PS Integrins and Laminins: Key Regulators of Cell Migration during Drosophila Embryogenesis

During embryonic development, there are numerous cases where organ or tissue formation depends upon the migration of primordial cells. In the Drosophila embryo, the visceral mesoderm (vm) acts as a substrate for the migration of several cell populations of epithelial origin, including the endoderm, the trachea and the salivary glands. These migratory processes require both integrins and laminins. The current model is that αPS1βPS (PS1) and/or αPS3βPS (PS3) integrins are required in migrating cells, whereas αPS2βPS (PS2) integrin is required in the vm, where it performs an as yet unidentified function. Here, we show that PS1 integrins are also required for the migration over the vm of cells of mesodermal origin, the caudal visceral mesoderm (CVM). These results support a model in which PS1 might have evolved to acquire the migratory function of integrins, irrespective of the origin of the tissue. This integrin function is highly specific and its specificity resides mainly in the extracellular domain. In addition, we have identified the Laminin α1,2 trimer, as the key extracellular matrix (ECM) component regulating CVM migration. Furthermore, we show that, as it is the case in vertebrates, integrins, and specifically PS2, contributes to CVM movement by participating in the correct assembly of the ECM that serves as tracks for migration

Functional evidence that a newly evolved Drosophila sperm-specific gene boost sperm competition.

In many species, both morphological and molecular traits related to sex and reproduction evolve faster in males than in females. Ultimately, rapid male evolution relies on the acquisition of genetic variation associated with differential reproductive success. Many newly evolved genes are associated with novel functions that might enhance male fitness. However, functional evidence of the adaptive role of recently originated genes in males is still lacking. The Sperm dynein intermediate chain multigene family, which encodes a Sperm dynein intermediate chain presumably involved in sperm motility, originated from complex genetic rearrangements in the lineage that leads to Drosophila melanogaster within the last 5.4 million years since its split from Drosophila simulans. We deleted all the members of this multigene family resident on the X chromosome of D. melanogaster by chromosome engineering and found that, although the deletion does not result in a reduction of progeny number, it impairs the competence of the sperm in the presence of sperm from wild-type males. Therefore, the Sperm dynein intermediate chain multigene family contributes to the differential reproductive success among males and illustrates precisely how quickly a new gene function can be incorporated into the genetic network of a species

An exploration of the sequence of a 2.9-Mb region of the genome of Drosophila melanogaster: the Adh region.

A contiguous sequence of nearly 3 Mb from the genome of Drosophila melanogaster has been sequenced from a series of overlapping P1 and BAC clones. This region covers 69 chromosome polytene bands on chromosome arm 2L, including the genetically well-characterized "Adh region." A computational analysis of the sequence predicts 218 protein-coding genes, 11 tRNAs, and 17 transposable element sequences. At least 38 of the protein-coding genes are arranged in clusters of from 2 to 6 closely related genes, suggesting extensive tandem duplication. The gene density is one protein-coding gene every 13 kb; the transposable element density is one element every 171 kb. Of 73 genes in this region identified by genetic analysis, 49 have been located on the sequence; P-element insertions have been mapped to 43 genes. Ninety-five (44%) of the known and predicted genes match a Drosophila EST, and 144 (66%) have clear similarities to proteins in other organisms. Genes known to have mutant phenotypes are more likely to be represented in cDNA libraries, and far more likely to have products similar to proteins of other organisms, than are genes with no known mutant phenotype. Over 650 chromosome aberration breakpoints map to this chromosome region, and their nonrandom distribution on the genetic map reflects variation in gene spacing on the DNA. This is the first large-scale analysis of the genome of D. melanogaster at the sequence level. In addition to the direct results obtained, this analysis has allowed us to develop and test methods that will be needed to interpret the complete sequence of the genome of this species.Before beginning a Hunt, it is wise to ask someone what you are looking for before you begin looking for it. Milne 192