13-48349024-G-GT

Position:

• chr13-48349024-G-GT

Variant summary

Our verdict is Pathogenic. Variant got 12 ACMG points: 12P and 0B. PVS1_Moderate PM2 PP5_Very_Strong

The ENST00000267163.6(RB1):​c.607+1_607+2insT variant causes a splice donor, intron change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.000000693 in 1,442,952 control chromosomes in the GnomAD database, with no homozygous occurrence. 1/1 splice prediction tools predicting alterations to normal splicing. Variant has been reported in ClinVar as Pathogenic (★★).

• Frequency:
  • Genomes: not found (cov: 32)
  • Exomes 𝑓: 6.9e-7 (0 hom.)
• Consequence: RB1 ENST00000267163.6 splice_donor, intron
• Clinical Significance: Pathogenic criteria provided, multiple submitters, no conflicts P:2
• Conservation: PhyloP100: 2.05

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 12 ACMG points.

• PVS1: Splicing +-2 bp (donor or acceptor) variant, product NOT destroyed by NMD, known LOF gene, truncates exone, which is 0.024040187 fraction of the gene. Cryptic splice site detected, with MaxEntScore 3.4, offset of 0 (no position change), new splice context is: aagGTtaag. Cryptic site results in inframe 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 13-48349024-G-GT is Pathogenic according to our data. Variant chr13-48349024-G-GT is described in ClinVar as [Pathogenic]. Clinvar id is 428720.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.607+2dupT		splice_region_variant, intron_variant		ENST00000267163.6	NP_000312.2
RB1	NM_001407165.1	c.607+2dupT		splice_region_variant, intron_variant			NP_001394094.1
RB1	NM_001407166.1	c.607+2dupT		splice_region_variant, intron_variant			NP_001394095.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
RB1	ENST00000267163.6	c.607+1_607+2insT		splice_donor_variant, intron_variant		1	NM_000321.3	ENSP00000267163.4
RB1	ENST00000467505.5	n.138-10993_138-10992insT		intron_variant		1		ENSP00000434702.1
RB1	ENST00000650461.1	c.607+1_607+2insT		splice_donor_variant, intron_variant				ENSP00000497193.1
RB1	ENST00000525036.1	n.769+1_769+2insT		splice_donor_variant, intron_variant		3

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome AF: 6.93e-7 AC: 1 AN: 1442952 Hom.: 0 Cov.: 30 AF XY: 0.00000139 AC XY: 1 AN XY: 717874

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: 0.0000118

Gnomad4 FIN exome AF: 0.00

Gnomad4 NFE exome AF: 0.00

Gnomad4 OTH exome AF: 0.00

GnomAD4 genome Cov.: 32

ClinVar

Significance: Pathogenic

Submissions summary: Pathogenic:2

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

Mar 26, 2019

This variant has been observed to be de novo in an individual affected with retinoblastoma (Invitae). ClinVar contains an entry for this variant (Variation ID: 428720). This variant is not present in population databases (ExAC no frequency). This sequence change falls in intron 6 of the RB1 gene. It does not directly change the encoded amino acid sequence of the RB1 protein, but it affects a nucleotide within the consensus splice site of the intron. For these reasons, this variant has been classified as Pathogenic. Nucleotide substitutions within the consensus splice site are a relatively common cause of aberrant splicing (PMID: 17576681, 9536098). Algorithms developed to predict the effect of sequence changes on RNA splicing suggest that this variant may disrupt the consensus splice site, but this prediction has not been confirmed by published transcriptional studies. -

Hereditary cancer-predisposing syndrome Pathogenic:1

Pathogenic, criteria provided, single submitter

clinical testing

Ambry Genetics

Jul 24, 2024

The c.607+2dupT intronic variant, results from a duplication of two nucleotides at nucleotide position 607 after intron 6 of the RB1 gene. This nucleotide position is highly conserved in available vertebrate species. In silico splice site analysis predicts that this alteration will weaken the native splice donor site. This variant has been observed in at least one individual with a personal and/or family history that is consistent with RB1-associated disease (Ambry internal data). This variant is considered to be rare based on population cohorts in the Genome Aggregation Database (gnomAD). 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

Splicing

Name	Calibrated prediction	Score	Prediction
SpliceAI score (max)		0.83		Details are displayed if max score is > 0.2
DS_DL_spliceai		0.83		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: rs1131690895; hg19: chr13-48923160;