NM_000304.4:c.233T>C

Variant names:

• chr17-15239557-A-G
• rs1555565276
• NM_000304.4:c.233T>C

Variant summary

Our verdict is Likely pathogenic. The variant received 7 ACMG points: 7P and 0B. PM1 PM2 PP3_Moderate PP5

The NM_000304.4(PMP22):​c.233T>C​(p.Leu78Pro) variant causes a missense change involving the alteration of a conserved nucleotide. 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 Conflicting classifications of pathogenicity (no stars). Synonymous variant affecting the same amino acid position (i.e. L78L) has been classified as Likely benign.

• Frequency: Genomes: not found (cov: 33)
• Consequence: PMP22 NM_000304.4 missense
• Clinical Significance: Conflicting classifications of pathogenicity criteria provided, conflicting classifications P:2 U:3
• Conservation: PhyloP100: 7.41
• Publications: 1 publications found

Genes affected

PMP22 (HGNC:9118): (peripheral myelin protein 22) This gene encodes an integral membrane protein that is a major component of myelin in the peripheral nervous system. Studies suggest two alternately used promoters drive tissue-specific expression. Various mutations of this gene are causes of Charcot-Marie-Tooth disease Type IA, Dejerine-Sottas syndrome, and hereditary neuropathy with liability to pressure palsies. Alternative splicing results in multiple transcript variants. [provided by RefSeq, Jul 2013]

PMP22 Gene-Disease associations (from GenCC):

• Charcot-Marie-Tooth disease type 1A

  Inheritance: AD Classification: DEFINITIVE, STRONG, SUPPORTIVE Submitted by: Orphanet, Labcorp Genetics (formerly Invitae), ClinGen, Laboratory for Molecular Medicine, Ambry Genetics
• hereditary neuropathy with liability to pressure palsies

  Inheritance: AD Classification: DEFINITIVE, STRONG, SUPPORTIVE Submitted by: Labcorp Genetics (formerly Invitae), Ambry Genetics, Orphanet
• Charcot-Marie-Tooth disease type 1E

  Inheritance: AD Classification: STRONG, MODERATE, SUPPORTIVE Submitted by: Ambry Genetics, PanelApp Australia, Orphanet, Labcorp Genetics (formerly Invitae)
• Charcot-Marie-Tooth disease type 3

  Inheritance: AD Classification: SUPPORTIVE Submitted by: Orphanet

ACMG classification

Our verdict: Likely_pathogenic. The variant received 7 ACMG points.

• PM1: In a hotspot region, there are 4 aminoacids with missense pathogenic changes in the window of +-8 aminoacids around while only 0 benign, 7 uncertain in NM_000304.4
• PM2: Very rare variant in population databases, with high coverage
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.87
• PP5: Variant 17-15239557-A-G is Pathogenic according to our data. Variant chr17-15239557-A-G is described in ClinVar as [Conflicting_classifications_of_pathogenicity]. Clinvar id is 431943.We mark this variant Likely_pathogenic, oryginal submissions are: {Uncertain_significance=2, Likely_pathogenic=2}.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
PMP22	NM_000304.4	c.233T>C	p.Leu78Pro	missense_variant	Exon 4 of 5	ENST00000312280.9	NP_000295.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
PMP22	ENST00000312280.9	c.233T>C	p.Leu78Pro	missense_variant	Exon 4 of 5	1	NM_000304.4	ENSP00000308937.3

Frequencies

GnomAD3 genomes Cov.: 33

GnomAD4 exome Cov.: 33

GnomAD4 genome Cov.: 33

ClinVar

Significance: Conflicting classifications of pathogenicity

Submissions summary: Pathogenic:2 Uncertain:3

Revision: criteria provided, conflicting classifications

Submissions by phenotype

not provided Pathogenic:1

Aug 03, 2016

GeneDx

Significance: Likely pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

The L78P variant has been previously reported in two related individuals with CMT1 (Pisciotta et al., 2009). It was not observed in approximately 6,500 individuals of European and African American ancestry in the NHLBI Exome Sequencing Project, indicating it is not a common benign variant in these populations. The L78P variant is a semi-conservative amino acid substitution, which may impact secondary protein structure as these residues differ in some properties. This substitution occurs at a position where amino acids with similar properties to Leucine are tolerated across species. In silico analysis predicts this variant is probably damaging to the protein structure/function. Additionally, missense variants in nearby residues have been reported in the Human Gene Mutation Database in association with CMT (Stenson et al., 2014), supporting the functional importance of this region of the protein. Therefore, this variant is likely pathogenic; however, the possibility that it is benign cannot be excluded. -

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

Sep 29, 2024

Labcorp Genetics (formerly Invitae), Labcorp

Significance: Likely pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

This sequence change replaces leucine, which is neutral and non-polar, with proline, which is neutral and non-polar, at codon 78 of the PMP22 protein (p.Leu78Pro). This variant is not present in population databases (gnomAD no frequency). This missense change has been observed in individuals with Charcot-Marie-Tooth disease (PMID: 19909487; internal data). ClinVar contains an entry for this variant (Variation ID: 431943). Invitae Evidence Modeling of protein sequence and biophysical properties (such as structural, functional, and spatial information, amino acid conservation, physicochemical variation, residue mobility, and thermodynamic stability) indicates that this missense variant is expected to disrupt PMP22 protein function with a positive predictive value of 95%. In summary, the currently available evidence indicates that the variant is pathogenic, but additional data are needed to prove that conclusively. Therefore, this variant has been classified as Likely Pathogenic. -

Charcot-Marie-Tooth disease Uncertain:1

-

Inherited Neuropathy Consortium

Significance: Uncertain significance

Review Status: no assertion criteria provided

Collection Method: literature only

- -

not specified Uncertain:1

Nov 23, 2016

Athena Diagnostics

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

- -

Charcot-Marie-Tooth disease type 1E Uncertain:1

Dec 27, 2023

3billion

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

The variant is not observed in the gnomAD v2.1.1 dataset. Predicted Consequence/Location: Missense variant In silico tool predictions suggest damaging effect of the variant on gene or gene product [REVEL: 0.88 (>=0.6, sensitivity 0.68 and specificity 0.92); 3Cnet: 0.99 (>=0.6, sensitivity 0.72 and precision 0.9)]. Same nucleotide change resulting in same amino acid change has been previously reported to be associated with PMP22-related disorder (ClinVar ID: VCV000431943 /PMID: 19909487). However, the evidence of pathogenicity is insufficient at this time. Therefore, this variant is classified as VUS according to the recommendation of ACMG/AMP guideline. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	0.89
BayesDel_addAF	Pathogenic	0.45	D
BayesDel_noAF	Pathogenic	0.41
CADD	Pathogenic	28
DANN	Benign	0.97
DEOGEN2	Pathogenic	0.89	D;D;D;D;D;.;.;D;.
Eigen	Pathogenic	0.73
Eigen_PC	Pathogenic	0.70
FATHMM_MKL	Pathogenic	0.99	D
LIST_S2	Benign	0.82	T;.;.;.;.;D;D;D;D
M_CAP	Uncertain	0.24	D
MetaRNN	Pathogenic	0.87	D;D;D;D;D;D;D;D;D
MetaSVM	Uncertain	0.77	D
MutationAssessor	Uncertain	2.8	M;M;M;.;.;.;.;.;.
PhyloP100		7.4
PrimateAI	Uncertain	0.72	T
PROVEAN	Pathogenic	-4.8	.;D;D;.;D;.;.;.;D
REVEL	Pathogenic	0.88
Sift	Uncertain	0.0010	.;D;D;.;D;.;.;.;D
Sift4G	Uncertain	0.0020	D;D;D;.;D;.;.;.;D
Polyphen		1.0	D;D;D;.;.;.;.;.;.
Vest4		0.88
MutPred		0.69		Loss of stability (P = 0.0322);Loss of stability (P = 0.0322);Loss of stability (P = 0.0322);Loss of stability (P = 0.0322);Loss of stability (P = 0.0322);.;.;Loss of stability (P = 0.0322);Loss of stability (P = 0.0322);
MVP		0.98
MPC		1.7
ClinPred		0.99	D
GERP RS		5.6
Varity_R		0.93
gMVP		0.97
Mutation Taster		=2/98	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: rs1555565276; hg19: chr17-15142874;