THURSDAY, Jan. 26 (HealthDay News) -- Newly discovered mutations in two adjacent genes cause a rare genetic brain condition called Joubert syndrome, according to a new study.
People with Joubert syndrome have malformation or underdevelopment of the cerebellum and brainstem, resulting in a range of physical and mental disabilities such as poor muscle control and mental retardation.
As many as four in 10 people with Joubert syndrome meet the criteria for an autism diagnosis and other neurocognitive disorders, according to background information in a news release about the research.
In the study, a team led by University of California, San Diego School of Medicine researchers found that mutations in two adjacent genes -- TMEM216 and TMEM138 -- cause Joubert syndrome.
"It is extraordinarily rare for two adjacent genes to cause the same human disease," team leader Dr. Joseph Gleeson, a professor of neurosciences and pediatrics, said in the university news release. "The mystery that emerged from this was whether these two adjacent, non-duplicated genes causing indistinguishable disease have functional connections at the gene or protein level."
The researchers conducted evolutionary analysis and concluded that the two genes became joined end-to-end about 260 million years ago. The connected genes then evolved simultaneously and became regulated by the same transcription factors, the authors reported in the study published online Jan. 26 in Science Express.
More information
The U.S. National Institute of Neurological Disorders and Stroke has more about Joubert syndrome.
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