NM_000321.3:c.2236G>C

Variant names:

• chr13-48465022-G-C
• rs958914211
• NM_000321.3:c.2236G>C

Variant summary

Our verdict is Uncertain significance. The variant received 2 ACMG points: 2P and 0B. PM2

The NM_000321.3(RB1):​c.2236G>C​(p.Glu746Gln) variant causes a missense change involving the alteration of a conserved nucleotide. The variant allele was found at a frequency of 0.00000374 in 1,068,334 control chromosomes in the GnomAD database, with no homozygous occurrence. Variant has been reported in ClinVar as Uncertain significance (★★). Another variant affecting the same amino acid position, but resulting in a different missense (i.e. E746G) has been classified as Uncertain significance.

• Frequency:
  • Genomes: not found (cov: 27)
  • Exomes 𝑓: 0.0000037 (0 hom.)
• Consequence: RB1 NM_000321.3 missense
• Clinical Significance: Uncertain significance criteria provided, multiple submitters, no conflicts U:3
• Conservation: PhyloP100: 9.60
• 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

ACMG classification

Our verdict: Uncertain_significance. The variant received 2 ACMG points.

• PM2: Very rare variant in population databases, with high coverage

Variant Effect in Transcripts

ACMG analysis was done for transcript: NM_000321.3. 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
	RB1	NM_000321.3	MANE Select	c.2236G>C	p.Glu746Gln	missense	Exon 22 of 27	NP_000312.2
	RB1	NM_001407165.1		c.2236G>C	p.Glu746Gln	missense	Exon 22 of 27	NP_001394094.1

Ensembl Transcripts

Selected	Gene	Transcript	Tags	HGVSc	HGVSp	Effect	Exon Rank	Protein	UniProt
	RB1	ENST00000267163.6	TSL:1 MANE Select	c.2236G>C	p.Glu746Gln	missense	Exon 22 of 27	ENSP00000267163.4
	RB1	ENST00000467505.6	TSL:1	n.*1604G>C		non_coding_transcript_exon	Exon 17 of 22	ENSP00000434702.1
	RB1	ENST00000467505.6	TSL:1	n.*1604G>C		3_prime_UTR	Exon 17 of 22	ENSP00000434702.1

Frequencies

GnomAD3 genomes Cov.: 27

GnomAD4 exome AF: 0.00000374 AC: 4 AN: 1068334 Hom.: 0 Cov.: 37 AF XY: 0.00000372 AC XY: 2 AN XY: 538280

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

African (AFR) AF: 0.000152 AC: 4 AN: 26372

American (AMR) AF: 0.00 AC: 0 AN: 38652

Ashkenazi Jewish (ASJ) AF: 0.00 AC: 0 AN: 17730

East Asian (EAS) AF: 0.00 AC: 0 AN: 22554

South Asian (SAS) AF: 0.00 AC: 0 AN: 79686

European-Finnish (FIN) AF: 0.00 AC: 0 AN: 38854

Middle Eastern (MID) AF: 0.00 AC: 0 AN: 3192

European-Non Finnish (NFE) AF: 0.00 AC: 0 AN: 800180

Other (OTH) AF: 0.00 AC: 0 AN: 41114

⚠️ The allele balance in gnomAD4 Exomes is highly skewed from 0.5 (p-value = 0.000173310), which strongly suggests a high chance of mosaicism in these individuals.

GnomAD4 genome Cov.: 27

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:3

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

Retinoblastoma Uncertain:1

Apr 30, 2024

Labcorp Genetics (formerly Invitae), Labcorp

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

This sequence change replaces glutamic acid, which is acidic and polar, with glutamine, which is neutral and polar, at codon 746 of the RB1 protein (p.Glu746Gln). This variant is not present in population databases (gnomAD no frequency). This variant has not been reported in the literature in individuals affected with RB1-related conditions. ClinVar contains an entry for this variant (Variation ID: 575364). Advanced modeling of protein sequence and biophysical properties (such as structural, functional, and spatial information, amino acid conservation, physicochemical variation, residue mobility, and thermodynamic stability) performed at Invitae indicates that this missense variant is not expected to disrupt RB1 protein function with a negative predictive value of 80%. 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.

not provided Uncertain:1

Mar 12, 2024

GeneDx

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

Not observed at significant frequency in large population cohorts (gnomAD); In silico analysis supports that this missense variant does not alter protein structure/function; Has not been previously published as pathogenic or benign to our knowledge; This variant is associated with the following publications: (PMID: 23516486)

Hereditary cancer-predisposing syndrome Uncertain:1

Nov 17, 2023

Ambry Genetics

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

The p.E746Q variant (also known as c.2236G>C), located in coding exon 22 of the RB1 gene, results from a G to C substitution at nucleotide position 2236. The glutamic acid at codon 746 is replaced by glutamine, an amino acid with highly similar properties. This amino acid position is well conserved in available vertebrate species. In addition, the in silico prediction for this alteration is inconclusive. Since supporting evidence is limited at this time, the clinical significance of this alteration remains unclear.

Computational scores

Source: dbNSFP v4.9

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Benign	0.18
BayesDel_addAF	Uncertain	0.13	D
BayesDel_noAF	Uncertain	-0.060
CADD	Pathogenic	29
DANN	Uncertain	1.0
DEOGEN2	Uncertain	0.62	D
Eigen	Pathogenic	0.72
Eigen_PC	Pathogenic	0.76
FATHMM_MKL	Pathogenic	0.99	D
LIST_S2	Uncertain	0.95	D
M_CAP	Uncertain	0.096	D
MetaRNN	Uncertain	0.58	D
MetaSVM	Uncertain	0.61	D
MutationAssessor	Benign	1.4	L
PhyloP100		9.6
PrimateAI	Uncertain	0.58	T
PROVEAN	Benign	-1.2	N
REVEL	Uncertain	0.58
Sift	Benign	0.11	T
Sift4G	Uncertain	0.015	D
Polyphen		0.99	D
Vest4		0.41
MutPred		0.46		Loss of loop (P = 0.0203)
MVP		0.80
MPC		1.2
ClinPred		0.94	D
GERP RS		5.5
Varity_R		0.60
gMVP		0.50
Mutation Taster		=62/38	polymorphism

Splicing

Name	Calibrated prediction	Score	Prediction
SpliceAI score (max)		0.020		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: rs958914211; hg19: chr13-49039158;