Growing up as a neural stem cell: The importance of clinging together and then letting go

Public release date: 25-Apr-2012 [ | E-mail | Share ]

Contact: Kim Irwin kirwin@mednet.ucla.edu 310-206-2805 University of California - Los Angeles Health Sciences

Can one feel too attached? Does one need to let go to mature? Neural stem cells have this problem, too.

As immature cells, neural stem cells must stick together in a protected environment called a niche in order to divide so they can make all of the cells that populate the nervous system. But when it's time to mature, or differentiate, the neural stem cells must stop dividing, detach from their neighbors and migrate to where they are needed to form the circuits necessary for humans to think, feel and interact with the world.

Now, stem cell researchers at UCLA have identified new components of the genetic pathway that controls the adhesive properties and proliferation of neural stem cells and the formation of neurons in early development.

The finding by scientists at the Eli and Edythe Broad Center of Regenerative Medicine and Stem Cell Research at UCLA could be important because errors in this pathway can lead to a variety of birth defects that affect the structure of the nervous system, as well as more subtle changes that impair cognitive and motor functions associated with disorders such as autism.

The results of the four-year study are published April 26, 2012 in the peer-reviewed journal Neuron.

The UCLA team found that a delicate balance of gene expression enables the pool of neural stem and progenitor cells in early development to initially increase and then quickly stop dividing to form neurons at defined times.

"One of the greatest mysteries in developmental biology is what constitutes the switch between stem cell proliferation and differentiation. In our studies of the formation of motor neurons, the cells that are essential for movement, we were able to uncover what controls the early expansion of neural stem and progenitor cells, and more importantly what stops their proliferation when there are enough precursors built up," said Bennett G. Novitch, an assistant professor of neurobiology, a Broad Stem Cell Research Center scientist and senior author of the study. "If the neurons don't form at the proper time, it could lead to deficits in their numbers and to catastrophic, potentially fatal neurological defects."

During the first trimester of development, the neural stem and progenitor cells form a niche, or safe zone, within the nervous system. The neural stem and precursor cells adhere to each other in a way that allows them to expand their numbers and keep from differentiating. A protein called N-cadherin facilitates this adhesion, Novitch said.

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Growing up as a neural stem cell: The importance of clinging together and then letting go