3-179209642-G-C

Position:

• chr3-179209642-G-C

Variant summary

Our verdict is Likely pathogenic. Variant got 9 ACMG points: 9P and 0B. PM1 PM2 PP2 PP3_Strong

The NM_006218.4(PIK3CA):​c.1193G>C​(p.Arg398Pro) variant causes a missense change involving the alteration of a conserved nucleotide. The variant allele was found at a frequency of 0.000000685 in 1,460,094 control chromosomes in the GnomAD database, with no homozygous occurrence. 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. R398H) has been classified as Uncertain significance.

• Frequency:
  • Genomes: not found (cov: 32)
  • Exomes 𝑓: 6.8e-7 (0 hom.)
• Consequence: PIK3CA NM_006218.4 missense
• Clinical Significance: Uncertain significance criteria provided, multiple submitters, no conflicts U:2
• Conservation: PhyloP100: 9.60

Genes affected

PIK3CA (HGNC:8975): (phosphatidylinositol-4,5-bisphosphate 3-kinase catalytic subunit alpha) Phosphatidylinositol 3-kinase is composed of an 85 kDa regulatory subunit and a 110 kDa catalytic subunit. The protein encoded by this gene represents the catalytic subunit, which uses ATP to phosphorylate PtdIns, PtdIns4P and PtdIns(4,5)P2. This gene has been found to be oncogenic and has been implicated in cervical cancers. A pseudogene of this gene has been defined on chromosome 22. [provided by RefSeq, Apr 2016]

ACMG classification

Verdict is Likely_pathogenic. Variant got 9 ACMG points.

• PM1: In a domain C2 PI3K-type (size 157) in uniprot entity PK3CA_HUMAN there are 36 pathogenic changes around while only 2 benign (95%) in NM_006218.4
• PM2: Very rare variant in population databases, with high coverage
• PP2: Missense variant in gene, where missense usually causes diseases (based on misZ statistic), PIK3CA. . Gene score misZ 5.5986 (greater than the threshold 3.09). Trascript score misZ 6.1406 (greater than threshold 3.09). GenCC has associacion of gene with hereditary breast carcinoma, vascular malformation, Cowden disease, Cowden syndrome 5, CLOVES syndrome, familial ovarian cancer, megalencephaly-capillary malformation-polymicrogyria syndrome, overgrowth syndrome and/or cerebral malformations due to abnormalities in MTOR pathway genes.
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.964

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
PIK3CA	NM_006218.4	c.1193G>C	p.Arg398Pro	missense_variant	7/21	ENST00000263967.4
PIK3CA	XM_006713658.5	c.1193G>C	p.Arg398Pro	missense_variant	7/21

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
PIK3CA	ENST00000263967.4	c.1193G>C	p.Arg398Pro	missense_variant	7/21	2	NM_006218.4	P1

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome AF: 6.85e-7 AC: 1 AN: 1460094 Hom.: 0 Cov.: 29 AF XY: 0.00 AC XY: 0 AN XY: 726342

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: 9.00e-7

Gnomad4 OTH exome AF: 0.00

GnomAD4 genome Cov.: 32

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:2

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

Inborn genetic diseases Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Ambry Genetics

Jan 31, 2022

The p.R398P variant (also known as c.1193G>C), located in coding exon 6 of the PIK3CA gene, results from a G to C substitution at nucleotide position 1193. The arginine at codon 398 is replaced by proline, an amino acid with dissimilar properties. This amino acid position is conserved. 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. -

Cowden syndrome Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Invitae

Oct 29, 2023

This sequence change replaces arginine, which is basic and polar, with proline, which is neutral and non-polar, at codon 398 of the PIK3CA protein (p.Arg398Pro). This variant is not present in population databases (gnomAD no frequency). This variant has not been reported in the literature in individuals affected with PIK3CA-related conditions. ClinVar contains an entry for this variant (Variation ID: 1745488). Advanced modeling of protein sequence and biophysical properties (such as structural, functional, and spatial information, amino acid conservation, physicochemical variation, residue mobility, and thermodynamic stability) has been performed at Invitae for this missense variant, however the output from this modeling did not meet the statistical confidence thresholds required to predict the impact of this variant on PIK3CA protein function. 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	Pathogenic	0.96
BayesDel_addAF	Pathogenic	0.40	D
BayesDel_noAF	Pathogenic	0.34
CADD	Pathogenic	31
DANN	Uncertain	1.0
DEOGEN2	Pathogenic	0.94	D;.
Eigen	Pathogenic	0.74
Eigen_PC	Pathogenic	0.68
FATHMM_MKL	Pathogenic	0.99	D
LIST_S2	Uncertain	0.97	D;D
M_CAP	Pathogenic	0.30	D
MetaRNN	Pathogenic	0.96	D;D
MetaSVM	Uncertain	0.35	D
MutationAssessor	Uncertain	2.3	M;.
MutationTaster	Benign	1.0	D
PrimateAI	Pathogenic	0.84	D
PROVEAN	Pathogenic	-5.4	D;.
REVEL	Pathogenic	0.87
Sift	Uncertain	0.0010	D;.
Sift4G	Benign	0.074	T;.
Polyphen		1.0	D;.
Vest4		0.87
MutPred		0.85		Loss of MoRF binding (P = 0.075);Loss of MoRF binding (P = 0.075);
MVP		0.89
MPC		2.2
ClinPred		1.0	D
GERP RS		4.3
RBP_binding_hub_radar		0.0
RBP_regulation_power_radar		1.1
Varity_R		0.96
gMVP		0.98

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

No publications associated with this variant yet.

Other links and lift over

hg19: chr3-178927430;