chr9-21971176-C-G

Position:

• chr9-21971176-C-G

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.183G>C​(p.Glu61Asp) variant causes a missense change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.000000693 in 1,443,704 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a benign outcome for this variant. 11/17 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: 6.9e-7 (0 hom.)
• Consequence: CDKN2A NM_000077.5 missense
• Clinical Significance: Uncertain significance criteria provided, single submitter U:1
• Conservation: PhyloP100: 0.114

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 repeat ANK 2 (size 28) in uniprot entity CDN2A_HUMAN there are 15 pathogenic changes around while only 3 benign (83%) in NM_000077.5
• PM2: Very rare variant in population databases, with high coverage
• BP4: Computational evidence support a benign effect (MetaRNN=0.18625996).

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
CDKN2A	NM_000077.5	c.183G>C	p.Glu61Asp	missense_variant	2/3	ENST00000304494.10	NP_000068.1
CDKN2A	NM_058195.4	c.226G>C	p.Ala76Pro	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.183G>C	p.Glu61Asp	missense_variant	2/3	1	NM_000077.5	ENSP00000307101	P2
CDKN2A	ENST00000579755.2	c.226G>C	p.Ala76Pro	missense_variant	2/3	1	NM_058195.4	ENSP00000462950

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome AF: 6.93e-7 AC: 1 AN: 1443704 Hom.: 0 Cov.: 31 AF XY: 0.00000139 AC XY: 1 AN XY: 718442

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: 9.01e-7

Gnomad4 OTH exome AF: 0.00

GnomAD4 genome Cov.: 32

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:1

Revision: criteria provided, single submitter

Submissions by phenotype

Familial melanoma Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Labcorp Genetics (formerly Invitae), Labcorp

Apr 23, 2021

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. Algorithms developed to predict the effect of missense changes on protein structure and function (SIFT, PolyPhen-2, Align-AGVD) all suggest that p.Glu61Asp in p16INK4a and p.Ala76Pro in p14ARF are likely to be tolerated, but these predictions have not been confirmed by published functional studies. This variant has not been reported in the literature in individuals with CDKN2A (p16INK4a)-related conditions. ClinVar contains an entry for this variant (Variation ID: 236982). This variant is not present in population databases (EXAC no frequency). This sequence change replaces glutamic acid with aspartic acid at codon 61 of the CDKN2A protein (p.Glu61Asp). The glutamic acid residue is moderately conserved and there is a small physicochemical difference between glutamic acid and aspartic acid. Alternatively, this sequence change replaces alanine with proline at codon 76 of the CDKN2A (p14ARF) protein (p.Ala76Pro). The alanine residue is moderately conserved and there is a small physicochemical difference between alanine and proline. The CDKN2A gene encodes two different proteins, p16INK4a and p14ARF, which are translated from alternative transcripts that have different open reading frames. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Uncertain	0.44
BayesDel_addAF	Uncertain	0.076	D
BayesDel_noAF	Benign	-0.13
CADD	Benign	17
DANN	Uncertain	0.99
DEOGEN2	Benign	0.028	T;T
Eigen	Benign	-0.86
Eigen_PC	Benign	-0.83
FATHMM_MKL	Benign	0.26	N
LIST_S2	Benign	0.49	.;T
M_CAP	Benign	0.081	D
MetaRNN	Benign	0.19	T;T
MetaSVM	Benign	-0.82	T
MutationTaster	Benign	1.0	N;N;N;N;N;N;N;N;N;N;N;N
PROVEAN	Benign	-1.9	.;N
REVEL	Benign	0.18
Sift	Benign	0.10	.;T
Sift4G	Benign	0.19	T;T
Vest4		0.33
MVP		0.75
ClinPred		0.31	T
GERP RS		1.8

Splicing

Name	Calibrated prediction	Score	Prediction
SpliceAI score (max)		0.040		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: rs878853645; hg19: chr9-21971175;