The candidate will pursue a research career that focuses on the embryonic differentiation of clonally-related neurons and on the way that differences in neuronal morphology, physiology and biochemistry (transmitter type) lead to differing anatomical and physiological connections in the neuronal circuitry of the mature central nervous system. Experiments proposed will address the lineal origins of stereotyped neuron groups which we have recently described in the adult ganglia of the grasshopper Schistocerca americana, and the expression of differing phenotypic traits in individually-identified neurons in these groups. A major prerequisite for the realization of these goals is for the candidate to develop proficiency in a number of methodologies, primarily those related to lineage analysis in the embryo. Expertise in these methods can be learned partially at Emory University and partially at the institutions of colleagues. A Research Career Development Award would greatly facilitate this process by providing the candidate with greater opportunity for research activities (85%) through reduction in commitments to teaching and university service.
Our specific aims i nvolve the study of one group of neurons that we suggest arise embryonically from a single neuroblast. The group contains some 20 neurons of diverse phenotype, including glutaminergic motor neurons, intersegmental interneurons that may be GABA-ergic, a multibranced efferent that may be homologous to peptidergic neurons from other insects and an indeterminate number of local interneurons. We will describe the anatomical and electrophysiological properties of the neurons in the group in the adult, so that we can identify each as an individual. We will determine which properties are shared by all members of the group and which are unique to some. We will then begin work on the embryo, to test our hypothesis that the neurons are clonally related. To trace lineage we will use conventional techniques for the intracellular injection of dye and newly-developed techniques for labeling with an altered nucleoside BUdR. The labeling with dyes, BUdR and other antibodies will be done in a closely timed series to determine the relative time of origin of the various neurons and of acquisition of differing phenotypic traits.
| Siegler, M V; Jia, X X (1999) Engrailed negatively regulates the expression of cell adhesion molecules connectin and neuroglian in embryonic Drosophila nervous system. Neuron 22:265-76 |
| Siegler, M V; Pankhaniya, R R (1997) Engrailed protein is expressed in interneurons but not motor neurons of the dorsal unpaired median group in the adult grasshopper. J Comp Neurol 388:658-68 |
| Campbell, H R; Thompson, K J; Siegler, M V (1995) Neurons of the median neuroblast lineage of the grasshopper: a population study of the efferent DUM neurons. J Comp Neurol 358:541-51 |
