18-23531708-C-A

Variant summary

Our verdict is Likely benign. Variant got -5 ACMG points: 0P and 5B. BP4_Strong BS1_Supporting

The NM_000271.5(NPC1):c.*494G>T variant causes a 3 prime UTR change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.000209 in 1,601,234 control chromosomes in the GnomAD database, including 2 homozygotes. In-silico tool predicts a benign outcome for this variant. Variant has been reported in ClinVar as Uncertain significance (★).

• Frequency:
  • Genomes: 𝑓 0.0012 (1 hom., cov: 32)
  • Exomes 𝑓: 0.00011 (1 hom.)
• Consequence: NPC1 NM_000271.5 3_prime_UTR
• Clinical Significance: Uncertain significance criteria provided, single submitter U:1
• Conservation: PhyloP100: -0.0360

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]

RMC1 (HGNC:24326): (regulator of MON1-CCZ1) This gene encodes a colon cancer associated protein. [provided by RefSeq, Jan 2013]

ACMG classification

Verdict is Likely_benign. Variant got -5 ACMG points.

• BP4: Computational evidence support a benign effect (BayesDel_noAF=-0.72).
• BS1: Variant frequency is greater than expected in population afr. gnomad4 allele frequency = 0.00116 (176/152196) while in subpopulation AFR AF= 0.00412 (171/41530). AF 95% confidence interval is 0.00361. There are 1 homozygotes in gnomad4. There are 78 alleles in male gnomad4 subpopulation. Median coverage is 32. This position pass quality control queck. Existence of Clinvar submissions makes me limit the strength of this signal to Supporting

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
NPC1	NM_000271.5	c.*494G>T		3_prime_UTR_variant	25/25	ENST00000269228.10
RMC1	NM_013326.5	c.*4C>A		3_prime_UTR_variant	20/20	ENST00000269221.8

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
RMC1	ENST00000269221.8	c.*4C>A		3_prime_UTR_variant	20/20	1	NM_013326.5	P1
NPC1	ENST00000269228.10	c.*494G>T		3_prime_UTR_variant	25/25	1	NM_000271.5	P1

Frequencies

GnomAD3 genomes AF: 0.00116 AC: 176 AN: 152078 Hom.: 1 Cov.: 32

Gnomad AFR AF: 0.00413

Gnomad AMI AF: 0.00

Gnomad AMR AF: 0.000262

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: 0.00

Gnomad OTH AF: 0.000479

GnomAD3 exomes AF: 0.000290 AC: 69 AN: 237580 Hom.: 0 AF XY: 0.000195 AC XY: 25 AN XY: 128152

Gnomad AFR exome AF: 0.00374

Gnomad AMR exome AF: 0.000229

Gnomad ASJ exome AF: 0.00

Gnomad EAS exome AF: 0.00

Gnomad SAS exome AF: 0.00

Gnomad FIN exome AF: 0.00

Gnomad NFE exome AF: 0.00

Gnomad OTH exome AF: 0.000345

GnomAD4 exome AF: 0.000109 AC: 158 AN: 1449038 Hom.: 1 Cov.: 31 AF XY: 0.000103 AC XY: 74 AN XY: 720240

Gnomad4 AFR exome AF: 0.00389

Gnomad4 AMR exome AF: 0.000147

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: 0.00000631

Gnomad4 OTH exome AF: 0.000301

GnomAD4 genome AF: 0.00116 AC: 176 AN: 152196 Hom.: 1 Cov.: 32 AF XY: 0.00105 AC XY: 78 AN XY: 74410

Gnomad4 AFR AF: 0.00412

Gnomad4 AMR AF: 0.000262

Gnomad4 ASJ AF: 0.00

Gnomad4 EAS AF: 0.00

Gnomad4 SAS AF: 0.00

Gnomad4 FIN AF: 0.00

Gnomad4 NFE AF: 0.00

Gnomad4 OTH AF: 0.000474

Alfa AF: 0.000576 Hom.: 0

Bravo AF: 0.00146

Asia WGS AF: 0.000577 AC: 2 AN: 3478

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:1

Revision: criteria provided, single submitter

Submissions by phenotype

Niemann-Pick disease, type C1 Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Illumina Laboratory Services, Illumina

Jan 13, 2018

This variant was observed in the ICSL laboratory as part of a predisposition screen in an ostensibly healthy population. It had not been previously curated by ICSL or reported in the Human Gene Mutation Database (HGMD: prior to June 1st, 2018), and was therefore a candidate for classification through an automated scoring system. Utilizing variant allele frequency, disease prevalence and penetrance estimates, and inheritance mode, an automated score was calculated to assess if this variant is too frequent to cause the disease. Based on the score, this variant could not be ruled out of causing disease and therefore its association with disease required further investigation. A literature search was performed for the gene, cDNA change, and amino acid change (if applicable). No publications were found based on this search. This variant was therefore classified as a variant of unknown significance for this disease. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
BayesDel_noAF	Benign	-0.72
Cadd	Benign	7.8
Dann	Benign	0.72

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: rs201277520; hg19: chr18-21111672;