chr9-21974695-CG-C

Position:

• chr9-21974695-CG-C

Variant summary

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

The NM_000077.5(CDKN2A):​c.132del​(p.Tyr44Ter) variant causes a frameshift change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.00000137 in 1,461,522 control chromosomes in the GnomAD database, with no homozygous occurrence. Variant has been reported in ClinVar as Pathogenic (★★). Variant results in nonsense mediated mRNA decay.

• Frequency:
  • Genomes: not found (cov: 32)
  • Exomes 𝑓: 0.0000014 (0 hom.)
• Consequence: CDKN2A NM_000077.5 frameshift
• Clinical Significance: Pathogenic criteria provided, multiple submitters, no conflicts P:3
• Conservation: PhyloP100: -1.03

Genes affected

CDKN2A (HGNC:1787): (cyclin dependent kinase inhibitor 2A) This gene generates several transcript variants which differ in their first exons. At least three alternatively spliced variants encoding distinct proteins have been reported, two of which encode structurally related isoforms known to function as inhibitors of CDK4 kinase. The remaining transcript includes an alternate first exon located 20 Kb upstream of the remainder of the gene; this transcript contains an alternate open reading frame (ARF) that specifies a protein which is structurally unrelated to the products of the other variants. This ARF product functions as a stabilizer of the tumor suppressor protein p53 as it can interact with, and sequester, the E3 ubiquitin-protein ligase MDM2, a protein responsible for the degradation of p53. In spite of the structural and functional differences, the CDK inhibitor isoforms and the ARF product encoded by this gene, through the regulatory roles of CDK4 and p53 in cell cycle G1 progression, share a common functionality in cell cycle G1 control. This gene is frequently mutated or deleted in a wide variety of tumors, and is known to be an important tumor suppressor gene. [provided by RefSeq, Sep 2012]

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 9-21974695-CG-C is Pathogenic according to our data. Variant chr9-21974695-CG-C is described in ClinVar as [Pathogenic]. Clinvar id is 429111.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
CDKN2A	NM_000077.5	c.132del	p.Tyr44Ter	frameshift_variant	1/3	ENST00000304494.10	NP_000068.1
CDKN2A	NM_058195.4	c.194-3488del		intron_variant		ENST00000579755.2	NP_478102.2

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
CDKN2A	ENST00000304494.10	c.132del	p.Tyr44Ter	frameshift_variant	1/3	1	NM_000077.5	ENSP00000307101	P2
CDKN2A	ENST00000579755.2	c.194-3488del		intron_variant		1	NM_058195.4	ENSP00000462950

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome AF: 0.00000137 AC: 2 AN: 1461522 Hom.: 0 Cov.: 32 AF XY: 0.00000138 AC XY: 1 AN XY: 727080

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

ClinVar

Significance: Pathogenic

Submissions summary: Pathogenic:3

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

Hereditary cancer-predisposing syndrome Pathogenic:2

Pathogenic, criteria provided, single submitter	clinical testing	Ambry Genetics	Jan 23, 2024	The c.132delC pathogenic mutation, located in coding exon 1 of the CDKN2A gene, results from a deletion of one nucleotide at nucleotide position 132, causing a translational frameshift with a predicted alternate stop codon (p.Y44*). This mutation and others causing protein truncation at the same position have been identified in families with multiple melanomas and pancreatic cancer (MacKie RM et al. J. Invest. Dermatol., 1998 Aug;111:269-72; Orlow I et al. J. Invest. Dermatol., 2007 May;127:1234-43; Soura E et al. J. Am. Acad. Dermatol., 2016 Mar;74:395-407; quiz 408-10). In addition to the clinical data presented in the literature, this alteration is expected to result in loss of function by premature protein truncation or nonsense-mediated mRNA decay. As such, this alteration is interpreted as a disease-causing mutation. -
Pathogenic, criteria provided, single submitter	clinical testing	Color Diagnostics, LLC DBA Color Health	Dec 14, 2019	This variant deletes 1 nucleotide in exon 1 of the CDKN2A gene, creating a frameshift and premature translation stop signal. This variant is expected to result in an absent or non-functional protein product. Splice site prediction tools suggest that this variant may not impact RNA splicing. To our knowledge, functional studies have not been performed for this variant. This variant has been observed in two individuals who each had two or more primary melanomas (PMID: 18363633, 26892650) and in the mother of one proband who was affected with pancreatic cancer (PMID: 26892650). This variant has not been identified in the general population by the Genome Aggregation Database (gnomAD). Loss of CDKN2A function is a known mechanism of disease. Based on the available evidence, this variant is classified as Pathogenic. -

Familial melanoma Pathogenic:1

Pathogenic, criteria provided, single submitter

clinical testing

Labcorp Genetics (formerly Invitae), Labcorp

Aug 11, 2023

This premature translational stop signal has been observed in individual(s) with melanoma and pancreatic cancer (PMID: 18363633, 26892650). This variant is not present in population databases (gnomAD no frequency). This sequence change creates a premature translational stop signal (p.Tyr44*) in the CDKN2A (p16INK4a) gene. It is expected to result in an absent or disrupted protein product. Loss-of-function variants in CDKN2A (p16INK4a) are known to be pathogenic (PMID: 15146471, 16905682). ClinVar contains an entry for this variant (Variation ID: 429111). For these reasons, this variant has been classified as Pathogenic. -

Computational scores

Source: dbNSFP v4.3

Splicing

Name	Calibrated prediction	Score	Prediction
SpliceAI score (max)		0.050		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: rs1131691187; hg19: chr9-21974694; COSMIC: COSV58697475; COSMIC: COSV58697475;