13-48380051-A-G

Variant names:

• chr13-48380051-A-G
• rs1555286568
• NM_000321.3:c.1390-2A>G

Variant summary

Our verdict is Pathogenic. The variant received 18 ACMG points: 18P and 0B. PVS1 PM2 PP5_Very_Strong

The NM_000321.3(RB1):​c.1390-2A>G variant causes a splice acceptor, intron change involving the alteration of a conserved nucleotide. The variant allele was found at a frequency of 0.00000178 in 1,122,088 control chromosomes in the GnomAD database, with no homozygous occurrence. 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 Likely pathogenic (★★).

• Frequency:
  • Genomes: not found (cov: 30)
  • Exomes 𝑓: 0.0000018 (0 hom.)
• Consequence: RB1 NM_000321.3 splice_acceptor, intron
• Scores: Splicing: ADA: 1.000
• Clinical Significance: Pathogenic/Likely pathogenic criteria provided, multiple submitters, no conflicts P:2
• Conservation: PhyloP100: 8.22
• Publications: 0 publications found

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]

RB1 Gene-Disease associations (from GenCC):

• hereditary retinoblastoma

  Inheritance: AD Classification: DEFINITIVE, STRONG, SUPPORTIVE Submitted by: Labcorp Genetics (formerly Invitae), Orphanet, G2P, Ambry Genetics
• retinoblastoma

  Inheritance: AD Classification: DEFINITIVE Submitted by: ClinGen
• melanoma

  Inheritance: AD Classification: MODERATE Submitted by: Ambry Genetics

LOC112268118 (HGNC:):

ACMG classification

Our verdict: Pathogenic. The variant received 18 ACMG points.

• PVS1: Splicing +-2 bp (donor or acceptor) variant, LoF is a know mechanism of disease, Cryptic splice site detected, with MaxEntScore 8, offset of 32, new splice context is: ttatccattcaaaattttAGgta. 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 13-48380051-A-G is Pathogenic according to our data. Variant chr13-48380051-A-G is described in ClinVar as Pathogenic/Likely_pathogenic. ClinVar VariationId is 495816.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
RB1	NM_000321.3	c.1390-2A>G		splice_acceptor_variant, intron_variant	Intron 14 of 26	ENST00000267163.6	NP_000312.2
RB1	NM_001407165.1	c.1390-2A>G		splice_acceptor_variant, intron_variant	Intron 14 of 26		NP_001394094.1
RB1	NM_001407166.1	c.1390-2A>G		splice_acceptor_variant, intron_variant	Intron 14 of 16		NP_001394095.1
LOC112268118	XR_002957522.2	n.-177T>C		upstream_gene_variant

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
RB1	ENST00000267163.6	c.1390-2A>G		splice_acceptor_variant, intron_variant	Intron 14 of 26	1	NM_000321.3	ENSP00000267163.4

Frequencies

GnomAD3 genomes Cov.: 30

GnomAD4 exome AF: 0.00000178 AC: 2 AN: 1122088 Hom.: 0 Cov.: 21 AF XY: 0.00000179 AC XY: 1 AN XY: 559710

⚠️ The allele balance in gnomAD version 4 Exomes is significantly skewed from the expected value of 0.5.

African (AFR) AF: 0.00 AC: 0 AN: 23560

American (AMR) AF: 0.00 AC: 0 AN: 23404

Ashkenazi Jewish (ASJ) AF: 0.00 AC: 0 AN: 19482

East Asian (EAS) AF: 0.00 AC: 0 AN: 27458

South Asian (SAS) AF: 0.00 AC: 0 AN: 64584

European-Finnish (FIN) AF: 0.00 AC: 0 AN: 40048

Middle Eastern (MID) AF: 0.00 AC: 0 AN: 3044

European-Non Finnish (NFE) AF: 0.00000228 AC: 2 AN: 875560

Other (OTH) AF: 0.00 AC: 0 AN: 44948

⚠️ The allele balance in gnomAD4 Exomes is highly skewed from 0.5 (p-value = 0), which strongly suggests a high chance of mosaicism in these individuals.

GnomAD4 genome Cov.: 30

ClinVar

Significance: Pathogenic/Likely pathogenic

Submissions summary: Pathogenic:2

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

not specified Pathogenic:1

Nov 07, 2018

Women's Health and Genetics/Laboratory Corporation of America, LabCorp

Significance: Likely pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

Variant summary: RB1 c.1390-2A>G is located in a canonical splice-site and is predicted to affect mRNA splicing resulting in a significantly altered protein due to either exon skipping, shortening, or inclusion of intronic material. Several computational tools predict a significant impact on normal splicing: Four predict the variant abolishes a 3' acceptor site. However, these predictions have yet to be confirmed by functional studies. The variant was absent in 29758 control chromosomes. c.1390-2A>G has been reported in the literature in one individual affected with Retinoblastoma. These data do not allow any conclusion about variant significance. To our knowledge, no experimental evidence demonstrating an impact on protein function has been reported. One clinical diagnostic laboratory has submitted clinical-significance assessments for this variant to ClinVar after 2014 without evidence for independent evaluation and classified the variant as pathogenic. Based on the evidence outlined above, the variant was classified as likely pathogenic.

Retinoblastoma Pathogenic:1

Nov 14, 2017

Labcorp Genetics (formerly Invitae), Labcorp

Significance: Pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

This sequence change affects an acceptor splice site in intron 14 of the RB1 gene. It is expected to disrupt RNA splicing and likely results in an absent or disrupted protein product. This variant is not present in population databases (ExAC no frequency). This variant has been reported in individuals affected with retinoblastoma (PMID: 27155049, Invitae). Donor and acceptor splice site variants typically lead to a loss of protein function (PMID: 16199547), and loss-of-function variants in RB1 are known to be pathogenic (PMID: 17096365). For these reasons, this variant has been classified as Pathogenic.

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
BayesDel_addAF	Pathogenic	0.63	D
BayesDel_noAF	Pathogenic	0.22
CADD	Pathogenic	32
DANN	Uncertain	0.99
DEOGEN2	Benign	0.0	.;.
Eigen	Pathogenic	1.1
Eigen_PC	Pathogenic	0.97
FATHMM_MKL	Pathogenic	1.0	D
LIST_S2	Benign	0.0	.;.
MetaRNN	Benign	0.0	.;.
MutationAssessor	Benign	0.0	.;.
PhyloP100		8.2
PROVEAN	Benign	0.0	.;.
REVEL	Benign	0.0
Sift	Pathogenic	0.0	.;.
Sift4G	Pathogenic	0.0	.;.
Vest4		0.0
GERP RS		5.5
Mutation Taster		=1/99	disease causing (ClinVar)

Splicing

Name	Calibrated prediction	Score	Prediction
dbscSNV1_ADA	Pathogenic	1.0
dbscSNV1_RF	Pathogenic	0.94
SpliceAI score (max)		0.96		Details are displayed if max score is > 0.2
DS_AG_spliceai		0.20		Position offset: 9
DS_AL_spliceai		0.96		Position offset: 2

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

Other links and lift over

dbSNP: rs1555286568; hg19: chr13-48954187;