Studies published by the journal Nature Genetics say that microcephaly, a disorder which leads to an abnormally small brain, has been traced in part to a flaw in a gene called WDR62 that plays a key role in the development of neurons.
Microcephaly, signalled by a small head and receding forehead, can be extremely disabling, handicapping speech and motor functions. There is no cure.
The WDR62 abnormality is one of a range of suspected genetic links to microcephaly. The condition also has environmental causes, including foetal exposure to alcohol, drugs and viruses such as chicken pox and German measles.
The studies are headed by C. Geoffrey Woods at Cambridge University and Christopher Walsh at the Boston Children's Hospital in Massachusetts.
Working separately, they spotted the WDR62 flaw by looking at the genomes of families with a history of microcephaly and by examining human and mouse embryonic cells in the lab.