1-161307388-T-C

Position:

• chr1-161307388-T-C

Variant summary

Our verdict is Uncertain significance. Variant got 5 ACMG points: 6P and 1B. PM1 PM2 PM5 BP4

The ENST00000533357.5(MPZ):​c.104A>G​(p.Asp35Gly) 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 1,461,884 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a benign outcome for this variant. 12/21 in silico tools predict a benign outcome for this variant. Variant has been reported in ClinVar as Uncertain significance (★★). Another variant affecting the same amino acid position, but resulting in a different missense (i.e. D35E) has been classified as Uncertain significance.

• Frequency:
  • Genomes: not found (cov: 32)
  • Exomes 𝑓: 6.8e-7 (0 hom.)
• Consequence: MPZ ENST00000533357.5 missense
• Clinical Significance: Uncertain significance criteria provided, multiple submitters, no conflicts U:2
• Conservation: PhyloP100: 2.58

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 Uncertain_significance. Variant got 5 ACMG points.

• PM1: In a hotspot region, there are 6 aminoacids with missense pathogenic changes in the window of +-8 aminoacids around while only 0 benign, 14 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 chr1-161307389-C-T is described in ClinVar as [Pathogenic]. Clinvar id is 462790.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars.
• BP4: Computational evidence support a benign effect (MetaRNN=0.266275).

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
MPZ	NM_000530.8	c.104A>G	p.Asp35Gly	missense_variant	2/6	ENST00000533357.5	NP_000521.2
MPZ	NM_001315491.2	c.104A>G	p.Asp35Gly	missense_variant	2/6		NP_001302420.1
MPZ	XM_017001321.3	c.134A>G	p.Asp45Gly	missense_variant	2/6		XP_016856810.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
MPZ	ENST00000533357.5	c.104A>G	p.Asp35Gly	missense_variant	2/6	1	NM_000530.8	ENSP00000432943	P1

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome AF: 6.84e-7 AC: 1 AN: 1461884 Hom.: 0 Cov.: 32 AF XY: 0.00 AC XY: 0 AN XY: 727244

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

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:2

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

not specified Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Athena Diagnostics

Feb 10, 2017

- -

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

Uncertain significance, criteria provided, single submitter

clinical testing

Labcorp Genetics (formerly Invitae), Labcorp

Jun 18, 2019

This sequence change replaces aspartic acid with glycine at codon 35 of the MPZ protein (p.Asp35Gly). The aspartic acid residue is highly conserved and there is a moderate physicochemical difference between aspartic acid and glycine. This variant is not present in population databases (ExAC no frequency). This variant has not been reported in the literature in individuals with MPZ-related conditions. ClinVar contains an entry for this variant (Variation ID: 447725). Algorithms developed to predict the effect of missense changes on protein structure and function are either unavailable or do not agree on the potential impact of this missense change (SIFT: "Deleterious"; PolyPhen-2: "Benign"; Align-GVGD: "Class C0"). This variant disrupts the p.Asp35 amino acid residue in MPZ. Other variant(s) that disrupt this residue have been determined to be pathogenic (PMID: 24444136, 20385006, 24053775). 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	0.23
BayesDel_addAF	Uncertain	0.083	D
BayesDel_noAF	Benign	-0.12
CADD	Benign	22
DANN	Benign	0.97
DEOGEN2	Benign	0.28	T
Eigen	Benign	-0.12
Eigen_PC	Benign	0.058
FATHMM_MKL	Benign	0.69	D
LIST_S2	Benign	0.85	T
M_CAP	Uncertain	0.11	D
MetaRNN	Benign	0.27	T
MetaSVM	Uncertain	-0.075	T
MutationAssessor	Benign	1.3	L
MutationTaster	Benign	1.0	D;D;D;D
PrimateAI	Uncertain	0.57	T
PROVEAN	Benign	-2.3	N
REVEL	Uncertain	0.32
Sift	Benign	0.52	T
Sift4G	Benign	0.32	T
Polyphen		0.012	B
Vest4		0.21
MutPred		0.61		Loss of catalytic residue at D35 (P = 0.0252);
MVP		0.80
MPC		0.99
ClinPred		0.67	D
GERP RS		5.3
Varity_R		0.74
gMVP		0.92

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: rs1553259811; hg19: chr1-161277178;