Inhibition of primordial germ cell proliferation by the medaka male determining gene Dmrt1bY

<p>Abstract</p> <p>Background</p> <p><it>Dmrt1 </it>is a highly conserved gene involved in the determination and early differentiation phase of the primordial gonad in vertebrates. In the fish medaka <it>dmrt1bY</it>, a functional duplicate of the autosomal <it>dmrt1a </it>gene on the Y-chromosome, has been shown to be the master regulator of male gonadal development, comparable to <it>Sry </it>in mammals. In males mRNA and protein expression was observed before morphological sex differentiation in the somatic cells surrounding primordial germ cells (PGCs) of the gonadal anlage and later on exclusively in Sertoli cells. This suggested a role for <it>dmrt1bY </it>during male gonad and germ cell development.</p> <p>Results</p> <p>We provide functional evidence that expression of <it>dmrt1bY </it>leads to negative regulation of PGC proliferation. Flow cytometric measurements revealed a G2 arrest of <it>dmrt1bY </it>expressing cells. Interestingly, also non-transfected cells displayed a significantly lower fraction of proliferating cells, pointing to a possible non-cell autonomous action of dmrt1bY. Injection of antisense morpholinos led to an increase of PGCs in genetically male embryos due to loss of proliferation inhibition.</p> <p>Conclusion</p> <p>In medaka, <it>dmrt1bY </it>mediates a mitotic arrest of PGCs in males prior to testes differentiation at the sex determination stage. This occurs possibly <it>via </it>a cross-talk of Sertoli cells and PGCs.</p

Role of Vibrio cholerae O139 Surface Polysaccharides in Intestinal Colonization

Since the first occurrence of O139 Vibrio cholerae as a cause of cholera epidemics, this serogroup has been investigated intensively, and it has been found that its pathogenicity is comparable to that of O1 El Tor strains. O139 isolates express a thin capsule, composed of a polymer of repeating units structurally identical to the lipopolysaccharide (LPS) O side chain. In this study, we investigated the role of LPS O side chain and capsular polysaccharide (CPS) in intestinal colonization by with genetically engineered mutants. We constructed CPS-negative, CPS/LPS O side chain-negative, and CPS-positive/LPS O side chain-negative mutants. Furthermore, we constructed two mutants with defects in LPS core oligosaccharide (OS) assembly. Loss of LPS O side chain or CPS resulted in a ≈30-fold reduction in colonization of the infant mouse small intestine, indicating that the presence of both LPS O side chain and CPS is important during the colonization process. The strain lacking both CPS and LPS O side chain and a CPS-positive, LPS O side chain-negative core OS mutant were both essentially unable to colonize. To characterize the role of surface polysaccharides in survival in the host intestine, resistance to several antimicrobial substances was investigated in vitro. These investigations revealed that the presence of CPS protects the cell against attack of the complement system and that an intact core OS is necessary for survival in the presence of bile

Inhibition of primordial germ cell proliferation by the medaka male determining gene Dmrt1bY-4

<p><b>Copyright information:</b></p><p>Taken from "Inhibition of primordial germ cell proliferation by the medaka male determining gene Dmrt1bY"</p><p>http://www.biomedcentral.com/1471-213X/7/99</p><p>BMC Developmental Biology 2007;7():99-99.</p><p>Published online 30 Aug 2007</p><p>PMCID:PMC2034567.</p><p></p> (A), female (B). Both sexes have a significantly higher number of PGCs in the right PGC lateral clump. C: Comparison of the PGC phenotype versus genotype (Dmrt1bY) at hatching stage. D: Offspring obtained by mating a Y/Yfemale with an Olvas X/Ymale. E: Comparison of the primordial gonad phenotype at hatching stage versus genotype (Yor Y). Identification of genetic sex in each individual was performed by PCR analysis for presence or absence after genomic DNA extraction. The fragments from either both Awr or Hd-rR-specific alleles were amplified with diagnostic primer sets. Scale bars: 7.5 μM

Inhibition of primordial germ cell proliferation by the medaka male determining gene Dmrt1bY-0

<p><b>Copyright information:</b></p><p>Taken from "Inhibition of primordial germ cell proliferation by the medaka male determining gene Dmrt1bY"</p><p>http://www.biomedcentral.com/1471-213X/7/99</p><p>BMC Developmental Biology 2007;7():99-99.</p><p>Published online 30 Aug 2007</p><p>PMCID:PMC2034567.</p><p></p>V:EGFP-SV40UTR control plasmid (A) while nuclear localized when transfected with pCMV:Dmrt1bY:GFP-SV40UTR construct (B). C and D: Radar histograms representing the DNA content distribution of Dmrt1bY:GFP relative to GFP (control) transfected cells expressed in percentage. "Ctr" and "GFP Ctr, GFP+" represent GFP negative and positive control cells in the plate tranfected with control GFP plasmid; similarly "Dmrt1bY, GFP+" and "Dmrt1b, GFP-" represent GFP negative and positive cells In the plate tranfected with Dmrt1bY:GFP plasmid. E and F: Cell cycle distribution reflected by DNA content in control stage 10 (MBT) and post-MBT (stage 13) -injected embryos

Inhibition of primordial germ cell proliferation by the medaka male determining gene Dmrt1bY-5

<p><b>Copyright information:</b></p><p>Taken from "Inhibition of primordial germ cell proliferation by the medaka male determining gene Dmrt1bY"</p><p>http://www.biomedcentral.com/1471-213X/7/99</p><p>BMC Developmental Biology 2007;7():99-99.</p><p>Published online 30 Aug 2007</p><p>PMCID:PMC2034567.</p><p></p>mordial gonad phenotype at hatching stage. B: male primordial gonad phenotype at hatching stage. C, D and E: fluorescence produced by BrdU incorporation colocalizes with GFP fluorescence of primordial germ cells in the Olvas transgenic line. GFP fluorescence (C), BrdU fluorescence (D), overlay (E). F: primordial gonad phenotype at hatching stage after Dmrt1bY morpholino injection in a genetic male