Research Interests 

We are focused upon understanding the properties and functioning of the critical components controlling reproduction in fish; reproduction in vertebrates is dependent on the coordinated actions of various hormones associated with the hypothalamus–pituitary-gonadal axis (HPG). The major components and functions of the mammalian hypothalamic-pituitary axis are conserved in fish. However, fish pituitaries exhibit three traits that distinguish them from those of mammals: first, hypothalamic axons in teleosts terminate within the pituitary parenchyma. In contrast, those of mammals discharge their output into the pituitary portal system in the median eminence. Second, the teleost pituitary is highly structured, and each cell type is located in a designated region. Third, while most studied tetrapod gonadotropes can produce LH and FSH in the same cell, fish gonadotropes secrete either FSH or LH. The high level of structural and functional conservation combined with these teleost-unique traits makes fish an exceptionally valuable model for studying the vertebrate reproductive axis's function and evolution. 

Our key goals are - 

  • To investigate the effect of GnRH and other reproduction-related neuropeptides on FSH and LH expression and release. 

  • To describe the nature of LH and FSH release from the pituitary in teleosts. 

  • To characterize GnRH and FSH or LH's specific relationships using transgenic lines that bear genetically-encoded calcium indicators in their gonadotropes and GnRH cells and Channel Rohodopsin their GnRH neurons. 

  • To investigate the cellular differentiation between FSH and LH using the nature of fish as a research model.  

Studies are undertaken in various genetically-modified fish (mainly zebrafish and tilapia) models created in our lab, using tissue clearing and expansion microscopy, single-cell electrophysiology and calcium imaging in pituitary and brain slices in vitro, single-cell RNAseq gene profiling, in vivo experiments of selected neuropeptides, primary pituitary cell-cultured, real-time PCR, specific ELISAs for steroids and protein hormones developed in our lab, protein modelling, immunofluorescence and in situ hybridization, receptor transactivation assays, histology, and more.   


  • Figure 3
  • Figure 4
  • Kobi's PNAS
  •  Joseph Aizen