Mice with a single missing gene have brains that are 35 percent larger than normal, a new study found. Though they have big brains the mice are as healthy and happy as normal mice.

The researchers created these mutant mice to learn more about Snf2l, which is known to play a role in folding up and organizing the cell's genetic material, and in turning genes on and off. They found that the mutant mice were completely normal, except that they had larger brains, more cells in all areas of the brain, and more actively dividing brain stem cells.

"This research represents a fundamental advance in our understanding of how the brain develops, and it also has important practical implications," study researcher David Picketts, of the University of Ottawa, in Canada, said in a statement.

The study findings, published in the April 17 issue of the journal Developmental Cell, could lead to new approaches to stimulate brain regeneration and may provide important insight into developmental disorders such as autism and Rett syndrome.

"The connections between Snf2l and brain developmental disorders are intriguing," Picketts said. "We're looking forward to further unraveling these connections and hopefully applying this research to help people who suffer from these conditions."

The mutant mice are also providing insight into developmental disorders that are associated with changes in brain size. For example, Picketts and his team found that Snf2l interacts with a gene which causes the intellectual disability disorder Rett syndrome in some people.

While the mutant mice without Snf1l have high levels of this gene and large brains, people with Rett syndrome lack Foxg1 and have small brains. Snf2l and Foxg1 seem to work against each other to balance brain size.

"If we could identify drugs that regulate Snfl2 activity, these could potentially be used to stimulate neural stem cells to help regenerate and repair damage in people who have suffered brain injuries or strokes," Picketts said. "We're still at the early stages of this research, but the possibilities are very exciting."