Discrete cell- and stage-specific localisation of fibroblast growth factors and receptor expression during testis development

Fibroblast growth factors (FGFs) are a family of heparin binding proteins i nvolved in many biological processes. These growth factors act through tyro sine kinase receptors (FGFRs); we have previously used immunohistochemistry to study FGFRs-1-4 in foetal, immature and adult rat testes, and found a d iscrete cell- and stage-specific localisation. Alternative mRNA splicing of FGFRs-1-3 leads to functional variants (IIIb and IIIc) with distinct ligan d binding affinities, therefore we have identified the specific expression of functional FGFR variants and the expression and localisation of FGF liga nds in testes from foetal, immature and adult rats. Using reverse transcrip tase-polymerase chain reaction (RT-PCR), we found that mRNAs for FGFR-1 III b and IIIc, FGFR-2 IIIc, FGFR-3 IIIc and FGFR-4 were expressed in foetal, i mmature and adult testes. Ligands FGFs-1-5, and -8, which can signal throug h these receptors, were also expressed in testes at each age. Localisation of the ligands FGFs-1, -3 and -4 to rat testes by immunohistochemistry show ed a discrete cell- and stage-specific localisation that altered during tes tis development. This study has shown that the ligands FGFs-1, -3 and -4 ar e expressed in the testis and have the capacity to signal through appropria te receptors that are also co-localised or expressed in adjacent cell types in the testis. Collectively, the expression profiles of the seven FGFR var iants and FGFs-1-5 and -8 suggest a functional importance in testicular dev elopment and spermatogenesis. It is concluded that, future studies on the r ole of other FGF ligands, in particular FGFs-1-4, are warranted.