A new family of growth factors produced by the fat body and active on Drosophila imaginal disc cells.

By fractionating conditioned medium (CM) from Drosophila imaginal disc cell cultures, we have identified a family of Imaginal Disc Growth Factors (IDGFs), which are the first polypeptide growth factors to be reported from invertebrates. The active fraction from CM, as well as recombinant IDGFs, cooperate with insulin to stimulate the proliferation, polarization and motility of imaginal disc cells. The IDGF family in Drosophila includes at least five members, three of which are encoded by three genes in a tight cluster.

Needs and targets for the multi sex combs gene product in Drosophila melanogaster.

We have analyzed the requirements for the multi sex combs (mxc) gene during development to gain further insight into the mechanisms and developmental processes that depend on the important trans-regulators forming the Polycomb group (PcG) in Drosophila melanogaster. mxc is allelic with the tumor suppressor locus lethal (1) malignant blood neoplasm (l(1)mbn). We show that the mxc product is dramatically needed in most tissues because its loss leads to cell death after a few divisions.

The multi sex combs gene of Drosophila melanogaster is required for proliferation of the germline.

We present a genetic analysis showing that the Drosophila melanogaster gene multi sex combs (mxc; Santamaria and Randsholt 1995) is needed for proliferation of the germline. Fertility is the feature most easily affected by weak hypomorphic mutations of this very pleiotropic locus. Pole cell formation and early steps of gonadogenesis conform to the wild-type in embryos devoid of zygotic mxc product.

Transposon-induced rearrangements in the duplicated locus ph of Drosophila melanogaster can create new chimeric genes functionally identical to the wild type.

Variation in the number of gene copies can play a major role in changing the coding capacities of eukaryotic genomes. Different mechanisms, such as unequal recombination or transposon-induced chromosome rearrangements, are believed to be responsible for these events. We have used the direct tandem duplication at the complex locus polyhomeotic (ph) of Drosophila melanogaster as a model system to study functional redundancy associated with chromosomal rearrangements, such as duplications or deletions.

A regulatory function for K10 in the establishment of dorsoventral polarity in the Drosophila egg and embryo.

Several lines of evidence suggest that the origin of pattern formation of Drosophila embryos must be traced back to oogenesis, to the polarity of the egg chamber. A few early-acting genes, K10, top, grk and cni, have been identified which are assumed to function in a signal transduction process between the germline oocyte and the somatic follicle cells, during which the egg chamber acquires a dorsoventral polarity. K10 has been cloned and was shown to encode a putative transcription factor specifically acting in the oocyte nucleus.