Fine scale analysis of gene expression in Drosophila melanogaster gonads reveals Programmed cell death 4 promotes the differentiation of female germline stem cells

Abstract

BackgroundGermline 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.ResultsHere 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.ConclusionsWe propose that Pdcd4 promotes the differentiation of GSC daughter cells by relieving the eIF4A-mediated inhibition of Bam.

The insulin receptor cellular IRES confers resistance to eIF4A inhibition

“…Blast analysis of human Pdcd4 with the Drosophila genome identifies a single homologous protein encoded by CG10990. Alignment of human PDCD4 and CG10990 indicate that important regions of the protein are conserved (Figure 1B) (Cash and Andrews, 2012). The two MA3 domains, including the acidic residues shown to be important for the interaction with eIF4A are conserved (Chang et al, 2009; Waters et al, 2011).…”

Histone demethylase RBP2 decreases miR-21 in blast crisis of chronic myeloid leukemia

“…PDCD4 is a tumor suppressor protein that inhibits cell proliferation [42], induces apoptosis [43], suppresses autophage [44], and promotes differentiation [35, 45, 46]. In K562 and HL60 cells, PDCD4 expression was downregulated or upregulated with miR-21 mimics or inhibitor treatment, respectively.…”

The Drosophila early ovarian transcriptome provides insight to the molecular causes of recombination rate variation across genomes

“…There are 7,914 genes expressed in Early regions compared to 7,557 genes in Late regions. These results suggest that roughly 50% of all genes are actively transcribed, a value similar to the typical percentage in other Drosophila tissues, based on mRNA seq [35] or array-based comparisons of germarium and testes [46% of all genes expressed; [36]]. The detection of 5% more genes being transcribed (i.e., above a FPKM threshold of 1) in Early relative to Late meiosis ( P  = 0.015) is accompanied by a reduced average level of transcription for active genes in early meiosis by more than 13% (average FPKM of 89.1 and 103.1 for Early and Late stages, respectively; Wilcoxon Matched Pairs Test, Z  = 44.5, P  < 1×10 -12 ).…”