RESUMEN
The segment polarity gene engrailed is involved in the determination of segment posterior identity in Drosophila. engrailed has been largely used for comparative developmental studies due to its evolutionary conservation from nematodes to humans. By in situ hybridization of an engrailed cDNA probe from Drosophila to polytene chromosomes of fourth instar larvae of Rhynchosciara americana we have shown that engrailed-like sequences must be localized in band 6 of chromosome A in this species. The pattern of engrailed protein expression during R. americana embryo development is diffuse at first evolving into a nuclear striped pattern after quite a length of time. In addition, our results suggest a possible developmentally regulated molecular modification of engrailed protein in R. americana embryos.
RESUMEN
Tau protein phosphorylation has been implicated as a main process that regulates microtubule dynamics. A large number of tau isoforms is generated by phosphorylation through the action of a diversity of kinases. We have analysed variations in tau phosphorylation by two-dimensional gel electrophoresis, where a great heterogeneity of isoforms can be detected. Using mouse brain slices from various developmental stages we have found preferential phosphorylation of low molecular weight tau isoforms in all the ages analysed. A greater isoform diversity was found in juvenile than in adult brain. Brain slices provide a tightly regulated environment that preserves cell compartmentalization and has shown to be very useful for studies on tau phosphorylation.