rs864622636

chr9-21974680-G-Achr9-21974680-G-Cchr9-21974680-G-T

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.148C>T(p.Gln50Ter) variant causes a stop gained, splice region change. 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 Pathogenic (★★). Synonymous variant affecting the same amino acid position (i.e. Q50Q) has been classified as Uncertain significance. Variant results in nonsense mediated mRNA decay.

• Frequency: Genomes: not found (cov: 33)
• Consequence: CDKN2A NM_000077.5 stop_gained, splice_region
• Clinical Significance: Pathogenic criteria provided, multiple submitters, no conflicts P:4
• Conservation: PhyloP100: 6.06

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 9-21974680-G-A is Pathogenic according to our data. Variant chr9-21974680-G-A is described in ClinVar as [Pathogenic]. Clinvar id is 220711.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
CDKN2A	NM_000077.5	c.148C>T	p.Gln50Ter	stop_gained, splice_region_variant	1/3	ENST00000304494.10
CDKN2A	NM_058195.4	c.194-3472C>T		intron_variant		ENST00000579755.2

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
CDKN2A	ENST00000304494.10	c.148C>T	p.Gln50Ter	stop_gained, splice_region_variant	1/3	1	NM_000077.5	P2
CDKN2A	ENST00000579755.2	c.194-3472C>T		intron_variant		1	NM_058195.4

Frequencies

GnomAD3 genomes Cov.: 33

GnomAD4 exome Cov.: 32

GnomAD4 genome Cov.: 33

ClinVar

Significance: Pathogenic

Submissions summary: Pathogenic:4

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

Melanoma and neural system tumor syndrome Pathogenic:1

Pathogenic, criteria provided, single submitter

clinical testing

Baylor Genetics

Feb 08, 2023

- -

not provided Pathogenic:1

Pathogenic, criteria provided, single submitter

clinical testing

GeneDx

May 23, 2016

This variant is denoted CDKN2A c.148C>T at the cDNA level and p.Gln50Ter (Q50X) at the protein level. The substitution creates a nonsense variant, which changes a Glutamine to a premature stop codon (CAG>TAG), and is predicted to cause loss of normal protein function through either protein truncation or nonsense-mediated mRNA decay. Consistent with predictions, Parry et al (1996) demonstrated via Cdk binding assays that this variant results in a truncated protein that is unable to bind to CDK2, CDK4, or CDK6. This variant has been reported in an individual with pancreatic cancer and her father with melanoma, and was also observed in at least one individual with multiple primary melanomas (Bartsch 2002, Pastorino 2008). Based on currently available evidence, we consider this variant pathogenic. -

Hereditary cancer-predisposing syndrome Pathogenic:1

Pathogenic, criteria provided, single submitter

clinical testing

Ambry Genetics

Apr 26, 2022

The p.Q50* pathogenic mutation (also known as c.148C>T), located in coding exon 1 of the CDKN2A gene, results from a C to T substitution at nucleotide position 148. This changes the amino acid from a glutamine to a stop codon within coding exon 1. This pathogenic variant has been identified in numerous individuals from melanoma and pancreatic cancer cohorts (Bartsch DK et al. Ann. Surg. 2002 Dec;236:730-7; Pastorino L et al. Pigment Cell Melanoma Res. 2008 Dec;21:700-9; Zhen DB et al. Genet. Med. 2015 Jul;17:569-77). The p.Q50* pathogenic mutation has also shown an inability to bind to Cdk4 and Cdk6 when assessed in vitro (Parry D et al. Mol. Cell. Biol. 1996 Jul;16:3844-52). 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. -

Familial melanoma Pathogenic:1

Pathogenic, criteria provided, single submitter

clinical testing

Invitae

May 15, 2023

This variant is not present in population databases (gnomAD no frequency). For these reasons, this variant has been classified as Pathogenic. ClinVar contains an entry for this variant (Variation ID: 220711). This variant is also known as 50Q>X. This premature translational stop signal has been observed in individual(s) with pancreatic cancer and melanoma (PMID: 12454511, 18983535, 25356972, 25877891). This sequence change creates a premature translational stop signal (p.Gln50*) 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). -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
BayesDel_addAF	Pathogenic	0.57	D
BayesDel_noAF	Pathogenic	0.59
Cadd	Pathogenic	43
Dann	Uncertain	1.0
Eigen	Pathogenic	0.91
Eigen_PC	Pathogenic	0.71
FATHMM_MKL	Uncertain	0.96	D
MutationTaster	Benign	1.0	A;A;A;A;D;D;D;D;D
Vest4		0.89
GERP RS		4.9

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: rs864622636; hg19: chr9-21974679; COSMIC: COSV58683786; COSMIC: COSV58683786;