Abstract: 67

EXPRESSION OF NEUROTROPIN LIGANDS (BRAIN-DERIVED NEUROTROPIC FACTOR AND NEUROTROPIN 4/5) AND RECEPTOR (trkB) DURING EMBRYONIC AND POSTNATAL RAT TESTIS DEVELOPMENT: POTENTIAL FOR COMPENSATION BETWEEN NEUROTROPIN LIGANDS AND RECEPTORS.

Andrea S. Cupp^{1 *}, Michael K. Skinner^{1 *}
Center for Reproductive Biology, and the Dept of Genetics and Cell Biology, Washington State University, Pullman, Washington, USA 99164-4234. ¹

The objective of this study was to determine if compensation of neurotropin ligands and receptors occur during critical processes in embryonic rat testis development. Previous data has implicated a role for Neurotropin-3 (NT3), Nerve growth factor (NGF), trkC and trkA in SCF and embryonic testis growth. However, examination of testes from NT3, trkA and trkC knockout mice showed no gross morphological abnormalities in SCF. Testes from NT3 and trkC knockout mice have reduced interstitial cell area. New results from trkC and trkA knockout mice suggest that there is increased somatic and germ cell apoptosis at different stages of testis development. Therefore, the hypothesis was tested that neurotropins produced by Sertoli cells induce migration of cells from the mesonephros that are required for SCF. In the absence of one neurotropin ligand or receptor other family members may compensate to allow for normal SCF and cell growth to occur. Immunohistochemical studies demonstrated that both Brain-Derived Neurotropic factor (BDNF) and Neurotropin 4/5 (NT₄/5), like NT3, are expressed in Sertoli cells at embryonic day 14 (E14). However, at postnatal day 0 (P0), P5 and P20, NT₄/5 was localized to germ cells. In contrast, BDNF remained localized to the Sertoli cells at P0, P5 and P20. Interestingly, trkB was not present at E14 (through RT-PCR), however, trkB protein was expressed in interstitial cells at E18 and P0 with localization to selective germ cells at P5. To extend these results, experiments are being conducted in the embryonic pig testis to determine conservation of neurotropin expression. Taken together, these results suggest that potential compensation may occur with different neurotropin ligands and receptors to accomplish critical events in embryonic and postnatal testis morphogenesis and development.

    This abstract is being presented on Sunday, August 1 at 8:00 AM to 10:15 AM at CUB 2nd Floor Ballroom.