Stable germline transgenesis using the Minos Tc1/mariner element in the sea urchin Lytechinus pictus

Stable transgenesis is a transformative tool in model organism biology. Although the sea urchin is one of the oldest animal models in cell and developmental biology, studies in this animal have largely relied on transient manipulation of wild animals, without a strategy for stable transgenesis. Here, we build on recent progress to develop a more genetically tractable sea urchin species, Lytechinus pictus, and establish a robust transgene integration method. Three commonly used transposons (Minos, Tol2 and piggyBac) were tested for non-autonomous transposition, using plasmids containing a polyubiquitin promoter upstream of a H2B-mCerulean nuclear marker. Minos was the only transposable element that resulted in significant expression beyond metamorphosis. F0 animals were raised to sexual maturity, and spawned to determine germline integration and transgene inheritance frequency, and to characterize expression patterns of the transgene in F1 progeny. The results demonstrate transgene transmission through the germline, the first example of a germline transgenic sea urchin and, indeed, of any echinoderm. This milestone paves the way for the generation of diverse transgenic resources that will dramatically enhance the utility, reproducibility and efficiency of sea urchin research.