Gian Gaetano Tartaglia Centre de Regulació Genòmica (CRG)

The determination of sex in mammals, and therefore in humans, is defined by the presence of sexual chromosomes: males carry a heteromorphic pair of chromosomes (XY) and females have two identical chromosomes (XX). A specific biological process called inactivation of the X chromosome involves the loss of function of one of the two chromosomes of the females: in this way the quantity of the inherited genes is balanced, avoiding the overexpression of their products (proteins) and the consequent onset of genetic anomalies like the triple X syndrome, also known as trisomy X.

We analyzed the process of inactivation of the X chromosome and in particular the role of the RNA molecule called Xist (X-Inactive-Specific-Transcript), its main regulator.

We studied the mechanism of action, structure and interactions of the Xist molecule. We observed that Xist acts as a “scaffold”, it provides scaffolding and at the same time attracts lots of proteins to organize the “silencing” of the X chromosome. The interaction network is so great that Xist and its partners proteins form a structure that resembles a corpuscle, conceptually similar to a drop of oil in water.


Cerase A, Armaos A, Neumayer C, Avner P, Guttman M & Tartaglia GG 2019, ‘Phase separation drives X-chromosome inactivation: a hypothesis‘, Nature Structural & Molecular Biology, volume 26, pp. 331-334.