Despite public awareness campaigns, Fetal Alcohol Spectrum Disorders (FASD) remain prevalent due to alcohol consumption by women who are pregnant or of child-bearing age. It is well appreciated that sensory and motor information processing is distorted in FASD, but alcohol effects on the thalamus, which likely mediates these functions, have not been widely investigated. Prenatal alcohol exposure (1) disrupts axonal connections between the thalamus and cortex which are required to appropriately receive and respond to sensory cues in the environment, (2) damages the ventral telencephalon (vTel), a critical intermediate target for proper development of these connections, and (3) alters guidance cues and signaling pathways that underlie cell and axon migration. We hypothesize that moderate alcohol exposure disrupts the Slit/Robo pathway, a family of guidance cues and receptors that can have both direct and indirect effects on forebrain axon formation. In this proposal we will investigate corridor-cell mediated thalamocortical axon (TCA) guidance into and within the vTel using a mouse model of FASD. Our experiments aim to (1) define the nature of TCA and corridor cell guidance errors in FASD and (2) establish Slit and Robo as molecular targets of FASD neuropathology in vivo. To analyze TCA guidance errors, we will use dye tracing and immunostaining to visualize these axons along their trajectory. To evaluate corridor cells, we will count and determine the distribution of these cells via immunostaining. To analyze alcohol-induced perturbations of Slit and Robo expression in vivo, we will perform western blotting and RT-PCR for each isoform. We will also use in vitro explant co-cultures to test Slit and Robo function. In the FASD brain, we expect TCAs to project inappropriately to intermediate and final targets and the corridor to be malformed. We also predict that Slit/Robo expression and function will be suppressed. Our findings will reveal the impact of moderate alcohol exposure on guidance mechanisms that are required for proper nervous system wiring, an area that is currently understudied. This work will also enhance understanding of cellular and molecular mechanisms that are likely to be involved in sensorimotor processing defects observed in human FASD. The proposed experiments will largely be carried out by undergraduates who will be mentored to provide them the guidance and expertise needed for success in science careers and graduate work.
The thalamus carries the majority of sensory and motor information from the periphery to the cortex and thus is a likely culprit of the sensorimotor abnormalities that characterize Fetal Alcohol Spectrum Disorders (FASD). We propose that inappropriate thalamic connections are formed during brain development because alcohol consistently damages an intermediate target these axons must traverse. Our studies will focus on corridor cells and the Slit/Robo pathway that guide these axons through this region to enhance understanding of the cellular and molecular mechanisms that underlie FASD neuropathology.
