Switch to survival

Asingle factor can promote both proliferation and differentiation of oligodendrocytes, according to Holly Colognato, Charles ffrench-Constant (University of Cambridge, Cambridge, UK), and colleagues. The added ingredient that makes the difference, and switches the signaling pathway downstream of the growth factor, is the extracellular protein laminin.

The laminin is found on axons in the central nervous system—the target of the oligodendrocytes. Before arriving at this target, the oligodendrocytes proliferate under the influence of several factors including neuregulin, whose actions are pro-proliferation and anti-differentiation.

As the cells mature, a proapoptotic protein called BAD accumulates. This may result in the death of excess oligodendrocytes that are far away from their target. But the Cambridge group found that cells close enough to an axon could counteract the accumulation of BAD. The ligation of oligodendrocyte integrin α6 with axon-supplied laminin...