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CONTRALATERAL MIGRATION OF OCULOMOTOR NEURONS IS REGULATED BY SLIT/ROBO SIGNALS
Christine Schlemmer
Program: NIH INBRE
Mentor: Grant Mastick
Department: Biology
University of Nevada, Reno
The oculomotor nuclei, located in the ventral embryonic midbrain, are comprised
of neurons that innervate the ipsilateral extraocular muscles, and the contralateral
dorsal rectus muscle. Correct innervation of the extraocular muscles is required to
align the eyes for binocular vision. All oculomotor axons initially extend from the
neural tube on the ventral aspect of the cephalic flexure to ipsilateral muscle
targets. However, a subset of the neurons that innervate the dorsal rectus muscle
later undertake a unique translocation of their cell bodies across the midline,
integrating into the contralateral nucleus. We aim to test the role of midline guidance cues in controlling the
contralateral migration. Slit1 and 2 are diffusible axon guidance cues expressed at the ventral midline. Robo 1 and
Robo 2 are known receptors for Slit, and axons expressing these receptors are repelled away from the
midline. Previous research shows that Slit/Robo signaling plays a role in neural cell positioning and migration
during embryonic development. In Slit mutant mice, the oculomotor nuclei have abnormalities in the axon-like
projections through the midline, and were found to migrate across the midline prematurely at embryonic day 11.
Normal migration occurs during embryonic days 13-15. We are testing the hypothesis that oculomotor neurons
express Robo 1 and Robo2, and that these repellent receptors act to maintain the ipsilateral position of
oculomotor neurons prior to E13. To characterize Robo expression during migration, cryostat sections were taken
coronal to the cephalic flexure through the oculomotor nuclei. The oculomotor nucleus was identified using
immunoflouresence for Islet-1, a transcription factor specific for motor neurons. We found Robo 2 co-labels with
Islet-1 prior to migration. Our results suggest that Slit 2 repulsion initially suppresses axonal growth into the
midline, restricting cell bodies to the ipsilateral nucleus. Suppression of Slit/Robo signaling allows for migration to
the contralateral nucleus.
PURIFICATION OF PDS5 C-TERMINAL PEPTIDE AND EXPRESSION OF RFP-PDS5 IN DROSPHILA
MELANOGASTER
Alexander Shaft
Program: NIH INBRE
Mentor: Chi-Yun Pai
Department: Biochemistry and Molecular Biology
University of Nevada, Reno
Pds5 is a nuclear protein that participates in sister chromatid condensation and
cohesion by interacting with the cohesin complex and possibly functioning as a
scaffold for other proteins. We have previously obtained genetic evidence that
Pds5 regulates transcription by interacting with chromatin insulators. In order to
better understand the role of Pds5 in transcription, we expressed His-tagged Pds5
in bacteria for antibody production, and fluorescent Pds5 in Drosophila
melanogaster to study the dynamic movement of the protein. To express 6xHis-
Pds5 in bacteria, a full-length or a truncated cDNA was introduced into E. coli. Purification of Pds5 was
successfully accomplished using detergents and SDS-PAGE. This purified Pds5 C-terminal peptide will be used for
the production of antibodies. For generating Pds5 transgenic flies, the full length Pds5 gene was cloned into P-
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