rs1243863645

chr18-23560296-CATG-C

Variant summary

Our verdict is Likely pathogenic. Variant got 7 ACMG points: 7P and 0B. PM1 PM2 PM4_Supporting PP3 PP5

The NM_000271.5(NPC1):c.813_815del(p.Ile271del) variant causes a inframe deletion change involving the alteration of a conserved nucleotide. The variant allele was found at a frequency of 0.0000031 in 1,614,066 control chromosomes in the GnomAD database, with no homozygous occurrence. Variant has been reported in ClinVar as Conflicting classifications of pathogenicity (no stars). Synonymous variant affecting the same amino acid position (i.e. I271I) has been classified as Likely benign.

• Frequency:
  • Genomes: 𝑓 0.0000066 (0 hom., cov: 32)
  • Exomes 𝑓: 0.0000027 (0 hom.)
• Consequence: NPC1 NM_000271.5 inframe_deletion
• Clinical Significance: Conflicting classifications of pathogenicity criteria provided, conflicting classifications P:3 U:2
• 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 Likely_pathogenic. Variant got 7 ACMG points.

• PM1: In a transmembrane_region Helical (size 20) in uniprot entity NPC1_HUMAN there are 4 pathogenic changes around while only 0 benign (100%) in NM_000271.5
• PM2: Very rare variant in population databases, with high coverage
• PM4: Nonframeshift variant in NON repetitive region in NM_000271.5. Strenght limited to Supporting due to length of the change: 1aa.
• PP3: No computational evidence supports a deleterious effect, but strongly conserved according to phyloP
• PP5: Variant 18-23560296-CATG-C is Pathogenic according to our data. Variant chr18-23560296-CATG-C is described in ClinVar as [Conflicting_classifications_of_pathogenicity]. Clinvar id is 449503.We mark this variant Likely_pathogenic, oryginal submissions are: {Likely_pathogenic=3, Uncertain_significance=1}.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
NPC1	NM_000271.5	c.813_815del	p.Ile271del	inframe_deletion	6/25	ENST00000269228.10

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
NPC1	ENST00000269228.10	c.813_815del	p.Ile271del	inframe_deletion	6/25	1	NM_000271.5	P1
NPC1	ENST00000591051.1	c.44_46del	p.Ile15del	inframe_deletion	1/18	2
NPC1	ENST00000540608.5	n.727_729del		non_coding_transcript_exon_variant	4/16	2

Frequencies

GnomAD3 genomes AF: 0.00000657 AC: 1 AN: 152194 Hom.: 0 Cov.: 32

Gnomad AFR AF: 0.00

Gnomad AMI AF: 0.00

Gnomad AMR AF: 0.00

Gnomad ASJ AF: 0.00

Gnomad EAS AF: 0.00

Gnomad SAS AF: 0.00

Gnomad FIN AF: 0.00

Gnomad MID AF: 0.00

Gnomad NFE AF: 0.0000147

Gnomad OTH AF: 0.00

GnomAD4 exome AF: 0.00000274 AC: 4 AN: 1461872 Hom.: 0 AF XY: 0.00000138 AC XY: 1 AN XY: 727236

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: 0.00000360

Gnomad4 OTH exome AF: 0.00

GnomAD4 genome AF: 0.00000657 AC: 1 AN: 152194 Hom.: 0 Cov.: 32 AF XY: 0.00 AC XY: 0 AN XY: 74354

Gnomad4 AFR AF: 0.00

Gnomad4 AMR AF: 0.00

Gnomad4 ASJ AF: 0.00

Gnomad4 EAS AF: 0.00

Gnomad4 SAS AF: 0.00

Gnomad4 FIN AF: 0.00

Gnomad4 NFE AF: 0.0000147

Gnomad4 OTH AF: 0.00

Bravo AF: 0.00000756

ClinVar

Significance: Conflicting classifications of pathogenicity

Submissions summary: Pathogenic:3 Uncertain:2

Revision: criteria provided, conflicting classifications

Submissions by phenotype

not provided Pathogenic:2

Likely pathogenic, criteria provided, single submitter	clinical testing	GeneDx	Apr 27, 2017	The c.813_815delCAT variant in the NPC1 gene has been reported in an individual with Neiman-Pick C disease with impaired cholesterol esterification rate who also possessed a second variant in the NPC1 gene (Sun et al.,2001). The c.813_815delCAT variant causes an in-frame deletion of one amino acid, Isoleucine 271, denotedp.Ile271del. This amino acid deletion occurs at a position that is conserved across species. The c.813_815delCATvariant is not observed in large population cohorts (Lek et al., 2016; 1000 Genomes Consortium et al., 2015; ExomeVariant Server).We interpret c.813_815delCAT as a likely pathogenic variant. -
Likely pathogenic, criteria provided, single submitter	clinical testing	AiLife Diagnostics, AiLife Diagnostics	Dec 28, 2021	- -

Niemann-Pick disease, type C1 Uncertain:2

Uncertain significance, no assertion criteria provided	clinical testing	Counsyl	Nov 17, 2017	- -
Uncertain significance, criteria provided, single submitter	clinical testing	Invitae	May 25, 2022	This variant, c.813_815del, results in the deletion of 1 amino acid(s) of the NPC1 protein (p.Ile271del), but otherwise preserves the integrity of the reading frame. This variant is not present in population databases (gnomAD no frequency). This variant has been observed in individual(s) with clinical features of Niemann-Pick disease type C (PMID: 11349231, 31130284). ClinVar contains an entry for this variant (Variation ID: 449503). Algorithms developed to predict the effect of sequence changes on RNA splicing suggest that this variant may create or strengthen a splice site. In summary, the available evidence is currently insufficient to determine the role of this variant in disease. Therefore, it has been classified as a Variant of Uncertain Significance. -

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 04, 2022

Variant summary: NPC1 c.813_815delCAT (p.Ile271del) results in an in-frame deletion that is predicted to remove one amino acid from the encoded protein. The variant was absent in 250742 control chromosomes. c.813_815delCAT has been reported in the literature in individuals affected with features of Niemann-Pick Disease Type C and in settings of clinical exome sequencing in an affected consanguineous population (example, Sun_2001, Monies_2019). These data indicate that the variant is likely to be associated with disease. To our knowledge, no experimental evidence demonstrating an impact on protein function has been reported. Four clinical diagnostic laboratories have submitted clinical-significance assessments for this variant to ClinVar after 2014 without evidence for independent evaluation. Multiple laboratories reported the variant with conflicting assessments (LP, n=2; VUS, n=2). Based on the evidence outlined above, the variant was classified as likely pathogenic. -

Computational scores

Source: dbNSFP v4.3

Splicing

Name	Calibrated prediction	Score	Prediction
SpliceAI score (max)		0.21		Details are displayed if max score is > 0.2
DS_DG_spliceai		0.21		Position offset: 13

Find out detailed SpliceAI scores and Pangolin per-transcript scores at spliceailookup.broadinstitute.org

Publications

LitVar

Other links and lift over

dbSNP: rs1243863645; hg19: chr18-21140260;