Duplication of gene on X chromosome causes gigantism

BETHESDA, Md., Dec. 4 (UPI) -- Two is often better than one, but not when it comes to the DNA and RNA that make up the human chromosome. Researchers now believe gene duplication in a specific region, key in the regulation of childhood growth, is responsible for the rare disorder known as gigantism.

"Finding the gene responsible for childhood overgrowth would be very helpful, but the much wider question is what regulates growth," Constantine Stratakis, lead author of the new study, said in a press release.

Gigantism is a rare medical condition whereby children grow rapidly. Those affected typically grow to be abnormally tall; gigantism patients may also have delayed puberty, outsized hands and feet, and double vision.

To locate the offending genes, researchers at the National Institutes of Health used whole-genome analysis to study the DNA of 43 people with gigantism. The chromosomes of those afflicted with the rare disorder were then compared to family members who were born without the defect.

The analysis showed that gene duplication varied among the study participants, but researchers were able to narrow down the offending portion of the X chromosome to a stretch containing four duplicated genes. Scientists determined the gene most likely responsible for gigantism was GPR101.

"We believe GPR101 is a major regulator of growth," Stratakis said.

The gene duplication that causes gigantism results in a malfunctioning pituitary, the pea-sized gland that produces growth hormones. Researchers found activity of GPR101 was up to 1,000 times stronger than normal in children with enlarged and overactive pituitary glands.

The research was published this week in the New England Journal of Medicine.

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Duplication of gene on X chromosome causes gigantism