9-21971034-C-A

Position:

• chr9-21971034-C-A

Variant summary

Our verdict is Uncertain significance. Variant got 2 ACMG points: 4P and 2B. PM1 PM2 BP4_Moderate

The NM_000077.5(CDKN2A):​c.325G>T​(p.Ala109Ser) variant causes a missense change involving the alteration of a non-conserved nucleotide. The variant was absent in control chromosomes in GnomAD project. In-silico tool predicts a benign outcome for this variant. 12/20 in silico tools predict a benign outcome for this variant. Variant has been reported in ClinVar as Uncertain significance (★★).

• Frequency:
  • Genomes: not found (cov: 32)
  • Exomes 𝑓: 0.0 (0 hom.)
  • Failed GnomAD Quality Control
• Consequence: CDKN2A NM_000077.5 missense
• Clinical Significance: Uncertain significance criteria provided, multiple submitters, no conflicts U:3
• Conservation: PhyloP100: -0.141

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 2 ACMG points.

• PM1: In a chain Cyclin-dependent kinase inhibitor 2A (size 155) in uniprot entity CDN2A_HUMAN there are 42 pathogenic changes around while only 12 benign (78%) in NM_000077.5
• PM2: Very rare variant in population databases, with high coverage
• BP4: Computational evidence support a benign effect (MetaRNN=0.24636382).

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
CDKN2A	NM_000077.5	c.325G>T	p.Ala109Ser	missense_variant	2/3	ENST00000304494.10	NP_000068.1
CDKN2A	NM_058195.4	c.368G>T	p.Cys123Phe	missense_variant	2/3	ENST00000579755.2	NP_478102.2

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
CDKN2A	ENST00000304494.10	c.325G>T	p.Ala109Ser	missense_variant	2/3	1	NM_000077.5	ENSP00000307101	P2
CDKN2A	ENST00000579755.2	c.368G>T	p.Cys123Phe	missense_variant	2/3	1	NM_058195.4	ENSP00000462950

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome Data not reliable, filtered out with message: AC0 AF: 0.00 AC: 0 AN: 1454012 Hom.: 0 Cov.: 31 AF XY: 0.00 AC XY: 0 AN XY: 723582

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: 0.00

Gnomad4 OTH exome AF: 0.00

GnomAD4 genome Cov.: 32

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:3

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

Hereditary cancer-predisposing syndrome Uncertain:2

Uncertain significance, criteria provided, single submitter	clinical testing	Color Diagnostics, LLC DBA Color Health	Sep 30, 2018	- -
Uncertain significance, criteria provided, single submitter	clinical testing	Ambry Genetics	Jan 30, 2024	The p.A109S variant (also known as c.325G>T), located in coding exon 2 of the CDKN2A gene, results from a G to T substitution at nucleotide position 325. The alanine at codon 109 is replaced by serine, an amino acid with similar properties. This amino acid position is not well conserved in available vertebrate species. In addition, the in silico prediction for this alteration is inconclusive. Based on the available evidence, the clinical significance of this alteration remains unclear. -

Familial melanoma Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Labcorp Genetics (formerly Invitae), Labcorp

Nov 25, 2023

The CDKN2A gene encodes two different proteins, p16INK4a and p14ARF, which are translated from alternative transcripts with different open reading frames. Both transcripts have been analyzed. We report either the variant with the higher classification or default to the CDKN2A (p16INK4a) variant. This report therefore includes the details for the CDKN2A (p16INK4a) variant. This sequence change replaces alanine, which is neutral and non-polar, with serine, which is neutral and polar, at codon 109 of the CDKN2A (p16INK4a) protein (p.Ala109Ser). This variant is not present in population databases (gnomAD no frequency). This missense change has been observed in individual(s) with melanoma (PMID: 28830923). This variant is also known as c.368G>T (p.Cys123Phe) in the CDKN2A (p14ARF) transcript. ClinVar contains an entry for this variant (Variation ID: 628079). 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. Experimental studies have shown that this missense change does not substantially affect CDKN2A (p16INK4a) function (PMID: 12606942). 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	0.14
BayesDel_addAF	Uncertain	0.10	D
BayesDel_noAF	Benign	-0.19
CADD	Benign	17
DANN	Benign	0.93
DEOGEN2	Benign	0.057	T;T;.;.;.;.;T;.
Eigen	Benign	-0.20
Eigen_PC	Benign	-0.18
FATHMM_MKL	Benign	0.27	N
LIST_S2	Benign	0.69	T;T;.;T;.;T;T;T
M_CAP	Uncertain	0.16	D
MetaRNN	Benign	0.25	T;T;T;T;T;T;T;T
MetaSVM	Benign	-0.84	T
MutationTaster	Benign	1.0	N;N;N;N;N;N;N;N;N;N;N;N
PrimateAI	Benign	0.34	T
PROVEAN	Benign	-0.44	N;.;.;N;.;.;.;.
REVEL	Uncertain	0.43
Sift	Benign	0.52	T;.;.;T;.;.;.;.
Sift4G	Benign	0.55	T;T;T;T;T;T;T;T
Polyphen		0.62	P;.;.;.;.;.;.;.
Vest4		0.17
MutPred		0.40		Loss of catalytic residue at A109 (P = 0.0135);Loss of catalytic residue at A109 (P = 0.0135);.;Loss of catalytic residue at A109 (P = 0.0135);.;.;.;.;
MVP		0.96
MPC		0.40
ClinPred		0.25	T
GERP RS		3.9
Varity_R		0.088
gMVP		0.52

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

Publications

LitVar

Other links and lift over

dbSNP: rs372481694; hg19: chr9-21971033;