Researchers at University of Tsukuba examined how twin organisms can emerge from a single fertilized egg by studying sea urchin embryos. Their findings revealed that when an early-stage embryo is split in half, each portion is able to regenerate its own developmental plan. The team uncovered the dynamic cellular processes and genetic programs that allow each fragment to reorganize and grow into a complete individual.

Tsukuba, Japan—In the late 19th century, German embryologist Hans Driesch showed that when fertilized sea urchin eggs were separated at the two-cell stage, each cell could still develop into a complete organism. Yet, for more than a century, the developmental process and molecular mechanisms that allow the embryo to re-establish its body axes (anterior-posterior, dorsal-ventral, and left-right) and resume normal development have remained largely unclear.

In this study, researchers combined advanced microscopy with molecular biology to uncover how each embryo fragment is able to reset its developmental blueprint and grow into a full individual. They also succeeded in visualizing axis reconstruction by tracking the cellular movements and activation of gene that drives this remarkable self-organizing ability.

This discovery offers fresh insight into a long-standing question in life sciences: how two complete individuals can emerge from one fertilized egg. Using sea urchins as a model, it may also provide valuable insights for future developmental studies, including the origins of monozygotic twinning in humans.

###
This work is supported by JST PRESTO Grant number JPMJPR194C, JST A-STEP Grant number JPMJTR204E, JSPS KAKENHI Grant number 23K23933 and 24K21959 to S.Y., and JST PRESTO Grant number JPMJPR1945 and JSPS KAKENHI Grant Numbers 19K20406 and 23K11312 to K.T.

Original Paper

Title of original paper:

Unraveling the regulative development and molecular mechanisms of identical sea urchin twins

Journal:

Nature Communications

DOI:

10.1038/s41467-025-63111-z

Correspondence

Associate Professor YAGUCHI Shunsuke
Institute of Life and Environmental Sciences, University of Tsukuba

Specially Appointed Lecturer TSUYUZAKI Koki
Department of Artificial Intelligence Medicine, Graduate School of Medicine, Chiba University

Related Link

Institute of Life and Environmental Sciences