Precerebellar cell groups in the hindbrain of the mouse defined by retrograde tracing and correlated with cumulative Wnt1-cre genetic labeling.
ABSTRACT The precerebellar nuclei are hindbrain and spinal cord centers that send fibers to the cerebellum. The neurons of the major hindbrain precerebellar nuclei are derived from the rhombic lip. Wnt1, a developmentally important gene involved in intercellular signaling, is expressed in the developing rhombic lip. We sought to investigate the relationship between the cell clusters expressing Wnt1 and the precerebellar nuclei in the hindbrain. We therefore defined the hindbrain precerebellar nuclei by retrograde tracing, following cerebellar injections of HRP, and compared these results with the cell clusters expressing Wnt1 in newborn mice. We found that 39 distinct hindbrain nuclei project to the cerebellum. Of these nuclei, all but three (namely the oral pontine reticular nucleus, the caudal pontine reticular nucleus, and the subcoeruleus nucleus) contain neurons expressing Wnt1. This shows a high degree of overlap between the precerebellar nuclei and the nuclei that express Wnt1. However, it should be noted that neurons expressing Wnt1 are also found in the superior olivary complex, which is a basal plate derivative lacking cerebellar projections.
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ABSTRACT: Saccadic omnipause neurons (OPNs) are essential for the generation of saccadic eye movements. In primates OPNs are located near the midline within the nucleus raphe interpositus (rip). In the present study we used several different neuroanatomical methods to investigate the transmitters associated with OPNs in the monkey. Immunolabeling for the calcium-binding protein parvalbumin was employed to mark OPNs in the monkey and define the homologous cell group in cat and human. The use of antibodies against GABA, glycine (GLY), glutamate (GLU), serotonin (5-HT), and tyrosine hydroxylase revealed that the somata of OPNs are GLY immunoreactive, but they are devoid of GABA and 5-HT immunostaining. In situ hybridization with the GAD67 mRNA probe confirmed the negative GABA immunostaining of OPNs. 3H-GLY was injected into a projection field of OPNs, the rostral interstitial nucleus of the medial longitudinal fascicle (riMLF)--the vertical saccadic burst neuron area. This resulted in selective retrograde labeling of the OPNs in rip, while no labeling was found in the superior colliculus, which sends an excitatory projection to the riMLF. The somata and dendrites of putative burst neurons in the riMLF were contacted by numerous GLY-immunoreactive terminals. The quantitative analysis of immunoreactive terminal-like structures contacting OPNs revealed a strong input from GLY- and GABA-positive terminals on somata and dendrites, whereas GLU-positive puncta were mainly confined to the dendrites. Very few 5-HT and catecholaminergic terminals contacted OPN somata. Our findings suggest that OPNs use GLY as a neurotransmitter, and they receive numerous contacts from GABAergic, glycinergic, and glutaminergic afferents, and significantly fewer from monoaminergic inputs.Journal of Neuroscience 05/1994; 14(4):2032-46. · 6.91 Impact Factor
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ABSTRACT: Recent studies have transformed our understanding of the embryonic rhombic lip by revealing the inductive cues, regional origins and guidance molecules that pattern the development of this important structure and its derivatives. In the cerebellum, a precise combination of anteroposterior and dorsalising cues induces a stream of migratory progenitors that give rise to the external granule cell layer, while more caudally, Netrin orchestrates the migration of hindbrain rhombic lip derivatives to form the precerebellar nuclei. The rhombic lip is thus emerging as a spatiotemporally distinct epithelium whose late appearance in both development and evolution is instrumental in generating a complex, functionally related but spatially distributed neural system.Current Opinion in Neurobiology 03/2001; 11(1):82-8. · 7.34 Impact Factor
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ABSTRACT: We investigated in the mouse and chick the neuroepithelial origin and development of the locus coeruleus (LoC), the most important noradrenergic neuronal population in the brain. We first studied the topography of the developing LoC in the hindbrain, using as markers the key noradrenergic marker gene Dbh and the transcription factors Phox2a and Phox2b (upstream of Dbh). In both mouse and chicken, LoC neurons first appear arranged linearly along the middle one-third of the alar plate of rhombomere 1 (r1), collinear to a reference ventricular longitudinal band that early on expresses Phox2a and Phox2b in the alar plate of r2 and later expands to r1. Double-labeling experiments with LoC markers (Dbh or Phox2a) and either alar (Pax7 and Rnx3) or basal (Otp) genetic markers suggested that LoC cells migrate from their origin in the alar plate to a final position in the lateral basal plate. To corroborate these suggestions experimentally and determine the precise origin of the LoC, we fate mapped the LoC in the chick at stage HH11 by using quail-chick homotopic grafts. The experimental results confirmed that the LoC originates in the alar plate throughout the rostrocaudal extent of r1 and ruled out a rostrocaudal translocation. They also corroborated a ventralward tangential migration of LoC cells into the lateral basal plate, where the postmigratory LoC primordium is located. Comparisons with neighboring alar r1-derived cell populations established that LoC neurons originate outside the cerebellum, in a matrix area intercalated dorsoventrally between the sources of the prospective vestibular and trigeminal columns.The Journal of Comparative Neurology 07/2006; 496(6):802-18. · 3.66 Impact Factor