drifter, a Drosophila POU-domain transcription factor, is required for correct differentiation and migration of tracheal cells and midline glia.

The Drosophila drifter (dfr) gene, previously referred to as Cf1a, encodes a POU-domain DNA-binding protein implicated as a neuron-specific regulator in the developing central nervous system (CNS). We have isolated full-length dfr cDNA clones that encode a 46-kD protein containing the conserved POU-domain DNA-binding domain. The use of alternate polyadenylation sites produces two dfr mRNA transcripts that are first expressed in stage 10 embryos at 5- to 6-hr of development. A specific anti-dfr polyclonal antiserum generated against a dfr-glutathione S-transferase fusion protein recognizes a 46-kD protein on Western blots and has been used to analyze the cell-specific distribution of dfr protein during embryonic development. dfr protein is distributed in a complex expression pattern including the tracheal system, the middle pair of midline glia, and selected CNS neurons. We have carried out a genetic characterization of the dfr locus, previously localized to region 65D of the third chromosome, by generating a series of overlapping deficiencies between 65A and 65E1 that were used to isolate dfrE82, an EMS-induced lethal allele. Analysis of dfrE82 mutant embryos shows a disruption of the developing tracheal tree as well as commissural defects in the developing CNS. Based on an examination of a cell-specific marker for tracheal cells and midline glia, these defects appear to be caused by a failure of these cells to follow their characteristic routes of migration. The dfrE82 tracheal phenotype is rescued by a dfr minigene present as a P-element transposon expressing wild-type dfr protein in tracheal cells. These results suggest that the dfr protein plays a fundamental role in the differentiation of tracheal cells and midline glia possibly by regulating the expression of essential cell-surface proteins required for cell-cell interactions involved in directed cell migrations.

Putting mass spectrometry in the hands of the end user.

The ease of use of the newer liquid chromatography-mass spectrometry interfaces has made possible the automated acquisition of spectra from large batch queues of samples. This fact, combined with the realization that unit molecular mass determination was the only datum desired by a majority of drug discovery synthetic chemists, led us to develop open access mass spectrometry in the early 1990s. Open access spectrometers now scan over 100,000 samples per year from synthesis laboratories at Pfizer. Our experiences with this novel use of mass spectrometry in a large research facility are discussed and we detail some of the pitfalls we believe to be common to this approach. In addition, we offer some reflection on the cultural changes we have observed in our research environment since this experiment began.