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SUMMARY:The auxetic nucleus: nuclear mechanics and its role in regulating 
 stem cell differentiation - Dr Kevin Chalut\, Department of Physics\, Cave
 ndish Laboratory\, University of Cambridge
DTSTART:20141024T150000Z
DTEND:20141024T160000Z
UID:TALK55254@talks.cam.ac.uk
CONTACT:Anna Walczyk
DESCRIPTION:Embryonic stem cells (ESCs) self-renew in a state of naïve pl
 uripotency\, in which they are competent to generate all somatic cells. It
  has been hypothesized that\, before irreversibly committing\, ESCs pass t
 hrough at least one metastable transition state. This transition would rep
 resent a gateway for differentiation and reprogramming of somatic cells. W
 e sought a mechanical phenotype of transition by probing the nuclear respo
 nse to compressive and tensile forces and found that\, only during transit
 ion\, nuclei of ESCs are auxetic: they displayed a cross-sectional expansi
 on when stretched and a cross-sectional contraction when compressed\, and 
 their stiffness increased under compression. We showed recently that the a
 uxetic phenotype of transition ESC nuclei is driven at least in part by gl
 obal chromatin decondensation. Our findings highlight the importance of nu
 clear structure in the regulation of differentiation and reprogramming. Im
 portantly\, there are also significant volume implications we explored for
  the auxetic phenotype in ESC nuclei during transition. Stretched auxetic 
 nuclei expand significantly in volume\, whilst compressed auxetic nuclei c
 ondense significantly in volume\; this is very unlike most materials\, whi
 ch tend to conserve or lose volume under stress. Therefore\, I will discus
 s how the physical properties of these nuclei in a dynamically remodeling 
 tissue could enhance differentiative capacity by acting as stress-driven a
 uxetic pumps to increase molecular turnover.
LOCATION: Cambridge University Engineering Department\, Lecture Room 6
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