THE CYCLOPS From Mythical Figure to Genetic Defect (Cyclopia Research Paper)

Abstract

Due to limited research opportunities, cyclopia remains a mysterious genetic defect in the 21st century. It is the most severe manifestation of alobar holoprosencephaly and triggers failure of forebrain separation during the early stages of embryogenesis. Hence, this research paper aims to examine how disruptions of embryonic brain development can result in cyclopia. The conducted research integrates embryological, molecular, genetic, and clinical evidence and analyzes relevant literature on neurulation, prosencephalon formation, Sonic-Hedgehog (SHH) signaling, neural crest cell development, and holoprosencephaly by utilizing published prenatal data and postnatal case reports found online. The reviewed and analyzed evidence displays that failure of ventral forebrain patterning and embryonic midline specifications during the embyonic development can cause the rise of cyclopia. Especially SHH signaling plays a crucial role in the process of facial and midline establishment and the separation of the single eye field into bilateral optic primordia. If the SHH activity is insufficient, the brain is unable to fully divide into two distinct hemispheres, causing the fusion of optic fields and severe craniofacial malformations. Although SHH dysfunction is often regarded as the primary conductor leading to cyclopia, additional formative regulators, chromosomal abnormalities, environmental factors, and gene-environmental interactions have been recognized as further contributors. Analysis of published case reports confirmed the consistent association of cyclopia with alobar holoprosencephaly, profound craniofacial defects, and lethality. Taking everything into consideration, cyclopia is considered the representant of an extreme but highly informative model of disturbed human midline development and provides significant insight into molecular mechanisms governing normal forebrain and craniofacial formation. Keywords: Cyclopia, Embryonic development, Neurulation, Forebrain formation; Holoprosencephaly; Sonic Hedgehog; SHH signaling; Craniofacial malformations; Synophthalmia