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Big Changes and Developmental Disorders

Some three percent of any given individual's genome is affected by large copy-number changes, writes Washington University School of Medicine in St. Louis' Michael White at Pacific Standard. While most people are just fine, in some cases, he adds, such CNVs can cause problems.

Down's syndrome, he says, is a common example of a large CNV, though smaller-sized CNVs have been linked to other developmental disorders like autism spectrum disorders, Williams syndrome, and Angelman syndrome.

Developmental disorders, White says, are "confusingly diverse, frustratingly subtle, and surprisingly common disorders are often caused by CNV mutations that are themselves confusingly diverse, frustratingly subtle in their effects, and surprisingly common in the population."

But recent studies are beginning to map out CNVs and find patterns among the mutations and symptoms. For instance, he notes that Evan Eichler's lab at the University of Washington homed in on a gene — ZMYND11 — that was mutated in a number of patients. Though some of the patient's symptoms varied as some people had intellectual disabilities while others had normal intelligence, they shared some symptoms such as subtle facial deformities, delayed speech, and behavioral difficulties. Finding commonalities among patients, he says, may help guide treatment.

"As geneticists dig into the seismic disruptions caused by CNVs, the confusing landscape of developmental disorders will begin to make more sense," White adds, noting that there still will be a "gray area" in which there may be people who carry the mutations but do not meet other criteria for diagnosis.