Molecular characterization of prosomeric and intraprosomeric subdivisions of the embryonic zebrafish diencephalon

Abstract

During development of the early neural tube, positional information provided by signaling gradients is translated into a grid of transverse and longitudinal transcription factor expression domains. Transcription factor specification codes defining distinct histogenetic domains within this grid are evolutionarily conserved across vertebrates and may reflect an underlying common vertebrate bauplan. When compared to the rich body of comparative gene expression studies of tetrapods, there is considerably less comparative data available for teleost fish. We used sensitive multicolor fluorescent in situ hybridization to generate a detailed map of regulatory gene expression domains in the embryonic zebrafish diencephalon. The high resolution of this technique allowed us to resolve abutting and overlapping gene expression of different transcripts. We found that the relative topography of gene expression patterns in zebrafish was highly similar to those of orthologous genes in tetrapods and consistent with a three-prosomere organization of the alar and basal diencephalon. Our analysis further demonstrated a conservation of intraprosomeric subdivisions within prosomeres 1, 2, and 3 (p1, p2, and p3). A tripartition of zebrafish p1 was identified reminiscent of precommissural (PcP), juxtacommissural (JcP), and commissural (CoP) pretectal domains of tetrapods. The constructed detailed diencephalic transcription factor gene expression map further identified molecularly distinct thalamic and prethalamic rostral and caudal domains and a prethalamic eminence histogenetic domain in zebrafish. Our comparative gene expression analysis conformed with the idea of a common bauplan for the diencephalon of anamniote and amniote vertebrates from fish to mammals.

Dbx1b defines the dorsal habenular progenitor domain in the zebrafish epithalamus

“…At 28 hpf, dbx1a and dbx1b showed similar yet distinct expression patterns (Additional file 1). As shown previously [20], dbx1a was expressed in sharply restricted domains in the diencephalon with prominent expression in the prethalamus and thalamus (Additional file 1: panel A). Expression of dbx1a and dbx1b was similar in the prethalamic region, but in the thalamic region dbx1b was expressed at a much lower level than dbx1a (Additional file 1; panel C).…”

Simultaneous high-resolution detection of multiple transcripts combined with localization of proteins in whole-mount embryos

“…In addition to the protocol employed above, we examined an optimized whole-mount FISH protocol for zebrafish embryos using a bench-made TSA substrate, permitting higher signal intensities and visualization of less abundant transcripts [8,21]. In comparison to the results obtained using standard FISH, this protocol resulted in a brighter signal for myoD mRNA (Figure 2E,F), coupled with reduced background signal from the yolk (Figure 2E, arrow).…”

The ascl1a and dlx genes have a regulatory role in the development of GABAergic interneurons in the zebrafish diencephalon

“…Additionally, there is an area dorsal to the dlx1a and dlx5a expression domains of the prethalamus that is gad1b positive and dlx negative (Fig. 1D, arrowhead) that may correspond to the rostral thalamus (Peukert et al, 2011; Lauter et al, 2013). …”