Scientists find impaired chromatin structure formation & imprinted gene involvement in Ret...( ather. Misregulation of imprinted genes...)

ather. Misregulation of imprinted genes has been implicated in several neurological disorders. Dr. Kohwi-Shigemtsu found that patients with RTT have twice the normal amount of DLX5. The team then attempted to determine how normal MeCP2 regulates the DLX5 gene and how this regulation goes awry in RTT.

In an unexpected twist, the scientists found that methylation of CpG islands had no impact on expression of DLX5. In fact, the CpG islands associated with DLX5 were unmethylated in both paternal alleles. Some other mechanism must therefore be responsible.

Imagine DNA like a slinky that can be stretched out or compacted. Rather than wire, a basic structural component determining the architecture of this slinky is chromatin. In order for genes along the slinky to be expressed they must be accessible to certain enzymes, and therefore that section of the slinky must be stretched out. Tightly compacted sections are silent because the genes cannot be accessed. In normal mice, they found that MeCP2 formed chromatin loops of silenced DNA in the vicinity of DLX5 by bringing together two sequences separated by more than 10,000 base pairs. This silent chromatin loop configuration was not able to form in the brains of the RTT mouse models.

"The Rett Syndrome community, comprised of both scientists and afflicted families, eagerly awaits the identification of MECP2 target genes, as these genes will likely lead to therapeutic interventions. I congratulate Dr. Kohwi-Shigematsu and her team on their discovery and am pleased that funding from the Rett Syndrome Research Foundation (RSRF) will allow them the opportunity to continue their work and unravel if and how DLX5 contributes to Rett Syndrome symptoms," said Monica Coenraads, co-founder and Director of Research for RSRF. Future experiments will include the analysis of gene expression in the neighboring chromatin affected by the loss of the silent loop structure.

Dr. Terumi Kohwi-Shigematsu explai
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Contact: Monica Coenraads
monica@rsrf.org
203-445-9233
Rett Syndrome Research Foundation
20-Dec-2004

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