9-21974815-C-T

Variant names:

• chr9-21974815-C-T
• rs771582621
• NM_000077.5:c.13G>A

Variant summary

Our verdict is Likely benign. The variant received -3 ACMG points: 0P and 3B. BP4_Moderate BS2_Supporting

The NM_000077.5(CDKN2A):​c.13G>A​(p.Ala5Thr) variant causes a missense change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.00000414 in 1,448,480 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a benign outcome for this variant. 15/21 in silico tools predict a benign 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. A5V) has been classified as Uncertain significance.

• Frequency:
  • Genomes: not found (cov: 32)
  • Exomes 𝑓: 0.0000041 (0 hom.)
• Consequence: CDKN2A NM_000077.5 missense
• Clinical Significance: Uncertain significance criteria provided, multiple submitters, no conflicts U:5
• Conservation: PhyloP100: -0.144
• Publications: 7 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_benign. The variant received -3 ACMG points.

• BP4: Computational evidence support a benign effect (MetaRNN=0.09369156).
• 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 rank	MANE	Protein	UniProt
CDKN2A	NM_000077.5	c.13G>A	p.Ala5Thr	missense_variant	Exon 1 of 3	ENST00000304494.10	NP_000068.1
CDKN2A	NM_058195.4	c.194-3607G>A		intron_variant	Intron 1 of 2	ENST00000579755.2	NP_478102.2

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
CDKN2A	ENST00000304494.10	c.13G>A	p.Ala5Thr	missense_variant	Exon 1 of 3	1	NM_000077.5	ENSP00000307101.5
CDKN2A	ENST00000579755.2	c.194-3607G>A		intron_variant	Intron 1 of 2	1	NM_058195.4	ENSP00000462950.1

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome AF: 0.00000414 AC: 6 AN: 1448480 Hom.: 0 Cov.: 32 AF XY: 0.00000278 AC XY: 2 AN XY: 720644

African (AFR) AF: 0.00 AC: 0 AN: 33322

American (AMR) AF: 0.00 AC: 0 AN: 44210

Ashkenazi Jewish (ASJ) AF: 0.00 AC: 0 AN: 25896

East Asian (EAS) AF: 0.00 AC: 0 AN: 39572

South Asian (SAS) AF: 0.00 AC: 0 AN: 85902

European-Finnish (FIN) AF: 0.00 AC: 0 AN: 45072

Middle Eastern (MID) AF: 0.00 AC: 0 AN: 5460

European-Non Finnish (NFE) AF: 0.00000541 AC: 6 AN: 1109046

Other (OTH) AF: 0.00 AC: 0 AN: 60000

GnomAD4 genome Cov.: 32

ExAC AF: 0.00000863 AC: 1

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:5

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

Hereditary cancer-predisposing syndrome Uncertain:2

Sep 25, 2021

Sema4, Sema4

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: curation

- -

May 31, 2024

Ambry Genetics

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

The p.A5T variant (also known as c.13G>A), located in coding exon 1 of the CDKN2A gene, results from a G to A substitution at nucleotide position 13. The alanine at codon 5 is replaced by threonine, an amino acid with similar properties. This variant has been identified in individuals diagnosed with melanoma (Soufir N et al. Br. J. Cancer 2004 Jan; 90(2):503-9; Puig S et al. Genet. Med. 2016 Jul;18(7):727-36; Taylor NJ et al. J Invest Dermatol, 2017 12;137:2606-2612). This amino acid position is conserved on limited sequence alignment. In addition, this alteration is predicted to be tolerated by in silico analysis. Based on the available evidence, the clinical significance of this variant remains unclear. -

not provided Uncertain:1

Aug 14, 2023

GeneDx

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

Not observed at significant frequency in large population cohorts (gnomAD); In silico analysis supports that this missense variant does not alter protein structure/function; Observed in individuals with a personal or family history of melanoma (Soufir et al., 2004; Miller et al., 2011; Puig et al., 2016); This variant is associated with the following publications: (PMID: 21085193, 25064638, 14735200, 21462282, 28830827, 26681309) -

Melanoma-pancreatic cancer syndrome Uncertain:1

Oct 02, 2023

Department of Pathology and Laboratory Medicine, Sinai Health System

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

- -

Familial melanoma Uncertain:1

Dec 02, 2023

Labcorp Genetics (formerly Invitae), Labcorp

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

This sequence change replaces alanine, which is neutral and non-polar, with threonine, which is neutral and polar, at codon 5 of the CDKN2A (p16INK4a) protein (p.Ala5Thr). This variant is not present in population databases (gnomAD no frequency). This missense change has been observed in individual(s) with melanoma (PMID: 14735200, 26681309, 28830827). ClinVar contains an entry for this variant (Variation ID: 233536). 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 tolerated. 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	0.089
BayesDel_addAF	Benign	-0.11	T
BayesDel_noAF	Benign	-0.40
CADD	Benign	9.8
DANN	Benign	0.95
DEOGEN2	Benign	0.098	T;T;.
Eigen	Benign	-1.1
Eigen_PC	Benign	-1.2
FATHMM_MKL	Benign	0.020	N
LIST_S2	Benign	0.44	T;T;T
M_CAP	Benign	0.011	T
MetaRNN	Benign	0.094	T;T;T
MetaSVM	Benign	-0.87	T
PhyloP100		-0.14
PrimateAI	Uncertain	0.62	T
PROVEAN	Benign	-0.91	N;.;N
REVEL	Benign	0.17
Sift	Uncertain	0.025	D;.;D
Sift4G	Uncertain	0.053	T;D;D
Polyphen		0.049	B;.;.
Vest4		0.15
MutPred		0.14		Gain of phosphorylation at E5 (P = 0.0271);Gain of phosphorylation at E5 (P = 0.0271);Gain of phosphorylation at E5 (P = 0.0271);
MVP		0.67
MPC		0.38
ClinPred		0.062	T
GERP RS		0.56
PromoterAI		-0.074	Neutral
Varity_R		0.047
gMVP		0.65
Mutation Taster		=16/84	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: rs771582621; hg19: chr9-21974814; COSMIC: COSV58720941;