James Walker, PhD studies orthologs of genes using genetic screens, biochemical, molecular and cellular biological techniques to understand neurodegenerative disease processes.

Research with Drosophila

1. The UAS/GAL4 system allows us to study gene expression in the fruit fly, Drosophila. A subset of neuroendocrine cells in the larval CNS is revealed using a neuropeptide-GAL4 line to drive a UAS-GFP reporter (green). In collaboration with Dr. Erik Johnson (Wake Forest University, NC).

subset of neuroendocrine cells in the larval CNS


2. The Drosophila ortholog of the Neurofibromatosis Type-1 (NF1) gene is expressed in a subset of neurons (stained red) in the larval CNS. The optic neuropil is revealed by staining for actin (green).

Drosophila ortholog, Neurofibromatosis Type-1


3. Insulin (stained in red) controls organism growth during fly development. Produced in seven neuroendocrine cells located on each side of the larval brain hemispheres (blue arrow), it is then transported through processes (yellow) and secreted into the hemolymph.

Insulin in neuroendocrine cells transported and secreted into hemolymph.


4. We have used genetic screens to identify modifiers of the NF1 growth defect in Drosophila. Fly pupae are shown, from left: wild-type, NF1 mutant (reduced in size) and three genetic enhancers in the NF1 mutant background. These enhancer mutations result in a further reduction of organism size and help reveal how NF1 regulates growth.

Enhancer mutations help reveal how NF1 regulates growth.


5. Genetic interactions between genes involved in Schwannomatosis. The Drosophila eye can be used to determine whether two genes interact with each other. Scanning electron micrographs of a wild-type eye (left) and an eye from animal mutant for two genes implicated in the development of schwannomas, which results in tissue overgrowth (right).

Scanning electron micrographs for genes implicated in development of schwannomas.