Putative roles for nitric oxide in development and plasticity - Nitric oxide synthase in the central nervous system of the zebrafish
Field:	Development and regeneration
Authors:	Holmqvist, Bo Ellingsen, Berit Ostholm, Thomas Fjose, Anders Seo, Hee-Chan Alm, Per
Address of presenting author:	Department of Pathology University of Lund 22185 Lund Sweden
E-mail:	bo.holmqvist@pat.lu.se
Phone:	46 46 173417
Fax:	46 46 143307
Text of abstract:	Nitric oxide (NO) is a signaling molecule produced in various tissues by the enzyme NO synthase (NOS). NO has been implicated in several normal physiological and pathological functions, including in development and plastic processes in the central nervous system. Recent studies emphasize involvement by NO in cellular proliferation, differentiation and apoptosis. The zebrafish (Telostei, Danio rerio) is a well suited model for morphological and genetical studies of vertebrate development. In the teleost brain new cells are added throughout life and it possesses an extraordinary capacity for cellular regeneration, events indicated to involve NO actions. We have therefore undertaken to investigate the NO producing systems in zebrafish. A partial 621bp gene with a nucleotide sequence corresponding to the neuronal NOS (nNOS) isoform was identified, showing about 88-97% identity to other known nNOS isoforms. The first expression of nNOS mRNA expressing cells appear in the embryonic forebrain at 19 hours post fertilization (h), in a distinct bilateral subpopulation of the ventrorostral cell cluster. Low expression appear in subsets of other forebrain cell clusters (dorso- and ventrorostral) at 24h. These nNOS cells coincide with the first differentiated neurons, and catecholaminergic and serotoninergic cells in the central nervous system. In adults, cellular nNOS mRNA expression, NOS immunoreactivity and activity (NADPH diaphorase) is present throughout the brain. nNOS mRNA expression is localized to different central brain nuclei and along ventricular regions of the proliferation zones. In the retina, NOS activity is present in most retinal layers whereas NOS immunoreactivity is restricted to photoreceptors. Low nNOS mRNA expression is indicated in the ganglion cell layer. Our studies show that NO-producing systems are present during embryonic development and have a widespread distribution in both brain and retina of adults. The data indicate that NO, to a large degree produced by nNOS, plays a combined role in brain development, neurophysiology and plasticity.
Keywords:	fish, brain, cell proliferation, neuron, differentiation

Created 2000-03-15