title: Fine scale analysis of gene expression in Drosophila melanogaster gonads reveals Programmed cell death 4 promotes the differentiation of female germline stem cells.
abstract: BACKGROUND
  Germline stem cells (GSCs) are present in the gonads of Drosophila females and males, and their proper maintenance, as well as their correct differentiation, is essential for fertility and fecundity. The molecular characterization of factors involved in maintenance and differentiation is a major goal both in Drosophila and stem cell research. While genetic studies have identified many of these key factors, the use of genome-wide expression studies holds the potential to greatly increase our knowledge of these pathways.
  
  
  RESULTS
  Here we report a genome-wide expression study that uses laser cutting microdissection to isolate germline stem cells, somatic niche cells, and early differentiating germ cells from female and male gonads. Analysis of this data, in association with two previously published genome-wide GSC data sets, revealed sets of candidate genes as putatively expressed in specific cell populations. Investigation of one of these genes, CG10990 the Drosophila ortholog of mammalian Programmed cell death 4 (Pdcd4), reveals expression in female and male germline stem cells and early differentiating daughter cells. Functional analysis demonstrates that while it is not essential for oogenesis or spermatogenesis, it does function to promote the differentiation of GSCs in females. Furthermore, in females, Pdcd4 genetically interacts with the key differentiation gene bag of marbles (bam) and the stem cell renewal factor eIF4A, suggesting a possible pathway for its function in differentiation.
  
  
  CONCLUSIONS
  We propose that Pdcd4 promotes the differentiation of GSC daughter cells by relieving the eIF4A-mediated inhibition of Bam.
authors.affiliation: Department of Biology, Indiana University, Myers Hall, 915 East Third St,, Bloomington, IN 47403, USA.
authors.forename: Amy C
authors.initials: AC
authors.lastname: Cash
authors.forename: Justen
authors.initials: J
authors.lastname: Andrews
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D051017:Apoptosis Regulatory Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D029721:Drosophila Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D004331:Drosophila melanogaster / Q000235:genetics*; D004843:Epistasis, Genetic; D039601:Eukaryotic Initiation Factor-4A / Q000235:genetics / Q000378:metabolism; D005260:Female; D005718:Gametogenesis / Q000235:genetics*; D015870:Gene Expression; D020869:Gene Expression Profiling; D005786:Gene Expression Regulation; D008297:Male; D008969:Molecular Sequence Data; D020411:Oligonucleotide Array Sequence Analysis; D010053:Ovary / Q000166:cytology* / Q000378:metabolism; D016601:RNA-Binding Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D017386:Sequence Homology, Amino Acid; D013234:Stem Cells / Q000378:metabolism / Q000502:physiology*; D013737:Testis / Q000166:cytology* / Q000378:metabolism
chemical_list: D051017:Apoptosis Regulatory Proteins; D029721:Drosophila Proteins; C572267:Pdcd4 protein, Drosophila; D016601:RNA-Binding Proteins; C091674:bam protein, Drosophila; D039601:Eukaryotic Initiation Factor-4A