This is an RSS newsfeed from BioMed Central It is intended to be used with an RSS reader. For more information about RSS newsfeeds from BioMed Central, visit http://www.biomedcentral.com/info/about/rss/ http://www.biomedcentral.com/bmcdevbiol/ The latest articles from BMC Developmental Biology (ISSN 1471-213X) published by BioMed Central Background: R-Spondin1 (Rspo1) is a novel regulator of the Wnt/beta-catenin signalling pathway. Loss-of-function mutations in human RSPO1 cause testicular differentiation in 46, XX females, pointing to a role in ovarian development. Here we report the cloning and comparative expression analysis of R-SPONDIN1 orthologues in the mouse, chicken and red-eared slider turtle, three species with different sex-determining mechanisms. Evidence is presented that this gene is an ancient component of the vertebrate ovary-determining pathway. Results: Gonadal RSPO1 gene expression is female up-regulated in the embryonic gonads in each species at the onset of sexual differentiation. In the mouse gonad, Rspo1 mRNA is expressed in the somatic cell lineage at the time of ovarian differentiation (E12.5- E15.5), with little expression in germ cells. However, the protein is localised in the cytoplasm and at the cell surface of both somatic (pre-follicular) and germ cells. In the chicken embryo, RSPO1 expression becomes elevated in females at the time of ovarian differentiation, coinciding with female-specific activation of the FOXL2 gene and estrogen synthesis. RSPO1 protein in chicken is localised in the outer cortical zone of the developing ovary, the site of primordial follicle formation and germ cell differentiation. Inhibition of estrogen synthesis with a specific aromatase inhibitor results in a decline in chicken RSPO1 expression, indicating that RSPO1 is influenced by estrogen. In the red-eared slider turtle, which exhibits temperature-dependent sex determination, up-regulation of RSPO1 occurs during the temperature-sensitive period, when gonadal development is responsive to temperature. Accordingly, RSPO1 expression is temperature-responsive, and is down-regulated in embryos shifted from female- to male-producing incubation temperatures. Conclusions: These results indicate that RSPO1 is up-regulated in the embryonic gonads of female vertebrates with different sex-determining mechanisms. In all instances, RSPO1 is expressed in the incipient ovary. These findings suggest that R-SPONDIN1 is an ancient, conserved part of the vertebrate ovary-determining pathway. http://www.biomedcentral.com/1471-213X/8/72 Craig A Smith, Christina M Shoemaker, Kelly N Roeszler, Joanna Queen, David P Crews and Andrew H Sinclair BMC Developmental Biology 2008, 8:72 2008-07-24 doi:10.1186/1471-213X-8-72 BMC Developmental Biology 1471-213X 8 72 2008-07-24 Background: Osteoblasts and adipocytes are derived from a common mesenchymal progenitor and an inverse relationship between expression of the two lineages is seen with certain experimental manipulations and in certain diseases, i.e., osteoporosis, but the cellular pathway(s) and developmental stages underlying the inverse relationship is still under active investigation. To determine which precursor mesenchymal cell types can differentiate into adipocytes, we compared the effects of BRL-49653 (BRL), a selective ligand for peroxisome proliferators-activated receptor (PPAR) gamma, a master transcription factor of adipogenesis, on osteo/adipogeneis in two different osteoblast culture models: the rat bone marrow (RBM) versus the fetal rat calvaria (RC) cell system. Results: BRL increased the number of adipocytes and corresponding marker expression, such as lipoprotein lipase, fatty acid-binding protein (aP2), and adipsin, in both culture models, but affected osteoblastogenesis only in RBM cultures, where a reciprocal decrease in bone nodule formation and osteoblast markers, e.g., osteopontin, alkaline phosphatase (ALP), bone sialoprotein, and osteocalcin was seen, and not in RC cell cultures. Even though adipocytes were histologically undetectable in RC cultures not treated with BRL, RC cells expressed PPAR and CCAAT/enhancer binding protein mRNAs throughout osteoblast development and their expression was increased by BRL. Some single cell-derived BRL-treated osteogenic RC colonies were stained not only with ALP/von Kossa but also with oil red O and co-expressed the mature adipocyte marker adipsin and the mature osteoblast marker OCN, as well as PPAR and CCAAT/enhancer binding protein mRNAs. Conclusions: The data show that there are clear differences in the capacity of BRL to alter the fate choices of precursor cells in stromal (RBM) versus calvarial (RC) cell populations and that recruitment of adipocytes can occur from multiple precursor cell pools (committed preadipocyte pool, multi-/bipotential osteo-adipoprogenitor pool and conversion of osteoprogenitor cells or osteoblasts into adipocytes (transdifferentiation or plasticity)). They also show that mechanisms beyond activation of PPAR gamma by its ligand are required for changing the fate of committed osteoprogenitor cells and/or osteoblasts into adipocytes. http://www.biomedcentral.com/1471-213X/8/71 Takuro Hasegawa, Kiyoshi Oizumi, Yuji Yoshiko, Kazuo Tanne, Norihiko Maeda and Jane E Aubin BMC Developmental Biology 2008, 8:71 2008-07-14 doi:10.1186/1471-213X-8-71 BMC Developmental Biology 1471-213X 8 71 2008-07-14 Background: Cystic fibrosis transmembrane conductance regulator (CFTR) was shown previously to modify stretch induced differentiation in the lung. The mechanism for CFTR modulation of lung development was examined by in utero gene transfer of either a sense or antisense construct to alter CFTR expression levels.The BAT-gal transgenic reporter mouse line, expressing β-galactosidase under a canonical Wnt/β-catenin-responsive promoter, was used to assess the relative roles of CFTR, Wnt, and parathyroid hormone-related peptide (PTHrP) in lung organogenesis. Adenoviruses containing full-length CFTR, a short anti-sense CFTR gene fragment, or a reporter gene as control were used in an intra-amniotic gene therapy procedure to transiently modify CFTR expression in the fetal lung. Results: A direct correlation between CFTR expression levels and PTHrP levels was found. An inverse correlation between CFTR and Wnt signaling activities was demonstrated. Conclusion: These data are consistent with CFTR participating in the mechanicosensory process essential to regulate Wnt/β-Catenin signaling required for lung organogenesis. http://www.biomedcentral.com/1471-213X/8/70 J Craig Cohen, Janet E Larson, Erin Killeen, Damon Love and Ken-Ichi Takemaru BMC Developmental Biology 2008, 8:70 2008-07-06 doi:10.1186/1471-213X-8-70 BMC Developmental Biology 1471-213X 8 70 2008-07-06 Background: Reelin and Notch-1 signaling pathways have been recently found to be necessary to induce the expression of brain lipid binding protein (BLBP) and to promote the process extension and the maturation of the neuronal progenitors, the radial glial cells. In this study, we report the cross talk between these two pathways. Results: Both in vitro Reelin treatment and overexpression of Notch-1 intracellular domain (NICD) induced BLBP expression and a radial glial phenotype in an immortalized human neural progenitor (HNP) cell line, isolated from the cortex of 14 weeks old fetus. Reelin treatment increased the level of NICD, indicating that Reelin signaling directly activates Notch-1. In addition, reducing NICD release, by inhibiting γ-secretase activity, inhibited the Reelin-induced radial glial phenotype in human neural progenitor cells. Furthermore, we found that Dab-1, an adaptor protein downstream of Reelin, was co-immunoprecipitated with Notch-1 and NICD. Conclusion: These data indicate that Reelin signaling induces BLBP expression and a radial glial phenotype in human neural progenitor cells via the activation of Notch-1. This study suggest that Reelin signaling may act to fine tune Notch-1 activation to favor the induction of a radial glial phenotype prenataly and would thus offer an insight into how Notch-1 signaling leads to different cellular fates at different developmental stages. http://www.biomedcentral.com/1471-213X/8/69 Serene Keilani and Kiminobu Sugaya BMC Developmental Biology 2008, 8:69 2008-07-01 doi:10.1186/1471-213X-8-69 BMC Developmental Biology 1471-213X 8 69 2008-07-01 Background: Metal-responsive transcription factor 1 (MTF-1), which binds to metal response elements (MREs), plays a central role in transition metal detoxification and homeostasis. A Drosophila interactome analysis revealed two candidate dMTF-1 interactors, both of which are related to the small regulatory protein Dumpy-30 (Dpy-30) of the worm C. elegans. Dpy-30 is the founding member of a protein family involved in chromatin modifications, notably histone methylation. Mutants affect mating type in yeast and male mating in C. elegans. Results: Constitutive expression of the stronger interactor, Dpy-30L1 (CG6444), in transgenic flies inhibits MTF-1 activity and results in elevated sensitivity to Cd(II) and Zn(II), an effect that could be rescued by co-overexpression of dMTF-1. Electrophoretic mobility shift assays (EMSA) suggest that Dpy-30L1 interferes with the binding of MTF-1 to its cognate MRE binding site. Dpy-30L1 is expressed in the larval brain, gonads, imaginal discs, salivary glands and in the brain, testes, ovaries and salivary glands of adult flies. Expression of the second interactor, Dpy-30L2 (CG11591), is restricted to larval male gonads, and to the testes of adult males. Consistent with these findings, dpy-30-like transcripts are also prominently expressed in mouse testes. Targeted gene disruption by homologous recombination revealed that dpy-30L1 knockout flies are viable and show no overt disruption of metal homeostasis. In contrast, the knockout of the male-specific dpy-30L2 gene results in male sterility, as does the double knockout of dpy-30L1 and dpy-30L2. A closer inspection showed that Dpy-30L2 is expressed in elongated spermatids but not in early or mature sperm. Mutant sperm had impaired motility and failed to accumulate in sperm storage organs of females. Conclusion: Our studies help to elucidate the physiological roles of the Dumpy-30 proteins, which are conserved from yeast to humans and typically act in concert with other nuclear proteins to modify chromatin structure and gene expression. The results from these studies reveal an inhibitory effect of Dpy-30L1 on MTF-1 and an essential role for Dpy-30L2 in male fertility. http://www.biomedcentral.com/1471-213X/8/68 Alla Vardanyan, Lilit Atanesyan, Dieter Egli, Sunil Jayaramaiah Raja, Monica Steinmann-Zwicky, Renate Renkawitz-Pohl, Oleg Georgiev and Walter Schaffner BMC Developmental Biology 2008, 8:68 2008-06-27 doi:10.1186/1471-213X-8-68 BMC Developmental Biology 1471-213X 8 68 2008-06-27 Background: GATA4 and FOG2 proteins are required for normal cardiac development in mice. It has been proposed that GATA4/FOG2 transcription complex exercises its function through gene activation as well as repression; however, targets of GATA4/FOG2 action in the heart remain elusive. Results: Here we report identification of the Lhx9 gene as a direct target of the GATA4/FOG2 complex. We demonstrate that the developing mouse heart normally expresses truncated isoforms of Lhx9 – Lhx9α and Lhx9β, and not the Lhx9-HD isoform that encodes a protein with an intact homeodomain. At E9.5 Lhx9α/β expression is prominent in the epicardial primordium, septum transversum while Lhx9-HD is absent from this tissue; in the E11.5 heart LHX9α/β-positive cells are restricted to the epicardial mesothelium. Thereafter in the control hearts Lhx9α/β epicardial expression is promptly down-regulated; in contrast, mouse mutants with Fog2 gene loss fail to repress Lhx9α/β expression. Chromatin immunoprecipitation from the E11.5 hearts demonstrated that Lhx9 is a direct target for GATA4 and FOG2. In transient transfection studies the expression driven by the cis-regulatory regions of Lhx9 was repressed by FOG2 in the presence of intact GATA4, but not the GATA4ki mutant that is impaired in its ability to bind FOG2. Conclusion: In summary, the Lhx9 gene represents the first direct target of the GATA4/FOG2 repressor complex in cardiac development. http://www.biomedcentral.com/1471-213X/8/67 Fatima O Smagulova, Nikolay L Manuylov, Lyndsay L Leach and Sergei G Tevosian BMC Developmental Biology 2008, 8:67 2008-06-24 doi:10.1186/1471-213X-8-67 BMC Developmental Biology 1471-213X 8 67 2008-06-24 Background: Epimorphic regeneration is the process by which complete regeneration of a complex structure such as a limb occurs through production of a proliferating blastema. This type of regeneration is rare among vertebrates but does occur in the African clawed frog Xenopus laevis, traditionally a model organism for the study of early development. Xenopus tadpoles can regenerate their tails, limb buds and the lens of the eye, although the ability of the latter two organs to regenerate diminishes with advancing developmental stage. Using a heat shock inducible transgene that remains silent unless activated, we have established a stable line of transgenic Xenopus (strain N1) in which the BMP inhibitor Noggin can be over-expressed at any time during development. Activation of this transgene blocks regeneration of the tail and limb of Xenopus tadpoles. Results: In the current study, we have taken advantage of the N1 transgenic line to directly compare morphology and gene expression in same stage regenerating vs. BMP signalling deficient, non-regenerating hindlimb buds. The wound epithelium of N1 transgenic hindlimb buds, which forms over the cut surface of the limb bud after amputation, does not transition normally into the distal thickened apical epithelial cap. Furthermore, the underlying mesenchyme remains rounded and does not expand to form a cone shaped blastema, a normal feature of successful regeneration. Using Affymetrix Gene Chip analysis, we have identified genes linked to regenerative success downstream of BMP signalling, including the BMP inhibitor Gremlin and the stress protein Hsp60 (no blastema in zebrafish). Gene Ontology analysis showed that genes involved in embryonic development and growth are significantly over-represented in regenerating early hindlimb buds and that successful regeneration in the Xenopus hindlimb depends on induction of stress response pathways. Conclusion: N1 transgenic hindlimbs, which do not regenerate, do not form an apical epithelial cap or cone shaped blastema following amputation. Comparison of gene expression in stage matched N1 vs. wild type hindlimb buds has revealed several new targets for regeneration research. http://www.biomedcentral.com/1471-213X/8/66 Esther J Pearl, Donna Barker, Robert C Day and Caroline W Beck BMC Developmental Biology 2008, 8:66 2008-06-23 doi:10.1186/1471-213X-8-66 BMC Developmental Biology 1471-213X 8 66 2008-06-23 Background: Serum response factor (SRF), a member of the MADS box family of nuclear transcription factors, plays an important role in cardiovascular development and function. Numerous studies demonstrate a central role for SRF in regulating smooth and cardiac muscle cell gene expression. Consistent with this, loss of SRF function blocks differentiation of coronary vascular smooth muscle cells from proepicardial precursors, indicating SRF is necessary for coronary vasculogenesis. The role of SRF in endothelial cell contribution during early vascular development, however, has not been addressed. To investigate this, we generated transgenic mice lacking expression of SRF in endothelial cells. Mice expressing Cre recombinase (Tie2Cre+) under Tie2 promoter control were bred to mice homozygous for Srf alleles containing loxP recombination sites within the Srf gene (Srff/f). Tie2 is a tyrosine kinase receptor expressed predominantly on endothelial cells that mediates signalling during different stages of blood vessel remodelling. Resulting embryos were harvested at specific ages for observation of physical condition and analysis of genotype. Results: Tie2Cre+/-Srff/f embryos appeared to develop normally compared to wild-type littermates until embryonic day 10.5 (E10.5). Beginning at E11.5, Tie2Cre+/-Srff/f embryos exhibited cerebrovascular hemorrhaging and severely disrupted vascular networks within the yolk sac. Hemorrhaging in mutant embryos became more generalized with age, and by E14.5, most Tie2Cre+/-Srff/f embryos observed were nonviable and grossly necrotic. Hearts of mutant embryos were smaller relative to overall body weight compared to wild-type littermates. Immunohistochemical analysis revealed the presence of vascular endothelial cells; however, vessels failed to undergo appropriate remodelling. Initial analysis by electron microscopy suggested a lack of appropriate cell-cell contacts between endothelial cells. Consistent with this, disrupted E-cadherin staining patterns were observed in mutant embryos. Conclusion: These results provide the first in vivo evidence in support of a role for SRF in endothelial cell function and strongly suggest SRF is required for appropriate vascular remodelling. http://www.biomedcentral.com/1471-213X/8/65 Mary L Holtz and Ravi P Misra BMC Developmental Biology 2008, 8:65 2008-06-20 doi:10.1186/1471-213X-8-65 BMC Developmental Biology 1471-213X 8 65 2008-06-20 Background: Male and female gametes follow diverse developmental pathways dictated by their distinct roles in fertilization. While oocytes of oviparous animals accumulate yolk in the cytoplasm, spermatozoa slough off most of their cytoplasm in the process of individualization. Mammalian spermatozoa released from the testis undergo extensive modifications in the seminal ducts involving a variety of glycoproteins. Ultrastructural studies suggest that glycoproteins are involved in sperm maturation in insects; however, their characterization at the molecular level is lacking. We reported previously that the circadian clock controls sperm release and maturation in several insect species. In the moth, Spodoptera littoralis, the secretion of glycoproteins into the seminal fluid occurs in a daily rhythmic pattern. The purpose of this study was to characterize seminal fluid glycoproteins in this species and elucidate their role in the process of sperm maturation. Results: We collected seminal fluid proteins from males before and after daily sperm release. These samples were separated by 2-D gel electrophoresis, and gels were treated with a glycoprotein-detecting probe. We observed a group of abundant glycoproteins in the sample collected after sperm release, which was absent in the sample collected before sperm release. Sequencing of these glycoproteins by mass spectroscopy revealed peptides bearing homology with components of yolk, which is known to accumulate in developing oocytes. This unexpected result was confirmed by Western blotting demonstrating that seminal fluid contains protein immunoreactive to antibody against yolk protein YP2 produced in the follicle cells surrounding developing oocytes. We cloned the fragment of yp2 cDNA from S. littoralis and determined that it is expressed in both ovaries and testes. yp2 mRNA and YP2 protein were detected in the somatic cyst cells enveloping sperm inside the testis. During the period of sperm release, YP2 protein appears in the seminal fluid and forms an external coat on spermatozoa. Conclusion: One of the yolk protein precursors YP2, which in females accumulate in the oocytes to provision developing embryos, appears to have a second male-specific role. It is produced in the testes and released into the seminal fluid where it interacts with sperm. These data reveal unexpected common factor in the maturation of insect eggs and sperm. http://www.biomedcentral.com/1471-213X/8/64 Piotr Bebas, Joanna Kotwica, Ewa Joachimiak and Jadwiga M Giebultowicz BMC Developmental Biology 2008, 8:64 2008-06-13 doi:10.1186/1471-213X-8-64 BMC Developmental Biology 1471-213X 8 64 2008-06-13 Background: Co-ordinated cell movement is a fundamental feature of developing embryos. Massive cell movements occur during vertebrate gastrulation and during the subsequent extension of the embryonic body axis. These are controlled by cell-cell signalling and a number of pathways have been implicated. Here we use long-term video microscopy in chicken embryos to visualize the migration routes and movement behaviour of mesoderm progenitor cells as they emerge from the primitive streak (PS) between HH stages 7 and 10. Results: We observed distinct cell movement behaviours along the length of the streak and determined that this is position dependent with cells responding to environmental cues. The behaviour of cells was altered by exposing embryos or primitive streak explants to cell pellets expressing Wnt3a and Wnt5a, without affecting cell fates, thus implicating these ligands in the regulation of cell movement behaviour. Interestingly younger embryos were not responsive, suggesting that Wnt3a and Wnt5a are specifically involved in the generation of posterior mesoderm, consistent with existing mouse and zebrafish mutants. To investigate which downstream components are involved mutant forms of dishevelled (dsh) and prickle1 (pk1) were electroporated into the primitive streak. These had differential effects on the behaviour of mesoderm progenitors emerging from anterior or posterior regions of the streak, suggesting that multiple Wnt pathways are involved in controlling cell migration during extension of the body axis in amniote embryos. Conclusion: We suggest that the distinct behaviours of paraxial and lateral mesoderm precursors are regulated by the opposing actions of Wnt5a and Wnt3a as they leave the primitive streak in neurula stage embryos. Our data suggests that Wnt5a acts via prickle to cause migration of cells from the posterior streak. In the anterior streak, this is antagonised by Wnt3a to generate non-migratory medial mesoderm. http://www.biomedcentral.com/1471-213X/8/63 Dylan Sweetman, Laura Wagstaff, Oliver Cooper, Cornelis Weijer and Andrea Münsterberg BMC Developmental Biology 2008, 8:63 2008-06-09 doi:10.1186/1471-213X-8-63 BMC Developmental Biology 1471-213X 8 63 2008-06-09