Evolution + Development

Whitehead Institute researchers have determined that the planarian flatworm regenerates missing tissues by using pluripotent adult stem cells. Until now, scientists could not determine whether the dividing cells in planarians, called neoblasts, are a mixture of specialized stem cells that each regenerates specific tissues, or if individual neoblasts are pluripotent and able to regenerate all tissues.

The first comprehensive comparison of Y chromosomes from two species sheds new light on Y chromosome evolution.  Contrary to a widely held scientific theory that the mammalian Y chromosome is slowly decaying or stagnating, new evidence suggests that in fact the Y is actually reinventing itself through continuous, wholesale renovation.

A previously undescribed molecular mechanism for changing the shape of cell sheets is demonstrated in the embryonic brain, using the zebrafish model. This process, termed "basal constriction", is likely to occur in different structures during development in all animals.