March 12, 2014

I love a lot of things that are rings, especially donuts. Turns out, though, that ring chromosomes are terrible news. A recent paper shows the loss of ring chromosomes when cells are reprogrammed, suggesting possible ‘chromosome therapy’ through cell reprogramming.

Ring chromosomes form when the two arms of a chromosome fuse, and are sometimes associated with large terminal deletions. These ring chromosomes lead to birth defects, mental disabilities, and growth retardation. Unfortunately, there are no treatments for ring chromosome disorders due the severity of the aberrations. In a recent study, Bershteyn and colleagues generated induced pluripotent stem cells (iPSCs) from cells of a Miller Dieker Syndrome patient with large deletions on ring chromosome 17. The induced stem cells lost the ring chromosome and duplicated the normal homologous chromosome through a mechanism called compensatory uniparental disomy. The images above show two karyotypes—one with the ring chromosome 17 (left, inset), and one without (right).

Bershteyn, M., Hayashi, Y., Desachy, G., Hsiao, E., Sami, S., Tsang, K., Weiss, L., Kriegstein, A., Yamanaka, S., & Wynshaw-Boris, A. (2014). Cell-autonomous correction of ring chromosomes in human induced pluripotent stem cells Nature, 507 (7490), 99-103 DOI: 10.1038/nature12923
Adapted by permission from Macmillan Publishers Ltd, copyright ©2014