rs764754259

Positions:

• chr13-48465369-G-A
• chr13-48465369-G-C

Variant summary

Our verdict is Pathogenic. Variant got 18 ACMG points: 18P and 0B. PVS1 PM2 PP5_Very_Strong

The NM_000321.3(RB1):​c.2489+1G>A variant causes a splice donor change involving the alteration of a conserved nucleotide. The variant was absent in control chromosomes in GnomAD project. In-silico tool predicts a pathogenic outcome for this variant. 3/3 splice prediction tools predicting alterations to normal splicing. Variant has been reported in ClinVar as Pathogenic (★★).

• Frequency:
  • Genomes: not found (cov: 29)
  • Exomes 𝑓: 0.0 (0 hom.)
  • Failed GnomAD Quality Control
• Consequence: RB1 NM_000321.3 splice_donor
• Scores: Splicing: ADA: 1.000
• Clinical Significance: Pathogenic criteria provided, multiple submitters, no conflicts P:3
• Conservation: PhyloP100: 8.71

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 Pathogenic. Variant got 18 ACMG points.

• PVS1: Splicing +-2 bp (donor or acceptor) variant, LoF is a know mechanism of disease, Cryptic splice site detected, with MaxEntScore 5.4, offset of -37, new splice context is: aagGTctgc. Cryptic site results in frameshift change. If cryptic site found is not functional and variant results in exon loss, it results in frameshift change.
• PM2: Very rare variant in population databases, with high coverage
• PP5: Variant 13-48465369-G-A is Pathogenic according to our data. Variant chr13-48465369-G-A is described in ClinVar as [Pathogenic]. Clinvar id is 428742.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
RB1	NM_000321.3	c.2489+1G>A		splice_donor_variant		ENST00000267163.6	NP_000312.2
RB1	NM_001407165.1	c.2489+1G>A		splice_donor_variant			NP_001394094.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
RB1	ENST00000267163.6	c.2489+1G>A		splice_donor_variant		1	NM_000321.3	ENSP00000267163	P1
RB1	ENST00000650461.1	c.2489+1G>A		splice_donor_variant				ENSP00000497193
RB1	ENST00000643064.1	c.194+83926G>A		intron_variant				ENSP00000496005

Frequencies

GnomAD3 genomes Cov.: 29

GnomAD4 exome Data not reliable, filtered out with message: AC0 AF: 0.00 AC: 0 AN: 1443438 Hom.: 0 Cov.: 34 AF XY: 0.00 AC XY: 0 AN XY: 719190

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: 0.00

Gnomad4 OTH exome AF: 0.00

GnomAD4 genome Cov.: 29

ExAC AF: 0.00000824 AC: 1

ClinVar

Significance: Pathogenic

Submissions summary: Pathogenic:3

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

Retinoblastoma Pathogenic:1

Pathogenic, criteria provided, single submitter

clinical testing

Labcorp Genetics (formerly Invitae), Labcorp

Jul 30, 2023

For these reasons, this variant has been classified as Pathogenic. RNA analysis provides insufficient evidence to determine the effect of this variant on RB1 splicing (Invitae). ClinVar contains an entry for this variant (Variation ID: 428742). This variant is also known as IVS23+1G>A. Disruption of this splice site has been observed in individual(s) with retinoblastoma (PMID: 23301675, 34190019). This variant is not present in population databases (gnomAD no frequency). This sequence change affects a donor splice site in intron 23 of the RB1 gene. It is expected to disrupt RNA splicing. Variants that disrupt the donor or acceptor splice site typically lead to a loss of protein function (PMID: 16199547), and loss-of-function variants in RB1 are known to be pathogenic (PMID: 17096365). -

not provided Pathogenic:1

Pathogenic, criteria provided, single submitter

clinical testing

GeneDx

Mar 26, 2021

Canonical splice site variant in a gene for which loss-of-function is a known mechanism of disease; This variant is associated with the following publications: (PMID: 23301675, 28028119, 23532519, 30031154) -

Hereditary cancer-predisposing syndrome Pathogenic:1

Pathogenic, criteria provided, single submitter

clinical testing

Ambry Genetics

Oct 22, 2019

The c.2489+1G>A intronic pathogenic mutation results from a G to A substitution one nucleotide after coding exon 23 of the RB1 gene. This alteration was identified in a patient with bilateral retinoblastoma and a soft tissue sarcoma. RT-PCR analysis demonstrated abnormal splicing (Chaussade A et al. Eur J Med Genet, 2019 Mar;62:217-223). In addition to the clinical data presented in the literature, alterations that disrupt the canonical splice site are expected to cause aberrant splicing, resulting in an abnormal protein or a transcript that is subject to nonsense-mediated mRNA decay. As such, this alteration is classified as a disease-causing mutation. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
BayesDel_addAF	Pathogenic	0.63	D
BayesDel_noAF	Pathogenic	0.37
CADD	Pathogenic	33
DANN	Uncertain	1.0
Eigen	Pathogenic	1.2
Eigen_PC	Pathogenic	1.1
FATHMM_MKL	Pathogenic	1.0	D
MutationTaster	Benign	1.0	D
GERP RS		5.7
RBP_binding_hub_radar		0.0
RBP_regulation_power_radar		1.7

Splicing

Name	Calibrated prediction	Score	Prediction
dbscSNV1_ADA	Pathogenic	1.0
dbscSNV1_RF	Pathogenic	0.93
SpliceAI score (max)		0.96		Details are displayed if max score is > 0.2
DS_DL_spliceai		0.96		Position offset: -1

Find out detailed SpliceAI scores and Pangolin per-transcript scores at spliceailookup.broadinstitute.org

Publications

LitVar

Other links and lift over

dbSNP: rs764754259; hg19: chr13-49039505; COSMIC: COSV57302985;