Patterns of Promoter-Driven Fluorescence in the Forebrain of Larval .

Microtubules are essential components of the cytoskeleton of all eukaryotic cells and consist of α- and β-tubulin heterodimers. Several tissue-specific isotypes of α- and β-tubulins, encoded by distinct genes, have been described in vertebrates. In the African clawed frog (), class II β-tubulin () is expressed exclusively in neurons, and its promoter is used to establish different transgenic frog lines. However, a thorough investigation of the expression pattern of has not been carried out yet. In this study, we describe the expression of -dependent Katushka fluorescence in the forebrain of premetamorphic at cellular resolution. To determine the exact location of Katushka-positive neurons in the forebrain nuclei and to verify the extent of neuronal Katushka expression, we used a transgenic frog line and performed several additional antibody stainings. We found -dependent fluorescence throughout the forebrain, but not in all neurons. In the olfactory bulb, -dependent fluorescence is present in axonal projections from the olfactory epithelium, cells in the mitral cell layer, and fibers of the extrabulbar system, but not in interneurons. We also detected -dependent fluorescence in parts of the basal ganglia, the amygdaloid complex, the pallium, the optic nerve, the preoptic area, and the hypothalamus. In the diencephalon, -dependent fluorescence occurred mainly in the prethalamus and thalamus. As in the olfactory system, not all neurons of these forebrain regions exhibited -dependent fluorescence. Together, our results present a detailed overview of the distribution of -dependent fluorescence in neurons of the forebrain of larval and clearly show that -dependent fluorescence cannot be used as a pan-neuronal marker.