AUTHOR=Daume Daniela , Offner Thomas , Hassenklöver Thomas , Manzini Ivan 

TITLE=Patterns of tubb2b Promoter-Driven Fluorescence in the Forebrain of Larval Xenopus laevis

JOURNAL=Frontiers in Neuroanatomy

VOLUME=16

YEAR=2022

URL=https://www.frontiersin.org/journals/neuroanatomy/articles/10.3389/fnana.2022.914281

DOI=10.3389/fnana.2022.914281

ISSN=1662-5129

ABSTRACT=<p>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 (<italic>Xenopus laevis</italic>), class II β-tubulin (<italic>tubb2b</italic>) 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 <italic>tubb2b</italic> has not been carried out yet. In this study, we describe the expression of <italic>tubb2b</italic>-dependent Katushka fluorescence in the forebrain of premetamorphic <italic>Xenopus laevis</italic> 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 <italic>tubb2b</italic>-dependent fluorescence throughout the <italic>Xenopus</italic> forebrain, but not in all neurons. In the olfactory bulb, <italic>tubb2b</italic>-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 <italic>tubb2b</italic>-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, <italic>tubb2b</italic>-dependent fluorescence occurred mainly in the prethalamus and thalamus. As in the olfactory system, not all neurons of these forebrain regions exhibited <italic>tubb2b</italic>-dependent fluorescence. Together, our results present a detailed overview of the distribution of <italic>tubb2b</italic>-dependent fluorescence in neurons of the forebrain of larval <italic>Xenopus laevis</italic> and clearly show that <italic>tubb2b</italic>-dependent fluorescence cannot be used as a pan-neuronal marker.</p>