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J.L. Perez, K.R. Van Quill, J.M. O'Brien; Expression of Truncated Mutant pRB in Retinoblastoma . Invest. Ophthalmol. Vis. Sci. 2006;47(13):2809.
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© ARVO (1962-2015); The Authors (2016-present)
>75% of germline retinoblastoma gene (RB1) mutations result in a premature stop codon and a predicted truncated protein product. It remains unclear whether these truncated mutant proteins are expressed in retinoblastoma (RB) tumors or whether their expression is blocked by nonsense–mediated mRNA decay (NMD), a cellular regulatory mechanism that recognizes and degrades mRNA transcripts containing a premature stop. This information could be useful in predicting disease phenotype in RB patients carrying truncating RB1 mutations. We investigated truncated mutant retinoblastoma protein expression in RB tumor specimens by immunohistochemistry and by genomic sequencing.
Sections from 10 archival retinoblastoma specimens were stained with antibodies recognizing N– and C–terminal sequences of the retinoblastoma protein (pRb) using the avidin/biotinylated peroxidase method. RB1 mutations in the same tumor specimens were characterized by DNA extraction, PCR, and exon–by–exon sequencing.
N– and C–terminal specific pRb antibodies showed cellular localization in normal retina consistent with previous reports. Expression of truncated mutant pRb can be detected by reaction with N–terminal and not C–terminal specific antibody. These results can be confirmed by RB1 sequence analysis.
By using immunhistochemistry and genomic sequencing we can correlate expression of truncated mutant pRb in tumor tissue with the presence of a truncating RB1 mutation in the same specimen.
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