Blame defective gene for malformed faces

Washington -  Scientists have located a gene whose mutation wrecks the shape of human faces as well as triggers mental retardation.

They looked at patients with Potocki-Shaffer syndrome, a rare disorder that can result in significant abnormalities such as a small head and chin and intellectual disability, and linked it to  mutation in the gene PHF21A, said Hyung-Goo Kim, molecular geneticist at the Medical College of Georgia Health Sciences University.

The scientists confirmed PHF21A's role by suppressing it in zebrafish, which developed head and brain abnormalities similar to those in patients. "With less PHF21A, brain cells died, so this  gene must play a big role in neuron (brain and nerve cell) survival," Kim, who led the study, was quoted as saying in The American Journal of Human Genetics.

They reconfirmed the role by giving the gene back to the malformed fish - studied for their adeptness at regeneration - which then became essentially normal. They also documented the gene's presence in normal mice, said a university statement.

While giving the normal gene unfortunately can't cure patients as it does the zebrafish, the scientists believe the finding will eventually enable genetic screening and possibly early  intervention during foetal development, including therapy to increase PHF21A levels, Kim said.

It also provides a compass for learning more about face, skull and brain formation.

The scientists zeroed in on the gene by using a distinctive chromosomal break found in patients with Potocki-Shaffer syndrome as a starting point. Chromosomes - packages of DNA and  protein - aren't supposed to break, and when they do, it can damage genes in the vicinity.

"We call this breakpoint mapping and the breakpoint is where the trouble is," said Lawrence C. Layman, professor of endocrinology at the Medical College of Georgia and study co-author.