John B. Thomas

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We have isolated the Drosophila homolog of the vertebrate islet-1 and islet-2 genes, two members of the LIM homeodomain family implicated in the transcriptional control of motor neuronal differentiation. Similar to vertebrates, Drosophila islet is expressed in a discrete subset of embryonic motor neurons and interneurons that includes the dopaminergic and(More)
Different classes of vertebrate motor neuron that innervate distinct muscle targets express unique combinations of LIM-homeodomain transcription factors, suggesting that a combinatorial code of LIM-homeodomain proteins may underlie the control of motor-neuron pathway selection. Studies of LIM-homeodomain genes in mouse, Drosophila melanogaster and(More)
Little is known about the mechanisms that generate neuronal specificity during development. Whereas the grasshopper embryo has been an ideal system for a cellular analysis of neuronal development, the Drosophila embryo has obvious attributes for a molecular genetic analysis. Here we show that the early Drosophila embryo is a miniature replica of the(More)
Homeobox transcription-factor codes control motor-neuron subtype identity and dorsal versus ventral axon guidance in both vertebrate and invertebrate nervous systems; however, the specific axon guidance-receptors that are regulated by these transcription factors to control pathfinding are poorly defined. In Drosophila, the Even-skipped (Eve) transcription(More)
By studying the effects of mutations on a simple circuit of identified neurons in Drosophila, we have found genes whose proper functioning is necessary to produce normal synaptic connections between the neurons. These neurons comprise the giant fiber (GF) system; the GFs are command neurons activated by a light-off stimulus and evoke a stereotyped pattern(More)
In nervous systems with bilateral symmetry, many neurons project axons across the midline to the opposite side. In each segment of the Drosophila embryonic nervous system, axons that display this projection pattern choose one of two distinct tracts: the anterior or posterior commissure. Commissure choice is controlled by Derailed, an atypical receptor(More)
During development, neurons are capable of selecting specific pathways that lead them to their appropriate target areas. A variety of molecular mechanisms are thought to be involved in pathway recognition, including cell adhesion, repulsion and chemotropism. However, apart from a few genes whose involvement has been shown genetically, the mechanisms(More)
Drosophila larval crawling is a simple behavior that allows us to dissect the functions of specific neurons in the intact animal and explore the roles of genes in the specification of those neurons. By inhibiting subsets of neurons in the PNS, we have found that two classes of multidendritic neurons play a major role in larval crawling. The bipolar(More)
The most commonly used enzymatic reporter molecule, Escherichia coli beta-galactosidase (beta-gal; beta-D-galactoside galactohydrolase, EC 3.2.1.23), fails to readily diffuse into axons; consequently, the morphologies of beta-gal-labeled neurons cannot directly be determined. For analysis of neuronal pathfinding and synaptic connectivity, this information(More)
Homer proteins have been proposed to play a role in synaptogenesis, synapse function, receptor trafficking, and axon pathfinding. Here we report the isolation and characterization of the Drosophila gene homer, the single Homer-related gene in fly. Using anti-Homer antibody we show that Homer is expressed in a broad range of tissues but is highly enriched in(More)