chr9-21974757-C-T

Position:

• chr9-21974757-C-T

Variant summary

Our verdict is Uncertain significance. Variant got 1 ACMG points: 4P and 3B. PM1 PM5 BP4_Moderate BS2_Supporting

The NM_000077.5(CDKN2A):​c.71G>A​(p.Arg24Gln) variant causes a missense change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.00000412 in 1,457,942 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a benign outcome for this variant. 13/20 in silico tools predict a benign outcome for this variant. Variant has been reported in ClinVar as Conflicting classifications of pathogenicity (no stars). Another variant affecting the same amino acid position, but resulting in a different missense (i.e. R24C) has been classified as Likely pathogenic.

• Frequency:
  • Genomes: not found (cov: 32)
  • Exomes 𝑓: 0.0000041 (0 hom.)
• Consequence: CDKN2A NM_000077.5 missense
• Clinical Significance: Conflicting classifications of pathogenicity criteria provided, conflicting classifications U:3 B:1
• Conservation: PhyloP100: 0.147

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 Uncertain_significance. Variant got 1 ACMG points.

• PM1: In a repeat ANK 1 (size 29) in uniprot entity CDN2A_HUMAN there are 5 pathogenic changes around while only 0 benign (100%) in NM_000077.5
• PM5: Other missense variant is known to change same aminoacid residue: Variant chrnull-null-null-null is described in UniProt as null.
• BP4: Computational evidence support a benign effect (MetaRNN=0.09134886).
• BS2: High AC in GnomAdExome4 at 6 AD gene. Variant has AC lower than other variant known as pathogenic in the gene, so the strength is limited to Supporting.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
CDKN2A	NM_000077.5	c.71G>A	p.Arg24Gln	missense_variant	1/3	ENST00000304494.10	NP_000068.1
CDKN2A	NM_058195.4	c.194-3549G>A		intron_variant		ENST00000579755.2	NP_478102.2

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
CDKN2A	ENST00000304494.10	c.71G>A	p.Arg24Gln	missense_variant	1/3	1	NM_000077.5	ENSP00000307101	P2
CDKN2A	ENST00000579755.2	c.194-3549G>A		intron_variant		1	NM_058195.4	ENSP00000462950

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD3 exomes AF: 0.0000127 AC: 3 AN: 236656 Hom.: 0 AF XY: 0.0000153 AC XY: 2 AN XY: 130408

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: 0.0000285

Gnomad OTH exome AF: 0.00

GnomAD4 exome AF: 0.00000412 AC: 6 AN: 1457942 Hom.: 0 Cov.: 32 AF XY: 0.00000414 AC XY: 3 AN XY: 725456

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: 0.0000166

GnomAD4 genome Cov.: 32

Alfa AF: 0.0000838 Hom.: 0

Bravo AF: 0.00000756

ExAC AF: 0.00000844 AC: 1

ClinVar

Significance: Conflicting classifications of pathogenicity

Submissions summary: Uncertain:3 Benign:1

Revision: criteria provided, conflicting classifications

Submissions by phenotype

Hereditary cancer-predisposing syndrome Uncertain:1 Benign:1

Uncertain significance, criteria provided, single submitter	clinical testing	Color Diagnostics, LLC DBA Color Health	Aug 01, 2023	This missense variant replaces arginine with glutamine at codon 24 of the CDKN2A (p16INK4A) protein. Computational prediction suggests that this variant may not impact protein structure and function (internally defined REVEL score threshold <= 0.5, PMID: 27666373). Some functional studies have shown the mutant protein to exhibit near normal CDK4 binding activity and cell cycle control activity (PMID: 19260062, 35001868), while other study has shown a significant loss of cell cycle control activity (PMID: 23190892). This variant has been observed in two individuals affected with multiple primary melanomas (PMID: 19260062, 21462282). This variant has been identified in 3/236656 chromosomes in the general population by the Genome Aggregation Database (gnomAD). 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. -
Likely benign, criteria provided, single submitter	clinical testing	Ambry Genetics	Sep 21, 2023	This alteration is classified as likely benign based on a combination of the following: seen in unaffected individuals, population frequency, intact protein function, lack of segregation with disease, co-occurrence, RNA analysis, in silico models, amino acid conservation, lack of disease association in case-control studies, and/or the mechanism of disease or impacted region is inconsistent with a known cause of pathogenicity. -

not provided Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Quest Diagnostics Nichols Institute San Juan Capistrano

Oct 03, 2019

- -

Familial melanoma Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Labcorp Genetics (formerly Invitae), Labcorp

Jan 02, 2024

This sequence change replaces arginine, which is basic and polar, with glutamine, which is neutral and polar, at codon 24 of the CDKN2A (p16INK4a) protein (p.Arg24Gln). This variant is present in population databases (rs104894097, gnomAD 0.003%). This missense change has been observed in individual(s) with multiple primary melanomas (PMID: 19260062, 21462282). ClinVar contains an entry for this variant (Variation ID: 406714). Algorithms developed to predict the effect of missense changes on protein structure and function output the following: SIFT: "Not Available"; PolyPhen-2: "Benign"; Align-GVGD: "Not Available". The glutamine amino acid residue is found in multiple mammalian species, which suggests that this missense change does not adversely affect protein function. Experimental studies are conflicting or provide insufficient evidence to determine the effect of this variant on CDKN2A (p16INK4a) function (PMID: 19260062, 23190892). This variant disrupts the p.Arg24 amino acid residue in CDKN2A (p16INK4a). Other variant(s) that disrupt this residue have been determined to be pathogenic (PMID: 9699728, 9856841, 15146471, 17909018, 18843795, 21801156). 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 v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Benign	0.12
BayesDel_addAF	Benign	-0.12	T
BayesDel_noAF	Benign	-0.33
CADD	Benign	17
DANN	Uncertain	1.0
DEOGEN2	Benign	0.064	T;T;.
Eigen	Benign	-0.62
Eigen_PC	Benign	-0.60
FATHMM_MKL	Benign	0.12	N
LIST_S2	Benign	0.34	T;T;T
M_CAP	Uncertain	0.099	D
MetaRNN	Benign	0.091	T;T;T
MetaSVM	Benign	-1.1	T
MutationTaster	Benign	1.0	N;N;N;N;N;N;N;N;N
PrimateAI	Benign	0.48	T
PROVEAN	Benign	-0.15	N;.;N
REVEL	Benign	0.16
Sift	Benign	0.51	T;.;T
Sift4G	Benign	0.54	T;T;T
Polyphen		0.26	B;.;.
Vest4		0.079
MutPred		0.52		Loss of methylation at R22 (P = 0.0377);Loss of methylation at R22 (P = 0.0377);Loss of methylation at R22 (P = 0.0377);
MVP		0.73
MPC		0.46
ClinPred		0.093	T
GERP RS		3.0
Varity_R		0.054
gMVP		0.81

Splicing

Name	Calibrated prediction	Score	Prediction
SpliceAI score (max)		0.17		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: rs104894097; hg19: chr9-21974756; COSMIC: COSV58724448; COSMIC: COSV58724448;