Temperature Sensitivity of Neural Tube Defects in Zoep Mutants

Neural tube defects (NTD) occur when the flat neural plate epithelium fails to fold into the neural tube, the precursor to the brain and spinal cord. Squint (Sqt/Ndr1), a Nodal ligand, and One-eyed pinhead (Oep), a component of the Nodal receptor, are required for anterior neural tube closure in zebrafish. The NTD in sqt and Zoep mutants are incompletely penetrant. The penetrance of several defects in sqt mutants increases upon heat or cold shock. In this project, undergraduate students tested whether temperature influences the Zoep open neural tube phenotype. Single pairs of adults were spawned at 28.5°C, the normal temperature for zebrafish, and one half of the resulting embryos were moved to 34°C at different developmental time points. Analysis of variance indicated temperature and clutch/genetic background significantly contributed to the penetrance of the open neural tube phenotype. Heat shock affected the embryos only at or before the midblastula stage. Many factors, including temperature changes in the mother, nutrition, and genetic background, contribute to NTD in humans. Thus, sqt and Zoep mutants may serve as valuable models for studying the interactions between genetics and the environment during neurulation.