NM_000310.4:c.888G>A

Variant names:

• chr1-40074094-C-T
• rs386833670
• NM_000310.4:c.888G>A

Variant summary

Our verdict is Uncertain significance. The variant received 5 ACMG points: 5P and 0B. PVS1_Moderate PM2 PP5

The NM_000310.4(PPT1):​c.888G>A​(p.Trp296*) variant causes a stop gained change involving the alteration of a conserved nucleotide. The variant was absent in control chromosomes in GnomAD project. 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)
• Consequence: PPT1 NM_000310.4 stop_gained
• Clinical Significance: Conflicting classifications of pathogenicity criteria provided, conflicting classifications P:2 U:1
• Conservation: PhyloP100: 7.69
• Publications: 3 publications found

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 Gene-Disease associations (from GenCC):

• neuronal ceroid lipofuscinosis

  Inheritance: AR Classification: DEFINITIVE Submitted by: ClinGen
• neuronal ceroid lipofuscinosis 1

  Inheritance: AR Classification: DEFINITIVE, STRONG, SUPPORTIVE Submitted by: Genomics England PanelApp, Labcorp Genetics (formerly Invitae), ClinGen, G2P, Orphanet, Myriad Women’s Health

ACMG classification

Our verdict: Uncertain_significance. The variant received 5 ACMG points.

• PVS1: Loss of function variant, product does not undergo nonsense mediated mRNA decay. Variant is located in the 3'-most exon, not predicted to undergo nonsense mediated mRNA decay. Fraction of 0.0358 CDS is truncated, and there are 3 pathogenic variants in the truncated region.
• PM2: Very rare variant in population databases, with high coverage
• PP5: Variant 1-40074094-C-T is Pathogenic according to our data. Variant chr1-40074094-C-T is described in ClinVar as Conflicting_classifications_of_pathogenicity. ClinVar VariationId is 56219.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
PPT1	NM_000310.4	c.888G>A	p.Trp296*	stop_gained	Exon 9 of 9	ENST00000642050.2	NP_000301.1
PPT1	NM_001363695.2	c.816G>A	p.Trp272*	stop_gained	Exon 8 of 8		NP_001350624.1
PPT1	NM_001142604.2	c.579G>A	p.Trp193*	stop_gained	Exon 6 of 6		NP_001136076.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
PPT1	ENST00000642050.2	c.888G>A	p.Trp296*	stop_gained	Exon 9 of 9		NM_000310.4	ENSP00000493153.1

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD2 exomes AF: 0.00000398 AC: 1 AN: 251384 AF XY: 0.00

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 FIN exome AF: 0.00

Gnomad NFE exome AF: 0.00000880

Gnomad OTH exome AF: 0.00

GnomAD4 exome Cov.: 31

GnomAD4 genome Cov.: 32

ExAC AF: 0.00000824 AC: 1

ClinVar

Significance: Conflicting classifications of pathogenicity

Submissions summary: Pathogenic:2 Uncertain:1

Revision: criteria provided, conflicting classifications

Submissions by phenotype

Neuronal ceroid lipofuscinosis 1 Pathogenic:2

Nov 18, 2023

Labcorp Genetics (formerly Invitae), Labcorp

Significance: Likely pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

This sequence change creates a premature translational stop signal (p.Trp296*) in the PPT1 gene. While this is not anticipated to result in nonsense mediated decay, it is expected to disrupt the last 11 amino acid(s) of the PPT1 protein. This variant is present in population databases (rs386833670, 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: 56219). 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. -

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Juha Muilu Group; Institute for Molecular Medicine Finland (FIMM)

Significance: Likely pathogenic

Review Status: no assertion criteria provided

Collection Method: literature only

- -

not provided Uncertain:1

Feb 18, 2021

GeneDx

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

Not observed in large population cohorts (Lek et al., 2016); Nonsense variant predicted to result in protein truncation as the last 11 amino acids are lost, although loss-of-function variants have not been reported downstream of this position in the protein; Reported in a patient with late-infantile NCL who harbored a second variant in PPT1; however, segregation analysis to determine phase was not provided (Das et al., 1998); Reported in a patient with late-infantile NCL who had reduced PPT protein level who harbored a second variant in PPT1; however, segregation analysis to determine phase of the variants was not provided (Das et al., 2001); This variant is associated with the following publications: (PMID: 8004106, 14997939, 12125808, 15965709, 9664077, 11440996, 10649502, 11332767, 11073228) -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
BayesDel_addAF	Pathogenic	0.58	D
BayesDel_noAF	Pathogenic	0.60
CADD	Pathogenic	40
DANN	Uncertain	0.99
Eigen	Pathogenic	1.1
Eigen_PC	Pathogenic	0.99
FATHMM_MKL	Pathogenic	0.97	D
PhyloP100		7.7
Vest4		0.87, 0.74
GERP RS		5.8
Mutation Taster		=2/198	disease causing (ClinVar)

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

Other links and lift over

dbSNP: rs386833670; hg19: chr1-40539766;