Expression of dlx genes in the normal and regenerating brain of adult zebrafish

Dysfunctions in the GABAergic system lead to various pathological conditions and impaired inhibitory function is one of the causes behind neuropathies characterized by neuronal hyper excitability. TheDlxhomeobox genes are involved in the development of nervous system, neural crest, branchial arches and developing appendages.Dlxgenes also take part in neuronal migration and differentiation during development, more precisely, in the migration and differentiation of GABAergic neurons. Functional analysis ofdlxgenes has mainly been carried out in developing zebrafish embryos and larvae, however information regarding the expression and roles of these genes in the adult zebrafish brain is still lacking. The extensive neurogenesis that takes place in the adult zebrafish brain, makes them a good model for the visualization of mechanisms involvingdlxgenes during adulthood in physiological conditions and during regeneration of the nervous system. We have identified the adult brain regions where transcripts ofdlx1a,dlx2a,dlx5aanddlx6agenes are normally found and have confirmed that within telencephalic domains, there is high overlapping expression of the fourdlxparalogs with a marker for GABAergic neurons. Co-localization analyses carried with the Tg(dlx6a-1.4kbdlx5a/dlx6a:GFP) reporter line have also shown that in some areas of the diencephalon, cells expressing thedlx5a/6abigene may have a neural stem cell identity. Furthermore, investigations in a response to stab wound lesions, have demonstrated a possible participation of thedlx5a/6abigene, most likely ofdlx5a, during regeneration of the adult zebrafish brain. These observations suggest a possible participation ofdlx-expressing cells during brain regeneration in adult zebrafish and also provide information on the role ofdlxgenes under normal physiological conditions in adults.