Caracterización funcional del gen "vertigial" de "Drosophila melanogaster"

Abstract

The development of Drosophila imaginal discs is a classical model to study the growth and genetic specification of growing organs. The growth, size and shape of an organ result from the coordination of different cellular processes (cell proliferation, cell death and the spatial arrangement of cells) in specific patterns during development. In turn, these processes are intimately related to mechanisms of positional specification dependent on the activity of genetic factors. However, the relationships between positional information and gene expression patterns are poorly understood. vestigial (vg) is an essential gene for the development of the wing in Drosophila (Kim et al., 1996; Williams et al., 1991; Williams et al., 1994). Vg function has been involved in the control of identity (Halder et al., 1998; Kim et al., 1996; Williams et al., 1991), cell proliferation and cell survival (Delanoue et al., 2004; Delanoue et al., 2002; Kim et al., 1996; Liu et al., 2000; Van de Bor et al., 1999) of the wing from early larval stages of development (Williams et al., 1991; Williams et al., 1993). Attending to its functionality, vg has been proposed to act as a “master gene” (Kim et al., 1996). However, I present evidences that its ectopic expression only elicits certain characteristics of wing blade development in specific genetic context. Furthermore, my results show a strong dependence of vg on wingless to initiate the wing blade developmental program. These findings suggest that the combinatorial function of different genes drives the developmental program of the wing blade. In this work it is also shown that Vg is heterogeneously expressed along the axes of growth (anterior-posterior A/P, proximo-distal P/D) in the wing blade. Moreover, differences in Vg expression among neighbour cells elicits, autonomously and non-autonomously, cell proliferation. The effects of vg on cell proliferation are correlated with changes in rate of cell proliferation. I show in addition that the heterogeneous distribution of Vg is required for the proper orientation of cell division. In this context, the expression of Vg appears to be related with the definition of positional information in the wing blade. Taken together these results, I conclude that the growth and shape of the wing blade could be modulated by local cell interactions triggered by differences in Vg expression