18-23539357-G-GAA

Variant names:

• chr18-23539357-G-GAA
• rs761910746
• NM_000271.5:c.2907_2908dupTT

Variant summary

Our verdict is Pathogenic. The variant received 11 ACMG points: 11P and 0B. PVS1 PM2 PP5

The NM_000271.5(NPC1):​c.2907_2908dupTT​(p.Ser970PhefsTer14) variant causes a frameshift change. The variant was absent in control chromosomes in GnomAD project. Variant has been reported in ClinVar as Likely pathogenic (no stars). Synonymous variant affecting the same amino acid position (i.e. S970S) has been classified as Uncertain significance. Variant results in nonsense mediated mRNA decay.

• Frequency: Genomes: not found (cov: 33)
• Consequence: NPC1 NM_000271.5 frameshift
• Clinical Significance: Likely pathogenic no assertion criteria provided P:1
• Conservation: PhyloP100: 7.13
• Publications: 2 publications found

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 Gene-Disease associations (from GenCC):

• Niemann-Pick disease, type C1

  Inheritance: AR Classification: DEFINITIVE, STRONG Submitted by: ClinGen, Laboratory for Molecular Medicine, Labcorp Genetics (formerly Invitae), G2P, Genomics England PanelApp, Myriad Women’s Health
• Niemann-Pick disease type C, adult neurologic onset

  Inheritance: AR Classification: SUPPORTIVE Submitted by: Orphanet
• Niemann-Pick disease type C, juvenile neurologic onset

  Inheritance: AR Classification: SUPPORTIVE Submitted by: Orphanet
• Niemann-Pick disease type C, late infantile neurologic onset

  Inheritance: AR Classification: SUPPORTIVE Submitted by: Orphanet
• Niemann-Pick disease type C, severe early infantile neurologic onset

  Inheritance: AR Classification: SUPPORTIVE Submitted by: Orphanet
• Niemann-Pick disease type C, severe perinatal form

  Inheritance: AR Classification: SUPPORTIVE Submitted by: Orphanet

ACMG classification

Our verdict: Pathogenic. The variant received 11 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 18-23539357-G-GAA is Pathogenic according to our data. Variant chr18-23539357-G-GAA is described in ClinVar as Likely_pathogenic. ClinVar VariationId is 553623.Status of the report is no_assertion_criteria_provided, 0 stars.

Variant Effect in Transcripts

ACMG analysis was done for transcript: NM_000271.5. You can select a different transcript below to see updated ACMG assignments.

RefSeq Transcripts

Selected	Gene	Transcript	Tags	HGVSc	HGVSp	Effect	Exon Rank	Protein	UniProt
	NPC1	NM_000271.5	MANE Select	c.2907_2908dupTT	p.Ser970PhefsTer14	frameshift	Exon 19 of 25	NP_000262.2

Ensembl Transcripts

Selected	Gene	Transcript	Tags	HGVSc	HGVSp	Effect	Exon Rank	Protein	UniProt
	NPC1	ENST00000269228.10	TSL:1 MANE Select	c.2907_2908dupTT	p.Ser970PhefsTer14	frameshift	Exon 19 of 25	ENSP00000269228.4
	NPC1	ENST00000591051.1	TSL:2	c.1983_1984dupTT	p.Ser662fs	frameshift	Exon 12 of 18	ENSP00000467636.1
	NPC1	ENST00000591075.1	TSL:4	n.540_541dupTT		non_coding_transcript_exon	Exon 1 of 3

Frequencies

GnomAD3 genomes Cov.: 33

GnomAD2 exomes AF: 0.00000399 AC: 1 AN: 250854 AF XY: 0.00000738

Gnomad AFR exome AF: 0.0000621

Gnomad AMR exome AF: 0.00

Gnomad ASJ exome AF: 0.00

Gnomad EAS exome AF: 0.00

Gnomad FIN exome AF: 0.00

Gnomad NFE exome AF: 0.00

Gnomad OTH exome AF: 0.00

GnomAD4 exome Cov.: 31

GnomAD4 genome Cov.: 33

Alfa AF: 0.0000116 Hom.: 0

Bravo AF: 0.00000378

ClinVar

Significance: Likely pathogenic

Submissions summary: Pathogenic:1

Revision: no assertion criteria provided

Submissions by phenotype

Niemann-Pick disease, type C1 Pathogenic:1

Nov 14, 2017

Counsyl

Significance: Likely pathogenic

Review Status: no assertion criteria provided

Collection Method: clinical testing

This submission and the accompanying classification are no longer maintained by the submitter. For more information on current observations and classification, please contact variantquestions@myriad.com.

Computational scores

Source: dbNSFP v4.9

Name	Calibrated prediction	Score	Prediction
PhyloP100		7.1
Mutation Taster		=0/200	disease causing (ClinVar)

Splicing

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

Other links and lift over

dbSNP: rs761910746; hg19: chr18-21119321;