Insulin-like 3 (INSL3) expression in Danio rerio: molecular and bioinformatics studies to explore evolution of Its function in Vertebrates

Insl3 is a member of the insulin-IGF-relaxin peptide superfamily. It is a small peptide hormone thatis synthesized as pre-prohormone and is secreted mainly ingonadal tissues in males and females1,2of all mammal so faranalyzed. The organization of insl3gene is similar to that of insulin andrelaxin consisting of two exons and one intron. Bioinformatics analyses that our group performed on almost all known insl3genes and cDNA sequences from DataBase reveals that its structure is conserved among fish and several non mammal vertebrate species but intron length is different. Results of RT-PCR analysis reveils that zebrafish embryos express insl3gene as both major and minor splice variants, the former encoding the normal protein, the latter a truncated peptide comprising a C-terminally extended B-domain. Results of in situhybridization experiments performed in order to localize the alternative transcriptsin male and female adult D. rerio and in silico analyses performed on proximal promoter provide molecular evidence on a possible functional role gain of a singlecopy insl3gene in mammalian testis development.