rs774943545

Positions:

• chr18-23533363-CTGAG-C

Variant summary

Our verdict is Pathogenic. Variant got 12 ACMG points: 12P and 0B. PVS1_Moderate PM2 PP5_Very_Strong

The NM_000271.5(NPC1):​c.3742_3745del​(p.Leu1248ValfsTer3) variant causes a frameshift change involving the alteration of a conserved nucleotide. The variant allele was found at a frequency of 0.0000174 in 1,613,708 control chromosomes in the GnomAD database, with no homozygous occurrence. Variant has been reported in ClinVar as Likely pathogenic (★★). Synonymous variant affecting the same amino acid position (i.e. L1248L) has been classified as Likely benign.

• Frequency:
  • Genomes: 𝑓 0.000020 (0 hom., cov: 33)
  • Exomes 𝑓: 0.000017 (0 hom.)
• Consequence: NPC1 NM_000271.5 frameshift
• Clinical Significance: Pathogenic/Likely pathogenic criteria provided, multiple submitters, no conflicts P:5
• Conservation: PhyloP100: 9.32

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 Pathogenic. Variant got 12 ACMG points.

• PVS1: Loss of function variant, product does not undergo nonsense mediated mRNA decay. Variant is located in the 3'-most 50 bp of the penultimate exon, not predicted to undergo nonsense mediated mRNA decay. Fraction of 0.0248 CDS is truncated, and there are 2 pathogenic variants in the truncated region.
• PM2: Very rare variant in population databases, with high coverage
• PP5: Variant 18-23533363-CTGAG-C is Pathogenic according to our data. Variant chr18-23533363-CTGAG-C is described in ClinVar as [Likely_pathogenic]. Clinvar id is 487441.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
NPC1	NM_000271.5	c.3742_3745del	p.Leu1248ValfsTer3	frameshift_variant	24/25	ENST00000269228.10

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
NPC1	ENST00000269228.10	c.3742_3745del	p.Leu1248ValfsTer3	frameshift_variant	24/25	1	NM_000271.5	P1

Frequencies

GnomAD3 genomes AF: 0.0000197 AC: 3 AN: 152200 Hom.: 0 Cov.: 33

Gnomad AFR AF: 0.00

Gnomad AMI AF: 0.00

Gnomad AMR AF: 0.00

Gnomad ASJ AF: 0.000864

Gnomad EAS AF: 0.00

Gnomad SAS AF: 0.00

Gnomad FIN AF: 0.00

Gnomad MID AF: 0.00

Gnomad NFE AF: 0.00

Gnomad OTH AF: 0.00

GnomAD3 exomes AF: 0.0000318 AC: 8 AN: 251390 Hom.: 0 AF XY: 0.0000147 AC XY: 2 AN XY: 135890

Gnomad AFR exome AF: 0.00

Gnomad AMR exome AF: 0.00

Gnomad ASJ exome AF: 0.000695

Gnomad EAS exome AF: 0.00

Gnomad SAS exome AF: 0.0000327

Gnomad FIN exome AF: 0.00

Gnomad NFE exome AF: 0.00

Gnomad OTH exome AF: 0.00

GnomAD4 exome AF: 0.0000171 AC: 25 AN: 1461508 Hom.: 0 AF XY: 0.0000206 AC XY: 15 AN XY: 727082

Gnomad4 AFR exome AF: 0.00

Gnomad4 AMR exome AF: 0.00

Gnomad4 ASJ exome AF: 0.000689

Gnomad4 EAS exome AF: 0.00

Gnomad4 SAS exome AF: 0.0000116

Gnomad4 FIN exome AF: 0.00

Gnomad4 NFE exome AF: 0.00000360

Gnomad4 OTH exome AF: 0.0000331

GnomAD4 genome AF: 0.0000197 AC: 3 AN: 152200 Hom.: 0 Cov.: 33 AF XY: 0.00 AC XY: 0 AN XY: 74340

Gnomad4 AFR AF: 0.00

Gnomad4 AMR AF: 0.00

Gnomad4 ASJ AF: 0.000864

Gnomad4 EAS AF: 0.00

Gnomad4 SAS AF: 0.00

Gnomad4 FIN AF: 0.00

Gnomad4 NFE AF: 0.00

Gnomad4 OTH AF: 0.00

Alfa AF: 0.0000868 Hom.: 0

Bravo AF: 0.0000113

ClinVar

Significance: Pathogenic/Likely pathogenic

Submissions summary: Pathogenic:5

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

Niemann-Pick disease, type C1 Pathogenic:3

Likely pathogenic, criteria provided, single submitter	clinical testing	Fulgent Genetics, Fulgent Genetics	May 14, 2022	- -
Likely pathogenic, criteria provided, single submitter	clinical testing	Counsyl	Jan 02, 2014	- -
Pathogenic, criteria provided, single submitter	clinical testing	Invitae	Oct 27, 2023	This sequence change creates a premature translational stop signal (p.Leu1248Valfs*3) in the NPC1 gene. While this is not anticipated to result in nonsense mediated decay, it is expected to disrupt the last 31 amino acid(s) of the NPC1 protein. This variant is present in population databases (rs774943545, gnomAD 0.06%). This premature translational stop signal has been observed in individuals with Niemann-Pick type C (PMID: 10521290, 19744920). It has also been observed to segregate with disease in related individuals. This variant is also known as c.3741_3744delACTC. ClinVar contains an entry for this variant (Variation ID: 487441). Experimental studies and prediction algorithms are not available or were not evaluated, and the functional significance of this variant is currently unknown. For these reasons, this variant has been classified as Pathogenic. -

Niemann-Pick disease, type C Pathogenic:1

Pathogenic, criteria provided, single submitter

clinical testing

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

Jul 03, 2017

Variant summary: The NPC1 c.3742_3745delCTCA (p.Leu1248Valfs) variant (also known as 3741_3744delACTC) results in a premature termination codon, predicted to cause a truncated or absent NPC1 protein due to nonsense mediated decay, which are commonly known mechanisms for disease. This variant was found in 5/121194 control chromosomes from ExAC at a frequency of 0.0000413, which does not exceed the estimated maximal expected allele frequency of a pathogenic NPC1 variant (0.0027735). The variant was detected in at least three patients with NPC. Variant downsteam of this variant c.3744_3747 delCAGT has also been reported in affected individual and listed as "DM-disease mutation" in HGMD, suggesitng this location is a mutation hotspot. Taken together, this variant is classified as pathogenic. -

not provided Pathogenic:1

Likely pathogenic, criteria provided, single submitter

clinical testing

GeneDx

Sep 19, 2019

Reported in a family with a patient with Niemann-Pick type II disease; however, additional clinical information and biochemical studies on the patient were not provided (Greer et al., 1999); Reported in two patients with Niemann-Pick type C1 disease who have second NPC1 variants; however, segregation information was not provided to establish phase of the variants; for one patient, variant was reported as c.3741_3744delACTC due to the use of alternative nomenclature (Garver et al., 2010); Frameshift variant in the C-terminus predicted to result in protein truncation, as the last 31 amino acids are lost and replaced with 2 incorrect amino acids; This variant is associated with the following publications: (PMID: 28193631, 19744920, 10521290, 28082351) -

Computational scores

Source: dbNSFP v4.3

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: rs774943545; hg19: chr18-21113327;