A particular nuclear hormone receptor called DAF-12 and molecules called microRNAs in the let-7 family form a molecular switch that encourages cells in the larvae of a model worm to shift to a more developed state, said a consortium led by researchers from Baylor College of Medicine in a report that appears online in the journal Science.

As organisms go through the stages of life, hormones coordinate the changes. Nuclear receptors respond to hormones to coordinate stage transitions, but how they do so is not well understood.

GOING FROM STAGE 2 TO STAGE 3

"We knew that nuclear hormone receptors were involved in stage 2 to stage 3 transitions in Caenorhabditis elegans," said Dr. Adam Antebi , associate professor in the Huffington Center on Aging at BCM and the report's senior author. "Another class of molecules called microRNAs is also involved in that transition. We hypothesized that maybe if they are involved in the same process, one turns on the other."

That turns out to be the case in C. elegans and may be true in more advanced organisms as well, he said.

A MODEL WORM ENABLES STUDIES

Scientists use the tiny worm called Caenorhabditis elegans to study such processes because it has a simple anatomy and life cycle. C. elegans develops from embryo through four larval stages into adulthood.

Each "stage" has specific programs of cell division, migration, differentiation and death that are crucial to the organism's final development…