dlx3b and dlx4b function in the development of Rohon-Beard sensory neurons and trigeminal placode in the zebrafish neurula

Abstract

Rohon-Beard sensory neurons, neural crest cells, and sensory placodes can be distinguished at the boundary of the embryonic epidermis (skin) and the neural plate. The inductive signals at the neural plate border region are likely to involve a gradient of bone morphogenic protein (BMP) in conjunction with FGF and Wnts and other signals. However, how these signals are transduced to produce the final cell fate remains to be determined. Recent evidence from Xenopus and chick suggest that Dlx genes are required for the generation of cell fates at the neural plate border (McLarren, K.W., Litsiou, A., Streit, A., 2003. DLX5 positions the neural crest and preplacode region at the border of the neural plate. Dev. Biol. 259, 34-47; Woda, J.M., Pastagia, J., Mercola, M., Artinger, K.B., 2003. Dlx proteins position the neural plate border and determine adjacent cell fates. Development 130, 331-342). In the present study, we extend these findings to zebrafish, where we unequivocally demonstrate that dlx3b and dlx4b function in a dose-dependent manner to specify cell fates such as Rohon-Beard sensory neurons and trigeminal sensory placodes. dlx function was examined by inhibiting: (1) protein levels with antisense morpholino oligonucleotides (MOs), and (2) activity by repressing the ability of dlx-homeodomain to bind to downstream targets (EnR-dlx3bhd mRNA; dlx3b homeodomain fused to Engrailed transcriptional repressor domain). Inhibition of dlx3b and dlx4b protein and activity resulted in the reduction or complete loss of Rohon-Beard (RB) sensory neurons and trigeminal (TG) sensory placodes. These data suggest that dlx3b and dlx4b function in the specification of RB neurons and trigeminal sensory placodes in zebrafish. Further, we have shown that dlx3b and dlx4b function in a non-cell-autonomous manner for RB neuron development; dlx3b and dlx4b act to regulate bmp2b expression at the non-neural ectodermal border. These data suggest that the contribution of dlx3b and dlx4b to neural plate border formation is partially non-cell-autonomous acting via BMP activity.

hand2 and Dlx genes specify dorsal, intermediate and ventral domains within zebrafish pharyngeal arches

“…We confirm that dlx3b-MO strongly reduces Dlx3b immunolabeling (data not shown) (Liu et al, 2003). We also confirm that dlx4b-MO strongly disrupts dlx4b transcripts (Kaji and Artinger, 2004), without affecting any other Dlx gene (data not shown). Furthermore, in support of previous work (Liu et al, 2003), co-injection of dlx3b-MO with dlx4b-MO phenocopies otolith losses seen in a deletion that contains dlx3b and dlx4b (data not shown).…”

Evolution of the neural crest viewed from a gene regulatory perspective

“…Thus, signaling cues are present in lamprey at a proper time and place to play an analogous function in neural crest specification as in other vertebrates. Similarly, the expression patterns of MsxA, ZicA, Dlx and Pax3/7 genes found within the neural plate border and adjacent territories appear to be conserved between jawless and jawed vertebrates (Aruga et al, 2002;Bang et al, 1999;Basch et al, 2006;Kaji and Artinger, 2004;Khadka et al, 2006;Luo et al, 2001;Monsoro-Burq et al, 2005;Sato et al, 2005;Tribulo et al, 2003). Thus, their combinatorial presence of signaling molecules and border specifier genes appears to be highly conserved in the neural plate border territory across vertebrates.…”

A Dlx2- and Pax6-Dependent Transcriptional Code for Periglomerular Neuron Specification in the Adult Olfactory Bulb

“…This allowed us to test the role of endogenous Dlx2, using a retroviral vector encoding a chimeric protein in which the Dlx2 homeodomain had been fused to the Engrailed repressor domain (Fig. 4 A) (see Material and Methods), thus converting Dlx2-mediated transactivation into repression (Harris et al, 2003;Woda et al, 2003;Kaji and Artinger, 2004) (Fig. 4 A, E).…”

“…However, before concluding this, we further examined the specificity of the Dlx2-Engrailed construct, beyond the previous data on the function of Dlx2-Engrailed fusion proteins as repressors and antagonists of the endogenous Dlx2 function (Harris et al, 2003;Woda et al, 2003;Kaji and Artinger, 2004). Because cells isolated from the E13 cerebral cortex contain very few, if any, Dlx2ϩ progenitors cells at this stage, we used them to determine potential off-target effects of Dlx2-Engrailed.…”