BAR HARBOR (AP) – Jackson Laboratory researchers have found new information about a brain disorder called porencephaly that most often affects infants.

Scientists at the Bar Harbor lab pinpointed a genetic mutation that causes the abnormality in humans as well as in lab mice.

Through their work, Drs. Douglas Gould and Simon W.M. John hope to improve prevention, early detection and treatment of several related vascular conditions.

Porencephaly occurs only rarely, Gould and John said. Affected infants usually are identified within a year after birth.

They display symptoms such as delayed growth and development, partial paralysis, poor muscle tone, seizures and abnormally large or small heads.

Affected individuals may also have poor speech development, seizures and mental retardation.

Such symptoms are known to be associated with cerebral hemorrhage – uncontrolled bleeding from vessels that supply the brain. But why some individuals develop cerebral hemorrhage around the time of birth has been poorly understood until now.

Gould and John identified a strain of mouse that predictably develops cerebral hemorrhage and porencephaly. By studying the animals’ DNA, the two found the affected mice had a mutation in the gene that produces a particular type of collagen, a fibrous protein found in connective tissue, bone and cartilage.

This protein is essential to the formation of structures known as “basement membranes,” which form the foundation of a variety of tissues, including a protective sheath on the outside of normal blood vessels.

The researchers concluded that instead of contributing as it should to the strength of blood vessels, the mutant protein builds up on the inner surface of the vessels, potentially damaging them.

A combination of the weakened structure of the blood vessels and the accumulation of the abnormal proteins on the inner lining increases the likelihood of hemorrhage, particularly at the time of birth, when passage through the birth canal exerts tremendous pressure on the head of the mouse.

Mouse DNA is similar to human DNA, one reason mice often are used in medical research.