9-21970982-A-C

Variant names:

• chr9-21970982-A-C
• rs104894098
• NM_000077.5:c.377T>G

Variant summary

Our verdict is Likely pathogenic. The variant received 8 ACMG points: 8P and 0B. PM1 PM2 PM5 PP3_Moderate

The NM_000077.5(CDKN2A):​c.377T>G​(p.Val126Gly) variant causes a missense 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 Uncertain significance (★★). Another variant affecting the same amino acid position, but resulting in a different missense (i.e. V126L) has been classified as Uncertain significance.

• Frequency: Genomes: not found (cov: 32)
• Consequence: CDKN2A NM_000077.5 missense
• Clinical Significance: Uncertain significance criteria provided, multiple submitters, no conflicts U:2
• Conservation: PhyloP100: 6.75
• Publications: 0 publications found

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]

CDKN2A Gene-Disease associations (from GenCC):

• melanoma, cutaneous malignant, susceptibility to, 2

  Inheritance: AD Classification: DEFINITIVE Submitted by: G2P
• melanoma-pancreatic cancer syndrome

  Inheritance: AD Classification: DEFINITIVE, STRONG Submitted by: Genomics England PanelApp, ClinGen, Labcorp Genetics (formerly Invitae), Ambry Genetics
• familial atypical multiple mole melanoma syndrome

  Inheritance: AD Classification: SUPPORTIVE Submitted by: Orphanet
• melanoma and neural system tumor syndrome

  Inheritance: AD Classification: LIMITED Submitted by: Ambry Genetics

ENSG00000264545 (HGNC:):

ACMG classification

Our verdict: Likely_pathogenic. The variant received 8 ACMG points.

• PM1: In a hotspot region, there are 3 aminoacids with missense pathogenic changes in the window of +-8 aminoacids around while only 6 benign, 39 uncertain in NM_000077.5
• PM2: Very rare variant in population databases, with high coverage
• PM5: Other missense variant is known to change same aminoacid residue: Variant chr9-21970982-A-T is described in ClinVar as Pathogenic. ClinVar VariationId is 9420.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars.
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.93

Variant Effect in Transcripts

ACMG analysis was done for transcript: NM_000077.5. 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
	CDKN2A	NM_000077.5	MANE Select	c.377T>G	p.Val126Gly	missense	Exon 2 of 3	NP_000068.1
	CDKN2A	NM_058195.4	MANE Plus Clinical	c.*21T>G		3_prime_UTR	Exon 2 of 3	NP_478102.2
	CDKN2A	NM_001195132.2		c.377T>G	p.Val126Gly	missense	Exon 2 of 4	NP_001182061.1

Ensembl Transcripts

Selected	Gene	Transcript	Tags	HGVSc	HGVSp	Effect	Exon Rank	Protein	UniProt
	CDKN2A	ENST00000304494.10	TSL:1 MANE Select	c.377T>G	p.Val126Gly	missense	Exon 2 of 3	ENSP00000307101.5
	CDKN2A	ENST00000498124.1	TSL:1	c.377T>G	p.Val126Gly	missense	Exon 2 of 4	ENSP00000418915.1
	CDKN2A	ENST00000380151.3	TSL:1	n.*300T>G		non_coding_transcript_exon	Exon 2 of 3	ENSP00000369496.3

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome Cov.: 31

GnomAD4 genome Cov.: 32

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:2

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

Hereditary cancer-predisposing syndrome Uncertain:1

Jan 07, 2025

Color Diagnostics, LLC DBA Color Health

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

The CDKN2A locus encodes two different gene products, p16INK4a and p14ARF (https://www.ncbi.nlm.nih.gov/books/NBK7030/). This missense variant replaces valine with glycine at codon 126 of the CDKN2A (p16INK4A) protein. Computational prediction is inconclusive regarding the impact of this variant on protein structure and function. To our knowledge, functional studies have not been reported for this variant. This variant has not been reported in individuals affected with CDKN2A-related disorders in the literature. This variant has not been identified in the general population by the Genome Aggregation Database (gnomAD). A different variant occurring at the same codon, p.Val126Asp, is a well documented pathogenic mutation (ClinVar Variation ID: 9420), indicating that valine at this position is important for CDKN2A protein function. The available evidence is insufficient to determine the role of this variant in disease conclusively. Therefore, this variant is classified as a Variant of Uncertain Significance.

Familial melanoma Uncertain:1

Oct 27, 2024

Labcorp Genetics (formerly Invitae), Labcorp

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

This sequence change replaces valine, which is neutral and non-polar, with glycine, which is neutral and non-polar, at codon 126 of the CDKN2A (p16INK4a) protein (p.Val126Gly). This variant is not present in population databases (gnomAD no frequency). This variant has not been reported in the literature in individuals affected with CDKN2A (p16INK4a)-related conditions. An algorithm developed to predict the effect of missense changes on protein structure and function (PolyPhen-2) suggests that this variant is likely to be disruptive. This variant disrupts the p.Val126 amino acid residue in CDKN2A (p16INK4a). Other variant(s) that disrupt this residue have been determined to be pathogenic (PMID: 7647780, 7987387, 8668202, 9425228, 10389768, 11595726, 15146471, 16905682). This suggests that this residue is clinically significant, and that variants that disrupt this residue are likely to be disease-causing. In summary, the available evidence is currently insufficient to determine the role of this variant in disease. Therefore, it has been classified as a Variant of Uncertain Significance.

Computational scores

Source: dbNSFP v4.9

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	0.63
BayesDel_addAF	Pathogenic	0.49	D
BayesDel_noAF	Pathogenic	0.46
CADD	Uncertain	23
DANN	Uncertain	0.99
DEOGEN2	Uncertain	0.56	D
Eigen	Uncertain	0.51
Eigen_PC	Uncertain	0.40
FATHMM_MKL	Pathogenic	0.98	D
LIST_S2	Benign	0.72	T
M_CAP	Pathogenic	0.53	D
MetaRNN	Pathogenic	0.93	D
MetaSVM	Uncertain	-0.099	T
PhyloP100		6.7
PrimateAI	Benign	0.46	T
PROVEAN	Pathogenic	-6.3	D
REVEL	Pathogenic	0.65
Sift	Pathogenic	0.0	D
Sift4G	Pathogenic	0.0	D
Polyphen		1.0	D
Vest4		0.67
MutPred		0.71		Gain of disorder (P = 0.0145)
MVP		1.0
MPC		1.4
ClinPred		0.97	D
GERP RS		5.8
PromoterAI		0.0091	Neutral
Varity_R		0.80
gMVP		0.78
Mutation Taster		=3/97	disease causing

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: rs104894098; hg19: chr9-21970981;