Development and Evolution of the Vertebrate Hypothalamus: Evidences in Chondrichthyans

Abstract

The hypothalamus is a conserved integrative center with a complex organization result of a complex patterning processes. Here we make use of a evo-devo approach and the theoretical framework of the prosomeric model to understand the organization of the vertebrate hypothalamus. We studied the gene expression patterns of ScFoxg1a, ScDlx2/5, ScOtp, ScShh, ScNkx2.1, ScTbr1, ScNeurog2, ScLhx5, ScLhx9, ScDlx2/5, ScNkx2.8, ScEmx2, ScLmx1b, ScPitx2, ScPitx3a, ScNeurog2, ScFoxa1 and ScFoxa2 besides immunoreactivity to Pax6, PCNA and other immunomarkers in the embryonic hypothalamus and neighbour prosencephalic territories of a cartilaginous fish, the catshark, Scyliorhinus canicula. Our comparative analysis reveals the existence of conserved traits but also suggests an alternative organization to that proposed by the prosomeric model for the hypothalamus and even for the anterior prosencephalon of vertebrates.