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Sea Urchins make a Comeback as a Model for Developmental Biology

Using CRISPR technology, researchers at the University of Tsukuba creates albino sea urchins for hope that it would be brought back to the forefront of studies in developmental biology.

In developmental biology, sea urchins represent more than 100 years of research and education. Its eggs are transparent, making embryonic development and the process of fertilization observable under a microscope from the 1800s. Beyond its embryo, sea urchins have long lives with some species living up to 200 years, making them interesting for developmental biologist to study ageing.

Along with its long life comes a long breeding cycle. The most studied species of sea urchins have breeding cycles of between one and two years. This poses a limitation for research that focuses on targeting specific genes which rely on quickly produced offspring. Due to this limitation and the need to understand precise functions of genes, sea urchins have fallen out of favour as an animal model in developmental biology.

Professor Shunsuke Yaguchi and his team at the University of Tsukuba Shimoda Marine Research Center feel that much can still be learned from sea urchin biology and set out to find a way to reduce the length of the breeding cycle. “We examined several species of sea urchins and modified their food supply and environment,” explains Professor Yaguchi. Through these efforts, they found Temnopleurus reevesii, a species that has a breeding cycle of only half a year.

In this proof of concept study, the research team focused on a gene responsible for producing the pigment that colour sea urchins. Using CRISPR technology, they knocked out a pigment gene in a natural Temnopleurus reevesii mutant that has a deep magenta colour. The result successfully produced albino mutants, however only the male sea urchins survived. Therefore, to create first-generation mutants, the team used eggs from wild-type T. reevesii and sperm from the knockout mutants. Then they used first-generation males and females to produce second-generation mutants that lacked both copies of the pigment gene.

These sea urchins were albino and could metamorphosize into juveniles and advance into adulthood. But the survival rate was quite low. “Many of the albino sea urchin larvae from the F2 generation could not survive exposure to ultraviolet light,” says Professor Yaguchi. “This suggests that the pigment might help protect sea urchins from UV light or fix the damaged tissue.”

“Having shown that gene editing is both possible and practical in this species of sea urchin, future research can use these techniques in sea urchins to advance the field of developmental biology. [APBN]