Body orientation affects brain ventricular system development and mechanosensory gene expression in zebrafish embryos

Most vertebrates maintain a horizontal body orientation. Whereas humans and great apes exhibit postures varying from horizontal to vertical. This exposes the body and its fluid-filled organs to changing gravitational vectors. This study examines how body position influences brain ventricular system development under normogravity. The zebrafish embryos were maintained in distinct orientations for 24 hours. The development of the Reissner fiber, an essential element of the brain ventricular system and proprioception, has been analyzed along with expression of genes associated with mechanotransduction and formation of Reissner fiber. Embryos held in vertical positions exhibited disrupted Reissner fiber, body axis deformities, and altered expression of gravity-responsive genes from the Hippo pathway, particularly yap1a . Among the genes regulating the development of Reissner fiber, the transcript level of chl1a/camel increased dramatically. These findings suggest that body orientation modulates cerebrospinal fluid flow and mechanosensory pathways during development. Understanding these effects provides insight into the mechanotransduction processes underlying proprioception and may inform studies of gravity's impact on vertebrate neurodevelopment.