ANATOMIC BRAIN ATLAS AND BRAIN MAP OF NEUROTROPHINS EXPRESSION IN A NEW MODEL ORGANISM: Nothobranchius furzeri

In biomedical and veterinary research, fish represent an extraordinary repertoire of models with which to carry out experiments. In the basic neuroscience, fish offer examples that indicate the usefulness of comparative neurobiological investigation in elucidating both normal and abnormal structure and function of the brain of vertebrates, and moreover they possess an enormous potential for the production of new neurons in the adult brain. In aging research, several fish species exhibit gerontological characteristics and provide research opportunities for disease modeling, drug discovery, and regenerative medicine.This PhD thesis has developed a new teleost model organism N. furzeri, which is the shortest-lived vertebrate which can be cultured in captivity. This teleost shows typical signs of aging and represents an ideal model to assess the role of different physiological and environmental parameters on aging and lifespan determination.The topic of this dissertation is the study of the organization of brain of N. furzeri and the neuroanatomical description of the occurrence of neurotrophins. The contruction of the brain atlas is a clear and fundamental guide to the structural and functional organization of the N. furzeri CNS, and provides informative reading for subsequent neurobiological surveys. The atlas has been the substratum for the neuroanatomical description of the occurrence of neurotrophins, both mRNA and protein, within the CNS. Neurotrophins are secreted proteins that link nervous system structure and function in vertebrates. They regulate neuronal survival, and regulate patterns of dendrites and axons, synaptic function, memory, learning, and cognition; abnormalities in neurotrophin function underlies neurological disorders. BDNF, NGF, NT-3, NT-4 and NT-6, all members of neurotrophins family, have been identified on expressed sequence tag (EST)-to-genome and genome-to-genome comparisons of N. furzeri and other teleosts. ISH and IHC analysis of cells expressing mRNAs for the neurotrophins revealed a specific expression pattern for each of the mRNAs and proteins. The analysis of sites of neurotrophin synthesis was performed with ISH technique using two LNA/DNA and oligonucleotide probes, encoding mature N. furzeri neurotrophin protein. The parallel immunohistochemical investigation, along with specific affinity-purified antibodies, was carried out to generate a detailed mapping of neurotrophin protein throughout the adult N. furzeri CNS. All neurotrophins occur in the brain of N. furzeri, except NT-3. The obtained results show a high level of correlation between ISH and IHC in the evaluation of neurotrophins in the brain of N. furzeri. The data, indeed, have revealed that several nuclei expressing neurotrophin mRNAs were correlated to the neurotrophin specific proteins throughout the CNS; the sites of mRNA synthesis and protein storage have suggested hypothesis on the mechanisms of retrograde/anterograde transport. Moreover, the sites of synthesis have been often identified as active proliferative areas of fish brain, where new neurons are generate or regenerate. The latter observation might suggest a role of neurotrophins in the neurogenic and regeneration activities.This work provides new aspects of neurotrophic factors in the CNS of vertebrates, and it opens the opportunity to use N. furzeri as alternative model to investigate neurotrophin function and model related diseases.