When we were developing in the womb, we were immersed in amniotic fluid. As our nervous systems formed, some of this fluid was trapped inside the neural tube, forming the cerebrospinal fluid that bathes our brains.

In the past, these fluids have been seen as a “cushion” or a place to dump waste products. But new research suggests that they actively participate in nervous system development.

Publishing this week in Developmental Cell, researchers led by Maria Lehtinen, PhD, and Kevin Chau in the Department of Pathology at Boston Children’s Hospital show that amniotic fluid and cerebrospinal fluid (CSF) contain rich portfolios of proteins that tell neural stem cells what to do — how to divide and what kinds of cells to make. They also show that the messages change in different phases of development. …