Zfrp8, theDrosophilaortholog ofPDCD2,functions in lymph gland development and controls cell proliferation

Abstract

We have identified a new gene, Zfrp8, as being essential for hematopoiesis in Drosophila. Zfrp8 (Zinc finger protein RP-8) is the Drosophila ortholog of the PDCD2 (programmed cell death 2) protein of unknown function, and is highly conserved in all eukaryotes. Zfrp8 mutants present a developmental delay, lethality during larval and pupal stages and hyperplasia of the hematopoietic organ, the lymph gland. This overgrowth results from an increase in proliferation of undifferentiated hemocytes throughout development and is accompanied by abnormal differentiation of hemocytes. Furthermore, the subcellular distribution of ␥-Tubulin and Cyclin B is affected. Consistent with this, the phenotype of the lymph gland of Zfpr8 heterozygous mutants is dominantly enhanced by the l(1)dd4 gene encoding Dgrip91, which is involved in anchoring ␥-Tubulin to the centrosome. The overgrowth phenotype is also enhanced by a mutation in Cdc27, which encodes a component of the anaphase-promoting complex (APC) that regulates the degradation of cyclins. No evidence for an apoptotic function of Zfrp8 was found. Based on the phenotype, genetic interactions and subcellular localization of Zfrp8, we propose that the protein is involved in the regulation of cell proliferation from embryonic stages onward, through the function of the centrosome, and regulates the level and localization of cell-cycle components. The overproliferation of cells in the lymph gland results in abnormal hemocyte differentiation.

ARF1–GTP regulates Asrij to provide endocytic control of Drosophila blood cell homeostasis

“…2 C and D; n = 10). Cyclin A accumulates during the transition from late S/G2 phase to mitosis (16). Abundant cyclin A was seen in ARF1-depleted lobes, indicating the cells were ready to enter mitosis ( Fig.…”

Zfrp8/PDCD2is required in ovarian stem cells and interacts with the piRNA pathway machinery

“…Zfrp8 was originally identified by its strong hematopoietic phenotype and lethality (Minakhina et al, 2007). Clonal analysis in lymph glands showed that Zfrp8 is essential in stem cells, as no persistent clones were recovered, but is dispensable in more mature cells, as transient Zfrp8 clones had the same developmental potential as wild-type clones (Minakhina and Steward, 2010), for clone nomenclature see Fox et al (Fox et al, 2008).…”

“…Transgenic fly lines were created following standard protocols (Rubin and Spradling, 1982; Brand and Perrimon, 1993). For RNAi experiments, flies were raised at 29°C.For genetic interaction experiments, the Zfpr8 null allele (Minakhina et al, 2007) was recombined/combined with alleles of each gene tested (supplementary material Table S1A,B). Eggs were collected from 5-to 7-day-old females and allowed to develop for 2 days at 25°C for examination of egg phenotypes.…”

Hematopoietic stem cells in Drosophila

“…Embryos and larval lymph glands were dissected, fixed, immunostained and analyzed as described (Jung et al, 2005;Minakhina et al, 2007). Antibodies specific for lamellocytes (L1) and for plasmatocytes (P1) were obtained from Dr I. Ando (Biological Research Center, Szeged, Hungary) and used at 1:400 dilution; rabbit anti-PPO2 antibody from George Christophides (Imperial College, London, 1:2000), rabbit anti-Pxn antibody from John Fessler and Sergey Sinenko (UCLA, 1:700), and anti-Antp antibody from the Developmental Studies Hybridoma Bank (Glicksman and Brower, DSHB, 1:20) were used as CC, PH and PSC markers, respectively.…”

“…Loss of Zfrp8 causes a unique phenotype in Drosophila. The lymph gland is enlarged already in midembryogenesis and by the late third instar larval stage, the lymph gland size is increased 10 to 50 times, accompanied by lamellocyte overproliferation (Minakhina et al, 2007).…”