%0 Journal Article
%T Hsp90 depletion goes wild
%A Mark L Siegal
%A Joanna Masel
%J BMC Biology
%D 2012
%I BioMed Central
%R 10.1186/1741-7007-10-14
%X See research article http://wwww.biomedcentral.com/1471-2148/12/25 webciteNearly 15 years ago, Rutherford and Lindquist [1] showed that reducing levels of the heat shock protein 90 (Hsp90) chaperone exposes a wide variety of phenotypes. Repeating the experiment in different strains of flies, each of which has a different genetic background, led to different Hsp90-dependent phenotypes. They argued that Hsp90 is an evolutionary 'capacitor' that creates robustness to the effects of mutations, allowing genetic variation to accumulate in a cryptic form, to be released later. This work prompted an explosion of interest in Waddington's much earlier work on the role of cryptic genetic variation in evolution [2]. Perhaps the time, technology and tractable model system had finally arrived to make progress.In a narrow interpretation of these data, Hsp90 is seen as a contributor to the extraordinary resistance of biological systems to common perturbations such as mutation. In a more expansive view, Hsp90 perturbation is seen to promote evolvability. In a new and stressful environment, cellular demand for Hsp90 will increase beyond its supply, mimicking the effects of artificial depletion. New and stressful environments are those in which new variants, such as those revealed by Hs90 depletion, are most likely to be adaptive. This adaptation might be temporary, lasting only as long as the environmental stress. In this case, the advantage of Hsp90-dependent phenotypes might be their easily reversible nature: when the stress is over, Hsp90 levels return to normal. Alternatively, if the new environment is sustained, an Hsp90-mediated phenotype might lose its initial dependence on Hsp90 through a process of genetic assimilation. Such genetic assimilation occurs readily in the laboratory [1], and might contribute to adaptation and so increase evolvability.There were both critics of and enthusiasts for this view of Hsp90 as evolutionary capacitor. The critics appreciated the 'coolness'
%U http://www.biomedcentral.com/1741-7007/10/14