Endocrine Abstracts

The full-length retinoblastoma interacting zinc-finger protein (RIZ), codified by ten exons, has tumour suppressive and differentiating properties and is known to be a downstream effector in classical oestrogen target tissue. In many normal and malignant tissues alternative splicing isoforms, RIZ1 and RIZ2, frame-shift mutations and/or exon deletions have been found, but their oncogenic role is still debated. Although the presence of RIZ1 in the testis has been described, in gonadal tumours the relative expression of two isoforms, the presence of gene product variants has not been investigated yet. Aim of this study was to evaluate RIZ expression in normal and malignant testis. We analysed five seminomas, four non-seminomas and four control testis tissue samples. RNAs were extracted on frozen samples and RIZ expression measured by semi-quantitative and quantitative Real time RT-PCR using RPS28 as housekeeping gene. In order to identify the presence of different length variants, we analysed the transcripts of the head exon1 and of the tail exons 9 and 10.

Results and discussion: RIZ transcript was found in all samples analysed. Moreover, exon 9-transcript levels were higher than C-terminal conventional tail exon 10 level, absent in one seminoma sample. Thus, the balance of head and tail exon transcript levels revealed a greater expression of a shorter RIZ gene isoform in seminomas vs non-seminomas and health testis samples. Our data suggest that shorter RIZ isoforms, prevalent in malignant testes, may exert a potential oncogenic and de-differentiating role in male gonad.

Disclosure: This work was supported by PRIN 2008 (grant number 20085Y7XT5_005 to AAS).