18-23545071-T-G

Position:

• chr18-23545071-T-G

Variant summary

Our verdict is Likely pathogenic. Variant got 9 ACMG points: 9P and 0B. PM1 PM2 PP3_Strong PP5

The NM_000271.5(NPC1):​c.1836A>C​(p.Glu612Asp) variant causes a missense change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.000000685 in 1,460,446 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 Conflicting classifications of pathogenicity (no stars).

• Frequency:
  • Genomes: not found (cov: 32)
  • Exomes 𝑓: 6.8e-7 (0 hom.)
• Consequence: NPC1 NM_000271.5 missense
• Clinical Significance: Conflicting classifications of pathogenicity criteria provided, conflicting classifications P:1 U:1
• Conservation: PhyloP100: -0.119

Genes affected

NPC1 (HGNC:7897): (NPC intracellular cholesterol transporter 1) This gene encodes a large protein that resides in the limiting membrane of endosomes and lysosomes and mediates intracellular cholesterol trafficking via binding of cholesterol to its N-terminal domain. It is predicted to have a cytoplasmic C-terminus, 13 transmembrane domains, and 3 large loops in the lumen of the endosome - the last loop being at the N-terminus. This protein transports low-density lipoproteins to late endosomal/lysosomal compartments where they are hydrolized and released as free cholesterol. Defects in this gene cause Niemann-Pick type C disease, a rare autosomal recessive neurodegenerative disorder characterized by over accumulation of cholesterol and glycosphingolipids in late endosomal/lysosomal compartments.[provided by RefSeq, Aug 2009]

ACMG classification

Verdict is Likely_pathogenic. Variant got 9 ACMG points.

• PM1: In a topological_domain Lumenal (size 248) in uniprot entity NPC1_HUMAN there are 30 pathogenic changes around while only 10 benign (75%) in NM_000271.5
• PM2: Very rare variant in population databases, with high coverage
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.983
• PP5: Variant 18-23545071-T-G is Pathogenic according to our data. Variant chr18-23545071-T-G is described in ClinVar as [Conflicting_classifications_of_pathogenicity]. Clinvar id is 555407.We mark this variant Likely_pathogenic, oryginal submissions are: {Uncertain_significance=1, Pathogenic=1}.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
NPC1	NM_000271.5	c.1836A>C	p.Glu612Asp	missense_variant	12/25	ENST00000269228.10	NP_000262.2

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
NPC1	ENST00000269228.10	c.1836A>C	p.Glu612Asp	missense_variant	12/25	1	NM_000271.5	ENSP00000269228	P1
NPC1	ENST00000591051.1	c.915A>C	p.Glu305Asp	missense_variant	5/18	2		ENSP00000467636
NPC1	ENST00000540608.5	n.1750A>C		non_coding_transcript_exon_variant	10/16	2

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome AF: 6.85e-7 AC: 1 AN: 1460446 Hom.: 0 Cov.: 33 AF XY: 0.00 AC XY: 0 AN XY: 726662

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: 9.00e-7

Gnomad4 OTH exome AF: 0.00

GnomAD4 genome Cov.: 32

ClinVar

Significance: Conflicting classifications of pathogenicity

Submissions summary: Pathogenic:1 Uncertain:1

Revision: criteria provided, conflicting classifications

Submissions by phenotype

Niemann-Pick disease, type C1 Pathogenic:1 Uncertain:1

Pathogenic, criteria provided, single submitter	clinical testing	Labcorp Genetics (formerly Invitae), Labcorp	Jan 12, 2024	This sequence change replaces glutamic acid, which is acidic and polar, with aspartic acid, which is acidic and polar, at codon 612 of the NPC1 protein (p.Glu612Asp). This variant is not present in population databases (gnomAD no frequency). This missense change has been observed in individual(s) with Niemann-Pick type C (PMID: 11349231, 32138288). ClinVar contains an entry for this variant (Variation ID: 555407). 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 expected to disrupt NPC1 protein function with a positive predictive value of 95%. For these reasons, this variant has been classified as Pathogenic. -
Uncertain significance, criteria provided, single submitter	clinical testing	Counsyl	Dec 04, 2017	- -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	0.89
BayesDel_addAF	Pathogenic	0.41	D
BayesDel_noAF	Pathogenic	0.35
CADD	Benign	18
DANN	Uncertain	1.0
DEOGEN2	Pathogenic	0.82	D
Eigen	Benign	-0.20
Eigen_PC	Benign	-0.44
FATHMM_MKL	Uncertain	0.83	D
LIST_S2	Uncertain	0.96	D
M_CAP	Pathogenic	0.50	D
MetaRNN	Pathogenic	0.98	D
MetaSVM	Pathogenic	0.89	D
MutationAssessor	Pathogenic	3.5	H
MutationTaster	Benign	0.86	D;D
PrimateAI	Uncertain	0.53	T
PROVEAN	Uncertain	-3.0	D
REVEL	Pathogenic	0.72
Sift	Pathogenic	0.0	D
Sift4G	Pathogenic	0.0	D
Polyphen		0.99	D
Vest4		0.72
MutPred		0.94		Gain of helix (P = 0.132);
MVP		0.89
MPC		0.71
ClinPred		0.99	D
GERP RS		-4.0
Varity_R		0.78
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: rs1555634739; hg19: chr18-21125035;