Carol A. Mason, PhD

In our studies of axon guidance in the visual pathways, we analyze the behaviors, cellular interactions and molecular directives of retinal axon growth cones during avoidance and crossing of the midline at the optic chiasm. This system is a model for axon navigation at the CNS midline, and for patterning the binocular projection. We have identified a molecular program of transcription factors and guidance receptors that regulate cell identity and projection of the ipsilateral retinal axon pathway through the optic chiasm. Current work aims to investigate transcriptional regulators and guidance mechanisms for the contralateral projection, and mechanisms of growth cone interactions with cells of the chiasm midline.

We have recently addressed whether the programs of gene expression that direct retinal axon decussation at the optic chiasm are relevant to the formation of connections of retinal axons in their first target, the lateral geniculate nucleus. We now aim to identify molecular regulators of axon-targeting and retinal ganglion cell axon arbor morphogenesis, and to analyze the interplay of molecular factors and neural activity in the targeting and refinement of eye-specific projections.

A genetic model for these studies is the albino. In both humans and rodents, lack of pigment in the eye leads to visual impairment due to the misrouting of retinal fibers at the optic chiasm to contralateral rather than ipsilateral targets. Albinism is caused by diverse genes controlling melanogenesis. We aim to study how factors in the melanogenic pathway from the retinal pigment epithelium (RPE) affect retinal patterning, and retinal ganglion cell specification and projection fate.