International Journal of Marine Science, 2024, Vol.14, No.4, 256-265 http://www.aquapublisher.com/index.php/ijms 261 al., 2020), BMP signaling, on the other hand, is involved in ventralizing signals that contribute to AP axis patterning (Tuazon and Mullins, 2015), The integration of these pathways through ciliary signaling ensures the coordinated development of the AP axis. 6 Experimental Models and Techniques 6.1 Model organisms in cilia research Model organisms have played a crucial role in advancing our understanding of cilia biology and their role in body axis development. The ciliate Tetrahymena thermophila has been a key model for studying intracellular patterns along the anteroposterior axis. Zebrafish research has provided insights into the role of cilia-driven cerebrospinal fluid flow in body axis morphogenesis, showing that cilia promote the formation of the Reissner fiber, which is essential for correct body axis development (Cantaut-Belarif et al., 2018; Zhang et al., 2018). It was found that mutations in the scospondin gene lead to impaired Reissner fiber formation, resulting in curled phenotypes in larvae. This phenomenon is evident early in development and shows significant differences among various mutants, highlighting the critical role of the Reissner fiber in spinal cord development (Figure 2). Additionally, a network of highly conserved kinases has been discovered to regulate organelle positioning by creating cortical inhibition zones (Cole and Gaertig, 2022). In vertebrates, mouse models have been pivotal in elucidating the role of planar cell polarity (PCP) genes, such as Vangl1 and Vangl2, in breaking left-right symmetry by controlling cilia positioning (Song et al., 2010). The medaka fish has also been used to study the role of the LIM protein Ajuba in ciliogenesis and left-right axis determination, emphasizing its important function in the cells lining the Kupffer's vesicle (Nagai et al., 2010). 6.2 Genetic and molecular tools Genetic and molecular tools have been crucial in dissecting the mechanisms of cilia function and axis development. Mutational analyses in Tetrahymena have revealed genes whose mutations cause organelle positioning defects, providing insights into the molecular underpinnings of anterior-posterior patterning (Cole and Gaertig, 2022, In mice, the removal of Vangl1 and Vangl2 has demonstrated the necessity of PCP in interpreting anterior-posterior patterning information and linking it to left-right asymmetry (Song et al., 2010), Knockdown experiments in medaka have shown that Ajuba is essential for ciliogenesis and left-right axis determination, with its absence leading to randomized organ asymmetries (Nagai et al., 2010), In zebrafish, the mutation of the scospondin gene has shown that the Reissner fiber is critical for body axis morphogenesis, linking cilia function to the control of body axis curvature (Cantaut-Belarif et al., 2018), Additionally, the knockdown of ift46 in zebrafish has revealed its essential role in ciliary development, with defects leading to multiple ciliopathies (Lee et al., 2015). 6.3 Imaging and visualization techniques Imaging and visualization techniques have been indispensable in studying cilia and their role in axis development. Classical microsurgical experiments in large ciliates, such as Stentor, have provided foundational observations that have been interpreted in light of recent molecular findings in Tetrahymena (Cole and Gaertig, 2022), In Xenopus, the use of imaging techniques has shown that mechanical strain during gastrulation plays a major role in determining the global axis of planar polarity in ciliated epithelia (Chien et al., 2015), Advanced imaging in zebrafish has demonstrated how cilia-driven cerebrospinal fluid flow directs the expression of urotensin neuropeptides, which are crucial for straightening the vertebrate body axis (Zhang et al., 2018), These techniques have also been used to visualize the Reissner fiber and its role in body axis morphogenesis, providing a deeper understanding of the interplay between cilia and cerebrospinal fluid flow (Cantaut-Belarif et al., 2018), Furthermore, imaging studies in zebrafish mutants have elucidated the role of motile cilia and cerebrospinal fluid flow in axial morphogenesis and spinal straightness, offering insights into conditions such as idiopathic scoliosis (Bearce and Grimes, 2020). 7 Disorders of Cilia Function 7.1 Ciliopathies and developmental defects Ciliopathies are a group of genetic disorders caused by defects in the structure or function of cilia, which are microtubule-based organelles protruding from the cell surface. These disorders are often pleiotropic, affecting
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