TY - JOUR
T1 - Early specification of ascidian larval motor neurons
AU - Katsuyama, Yu
AU - Okada, Toshiaki
AU - Matsumoto, Jun
AU - Ohtsuka, Yukio
AU - Terashima, Toshio
AU - Okamura, Yasushi
N1 - Funding Information:
We thank Dr. Harumasa Okamoto, chairman of the laboratory in AIST, for his support throughout this work, and members of the laboratory for their advice and discussion. We thank Dr. Andrew McMahon (Harvard University) for providing plasmids of zebrafish Shh, constitutive active PKA, and PKI; Noriyuki Satoh (Kyoto University) and Takahito Miya (Tokyo Institute of Technology) for providing the plasmids of ascidian BMP homologue; Tetsuya Koide (UCI) for providing a plasmid coding dominant-negative Xenopus BMP receptor; Kiyokazu Agata (RIKEN CDB) for facilitating our experiments in his laboratory; and Masanori Taira (Tokyo University), Xi He (Harvard Medical School), Raymond Habas (NIH), and Hiro Watari (AIST) for critical reading of the manuscript. YK was supported by NEDO and National Institute Post Doctoral Fellowship. YO was supported by a research grant from the Naito Foundation. YK and YO were supported by Grants-in-Aid for Scientific Research from the Ministry of Education, Culture, Sports, Science and Technology, Japan.
PY - 2005/2/15
Y1 - 2005/2/15
N2 - In the tadpole larvae of the ascidian Halocynthia roretzi, six motor neurons, Moto-A, -B, and -C (a pair of each), are localized proximal to the caudal neural tube and show distinct morphology and innervation patterns. To gain insights into early mechanisms underlying differentiation of individual motor neurons, we have isolated an ascidian homologue of Islet, a LIM type homeobox gene. Earliest expression of Islet was detected in a pair of bilateral blastomeres on the dorsal edge of the late gastrula. At the neurula stage, this expression began to disappear and more posterior cells started to express Islet. Compared to expression of a series of motor neuron genes, it was confirmed that early Islet-positive blastomeres are the common precursors of Moto-A and -B, and late Islet-positive cells in the posterior neural tube are the precursors of Moto-C. Overexpression of Islet induced ectopic expression of motor neuron markers, suggesting that Islet is capable of regulating motor neuron differentiation. Since early expression of Islet colocalizes with that of HrBMPb, the ascidian homologue of BMP2/4, we tested a role of BMP in specification of the motor neuron fate. Overexpression of HrBMPb led to expansion of Lim and Islet expression toward the central area of the neural plate, and microinjection of mRNA coding for a dominant-negative BMP receptor weakened the expression of these genes. Our results suggest that determination of the ascidian motor neuron fate takes place at late gastrula stage and local BMP signaling may play a role in this step.
AB - In the tadpole larvae of the ascidian Halocynthia roretzi, six motor neurons, Moto-A, -B, and -C (a pair of each), are localized proximal to the caudal neural tube and show distinct morphology and innervation patterns. To gain insights into early mechanisms underlying differentiation of individual motor neurons, we have isolated an ascidian homologue of Islet, a LIM type homeobox gene. Earliest expression of Islet was detected in a pair of bilateral blastomeres on the dorsal edge of the late gastrula. At the neurula stage, this expression began to disappear and more posterior cells started to express Islet. Compared to expression of a series of motor neuron genes, it was confirmed that early Islet-positive blastomeres are the common precursors of Moto-A and -B, and late Islet-positive cells in the posterior neural tube are the precursors of Moto-C. Overexpression of Islet induced ectopic expression of motor neuron markers, suggesting that Islet is capable of regulating motor neuron differentiation. Since early expression of Islet colocalizes with that of HrBMPb, the ascidian homologue of BMP2/4, we tested a role of BMP in specification of the motor neuron fate. Overexpression of HrBMPb led to expansion of Lim and Islet expression toward the central area of the neural plate, and microinjection of mRNA coding for a dominant-negative BMP receptor weakened the expression of these genes. Our results suggest that determination of the ascidian motor neuron fate takes place at late gastrula stage and local BMP signaling may play a role in this step.
KW - Ascidian
KW - BMP
KW - Ion channel genes
KW - LIM
KW - Motor neuron
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U2 - 10.1016/j.ydbio.2004.11.007
DO - 10.1016/j.ydbio.2004.11.007
M3 - Article
C2 - 15680352
AN - SCOPUS:12944297722
VL - 278
SP - 310
EP - 322
JO - Developmental Biology
JF - Developmental Biology
SN - 0012-1606
IS - 2
ER -