Saturday, 18 January 2014


If you are a female, you have 2 X chromosomes, coming from each parent, but only one of them is usually active in any given cell, while the other one is silenced.  Scientists from Johns Hopkins University School of Medicine, led by Dr. Jeremy Nathans, have color coded the X chromosomes by making them express different color fluorescent proteins (FP).  Thus, if a cell inactivates maternal X chromosome, then the red FP from the paternal X chromosome is expressed, “painting” the cell and all its progeny red.  If the paternal X chromosome is inactivated, then the cell and its progeny turn green due to the expression of the green FP gene placed on the maternal X chromosome.
   Similar phenomenon occurs naturally in calico cats whose fur color depends on which X chromosome is inactivated in that patch of skin.  Now, with the red and green FP technology, this process can be visualized in all parts of the body! This will enable scientists to look at expression of particular X chromosome genes linked to diseases for which women are typically carriers, but might be affected locally, in some parts of their bodies.  It will also be extremely useful for developmental studies.

Hao Wu, Junjie Luo, Huimin Yu, Amir Rattner, Alisa Mo, Yanshu Wang, Philip M. Smallwood, Bracha Erlanger, Sarah J. Wheelan, Jeremy Nathans, Cellular Resolution Maps of X Chromosome Inactivation: Implications for Neural Development, Function, and Disease, Neuron, Volume 81, Issue 1, 8 January 2014, Pages 103-119