A newly identified genetic disease is responsible for altering brain size and potential developmental delay, British researchers report today.
Doctors at the Manchester Centre for Genomic Medicine, UK, noticed three children with large or small brains and developmental delay, and noticed that they had mutations in a gene called RAC1. Dr Siddharth Banka and colleagues investigated further, with the help of collaborators from the Netherlands and the US.
The team recruited four more children with mutations in RAC1 and altered brain-sizes. This condition seemed to be linked to epilepsy and heart defect in these children. The Manchester researchers then used mouse cells and found that mutations in RAC1 affect the shape of the cells. This finding was replicated by collaborators at in the US in tests on zebrafish.
Details of the experiments appear today in The American Journal of Human Genetics.
Dr Banka says: "Evolution has tinkered with thousands of genes over millions of years, to shape the human brain, an organ that is remarkably consistent in its appearance and size across billions of people. However, occasionally a tiny little alteration in just one of these thousands of genes can have devastating effects, reflecting the fine balance of this complex genetic orchestra."
Collaborator Dr Margot Reijnders of the Radboud University in Nijmegen, the Netherlands, added: "Remarkably, evolution has hardly meddled with RAC1. In fact, the RAC1 of the humble roundworm is not very different from the RAC1 present in your and my cells.
"This astonishing conservation across eons indicates the fundamental role of RAC1 in life. Hence, in some ways it is not surprising that a small alteration in this gene is difficult for us to tolerate.
“These findings open new doors to our understanding of the development of the brain. We suspect RAC1 plays an important role in other genetic diseases as well."
The American Journal of Human Genetics 6 September 2017.
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