid substitution, which is likely to impact secondary protein structure as these residues differ in polarity, charge, size and/or other properties. Furthermore, multiple missense variants in nearby residues and at the same residue (R36W) have been reported in the Human Gene Mutation Database in association with MPZ-related disorders (Stenson et al., 2014), supporting the functional importance of this region of the protein. However, this substitution occurs at a position that is not conserved. In silico analysis is inconsistent in its predictions as to whether or not the variant is damaging to the protein structure/function. Therefore, this variant is likely pathogenic; however, the possibility that it is benign cannot be excluded. -

Charcot-Marie-Tooth disease Uncertain:1

-

Inherited Neuropathy Consortium

Significance: Uncertain significance

Review Status: no assertion criteria provided

Collection Method: literature only

- -

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

Oct 14, 2023

Labcorp Genetics (formerly Invitae), Labcorp

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

This sequence change replaces arginine, which is basic and polar, with glycine, which is neutral and non-polar, at codon 36 of the MPZ protein (p.Arg36Gly). This variant is present in population databases (no rsID available, gnomAD 0.0009%). This missense change has been observed in individual(s) with hereditary sensory and motor neuropathy (PMID: 23279346). ClinVar contains an entry for this variant (Variation ID: 420151). 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. 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: 16616847, 26310628). This suggests that this residue is clinically significant, and that variants that disrupt this residue are likely to be disease-causing. In summary, the available evidence is currently insufficient to determine the role of this variant in disease. Therefore, it has been classified as a Variant of Uncertain Significance. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Benign	0.25
BayesDel_addAF	Pathogenic	0.24	D
BayesDel_noAF	Uncertain	0.11
CADD	Uncertain	23
DANN	Uncertain	0.99
DEOGEN2	Benign	0.24	T
Eigen	Benign	-0.30
Eigen_PC	Benign	-0.15
FATHMM_MKL	Benign	0.69	D
LIST_S2	Benign	0.82	T
M_CAP	Uncertain	0.12	D
MetaRNN	Uncertain	0.68	D
MetaSVM	Benign	-0.43	T
MutationAssessor	Benign	0.73	N
PhyloP100		3.5
PrimateAI	Benign	0.39	T
PROVEAN	Benign	-1.8	N
REVEL	Uncertain	0.59
Sift	Benign	0.062	T
Sift4G	Benign	0.47	T
Polyphen		0.10	B
Vest4		0.79
MutPred		0.43		Loss of solvent accessibility (P = 0.0159);
MVP		0.98
MPC		0.87
ClinPred		0.61	D
GERP RS		2.7
PromoterAI		-0.042	Neutral
RBP_binding_hub_radar		0.0
RBP_regulation_power_radar		1.6
Varity_R		0.65
gMVP		0.89
Mutation Taster		=1/99	disease causing (ClinVar)

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

Other links and lift over

dbSNP: rs864622732; hg19: chr1-161277176; COSMIC: COSV60669498; COSMIC: COSV60669498;