Anti-Müllerian-hormone and gonadotropin dependent changes in testis and pituitary of a cichlid fish, the Nile tilapia (Oreochromis niloticus).

• Applicant: Dr. Frank Pfennig
• Subject Area: Animal Physiology and Biochemistry
• Term: from 2016 to 2020
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 321375215

Nile tilapia is an African cichlid and develops social hierarchies with dominant and subordinate animals. Dominant males have high levels of follicle stimulating hormone (FSH) and spermatogenesis is activated. A dominant individual can suppress the reproductive function of subordinates. Spermatogenesis of vertebrates is controlled by gonadotropins (like FSH) and androgens (like testosterone). The Anti-Müllerian-hormone (AMH) is an important regulator of germ cell development and steroid production in the gonads of vertebrates. AMH is differentially expressed in the testes from dominant and subordinate tilapia males. We want to explore the interrelations of these hormones. We use tilapia as a model fish with the aim to correlate changes in the social status with the endocrine and paracrine control of spermatogenesis. By the use of ex vivo testis-organ cultures we will investigate the influence of recombinant FSH, 11-Ketotestosteron (11-KT) and recombinant AMH on testis development. Expression and cytological analysis will be performed by quantitative PCR and immune-histological detection of selected key genes and by estimation of proliferation and apoptosis at the cellular level. Furthermore, the analysis of the transcriptome of the hormone-treated testis-cultures will be used to identify AMH target genes and to obtain information about FSH and 11-KT dependent or independent expression of AMH controlled genes. The identified differentially expressed genes of the treated organ cultures will be compared with the transcriptome data from dominant and subordinate males.Social dominance is accompanied by a hyperplasia of gonadotropic cells. AMH is also present outside of the gonads in brain and pituitary of Nile tilapia and is a strong candidate for regulation of cell proliferation and development. Therefore, we also intend to investigate the influence of AMH on gonadotropic cells by organotypic brain-slice cultures. AMH can be allocated also via the blood stream and by an AMH specific ELISA we will determine the serum level in dominant and subordinate males. The outcome of this project will give insight into hormonal control and the role of the social status and social stress on gonad development and reproduction in Nile tilapia, which is an economically important species. The results will also help to unravel the complex endocrine control of spermatogenesis in mammals.

• DFG Programme: Research Grants
• International Connection: Israel
• International Co-Applicant: Professorin Berta Levavi-Sivan, Ph.D.