Favero, C. | bioRxiv Science

bioRxiv2022

Prenatal alcohol exposure alters axon formation and Robo/Slit guidance cue expression in the internal capsule at E15.5

We previously showed the prenatal alcohol exposure (PAE) induced precocious growth of E15.5 internal capsule axons. We set out to further delineate which axon tracts were affected and a potential mechanism for this phenomenon. Pregnant Swiss Webster mice were exposed to saline or 20% ethanol via subcutaneous injection from embryonic days (E) 7.5 until E14.5. E15.5 embryos were captured via C-section and brains were either fixed for immunostaining or flash frozen for tissue punches. To identify internal capsule axons we performed immunohistochemistry using L1 antibody to visualize all internal capsule axons and NetrinG1 antibody to identify thalamocortical axons specifically. mRNA was extracted from tissue punches to visualize Slit1, Robo1, Slit2, and Robo2 gene expression levels via real time RT PCR. We found that L1-expressing axons exhibited increased axon crossing in females with the opposite effect in males and no difference in Netrin-G1-expressing axons. We also found PAE increased Robo1 mRNA. Taken together, our results indicate that PAE elicits specific effects on axon trajectories, potentially via the Slit/Robo guidance family of repellents and receptors. These findings add to the growing body of evidence demonstrating alcohol disruptions of axon growth and guidance during embryonic development that may contribute to connectivity errors that characterize Fetal Alcohol Spectrum Disorders.

neuroscience↗

bioRxiv2020

Moderate prenatal ethanol exposure increases total length of L1 axons in E15.5 mice

Public health campaigns broadcast the link between heavy alcohol consumption during pregnancy and physical, cognitive, and behavioral birth defects; however, they appear less effective in deterring moderate consumption prevalent in women who are pregnant or of childbearing age. The incidence of mild Fetal Alcohol Spectrum Disorders (FASD) is likely underestimated because the affected individuals lack physical signs such as retarded growth and facial dysmorphology and cognitive/behavioral deficits are not commonly detected until late childhood. Sensory information processing is distorted in FASD, but alcohol effects on the development of axons that mediate these functions are not widely investigated. We hypothesize that alcohol exposure alters axon growth and guidance contributing to the aberrant connectivity that is a hallmark of FASD. To test this, we administered alcohol to pregnant dams from embryonic day (E) 7.5 to 14.5, during the time that axons which form the major forebrain tracts are growing. We found that moderate alcohol exposure had no effect on body weight of E15.5 embryos, but significantly increased the length of L1+ axons. Our findings support our hypothesis. Future studies will investigate cellular, molecular, and functional mechanisms that underlie these effects.

developmental biology↗