Variation in Spot and Stripe Patterns in Original and Regenerated Zebrafish Caudal Fins.

Tissue regeneration requires not only the replacement of lost cells and tissues, but also the recreation of morphologies and patterns. Skin pigment pattern is a relatively simple system that can allow researchers to uncover the underlying mechanisms of pattern formation. To gain insight into how pigment patterns form, undergraduate students in the senior level course Developmental Biology designed an experiment that assayed pigment patterns in original and regenerated caudal fins of wild-type, striped, and mutant, spotted zebrafish. A majority of the WT fins regenerated with a similar striped pattern. In contrast, the pattern of spots even in the original fins of the mutants varied among individual fish. Similarly, the majority of the spots in the mutants did not regenerate with the same morphology, size, or spacing as the original fins. This was true even when only a small amount of fin was removed, leaving most of the fin to potentially reseed the pattern in the regenerating tissue. This suggests that the mechanism that creates the wild-type, striped pattern persists to recreate the pattern during regeneration. The mechanism that creates the spots in the mutants, however, must include an unknown element that introduces variability.

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.