1-161307278-C-A

Position:

• chr1-161307278-C-A

Variant summary

Our verdict is Likely pathogenic. Variant got 6 ACMG points: 6P and 0B. PM1 PM2 PP3_Moderate

The NM_000530.8(MPZ):​c.214G>T​(p.Gly72Trp) variant causes a missense change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.00000205 in 1,461,864 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a pathogenic 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. G72A) has been classified as Uncertain significance.

• Frequency:
  • Genomes: not found (cov: 32)
  • Exomes 𝑓: 0.0000021 (0 hom.)
• Consequence: MPZ NM_000530.8 missense
• Clinical Significance: Uncertain significance criteria provided, multiple submitters, no conflicts U:2
• Conservation: PhyloP100: 3.26

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 6 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
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.844

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
MPZ	NM_000530.8	c.214G>T	p.Gly72Trp	missense_variant	2/6	ENST00000533357.5	NP_000521.2
MPZ	NM_001315491.2	c.214G>T	p.Gly72Trp	missense_variant	2/6		NP_001302420.1
MPZ	XM_017001321.3	c.244G>T	p.Gly82Trp	missense_variant	2/6		XP_016856810.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
MPZ	ENST00000533357.5	c.214G>T	p.Gly72Trp	missense_variant	2/6	1	NM_000530.8	ENSP00000432943.1

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD3 exomes AF: 0.00000796 AC: 2 AN: 251268 Hom.: 0 AF XY: 0.00 AC XY: 0 AN XY: 135826

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 SAS exome AF: 0.0000654

Gnomad FIN exome AF: 0.00

Gnomad NFE exome AF: 0.00

Gnomad OTH exome AF: 0.00

GnomAD4 exome AF: 0.00000205 AC: 3 AN: 1461864 Hom.: 0 Cov.: 32 AF XY: 0.00000275 AC XY: 2 AN XY: 727230

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: 0.0000116

Gnomad4 FIN exome AF: 0.00

Gnomad4 NFE exome AF: 0.00000180

Gnomad4 OTH exome AF: 0.00

GnomAD4 genome Cov.: 32

ExAC AF: 0.00000824 AC: 1

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:2

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

Inborn genetic diseases Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Ambry Genetics

Oct 12, 2020

The p.G72W variant (also known as c.214G>T), located in coding exon 2 of the MPZ gene, results from a G to T substitution at nucleotide position 214. The glycine at codon 72 is replaced by tryptophan, an amino acid with highly dissimilar properties. This amino acid position is well conserved in available vertebrate species. In addition, the in silico prediction for this alteration is inconclusive. Since supporting evidence is limited at this time, the clinical significance of this alteration remains unclear. -

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

Uncertain significance, criteria provided, single submitter

clinical testing

Labcorp Genetics (formerly Invitae), Labcorp

Jul 11, 2022

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. 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: "Possibly Damaging"; Align-GVGD: "Class C15"). ClinVar contains an entry for this variant (Variation ID: 531682). This variant has not been reported in the literature in individuals affected with MPZ-related conditions. This variant is present in population databases (rs749459367, gnomAD 0.006%). This sequence change replaces glycine, which is neutral and non-polar, with tryptophan, which is neutral and slightly polar, at codon 72 of the MPZ protein (p.Gly72Trp). -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	0.57
BayesDel_addAF	Uncertain	0.047	T
BayesDel_noAF	Uncertain	0.010
CADD	Pathogenic	31
DANN	Uncertain	1.0
DEOGEN2	Uncertain	0.73	D
Eigen	Uncertain	0.57
Eigen_PC	Uncertain	0.50
FATHMM_MKL	Benign	0.62	D
LIST_S2	Benign	0.79	T
M_CAP	Pathogenic	0.34	D
MetaRNN	Pathogenic	0.84	D
MetaSVM	Uncertain	-0.094	T
MutationAssessor	Pathogenic	3.0	M
PrimateAI	Uncertain	0.59	T
PROVEAN	Pathogenic	-5.1	D
REVEL	Pathogenic	0.70
Sift	Pathogenic	0.0	D
Sift4G	Pathogenic	0.0010	D
Polyphen		1.0	D
Vest4		0.70
MutPred		0.59		Gain of solvent accessibility (P = 0.0062);
MVP		0.87
MPC		1.5
ClinPred		0.97	D
GERP RS		4.4
RBP_binding_hub_radar		0.0
RBP_regulation_power_radar		1.1
Varity_R		0.86
gMVP		0.95

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: rs749459367; hg19: chr1-161277068;