Two More "Brain-builder" Proteins

In my chapter BRAIN-BUILDERS I recount the tale of how the discovery of two genes responsible for microcephaly - ASPM and Microcephalin - has an evolutionary dimension in that both genes have accumulated substantial sequence evolution since the split from the common ancestor. Both genes affect the plane of the spindle in mitotic cell division of neuron progenitor cells such that cells can be kept in the totipotent state for longer - squeezing proliferation power out of the neuro-epithelium. Now a group of scientists at the Picower Institute at MIT have discovered two more proteins - Cdk5rap2 and pericentrin - that work together to regulate neural growth in the developing brain. Loss of function of these proteins, they report, causes microcephaly and osteodysplastic primordial dwarfism. Their normal action takes place in the developing neocortex and their mode of action was discovered using "knock out' mice.