Counts were made of the number of motoneurons innervating the hind limbs of 10-day normal and paralysed chick embryos whose right hind limb buds had been subjected to varying degrees of amputation prior to innervation. The number of motoneurons on the intact sides of the paralysed embryos was found to be similar to the number present in normal embryos prior to the major period of motoneuron dea...

Proximal spinal muscular atrophy (SMA) is a motoneuron disease for which there is currently no effective treatment. In animal models of SMA, spinal motoneurons exhibit reduced axon elongation and growth cone size. These defects correlate with reduced beta-actin messenger RNA and protein levels in distal axons. We show that survival motoneuron gene (Smn)-deficient motoneurons exhibit severe defe...

We provide the first analysis of how a segmentally reiterated pattern of neurons is specified along the anteroposterior axis of the vertebrate spinal cord by investigating how zebrafish primary motoneurons are patterned. Two identified primary motoneuron subtypes, MiP and CaP, occupy distinct locations within the ventral neural tube relative to overlying somites, express different genes and inn...

Muscle atrophy and diaphragmatic palsy are the clinical characteristics of spinal muscular atrophy with respiratory distress type 1 (SMARD1), and are well represented in the neuromuscular degeneration (Nmd(2J) ) mouse, modeling the juvenile form of SMARD1. Both in humans and mice mutations in the IGHMBP2 gene lead to motoneuron degeneration. We could previously demonstrate that treatment with a...

Motoneurons in the spinal nucleus of the bulbocavernosus (SNB) and their target muscles in the perineum, bulbocavernosus (BC), and levator ani (LA) normally degenerate in female rodents. Death of the motoneurons and muscles can be prevented by androgen treatments around the time of birth. To identify the intracellular mechanisms underlying hormone-dependent survival of this neuromuscular system...

Zebrafish embryos exhibit spontaneous contractions of the musculature as early as 18-19 h post fertilization (hpf) when removed from their protective chorion. These movements are likely initiated by early embryonic central nervous system activity. We have made the observation that narrowminded mutant embryos (hereafter, nrd(-/-)) lack normal embryonic motor output upon dechorionation. However, ...

Blood vessels and neurons grow often side by side. However, the molecular and cellular mechanisms underlying their parallel development remain unclear. Here, we report that a subpopulation of secondary motoneurons extends axons ventrally outside of the neural tubes and rostrocaudally as a fascicle beneath the dorsal aorta (DA) in zebrafish. We tried to clarify the mechanism by which these moton...

We determined the contribution of glutamate receptor subtypes to developing excitatory synaptic transmission in isolated spinal cord of rat embryos. Using electrophysiological and morphological techniques, we studied the pattern of development of synapses between dorsal root afferents and motoneurons in lumbar spinal cords of 15 to Pl-d-old rat embryos. Motoneuron dendritic fields and afferent ...