Molecular genetics of human microcephaly

Human microcephaly comprises a heterogeneous group of conditions that are c haracterized by a failure of normal brain growth. Microcephaly can be cause d by many injurious or degenerative conditions, or by developmental malform ations in which the growth of the brain is impaired as a result of defects in pattern formation, cell proliferation, cell survival, cell differentiati on, or cell growth. These latter forms of congenital microcephaly are frequ ently inherited, usually as recessive traits, and are associated with menta l retardation and sometimes epilepsy, Some of the genes that cause congenit al microcephaly are likely to control crucial aspects of neural development , and may also be involved in the evolutionary explosion of cortical size t hat characterizes primates. There has recently been a rapid advance in the use of genetic mapping techniques to identify genetic loci responsible for microcephaly, Although several loci have been mapped, the condition is clea rly genetically and clinically heterogeneous, curt Opin Neurol 14:151-156 ( C) 2001 Lippincott Williams & Wilkins.