Biophysical connectivity explains population genetic structure in a highly dispersive marine species

Connectivity, the exchange of individuals among locations, is a fundamental ecological process that explains how otherwise disparate populations interact. For most marine organisms, dispersal occurs primarily during a pelagic larval phase that connects populations. We paired population structure from comprehensive genetic sampling and biophysical larval transport modeling to describe how spiny lobster (Panulirus argus) population differentiation is related to biological oceanography. A total of 581 lobsters were genotyped with 11 microsatellites from ten locations around the greater Caribbean. The overall F _ST of 0.0016 (P = 0.005) suggested low yet significant levels of structuring among sites. An isolation by geographic distance model did not explain spatial patterns of genetic differentiation in P. argus (P = 0.19; Mantel r = 0.18), whereas a biophysical connectivity model provided a significant explanation of population differentiation (P = 0.04; Mantel r = 0.47). Thus, even for a widely dispersing species, dispersal occurs over a continuum where basin-wide larval retention creates genetic structure. Our study provides a framework for future explorations of wide-scale larval dispersal and marine connectivity by integrating empirical genetic research and probabilistic modeling.

     

Simultaneous detection of cytokine and immunophenotype at the single cell level by immunoenzymatic double staining

Summary The goal of this study was to establish a generally applicable immunoenzymatic method for the simultaneous detection of cytokine and immunophenotype at the single cell level. Evaluating various cell preparations and staining protocols, we found that permeabilization by saponin (0.1%) is very efficient, in combination with glutaraldehyde (0.04%) as fixative. Among various staining procedures, sequential immunoperoxidase labelling of the cytokine by use of diaminobenzidine, and detection of the immunophenotype by use of 4-chloronaphthol proved most discriminative. The typical localization of the cytokine reaction product (Golgi staining) within the cell, and the ringlike staining for the immunophenotype on the cell surface, allowed precise identification of double-labelled cells. Primary monoclonal antibodies from the same species could be used without loss of sensitivity and specificity for either or both antigens. This method thus provides the opportunity to study morphology, cytokine and immunophenotype simultaneously at the single cell level with standard equipment. Its application for the analysis of tissue samples is in progress, and may allow us to incorporate the cytokine-type as a new parameter in histopathological diagnostics.     

Distinct and sequential tissue-specific activities of the LIM-class homeobox gene Lim1 for tubular morphogenesis during kidney development

Kidney organogenesis requires the morphogenesis of epithelial tubules. Inductive interactions between the branching ureteric buds and the metanephric mesenchyme lead to mesenchyme-to-epithelium transitions and tubular morphogenesis to form nephrons, the functional units of the kidney. The LIM-class homeobox gene Lim1 is expressed in the intermediate mesoderm, nephric duct, mesonephric tubules, ureteric bud, pretubular aggregates and their derivatives. Lim1-null mice lack kidneys because of a failure of nephric duct formation, precluding studies of the role of Lim1 at later stages of kidney development. Here, we show that Lim1 functions in distinct tissue compartments of the developing metanephros for both proper development of the ureteric buds and the patterning of renal vesicles for nephron formation. These observations suggest that Lim1 has essential roles in multiple steps of epithelial tubular morphogenesis during kidney organogenesis. We also demonstrate that the nephric duct is essential for the elongation and maintenance of the adjacent Mullerian duct, the anlage of the female reproductive tract.     

Marsupial anti-Mullerian hormone gene structure,regulatory elements,and expression

During male sexual development in reptiles, birds, and mammals, anti-Müllerian hormone (AMH) induces the regression of the Müllerian ducts that normally form the primordia of the female reproductive tract. Whereas Müllerian duct regression occurs during fetal development in eutherian mammals, in marsupial mammals this process occurs after birth. To investigate AMH in a marsupial, we isolated an orthologue from the tammar wallaby (Macropus eugenii) and characterized its expression in the testes and ovaries during development. The wallaby AMH gene is highly conserved with the eutherian orthologues that have been studied, particularly within the encoded C-terminal mature domain. The N-terminus of marsupial AMH is divergent and larger than that of eutherian species. It is located on chromosome 3/4, consistent with its autosomal localization in other species. The wallaby 5' regulatory region, like eutherian AMH genes, contains binding sites for SF1, SOX9, and GATA factors but also contains a putative SRY-binding site. AMH expression in the developing testis begins at the time of seminiferous cord formation at 2 days post partum, and Müllerian duct regression begins shortly afterward. In the developing testis, AMH is localized in the cytoplasm of the Sertoli cells but is lost by adulthood. In the developing ovary, there is no detectable AMH expression, but in adults it is produced by the granulosa cells of primary and secondary follicles. It is not detectable in atretic follicles. Collectively, these studies suggest that AMH expression has been conserved during mammalian evolution and is intimately linked to upstream sex determination mechanisms.     

Bmp4 in limb bud mesoderm regulates digit pattern by controlling AER development

In the developing limb, Bmp4 is expressed in the apical ectodermal ridge (AER) and underlying mesoderm. Insight into the function of Bmp4 in limb development has been hampered by the early embryonic lethality of Bmp4 null embryos. We directly investigated Bmp4 using a conditional null allele of Bmp4 and the Prx1(cre) transgene to inactivate Bmp4 in limb bud mesoderm. The limb bud mesoderm of Prx1(cre);Bmp4 mutants was defective in production of Bmp4 but still competent to respond to Bmp signaling. Prx1(cre);Bmp4 mutant embryos had defective digit patterning including hindlimb preaxial polydactyly with posterior digit transformations. The Prx1(cre);Bmp4 mutants also had postaxial polydactyly with digit five duplications. Bmp4 mutant limbs had delayed induction and maturation of the AER that resulted in expanded Shh signaling. Moreover, the AER persisted longer in the Bmp4 mutant limb buds exposing the forming digits to prolonged Fgf8 signaling. Our data show that Bmp4 in limb mesoderm regulates AER induction and maturation and implicate signaling from the AER in regulation of digit number and identity.     

OVCA1: tumor suppressor gene

OVCA1, also known as DPH2L1, is a tumor suppressor gene associated with ovarian carcinoma and other tumors. Ovca1 homozygous mutant mice die at birth with developmental delay and cell-autonomous proliferation defects. Ovca1 heterozygous mutant mice are tumor-prone but rarely develop ovarian tumors. OVCA1 appears to be the homolog of yeast DPH2, which participates in the first biosynthetic step of diphthamide, by modification of histidine on translation elongation factor 2 (EF-2). Yeast dph2 mutants are resistant to diphtheria toxin, which catalyses ADP ribosylation of EF-2 at diphthamide. Thus, there appears to be growing evidence implicating alterations in protein translation with tumorigenesis.