rs761068783

Positions:

• chr13-48473361-A-C
• chr13-48473361-A-G

Variant summary

Our verdict is Uncertain significance. Variant got 4 ACMG points: 4P and 0B. PM1 PM2

The NM_000321.3(RB1):​c.2491A>C​(p.Ile831Leu) variant causes a missense, splice region change. The variant was absent in control chromosomes in GnomAD project. 3/3 splice prediction tools predict no significant impact on normal splicing. Variant has been reported in ClinVar as Uncertain significance (★).

• Frequency: Genomes: not found (cov: 32)
• Consequence: RB1 NM_000321.3 missense, splice_region
• Scores: Splicing: ADA: 0.4794
• Clinical Significance: Uncertain significance criteria provided, single submitter U:1
• Conservation: PhyloP100: 6.25

Genes affected

RB1 (HGNC:9884): (RB transcriptional corepressor 1) The protein encoded by this gene is a negative regulator of the cell cycle and was the first tumor suppressor gene found. The encoded protein also stabilizes constitutive heterochromatin to maintain the overall chromatin structure. The active, hypophosphorylated form of the protein binds transcription factor E2F1. Defects in this gene are a cause of childhood cancer retinoblastoma (RB), bladder cancer, and osteogenic sarcoma. [provided by RefSeq, Jul 2008]

ACMG classification

Verdict is Uncertain_significance. Variant got 4 ACMG points.

• PM1: In a region_of_interest Domain C; mediates interaction with E4F1 (size 157) in uniprot entity RB_HUMAN there are 8 pathogenic changes around while only 0 benign (100%) in NM_000321.3
• PM2: Very rare variant in population databases, with high coverage

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
RB1	NM_000321.3	c.2491A>C	p.Ile831Leu	missense_variant, splice_region_variant	24/27	ENST00000267163.6	NP_000312.2
RB1	NM_001407165.1	c.2491A>C	p.Ile831Leu	missense_variant, splice_region_variant	24/27		NP_001394094.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
RB1	ENST00000267163.6	c.2491A>C	p.Ile831Leu	missense_variant, splice_region_variant	24/27	1	NM_000321.3	ENSP00000267163	P1
RB1	ENST00000650461.1	c.2491A>C	p.Ile831Leu	missense_variant, splice_region_variant	24/27			ENSP00000497193
RB1	ENST00000643064.1	c.194+91918A>C		intron_variant				ENSP00000496005

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome Cov.: 28

GnomAD4 genome Cov.: 32

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:1

Revision: criteria provided, single submitter

Submissions by phenotype

Retinoblastoma Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Labcorp Genetics (formerly Invitae), Labcorp

Jun 09, 2023

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. 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 disruptive. ClinVar contains an entry for this variant (Variation ID: 1041083). This variant has not been reported in the literature in individuals affected with RB1-related conditions. This variant is not present in population databases (gnomAD no frequency). This sequence change replaces isoleucine, which is neutral and non-polar, with leucine, which is neutral and non-polar, at codon 831 of the RB1 protein (p.Ile831Leu). -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Benign	0.26
BayesDel_addAF	Uncertain	0.040	T
BayesDel_noAF	Benign	-0.18
CADD	Benign	23
DANN	Benign	0.97
DEOGEN2	Benign	0.31	T;.
Eigen	Uncertain	0.34
Eigen_PC	Uncertain	0.45
FATHMM_MKL	Pathogenic	0.99	D
LIST_S2	Uncertain	0.90	D;D
M_CAP	Benign	0.063	D
MetaRNN	Uncertain	0.54	D;D
MetaSVM	Benign	-0.33	T
MutationAssessor	Benign	1.2	L;.
MutationTaster	Benign	1.0	D
PrimateAI	Pathogenic	0.80	T
PROVEAN	Benign	-0.27	N;.
REVEL	Uncertain	0.43
Sift	Benign	0.62	T;.
Sift4G	Benign	0.18	T;.
Polyphen		0.73	P;.
Vest4		0.47
MutPred		0.64		Gain of catalytic residue at L832 (P = 0.0096);Gain of catalytic residue at L832 (P = 0.0096);
MVP		0.72
MPC		1.0
ClinPred		0.89	D
GERP RS		5.7
Varity_R		0.56
gMVP		0.093

Splicing

Name	Calibrated prediction	Score	Prediction
dbscSNV1_ADA	Benign	0.48
dbscSNV1_RF	Benign	0.56
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: rs761068783; hg19: chr13-49047497;