A fifth locus for primary autosomal recessive microcephaly maps to chromosome 1q31

Primary microcephaly is a genetic disorder in which an affected individual has a head circumference >3 SDs below the age- and sex-related mean. A smal l but apparently normally formed brain is the reason for the reduced head c ircumference, and, probably because of this, all affected individuals are m entally retarded. The condition is genetically heterogeneous, and four loci have already been identified. We now report a fifth locus, MCPH5, which is an 8-cM region mapping to chromosome 1q31, defined by the markers GATA135F 02 and D1S1678.