chr18-23535665-A-G

Position:

• chr18-23535665-A-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.3281T>C​(p.Ile1094Thr) variant causes a missense change involving the alteration of a conserved nucleotide. The variant allele was found at a frequency of 0.00000205 in 1,461,832 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: 0.0000021 (0 hom.)
• Consequence: NPC1 NM_000271.5 missense
• 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 9 ACMG points.

• PM1: In a hotspot region, there are 4 aminoacids with missense pathogenic changes in the window of +-8 aminoacids around while only 0 benign, 5 uncertain in NM_000271.5
• PM2: Very rare variant in population databases, with high coverage
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.984
• PP5: Variant 18-23535665-A-G is Pathogenic according to our data. Variant chr18-23535665-A-G is described in ClinVar as [Conflicting_classifications_of_pathogenicity]. Clinvar id is 547997.We mark this variant Likely_pathogenic, oryginal submissions are: {Likely_pathogenic=1, Pathogenic=1, Uncertain_significance=1}.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
NPC1	NM_000271.5	c.3281T>C	p.Ile1094Thr	missense_variant	22/25	ENST00000269228.10

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
NPC1	ENST00000269228.10	c.3281T>C	p.Ile1094Thr	missense_variant	22/25	1	NM_000271.5	P1

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD3 exomes AF: 0.00000398 AC: 1 AN: 251410 Hom.: 0 AF XY: 0.00000736 AC XY: 1 AN XY: 135878

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: 0.0000327

Gnomad FIN exome AF: 0.00

Gnomad NFE exome AF: 0.00

Gnomad OTH exome AF: 0.00

GnomAD4 exome AF: 0.00000205 AC: 3 AN: 1461832 Hom.: 0 Cov.: 32 AF XY: 0.00000138 AC XY: 1 AN XY: 727214

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: 0.0000116

Gnomad4 FIN exome AF: 0.00

Gnomad4 NFE exome AF: 0.00000180

Gnomad4 OTH exome AF: 0.00

GnomAD4 genome Cov.: 32

Alfa AF: 0.0000282 Hom.: 0

Bravo AF: 0.00000756

ClinVar

Significance: Conflicting classifications of pathogenicity

Submissions summary: Pathogenic:3 Uncertain:2

Revision: criteria provided, conflicting classifications

Submissions by phenotype

Niemann-Pick disease, type C1 Pathogenic:2 Uncertain:2

Uncertain significance, no assertion criteria provided	clinical testing	Natera, Inc.	Sep 16, 2020	- -
Pathogenic, criteria provided, single submitter	clinical testing	Mayo Clinic Laboratories, Mayo Clinic	Aug 11, 2017	- -
Likely pathogenic, criteria provided, single submitter	clinical testing	Labcorp Genetics (formerly Invitae), Labcorp	Mar 24, 2023	In summary, the currently available evidence indicates that the variant is pathogenic, but additional data are needed to prove that conclusively. Therefore, this variant has been classified as Likely Pathogenic. 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. ClinVar contains an entry for this variant (Variation ID: 547997). This missense change has been observed in individuals with Niemann-Pick disease type C (PMID: 12408188, 23433426, 27139891). This variant is present in population databases (no rsID available, gnomAD 0.003%). This sequence change replaces isoleucine, which is neutral and non-polar, with threonine, which is neutral and polar, at codon 1094 of the NPC1 protein (p.Ile1094Thr). -
Uncertain significance, criteria provided, single submitter	clinical testing	Myriad Genetics, Inc.	Nov 11, 2021	NM_000271.4(NPC1):c.3281T>C(I1094T) is a missense variant classified as a variant of uncertain significance in the context of Niemann-Pick disease type C1. I1094T has been observed in cases with relevant disease (PMID: 27139891, 23433426, 12955717, 12408188). Functional assessments of this variant are not available in the literature. I1094T has been observed in population frequency databases (gnomAD: SAS 0.003%). In summary, there is insufficient evidence to classify NM_000271.4(NPC1):c.3281T>C(I1094T) as pathogenic or benign. Please note: this variant was assessed in the context of healthy population screening. -

NPC1-related disorder Pathogenic:1

Likely pathogenic, no assertion criteria provided

clinical testing

PreventionGenetics, part of Exact Sciences

Mar 08, 2024

The NPC1 c.3281T>C variant is predicted to result in the amino acid substitution p.Ile1094Thr. This variant has been reported in the compound heterozygous state with another NPC1 variant in two sets of siblings affected with Niemann-Pick disease type C (Family 3 in Kaminski et al 2002. PubMed ID: 12408188; Pts 020 and 021 in Stampfer et al. 2013. PubMed ID: 23433426). This variant is reported in 0.0033% of alleles in individuals of South Asian descent in gnomAD. This variant is interpreted as likely pathogenic. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	0.79
BayesDel_addAF	Pathogenic	0.39	D
BayesDel_noAF	Pathogenic	0.42
CADD	Pathogenic	26
DANN	Uncertain	1.0
DEOGEN2	Pathogenic	0.83	D
Eigen	Pathogenic	0.81
Eigen_PC	Pathogenic	0.80
FATHMM_MKL	Pathogenic	0.99	D
LIST_S2	Uncertain	0.93	D
M_CAP	Uncertain	0.27	D
MetaRNN	Pathogenic	0.98	D
MetaSVM	Pathogenic	0.85	D
MutationAssessor	Pathogenic	3.7	H
MutationTaster	Benign	1.0	D;D
PrimateAI	Uncertain	0.55	T
PROVEAN	Uncertain	-3.5	D
REVEL	Pathogenic	0.90
Sift	Uncertain	0.016	D
Sift4G	Uncertain	0.030	D
Polyphen		0.73	P
Vest4		0.97
MutPred		0.88		Loss of stability (P = 0.0044);
MVP		0.97
MPC		0.86
ClinPred		0.97	D
GERP RS		5.9
RBP_binding_hub_radar		0.0
RBP_regulation_power_radar		1.7
Varity_R		0.68
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: rs1338658857; hg19: chr18-21115629;