What's still not clear is whether the disease limits the eventual lifespan of patients.
Distinct genetic cause
Many CS traits, including a very happy disposition, appear similar to those of another autism-like condition, Angelman Syndrome, but the study defines important differences.
Among the most important ones is that the two syndromes have distinct genetic underpinnings. In all CS cases, said Morrow who treats autism patients at the E. P. Bradley Hospital in East Providence, boys have a mutation on the SLC9A6 gene on the X chromosome that disables production of a protein called NHE6 that is important for neurological development.
Girls, who have two X chromosomes, can also be carriers of CS mutations, but they appear to be affected differently and less severely or not at all, the study reports.
The connection to the SLC9A6 gene was first discovered in 2008. In analyzing the genomes of each patient and their parents in the new study, lead authors Matthew Pescosolido, a graduate student, and David Stein, a former undergraduate, found that each boy had only one mutation, but there were many different ones across the entire group. More often than not, they determined, the mutation was not inherited, but an unlucky "de novo" change that occurred in the affected boy. In two situations, boys in unrelated families happened to share the same mutation. These recurrent mutations suggest that there may be hotspots in the DNA for mutation at these sites, Morrow said, although further research will be necessary to sort this out.
Morrow said there is evidence that SLC9A6 mutations and therefore CS may be a relatively common source of X-linked intellectual disability. One study, for example found that SLC9A6 mutations in two of 200 people suspected of having X-linked ID. An
|Contact: David Orenstein|