9-21971162-T-G

Variant names:

• chr9-21971162-T-G
• rs756750256
• NM_000077.5:c.197A>C

Variant summary

Our verdict is Likely pathogenic. The variant received 6 ACMG points: 6P and 0B. PM1 PM2 PP3_Moderate

The NM_000077.5(CDKN2A):​c.197A>C​(p.His66Pro) 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 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. H66R) has been classified as Likely benign.

• Frequency: Genomes: not found (cov: 32)
• Consequence: CDKN2A NM_000077.5 missense
• Clinical Significance: Uncertain significance criteria provided, multiple submitters, no conflicts U:3
• Conservation: PhyloP100: 0.647
• Publications: 33 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 6 ACMG points.

• PM1: In a hotspot region, there are 8 aminoacids with missense pathogenic changes in the window of +-8 aminoacids around while only 0 benign, 15 uncertain in NM_000077.5
• PM2: Very rare variant in population databases, with high coverage
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.909

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
CDKN2A	NM_000077.5	c.197A>C	p.His66Pro	missense_variant	Exon 2 of 3	ENST00000304494.10	NP_000068.1
CDKN2A	NM_058195.4	c.240A>C	p.Pro80Pro	synonymous_variant	Exon 2 of 3	ENST00000579755.2	NP_478102.2

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
CDKN2A	ENST00000304494.10	c.197A>C	p.His66Pro	missense_variant	Exon 2 of 3	1	NM_000077.5	ENSP00000307101.5
CDKN2A	ENST00000579755.2	c.240A>C	p.Pro80Pro	synonymous_variant	Exon 2 of 3	1	NM_058195.4	ENSP00000462950.1

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome Cov.: 31

GnomAD4 genome Cov.: 32

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:3

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

not provided Uncertain:1

Jul 13, 2016

GeneDx

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

This variant is denoted CDKN2A c.197A>C at the cDNA level, p.His66Pro (H66P) at the protein level, and results in the change of a Histidine to a Proline (CAC>CCC). This variant has been observed in one family with history of melanoma and pancreatic cancer, but co-segregation studies were not completed (Lynch 2003). CDKN2A His66Pro was not observed in approximately 6,300 individuals of European and African American ancestry in the NHLBI Exome Sequencing Project, suggesting it is not a common benign variant in these populations. Since Histidine and Proline differ in polarity, charge, size or other properties, this is considered a non-conservative amino acid substitution. CDKN2A His66Pro occurs at a position that is not conserved and is located in the 2nd ANK repeat (UniProt). In silico analyses predict that this variant is probably damaging to protein structure and function. Based on currently available evidence, it is unclear whether CDKN2A His66Pro is a pathogenic or benign variant. We consider it to be a variant of uncertain significance. -

Melanoma Uncertain:1

Jan 01, 2017

Centre for Mendelian Genomics, University Medical Centre Ljubljana

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

- -

Hereditary cancer-predisposing syndrome Uncertain:1

Jan 26, 2022

Ambry Genetics

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

The p.H66P variant (also known as c.197A>C), located in coding exon 2 of the CDKN2A gene, results from an A to C substitution at nucleotide position 197. The histidine at codon 66 is replaced by proline, an amino acid with similar properties. This alteration was identified in a clinically suspicious hereditary breast/ovarian cancer family without a pathogenic variant in BRCA1 or BRCA2 (Bonache S et al. J Cancer Res Clin Oncol, 2018 Dec;144:2495-2513). This amino acid position is not well conserved in available vertebrate species. In addition, this alteration is predicted to be deleterious by in silico analysis. Since supporting evidence is limited at this time, the clinical significance of this alteration remains unclear. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	0.70
BayesDel_addAF	Pathogenic	0.37	D
BayesDel_noAF	Pathogenic	0.30
CADD	Benign	23
DANN	Uncertain	0.99
DEOGEN2	Uncertain	0.55	D;T;.;.;.;.;T;.
Eigen	Uncertain	0.41
Eigen_PC	Uncertain	0.41
FATHMM_MKL	Uncertain	0.86	D
LIST_S2	Benign	0.77	T;T;.;T;.;T;T;T
M_CAP	Pathogenic	0.81	D
MetaRNN	Pathogenic	0.91	D;D;D;D;D;D;D;D
MetaSVM	Pathogenic	0.83	D
PhyloP100		0.65
PrimateAI	Uncertain	0.54	T
PROVEAN	Pathogenic	-5.8	D;.;.;D;.;.;.;.
REVEL	Pathogenic	0.79
Sift	Uncertain	0.028	D;.;.;D;.;.;.;.
Sift4G	Benign	0.065	T;T;T;T;T;T;T;D
Polyphen		0.99	D;.;.;.;.;.;.;.
Vest4		0.50
MutPred		0.73		Gain of glycosylation at H66 (P = 0.0374);Gain of glycosylation at H66 (P = 0.0374);.;Gain of glycosylation at H66 (P = 0.0374);.;.;.;.;
MVP		1.0
MPC		1.5
ClinPred		0.84	D
GERP RS		5.8
PromoterAI		0.012	Neutral
Varity_R		0.71
gMVP		0.90
Mutation Taster		=0/100	disease causing

Splicing

Name	Calibrated prediction	Score	Prediction
SpliceAI score (max)		0.030		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: rs756750256; hg19: chr9-21971161; COSMIC: COSV58717748;