17-7674197-T-G

Variant names:

• chr17-7674197-T-G
• rs587781433
• NM_000546.6:c.766A>C

Variant summary

Our verdict is Likely pathogenic. The variant received 9 ACMG points: 9P and 0B. PM1 PM2 PP3_Strong PP5

The NM_000546.6(TP53):​c.766A>C​(p.Thr256Pro) variant causes a missense change. 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 Conflicting classifications of pathogenicity (no stars). Another variant affecting the same amino acid position, but resulting in a different missense (i.e. T256I) has been classified as Uncertain significance.

• Frequency: Genomes: not found (cov: 30)
• Consequence: TP53 NM_000546.6 missense
• Clinical Significance: Conflicting classifications of pathogenicity criteria provided, conflicting classifications P:3 U:3
• Conservation: PhyloP100: 6.24
• Publications: 55 publications found

Genes affected

TP53 (HGNC:11998): (tumor protein p53) This gene encodes a tumor suppressor protein containing transcriptional activation, DNA binding, and oligomerization domains. The encoded protein responds to diverse cellular stresses to regulate expression of target genes, thereby inducing cell cycle arrest, apoptosis, senescence, DNA repair, or changes in metabolism. Mutations in this gene are associated with a variety of human cancers, including hereditary cancers such as Li-Fraumeni syndrome. Alternative splicing of this gene and the use of alternate promoters result in multiple transcript variants and isoforms. Additional isoforms have also been shown to result from the use of alternate translation initiation codons from identical transcript variants (PMIDs: 12032546, 20937277). [provided by RefSeq, Dec 2016]

TP53 Gene-Disease associations (from GenCC):

• breast cancer

  Inheritance: AD Classification: DEFINITIVE Submitted by: Ambry Genetics
• Li-Fraumeni syndrome

  Inheritance: AD Classification: DEFINITIVE, STRONG, SUPPORTIVE Submitted by: Labcorp Genetics (formerly Invitae), G2P, ClinGen, Orphanet
• Li-Fraumeni syndrome 1

  Inheritance: AD Classification: DEFINITIVE, STRONG Submitted by: Ambry Genetics, Genomics England PanelApp
• adrenocortical carcinoma, hereditary

  Inheritance: AD Classification: STRONG Submitted by: Ambry Genetics
• sarcoma

  Inheritance: AD Classification: STRONG Submitted by: Genomics England PanelApp
• bone marrow failure syndrome 5

  Inheritance: AD Classification: MODERATE Submitted by: Ambry Genetics
• colorectal cancer

  Inheritance: AD Classification: MODERATE Submitted by: Ambry Genetics
• choroid plexus carcinoma

  Inheritance: AD Classification: SUPPORTIVE Submitted by: Orphanet

ACMG classification

Our verdict: Likely_pathogenic. The variant received 9 ACMG points.

• PM1: In a hotspot region, there are 41 aminoacids with missense pathogenic changes in the window of +-8 aminoacids around while only 7 benign, 31 uncertain in NM_000546.6
• PM2: Very rare variant in population databases, with high coverage
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.987
• PP5: Variant 17-7674197-T-G is Pathogenic according to our data. Variant chr17-7674197-T-G is described in ClinVar as Conflicting_classifications_of_pathogenicity. ClinVar VariationId is 528269.

Variant Effect in Transcripts

ACMG analysis was done for transcript: NM_000546.6. You can select a different transcript below to see updated ACMG assignments.

RefSeq Transcripts

Selected	Gene	Transcript	Tags	HGVSc	HGVSp	Effect	Exon Rank	Protein	UniProt
	TP53	NM_000546.6	MANE Select	c.766A>C	p.Thr256Pro	missense	Exon 7 of 11	NP_000537.3
	TP53	NM_001126112.3		c.766A>C	p.Thr256Pro	missense	Exon 7 of 11	NP_001119584.1
	TP53	NM_001407262.1		c.766A>C	p.Thr256Pro	missense	Exon 8 of 12	NP_001394191.1

Ensembl Transcripts

Selected	Gene	Transcript	Tags	HGVSc	HGVSp	Effect	Exon Rank	Protein	UniProt
	TP53	ENST00000269305.9	TSL:1 MANE Select	c.766A>C	p.Thr256Pro	missense	Exon 7 of 11	ENSP00000269305.4
	TP53	ENST00000445888.6	TSL:1	c.766A>C	p.Thr256Pro	missense	Exon 7 of 11	ENSP00000391478.2
	TP53	ENST00000610292.4	TSL:1	c.649A>C	p.Thr217Pro	missense	Exon 6 of 10	ENSP00000478219.1

Frequencies

GnomAD3 genomes Cov.: 30

GnomAD4 exome Cov.: 32

GnomAD4 genome Cov.: 30

ClinVar

Significance: Conflicting classifications of pathogenicity

Submissions summary: Pathogenic:3 Uncertain:3

Revision: criteria provided, conflicting classifications

Submissions by phenotype

Li-Fraumeni syndrome 1 Pathogenic:1 Uncertain:1

Feb 16, 2024

Myriad Genetics, Inc.

Significance: Likely pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

This variant is considered likely pathogenic. Functional studies indicate this variant impacts protein function [PMID: 29979965]. This variant is expected to disrupt protein structure [Myriad internal data].

Jun 18, 2022

Genome-Nilou Lab

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

Hereditary cancer-predisposing syndrome Pathogenic:1 Uncertain:1

Jun 12, 2025

Ambry Genetics

Significance: Pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

The p.T256P variant (also known as c.766A>C), located in coding exon 6 of the TP53 gene, results from an A to C substitution at nucleotide position 766. The threonine at codon 256 is replaced by proline, an amino acid with highly similar properties. This alteration has been reported in an individual with osteosarcoma (Perry JA et al. Proc. Natl. Acad. Sci. U.S.A., 2014 Dec;111:E5564-73). This variant is in the DNA binding domain of the TP53 protein and is reported to have non-functional transactivation in yeast based assays (Kato S et al. Proc. Natl. Acad. Sci. USA. 2003 Jul;100:8424-9). Studies conducted in human cell lines indicate this alteration is deficient at growth suppression and has a dominant negative effect (Kotler E et al. Mol.Cell. 2018 Jul;71:178-190.e8; Giacomelli AO et al. Nat. Genet. 2018 Oct;50:1381-1387). This amino acid position is highly conserved in available vertebrate species. This variant is considered to be rare based on population cohorts in the Genome Aggregation Database (gnomAD). In addition, this alteration is predicted to be deleterious by in silico analysis. Based on the supporting evidence, this alteration is interpreted as a disease-causing mutation.

Jun 18, 2022

Genome-Nilou Lab

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

not provided Pathogenic:1

Jul 18, 2023

GeneDx

Significance: Pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

Published functional studies demonstrate a damaging effect: non-functional transactivation and impaired growth suppression ability (Kato et al., 2003; Giacomelli et al., 2018; Kotler et al., 2018); Not observed at significant frequency in large population cohorts (gnomAD); In silico analysis supports that this missense variant has a deleterious effect on protein structure/function; This variant is associated with the following publications: (PMID: 15510160, 30224644, 12826609, 29979965, 30076369, 25512523)

Li-Fraumeni syndrome Uncertain:1

Nov 23, 2023

Labcorp Genetics (formerly Invitae), Labcorp

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

This sequence change replaces threonine, which is neutral and polar, with proline, which is neutral and non-polar, at codon 256 of the TP53 protein (p.Thr256Pro). This variant is not present in population databases (gnomAD no frequency). This missense change has been observed in individual(s) with osteosarcoma (PMID: 25512523). ClinVar contains an entry for this variant (Variation ID: 528269). Advanced modeling performed at Invitae incorporating data from internal and/or published experimental studies (PMID: 12826609, 29979965, 30224644) indicates that this missense variant is expected to disrupt TP53 function with a positive predictive value of 97.5%. Experimental studies have shown that this missense change affects TP53 function (PMID: 12826609, 29979965, 30224644). 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 v4.9

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	0.99
BayesDel_addAF	Pathogenic	0.56	D
BayesDel_noAF	Pathogenic	0.57
CADD	Uncertain	24
DANN	Uncertain	1.0
DEOGEN2	Pathogenic	0.87	D
Eigen	Uncertain	0.56
Eigen_PC	Uncertain	0.42
FATHMM_MKL	Pathogenic	0.99	D
LIST_S2	Pathogenic	0.99	D
M_CAP	Pathogenic	0.86	D
MetaRNN	Pathogenic	0.99	D
MetaSVM	Pathogenic	1.0	D
MutationAssessor	Pathogenic	3.3	M
PhyloP100		6.2
PrimateAI	Uncertain	0.66	T
PROVEAN	Pathogenic	-5.3	D
REVEL	Pathogenic	0.94
Sift	Pathogenic	0.0	D
Sift4G	Pathogenic	0.0010	D
Polyphen		1.0	D
Vest4		0.86
MutPred		0.92		Gain of glycosylation at T253 (P = 0.0453)
MVP		1.0
MPC		0.41
ClinPred		1.0	D
GERP RS		3.5
Varity_R		0.99
gMVP		0.90

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: rs587781433; hg19: chr17-7577515; COSMIC: COSV52801994; COSMIC: COSV52801994;