Tocotrienol: The Natural Vitamin E to Defend the Nervous System?

Abstract Vitamin E (VitE) deficiency results in embryonic lethality. Knockdown of the gene ttpa encoding for the VitE regulatory protein [α-tocopherol transfer protein (α-TTP)] in zebrafish embryos causes death within 24 h post-fertilization (hpf). To test the hypothesis that VitE, not just α-TTP, is necessary for nervous system development, adult 5D strain zebrafish, fed either VitE sufficient (E+) or deficient (E−) diets, were spawned to obtain E+ and E− embryos, which were subjected to RNA in situ hybridization and RT-qPCR. Ttpa was expressed ubiquitously in embryos up to 12 hpf. Early gastrulation (6 hpf) assessed by goosecoid expression was unaffected by VitE status. By 24 hpf, embryos expressed ttpa in brain ventricle borders, which showed abnormal closure in E− embryos. They also displayed disrupted patterns of paired box 2a (pax2a) and SRY-box transcription factor 10 (sox10) expression in the midbrain-hindbrain boundary, spinal cord and dorsal root ganglia. In E− embryos, the collagen sheath notochord markers (col2a1a and col9a2) appeared bent. Severe developmental errors in E− embryos were characterized by improper nervous system patterning of the usually carefully programmed transcriptional signals. Histological analysis also showed developmental defects in the formation of the fore-, mid- and hindbrain and somites of E− embryos at 24 hpf. Ttpa expression profile was not altered by the VitE status demonstrating that VitE itself, and not ttpa, is required for development of the brain and peripheral nervous system in this vertebrate embryo model.

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Vitamin E is Necessary to Protect Neural Crest Cells in Developing Zebrafish Embryos

Current Developments in Nutrition ◽

10.1093/cdn/nzaa057_025 ◽

2020 ◽

Vol 4 (Supplement_2) ◽

pp. 1209-1209

Author(s):

Brian Head ◽

Jane La Du ◽

Robyn Tanguay ◽

Chrissa Kioussi ◽

Maret Traber

Keyword(s):

Nervous System ◽

Vitamin E ◽

Neural Crest ◽

System Development ◽

Neural Crest Cells ◽

Nervous System Development ◽

Neural Plate ◽

Zebrafish Embryos ◽

Normal Brain ◽

Collagen Formation

Abstract Objectives Vitamin E (VitE) deficiency causes vertebrate embryonic lethality. The alpha-tocopherol transfer protein (Ttpa) likely regulates VitE distribution in the early zebrafish embryo because Ttpa knockdown causes impaired nervous system development and embryonic death by 15–18 hours post-fertilization (hpf). We propose that VitE is necessary for normal brain and peripheral nervous system development. Methods Zebrafish embryos are obtained from adults fed either VitE sufficient (E+) or deficient (E–) diets for at least 80 days. Embryos at 12 and 24 hpf are subjected to RNA whole mount in situ hybridization (WISH). RNA is also collected from embryos at 12, 18 and 24 hpf for RT-qPCR of specific targets. Results At 12 hpf, the midbrain-hindbrain boundary and otic placodes are malformed in E– embryos, as shown by Pax2a expression. Similarly, Sox10 expression shows that E– embryos lack clear neural plate borders. Nonetheless, in 12 hpf E + and E− embryos Ttpa is localized similarly throughout the nervous system. Pax2a expression initiates collagen formation in the developing notochord. Collagen genes, col2a1a and col9a2, expression patterns showed abnormal notochord structures in 24 hpf E– embryos. At 24 hpf in E + embryos, Sox10 expressing-neural crest cells are localized both in the central nervous system and dorsal root ganglia (DRG), while the Sox10 signal is diminished in E– embryos in both the DRG and early enteric nervous system. At 24 hpf, Ttpa expression outlines the brain ventricle borders; critically E– embryos show reduced Ttpa signal and impaired ventricle closing. Gene expression by qPCR will be used to confirm these results. Conclusions This VitE deficient embryo model suggests that the carefully programmed development of the nervous system is distorted due to lack of adequate VitE. Thus, Ttpa and VitE are critical molecules for neural plate and neural tube formation, and neural crest cell migration. Funding Sources The authors received no specific funding for this work.

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