The spatial and temporal pattern of C-Lmx1 expression in the neuroectoderm during chick neurulation

Abstract

C-Lmx1 has been shown to be a key regulatory gene for specification of dorsoventral pattern during vertebrate limb development. Here, we describe its earlier pattern of expression during and shortly after neurulation. Transcripts are first expressed in the mesoderm of the head process and rostral tip of the primitive streak at the late gastrula/early neurula stage (stage 4). As neurulation occurs with shaping of the neural plate, C-Lmx1 is expressed in a butterfly-like pattern in the lateral neuroectoderm. During bending of the neural plate, C-Lmx1 expression becomes localized to three areas of the bending neuroectoderm: the median hingepoint (future floor plate of the neural tube) and the paired dorsolateral regions of the neuroepithelium, including the dorsolateral hingepoints and the adjacent neuroectodermal and epidermal ectodermal components of the neural folds. After closure of the neural groove and formation of the primary brain vesicles, C-Lmx1 is expressed in the dorsal neural tube along the entire length of the neuraxis, as well as in the floor plate at the brain but not spinal cord levels. At the midbrain and rostral hindbrain levels, C-Lmx1 is heavily expressed. Here, in addition to expression in the dorsal neural tube and floor plate, it is expressed in the lateral walls of the neural tube, with the exception of the levels of rhombomeres 2 and 4. C-Lmx1 is also expressed in several other discrete domains during and shortly after neurulation, including the prechordal plate and rostral head mesenchyme, foregut endoderm, otic placode and vesicle, dorsal somitic mesoderm, midline endoderm at the level of the caudal spinal cord, mesonephroi and limb bud mesoderm.

Control of Roof Plate Development and Signaling by Lmx1b in the Caudal Vertebrate CNS

“…1 A-F ) (Yuan and Schoenwolf, 1999;Gross et al, 2002;Muller et al, 2002). In the chick caudal CNS, we first detected Lmx1b expression at the beginning of neurulation, specifically in the elevating and converging neural folds (Fig.…”

“…In the CNS, Lmx1b is expressed in the isthmus, developing serotonergic and dopaminergic neurons of the hindbrain and midbrain, and a subset of dorsal interneurons of the spinal cord. Lmx1b is also expressed in the roof plate and floor plate of the neural tube (Yuan and Schoenwolf, 1999;Adams et al, 2000;Smidt et al, 2000;Gross et al, 2002;Matsunaga et al, 2002;Muller et al, 2002;Ding et al, 2003). Although the role of Lmx1b in the isthmus (Adams et al, 2000;Matsunaga et al, 2002) and serotonergic and dopaminergic neurons (Smidt et al, 2000;Ding et al, 2003) is clearly established, its function in dorsal spinal cord development is unclear.…”

The dorsal neural tube: A dynamic setting for cell fate decisions

“…Lmx1a was initially considered to fulfill such a requirement because it is specifically expressed in the dorsal NT but not in emigrating or migrating NC (Yuan and Schoenwolf, 1999;Millen et al, 2004). Moreover, overexpression of Lmx1a promoted RP properties but had no apparent effect on NC development (Chizhikov and Millen, 2004a,b).…”

Distinct activities of Msx1 and Msx3 in dorsal neural tube development

“…To determine whether the mouse Msx genes could influence roof-plate differentiation in chick neural tube, we examined three roof-plate markers: Bmp4 (Liem et al, 1995), Wnt1 (Parr et al, 1993) and Lmx1 (Millonig et al, 2000;Yuan and Schoenwolf, 1999) in electroporated embryos. Activation of Bmp signaling by ca-Bmpr1 induced the expression of Bmp4, Wnt1 and Lmx1 in the dorsal neural tube after 24 hours (Fig.…”