1-161307328-C-T

Variant names:

• chr1-161307328-C-T
• rs281865133
• NM_000530.8:c.164G>A

Variant summary

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

The NM_000530.8(MPZ):​c.164G>A​(p.Ser55Asn) variant causes a missense change. The variant was absent in control chromosomes in GnomAD project. In-silico tool predicts a benign outcome for this variant. 13/21 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. S55I) has been classified as Uncertain significance.

• Frequency: Genomes: not found (cov: 32)
• Consequence: MPZ NM_000530.8 missense
• Clinical Significance: Uncertain significance criteria provided, single submitter U:1
• Conservation: PhyloP100: 4.21

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 12 aminoacids with missense pathogenic changes in the window of +-8 aminoacids around while only 0 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 chr1-161307328-C-A is described in Lovd as [Likely_pathogenic].
• BP4: Computational evidence support a benign effect (MetaRNN=0.29544336).

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
MPZ	NM_000530.8	c.164G>A	p.Ser55Asn	missense_variant	Exon 2 of 6	ENST00000533357.5	NP_000521.2
MPZ	NM_001315491.2	c.164G>A	p.Ser55Asn	missense_variant	Exon 2 of 6		NP_001302420.1
MPZ	XM_017001321.3	c.194G>A	p.Ser65Asn	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.164G>A	p.Ser55Asn	missense_variant	Exon 2 of 6	1	NM_000530.8	ENSP00000432943.1

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome Cov.: 32

GnomAD4 genome Cov.: 32

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:1

Revision: criteria provided, single submitter

Submissions by phenotype

Inborn genetic diseases Uncertain:1

Mar 27, 2023

Ambry Genetics

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

The c.164G>A (p.S55N) alteration is located in exon 2 (coding exon 2) of the MPZ gene. This alteration results from a G to A substitution at nucleotide position 164, causing the serine (S) at amino acid position 55 to be replaced by an asparagine (N). Based on insufficient or conflicting evidence, the clinical significance of this alteration remains unclear. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Benign	0.19
BayesDel_addAF	Benign	-0.065	T
BayesDel_noAF	Benign	-0.33
CADD	Benign	23
DANN	Uncertain	0.99
DEOGEN2	Benign	0.26	T
Eigen	Benign	-0.026
Eigen_PC	Benign	0.16
FATHMM_MKL	Uncertain	0.86	D
LIST_S2	Benign	0.81	T
M_CAP	Benign	0.012	T
MetaRNN	Benign	0.30	T
MetaSVM	Benign	-0.96	T
MutationAssessor	Benign	1.5	L
PrimateAI	Uncertain	0.70	T
PROVEAN	Benign	-1.6	N
REVEL	Benign	0.12
Sift	Benign	0.42	T
Sift4G	Benign	0.31	T
Polyphen		0.012	B
Vest4		0.43
MutPred		0.49		Loss of sheet (P = 0.302);
MVP		0.74
MPC		0.51
ClinPred		0.72	D
GERP RS		5.3
Varity_R		0.54
gMVP		0.82

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: rs281865133; hg19: chr1-161277118;