Morphogenetic activity of the human brain neuroepithelium during early neurulation

BACKGROUND: During the embryonic period — from the emergence of the first neural folds to the formation of the primary neural tube closure zone — the neural plate undergoes active remodeling. According to current understanding, the first signs of the nervous system appear during neurulation on Carnegie stage 8. Two days later, the neural plate begins to form a tubular structure (stage 10). It has been established that during neurulation, the developing nervous system is particularly vulnerable to various damaging influences, yet this critical period remains the least studied stage of development. AIM: The aim was to describe the embryonic remodeling events of the human neural plate from the presomite to the 8-somite stage in the developing brain region. MATERIALS AND METHODS: We examined autopsy specimens of cytotrophoblasts from 18 women who died in accidents. After isolating cytotrophoblasts from the uterine wall, we performed macroscopic analysis of their contents and histological examination of embryos using serial sections. RESULTS: Studies on human rostral neurulation dynamics have revealed previously unknown morphogenetic transformations of the neuroepithelium. These included duplication of the neural plate marginal folds, formation of transient neuroectodermal ridges, and other temporary embryonic structures. To date, these human-specific but provisional brain morphogenetic events have remained unrecognized, and their underlying mechanisms unexplored. CONCLUSION: Early embryonic brain morphogenesis in humans involves a complex sequence of coenogenetic neuroepithelial movements. The rostral neural plate generates transient (provisional) structures that sequentially reshape the brain primordium. Their emergence and disappearance likely reflect hidden mechanisms encoding positional information, which ultimately determines the differentiation of major human brain regions.