rs1555632977

Positions:

• chr18-23538616-CCT-C

Variant summary

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

The ENST00000269228.10(NPC1):​c.2965_2966del​(p.Arg989AlafsTer17) variant causes a frameshift change. The variant allele was found at a frequency of 0.00000137 in 1,461,862 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. R989R) has been classified as Likely benign. Variant results in nonsense mediated mRNA decay.

• Frequency:
  • Genomes: not found (cov: 32)
  • Exomes 𝑓: 0.0000014 (0 hom.)
• Consequence: NPC1 ENST00000269228.10 frameshift
• Clinical Significance: Pathogenic/Likely pathogenic criteria provided, multiple submitters, no conflicts P:2
• Conservation: PhyloP100: 6.08

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 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 18-23538616-CCT-C is Pathogenic according to our data. Variant chr18-23538616-CCT-C is described in ClinVar as [Likely_pathogenic]. Clinvar id is 555442.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.2965_2966del	p.Arg989AlafsTer17	frameshift_variant	20/25	ENST00000269228.10	NP_000262.2

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
NPC1	ENST00000269228.10	c.2965_2966del	p.Arg989AlafsTer17	frameshift_variant	20/25	1	NM_000271.5	ENSP00000269228	P1
NPC1	ENST00000591051.1	c.2043_2044del	p.Arg682AlafsTer17	frameshift_variant	13/18	2		ENSP00000467636
NPC1	ENST00000591075.1	n.598_599del		non_coding_transcript_exon_variant	2/3	4
NPC1	ENST00000591955.1	n.308_309del		non_coding_transcript_exon_variant	1/2	4

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome AF: 0.00000137 AC: 2 AN: 1461862 Hom.: 0 AF XY: 0.00000138 AC XY: 1 AN XY: 727230

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: 0.00000180

Gnomad4 OTH exome AF: 0.00

GnomAD4 genome Cov.: 32

ClinVar

Significance: Pathogenic/Likely pathogenic

Submissions summary: Pathogenic:2

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

Niemann-Pick disease, type C1 Pathogenic:2

Pathogenic, criteria provided, single submitter	clinical testing	Labcorp Genetics (formerly Invitae), Labcorp	Mar 21, 2023	This variant is not present in population databases (gnomAD no frequency). This sequence change creates a premature translational stop signal (p.Arg989Alafs*17) 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). For these reasons, this variant has been classified as Pathogenic. ClinVar contains an entry for this variant (Variation ID: 555442). This variant is also known as delAG (2963–2964). This premature translational stop signal has been observed in individual(s) with Niemann-Pick type C (PMID: 10521290). -
Likely pathogenic, criteria provided, single submitter	clinical testing	Counsyl	Dec 05, 2017	- -

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: rs1555632977; hg19: chr18-21118580;