chr18-23539936-G-C

Position:

• chr18-23539936-G-C

Variant summary

Our verdict is Pathogenic. Variant got 18 ACMG points: 18P and 0B. PVS1 PM2 PP5_Very_Strong

The NM_000271.5(NPC1):​c.2670C>G​(p.Tyr890*) variant causes a stop gained change. The variant allele was found at a frequency of 0.000000684 in 1,461,882 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 Likely pathogenic (★★). Variant results in nonsense mediated mRNA decay.

• Frequency:
  • Genomes: not found (cov: 33)
  • Exomes 𝑓: 6.8e-7 (0 hom.)
• Consequence: NPC1 NM_000271.5 stop_gained
• Clinical Significance: Pathogenic/Likely pathogenic criteria provided, multiple submitters, no conflicts P:3
• Conservation: PhyloP100: 4.05

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]

NPC1 (HGNC:):

ACMG classification

Verdict is Pathogenic. Variant got 18 ACMG points.

• PVS1: Loss of function variant, product undergoes nonsense mediated mRNA decay. LoF is a known mechanism of disease.
• PM2: Very rare variant in population databases, with high coverage
• PP5: Variant 18-23539936-G-C is Pathogenic according to our data. Variant chr18-23539936-G-C is described in ClinVar as [Likely_pathogenic]. Clinvar id is 495788.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
NPC1	NM_000271.5	c.2670C>G	p.Tyr890*	stop_gained	18/25	ENST00000269228.10	NP_000262.2

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
NPC1	ENST00000269228.10	c.2670C>G	p.Tyr890*	stop_gained	18/25	1	NM_000271.5	ENSP00000269228.4

Frequencies

GnomAD3 genomes Cov.: 33

GnomAD3 exomes AF: 0.00000795 AC: 2 AN: 251480 Hom.: 0 AF XY: 0.00 AC XY: 0 AN XY: 135912

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: 0.00

Gnomad FIN exome AF: 0.00

Gnomad NFE exome AF: 0.0000176

Gnomad OTH exome AF: 0.00

GnomAD4 exome AF: 6.84e-7 AC: 1 AN: 1461882 Hom.: 0 Cov.: 35 AF XY: 0.00 AC XY: 0 AN XY: 727242

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.: 33

Bravo AF: 0.00000378

ExAC AF: 0.00000824 AC: 1

ClinVar

Significance: Pathogenic/Likely pathogenic

Submissions summary: Pathogenic:3

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

Niemann-Pick disease, type C1 Pathogenic:2

Likely pathogenic, criteria provided, single submitter	clinical testing	Counsyl	Feb 01, 2017	- -
Pathogenic, criteria provided, single submitter	clinical testing	Labcorp Genetics (formerly Invitae), Labcorp	Nov 05, 2023	This sequence change creates a premature translational stop signal (p.Tyr890*) in the NPC1 gene. It is expected to result in an absent or disrupted protein product. Loss-of-function variants in NPC1 are known to be pathogenic (PMID: 9211850). This variant is present in population databases (rs780592540, gnomAD 0.0009%). This premature translational stop signal has been observed in individual(s) with Niemann-Pick Type C (PMID: 11349231). ClinVar contains an entry for this variant (Variation ID: 495788). For these reasons, this variant has been classified as Pathogenic. -

Niemann-Pick disease, type C Pathogenic:1

Likely pathogenic, criteria provided, single submitter

clinical testing

Women's Health and Genetics/Laboratory Corporation of America, LabCorp

Aug 03, 2017

Variant summary: The c.2670 (p.Tyr890*) variant in NPC1 gene is a nonsense change that results in the loss of the 389 amino acids of the protein (~30%). This change is predicted to cause loss of normal protein function through protein truncation or nonsense-mediated mRNA decay. The variant is present in the large control population dataset of ExAC at a low frequency of 8.238e-06 (1/121384 chrs tested), which does not exceed the maximal expected frequency of a pathogenic allele (0.0027) in this gene. The variant has been identified in compound heterozygosity with known pathogenic allele in affected siblings presented with the classical biochemical phenotype NPC-1 characterized by massive lysosomal/ LE accumulation of unesterified cholesterol in cultured fibroblasts. Taken together, the variant was classified as Likely Pathogenic. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
BayesDel_addAF	Pathogenic	0.63	D
BayesDel_noAF	Pathogenic	0.65
CADD	Pathogenic	42
DANN	Uncertain	1.0
Eigen	Pathogenic	0.89
Eigen_PC	Pathogenic	0.78
FATHMM_MKL	Pathogenic	0.99	D
Vest4		0.98
GERP RS		5.7
RBP_binding_hub_radar		0.0
RBP_regulation_power_radar		1.7

Splicing

Name	Calibrated prediction	Score	Prediction
SpliceAI score (max)		0.010		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: rs780592540; hg19: chr18-21119900;