DLX5 positions the neural crest and preplacode region at the border of the neural plate

Abstract

The neural crest and sensory placodes arise from a region of the embryonic ectoderm that lies between the neural plate and future epidermis. While some of the signalling pathways that are involved in cell fate determination at the border of the neural plate have been characterised, it is still unclear how different signals are integrated. Transcription factors of the DLX gene family that may mediate such cell fate decisions are expressed at the border of the neural plate. Here, we demonstrate that DLX5 is involved in positioning this border by repressing neural properties and simultaneously by promoting the formation of border-like cells that express the neural fold markers MSX1 and BMP4 and the preplacodal region marker SIX4. However, DLX5 is not sufficient to impart epidermal character or to specify cell fates that arise at the border of the neural plate, like neural crest or fully formed sensory placodes, in a cell-autonomous manner. Additional signals are generated when mature neural plate and epidermis interact and these are required for neural crest formation. We propose that patterning of the embryonic ectoderm is a multistep process that sequentially subdivides the ectoderm into regions with defined cell fates.

Dlx5/6‐enhancer directed expression of Cre recombinase in the pharyngeal arches and brain

“…These cells are presumably neural crest-derived, although expression in resident non-neural crest mesenchyme cannot be excluded. While DLX5 expression has been found along the border of the chick neural plate prior to crest cell migration (McLarren et al, 2003), we did not detect β-gal staining or Cre expression within the hindbrain or in streams extending from the hindbrain towards the pharyngeal arches. This supports previous studies in which neither Dlx5 nor Dlx6 expression has been observed in premigratory neural crest cells (Acampora et al, 1999;Depew et al, 1999;Robledo et al, 2002;Zerucha et al, 2000).…”

AP2γ regulates neural and epidermal development downstream of the BMP pathway at early stages of ectodermal patterning

“…Furthermore, AP2γ has redundant activities with AP2α in neural crest induction and nonneural ectoderm derivative development [26]. Other factors such as Pax7, Msx1, Zic1, Dlx5 and AP2α were shown as neural border specifiers [30,[63][64][65][66][67][68]. During early neuralization of the chick embryo, some factors are mainly expressed in the peripheral (Pax7, Dlx5 and AP2α) or caudal (Msx1) ectoderm and the expressions of others (Zic1) partially overlaps with cSox2 expression [68].…”

The preplacodal region: an ectodermal domain with multipotential progenitors that contribute to sense organs and cranial sensory ganglia

“…2C) (Mishima and Tomarev, 1998;Esteve and Bovolenta, 1999;Sahly, et al, 1999;Kobayashi, et al, 2000;Pandur and Moody, 2000;McLarren, et al, 2003;Bessarab, et al, 2004;Schlosser and Ahrens, 2004;Litsiou, et al, 2005). Simultaneously, precursors for all placodes become concentrated in the Six/Eya + territory to form a contiguous, unique domain: the preplacodal region (Streit, 2002;Bhattacharyya, et al, 2004) (Fig.…”

“…FoxiI ) the ectoderm next to the neural plate. Thus, at early neurula stages a contiguous stripe of ectoderm coexpresses pre-neural and non-neural ectoderm markers and has therefore been termed the 'border' (Streit and Stern, 1999;McLarren, et al, 2003;Woda, et al, 2003;Meulemans and Bronner-Fraser, 2004). Within the border region precursors for neural, neural crest, epidermis and placodes remain interspersed (Kozlowski, et al, 1997;Streit, 2002;Bhattacharyya, et al, 2004).…”