18-23544496-C-T

Position:

• chr18-23544496-C-T

Variant summary

Our verdict is Likely pathogenic. Variant got 8 ACMG points: 8P and 0B. PM1 PM2 PP3_Strong

The NM_000271.5(NPC1):​c.1978G>A​(p.Gly660Ser) variant causes a missense change involving the alteration of a conserved nucleotide. The variant allele was found at a frequency of 0.00000137 in 1,461,888 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 Uncertain significance (★★).

• Frequency:
  • Genomes: not found (cov: 32)
  • Exomes 𝑓: 0.0000014 (0 hom.)
• Consequence: NPC1 NM_000271.5 missense
• Clinical Significance: Uncertain significance criteria provided, multiple submitters, no conflicts U:2
• Conservation: PhyloP100: 7.90

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 Likely_pathogenic. Variant got 8 ACMG points.

• PM1: In a mutagenesis_site Loss of function. (size 0) in uniprot entity NPC1_HUMAN
• PM2: Very rare variant in population databases, with high coverage
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.994

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
NPC1	NM_000271.5	c.1978G>A	p.Gly660Ser	missense_variant	13/25	ENST00000269228.10	NP_000262.2

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
NPC1	ENST00000269228.10	c.1978G>A	p.Gly660Ser	missense_variant	13/25	1	NM_000271.5	ENSP00000269228.4
NPC1	ENST00000591051.1	c.1054G>A	p.Gly352Ser	missense_variant	6/18	2		ENSP00000467636.1
NPC1	ENST00000540608.5	n.1892G>A		non_coding_transcript_exon_variant	11/16	2

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome AF: 0.00000137 AC: 2 AN: 1461888 Hom.: 0 Cov.: 32 AF XY: 0.00 AC XY: 0 AN XY: 727246

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

Bravo AF: 0.00000378

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:2

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

Niemann-Pick disease, type C1 Uncertain:2

Uncertain significance, criteria provided, single submitter	clinical testing	Labcorp Genetics (formerly Invitae), Labcorp	Dec 24, 2021	This sequence change replaces glycine, which is neutral and non-polar, with serine, which is neutral and polar, at codon 660 of the NPC1 protein (p.Gly660Ser). This variant is not present in population databases (gnomAD no frequency). This missense change has been observed in individual(s) with Niemann-Pick disease type C (PMID: 12955717). ClinVar contains an entry for this variant (Variation ID: 558673). 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. 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. -
Uncertain significance, criteria provided, single submitter	clinical testing	Counsyl	Jun 04, 2018	- -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Uncertain	0.47
BayesDel_addAF	Pathogenic	0.55	D
BayesDel_noAF	Pathogenic	0.55
CADD	Uncertain	25
DANN	Uncertain	1.0
DEOGEN2	Pathogenic	0.93	D
Eigen	Uncertain	0.58
Eigen_PC	Uncertain	0.44
FATHMM_MKL	Pathogenic	1.0	D
LIST_S2	Uncertain	0.91	D
M_CAP	Pathogenic	0.43	D
MetaRNN	Pathogenic	0.99	D
MetaSVM	Pathogenic	1.1	D
MutationAssessor	Pathogenic	2.9	M
MutationTaster	Benign	1.0	D;D
PrimateAI	Uncertain	0.58	T
PROVEAN	Pathogenic	-6.0	D
REVEL	Pathogenic	0.93
Sift	Pathogenic	0.0	D
Sift4G	Pathogenic	0.0	D
Polyphen		1.0	D
Vest4		0.94
MutPred		0.95		Gain of catalytic residue at G660 (P = 0.1152);
MVP		0.96
MPC		0.91
ClinPred		1.0	D
GERP RS		4.8
RBP_binding_hub_radar		0.0
RBP_regulation_power_radar		1.1
Varity_R		0.94
gMVP		0.93

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: rs1555634490; hg19: chr18-21124460;