rs386833644

Positions:

• chr1-40091363-CA-C

Variant summary

Our verdict is Pathogenic. Variant got 18 ACMG points: 18P and 0B. PVS1 PM2 PP5_Very_Strong

The NM_000310.4(PPT1):​c.398delT​(p.Met133fs) variant causes a frameshift change involving the alteration of a conserved nucleotide. The variant allele was found at a frequency of 0.00000342 in 1,461,846 control chromosomes in the GnomAD database, with no homozygous occurrence. Variant has been reported in ClinVar as Likely pathogenic (★★). Variant results in nonsense mediated mRNA decay.

• Frequency:
  • Genomes: not found (cov: 31)
  • Exomes 𝑓: 0.0000034 (0 hom.)
• Consequence: PPT1 NM_000310.4 frameshift
• Clinical Significance: Pathogenic/Likely pathogenic criteria provided, multiple submitters, no conflicts P:6
• Conservation: PhyloP100: 8.90

Genes affected

PPT1 (HGNC:9325): (palmitoyl-protein thioesterase 1) The protein encoded by this gene is a small glycoprotein involved in the catabolism of lipid-modified proteins during lysosomal degradation. The encoded enzyme removes thioester-linked fatty acyl groups such as palmitate from cysteine residues. Defects in this gene are a cause of infantile neuronal ceroid lipofuscinosis 1 (CLN1, or INCL) and neuronal ceroid lipofuscinosis 4 (CLN4). Two transcript variants encoding different isoforms have been found for this gene.[provided by RefSeq, Dec 2008]

PPT1 (HGNC:):

ACMG classification

Verdict is Pathogenic. Variant got 18 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 1-40091363-CA-C is Pathogenic according to our data. Variant chr1-40091363-CA-C is described in ClinVar as [Likely_pathogenic]. Clinvar id is 56192.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars. Variant chr1-40091363-CA-C is described in Lovd as [Pathogenic].

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
PPT1	NM_000310.4	c.398delT	p.Met133fs	frameshift_variant	4/9	ENST00000642050.2	NP_000301.1
PPT1	NM_001363695.2	c.398delT	p.Met133fs	frameshift_variant	4/8		NP_001350624.1
PPT1	NM_001142604.2	c.125-1852delT		intron_variant			NP_001136076.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
PPT1	ENST00000642050.2	c.398delT	p.Met133fs	frameshift_variant	4/9		NM_000310.4	ENSP00000493153.1

Frequencies

GnomAD3 genomes Cov.: 31

GnomAD3 exomes AF: 0.00000398 AC: 1 AN: 251274 Hom.: 0 AF XY: 0.00000736 AC XY: 1 AN XY: 135816

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: 0.00

Gnomad FIN exome AF: 0.00

Gnomad NFE exome AF: 0.00000880

Gnomad OTH exome AF: 0.00

GnomAD4 exome AF: 0.00000342 AC: 5 AN: 1461846 Hom.: 0 Cov.: 32 AF XY: 0.00000413 AC XY: 3 AN XY: 727226

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: 0.00000450

Gnomad4 OTH exome AF: 0.00

GnomAD4 genome Cov.: 31

ClinVar

Significance: Pathogenic/Likely pathogenic

Submissions summary: Pathogenic:6

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

Neuronal ceroid lipofuscinosis 1 Pathogenic:5

Pathogenic, criteria provided, single submitter	clinical testing	Labcorp Genetics (formerly Invitae), Labcorp	Sep 24, 2023	This sequence change creates a premature translational stop signal (p.Met133Argfs*4) in the PPT1 gene. It is expected to result in an absent or disrupted protein product. Loss-of-function variants in PPT1 are known to be pathogenic (PMID: 10679943, 21990111). This variant is present in population databases (rs386833644, gnomAD 0.0009%). This premature translational stop signal has been observed in individual(s) with neuronal ceroid lipofuscinosis (PMID: 9664077). ClinVar contains an entry for this variant (Variation ID: 56192). For these reasons, this variant has been classified as Pathogenic. -
Pathogenic, criteria provided, single submitter	clinical testing	Baylor Genetics	Aug 23, 2023	- -
Likely pathogenic, no assertion criteria provided	literature only	Juha Muilu Group; Institute for Molecular Medicine Finland (FIMM)	-	- -
Likely pathogenic, criteria provided, single submitter	clinical testing	Counsyl	May 16, 2016	- -
Likely pathogenic, criteria provided, single submitter	clinical testing	Centogene AG - the Rare Disease Company	Apr 30, 2021	- -

Neuronal ceroid lipofuscinosis Pathogenic:1

Pathogenic, criteria provided, single submitter

clinical testing

Women's Health and Genetics/Laboratory Corporation of America, LabCorp

Nov 24, 2021

Variant summary: PPT1 c.398delT (p.Met133ArgfsX4) results in a premature termination codon, predicted to cause a truncation of the encoded protein or absence of the protein due to nonsense mediated decay, which are commonly known mechanisms for disease. Truncations downstream of this position have been classified as pathogenic by our laboratory. The variant allele was found at a frequency of 4e-06 in 251274 control chromosomes (gnomAD). c.398delT has been reported in the literature in 3 compound heterozygous siblings affected with Neuronal Ceroid-Lipofuscinosis (Batten Disease) (Das_1998, Hofmann_1999). These data indicate that the variant is likely to be associated with disease. Experimental evidence derived from analysis of postmortem brain tissue from one compound heterozygous patient, demonstrated presence of numerous apoptotic cells and abnormally low levels of soluble synaptic vesicle proteins (Kim_2006, 2008). A ClinVar submitter (evaluation after 2014) cites the variant as likely pathogenic. Based on the evidence outlined above, the variant was classified as pathogenic. -

Computational scores

Source: dbNSFP v4.3

Splicing

Name	Calibrated prediction	Score	Prediction
SpliceAI score (max)		0.010		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: rs386833644; hg19: chr1-40557035;