Novel functions of the Drosophila Mps1 homologue, altered disjunction (ald), regulating epithelial integrity. Beatriz Perez San Juan, Antonio Baonza Cuenca. Developmental Biology, CBMSO, Madrid, Madrid, Spain.

   Mps1 (Mono-polar spindle 1) is an evolutionary conserved serine treonine kinase that regulates normal mitotic progression and the spindle checkpoint in response to stress. Changes in Mps1 protein levels have been related with the development of cancer in human. This tumor-promoting function it's been attributed to the chromosomal instability observed when the activity of this kinase is modified. However, other functions of this kinase involved in tumor progression still remain unknown. We have analyzed the function of the Drosophila melanogaster Mps1 homologue, altered disjunction (ald). Our data indicate that the alteration of the activity of ald causes the lost of the adherents junctions components and the disruption of the apico-basal polarity domains, compromising the epithelial integrity. These cells undergo a pseudo epithelial to mesenchimal transition (EMT) and acquire cell motility and invasiveness. Ald mediates part of these effects regulating the activity of Rho1 and the Myosin II light chain (sqh). These results uncovered novel functions for this kinase that can help to understand its contribution to the development of tumors.