College of Health

Vitamin E (VitE) is necessary for embryo development and its deficiency causes developmental errors that occur at embryologically similar periods in rodents, humans and zebrafish. Zebrafish embryos are studied because their neurodevelopment has a high degree of genetic homology to humans. Adult zebrafish are fed VitE sufficient (E+) or deficient (E–) diets and then are spawned to produce E+ and E– embryos. E– embryos experience increased phospholipid and choline utilization, which causes methyl donor depletion and energy metabolism derangements. Thus, we hypothesize that VitE deficiency disrupts developmental transcriptional profiles, which then disrupt neurogenesis. To test this hypothesis E+ and E– embryos were subjected to histologic analysis, RNA in situ hybridization and qPCR analyses. Ttpa, the gene encoding for the VitE regulatory protein was expressed as early as 6 hours post-fertilization (hpf) throughout the embryo, and by 24 hpf was abundantly localized at the brain ventricle borders, which was distorted in E– embryos. Brain development is coordinated by gene networks beginning with gastrulation at 6 hpf; therefore, such genes were evaluated. Nervous system induction (assessed with goosecoid expression) was unaffected by VitE status. Pax2a and sox10, normally expressed in the developing midbrain-hindbrain boundary and spinal cord neurons, were incorrectly localized in E– embryos at 12 and 24 hpf. Downstream targets, col2a1a and col9a2, were expressed in the notochord collagen sheath and showed malformed body structures in E– embryos. Histological analyses demonstrated severe defects in the brain and somites of E– embryos at 24 hpf. qPCR results showed no differences at 12 hpf, and that only pax2a was significantly down-regulated in E– embryos at 24 hpf. Thus, VitE plays a critical role in maintaining the developing nervous system by ensuring proper gene expression and localization during embryo development to subsequently prevent physical deformation of the brain and peripheral nervous system.