Analysis of factors and mechanisms that control growth in the genital disc of drosophila

Abstract

The relation among proliferation and death duringgrowth is explained by the competition mechanism. This sees, the cells growth,in relation with their neighbors; if the rhythms of growth are notcoincidental, the lower growing cells are removed by apoptosis.There is aspecial type of cell competition called morphogenetic apoptosis.This occurs ifdiscontinuities in the growth /surviving signals Dpp/Wg are induced.Under thesecircumstances death mediated by the JNK mechanism is observed at the borders ofthe discontinuities. A tissue-physiologycal scenario for such discontinuitiescould be the time/place when Dpp and Wg expressions start. The differences inthe amount among, expressing and non expressing cells should be high at the beginningbut should decreased as development progress. In accordance, morphogeneticapoptosis must occurs at the borders of Dpp/Wg expressions. We tested this ideain the genital disc of Drosophilawhere the activation of Dpp occurs late in development, there is a celldivision arrest up to that time, and death plays roles. We center our analysisin the activities of Dpp, JNK, the pro-apoptotic genes RGH and the enzymes caspases.Our main results indicated there is cell competition/morphogenetic apoptosis atthe borders of Dpp expression, revealed principally not by the death but forits compensatory proliferation. The net balance among death/proliferationappeared cero, so physiologycal cell competition does not vary the size. Thelevels of active JNK and caspases are important for: the execution of death,the control of proliferation, and the occurrence of compensatory proliferation.TheJNK/capases activity over proliferation determines them as factors of cellcompetition.