Development and 3D architecture of the inactive X chromosome (Barr body)

X chromosome inactivation in female mammals, driven by spreading of Xist-RNA in cis leads to chromatin compaction of the inactive X (Xi) territory forming the Barr body as a structural hallmark of female nuclei. Using 3D-structured illumination microscopy we (I) explore the spatio-temporal process of Barr body formation in early differentiating mouse embryonic stem cells (mESCs) and (II) compare the three-dimensional ultrastructure of Xi with active chromosome territories (CTs) in man and mouse.

We consider the Barr body structure as special case maintaining basic principles of global CT organization. The Barr body differs however from active CTs by a closing up of CD clusters and a partially collapsed active nuclear compartment which is typically found in active CTs.

Relevant publications from our group:

Smeets D et al. (in preparation)

Markaki Y, Smeets D, Fiedler S, Schmid VJ, Schermelleh L, Cremer T, Cremer M (2012) The potential of 3D-FISH and super-resolution structured illumination microscopy for studies of 3D nuclear architecture. BioEssays 34: 412-26

Teller K, Illner D, Thamm S, Casas-Delucchi CS, Versteeg R, Indemans M, Cremer T, Cremer M (2011) A top-down analysis of Xa- and Xi-territories reveals differences of higher order structure at ≥20 Mb genomic length scales. Nucleus 2: 465-477

Eils R, Dietzel S, Bertin E, Schröck E, Speicher MR, Ried T, Robert-Nicoud M, Cremer C, Cremer T (1996) Three-dimensional reconstruction of painted human interphase chromosomes: active and inactive X-chromosome territories have similar volumes but differ in surface and shape. J Cell Biol 135, 1427-1440