The mitogenome of Onchocerca volvulus from the Brazilian Amazonia focus

We report here the first complete mitochondria genome of Onchocerca volvulus from a focus outside of Africa. An O. volvulus mitogenome from the Brazilian Amazonia focus was obtained using a combination of high-throughput and Sanger sequencing technologies. Comparisons made between this mitochondrial genome and publicly available mitochondrial sequences identified 46 variant nucleotide positions and suggested that our Brazilian mitogenome is more closely related to Cameroon-origin mitochondria than West African-origin mitochondria. As well as providing insights into the origins of Latin American onchocerciasis, the Brazilian Amazonia focus mitogenome may also have value as an epidemiological resource.     

Goosecoid acts cell autonomously in mesenchyme-derived tissues during craniofacial development.

Mice homozygous for a targeted deletion of the homeobox gene Goosecoid (Gsc) have multiple craniofacial defects. To understand the mechanisms responsible for these defects, the behavior of Gsc-null cells was examined in morula aggregation chimeras. In these chimeras, Gsc-null cells were marked with beta-galactosidase (beta-gal) activity using the ROSA26 lacZ allele. In addition, mice with a lacZ gene that had been introduced into the Gsc locus were used as a guide to visualize the location of Gsc-expressing cells. In Gsc-null<->wild-type chimeras, tissues that would normally not express Gsc were composed of both Gsc-null and wild-type cells that were well mixed, reflecting the overall genotypic composition of the chimeras. However, craniofacial tissues that would normally express Gsc were essentially devoid of Gsc-null cells. Furthermore, the nasal capsules and mandibles of the chimeras had defects similar to Gsc-null mice that varied in severity depending upon the proportion of Gsc-null cells. These results combined with the analysis of Gsc-null mice suggest that Gsc functions cell autonomously in mesenchyme-derived tissues of the head. A developmental analysis of the tympanic ring bone, a bone that is always absent in Gsc-null mice because of defects at the cell condensation stage, showed that Gsc-null cells had the capacity to form the tympanic ring condensation in the presence of wild-type cells. However, analysis of the tympanic ring bones of 18.5 d.p.c. chimeras suggests that Gsc-null cells were not maintained. The participation of Gsc-null cells in the tympanic ring condensation of chimeras may be an epigenetic phenomenon that results in a local environment in which more precursor cells are present. Thus, the skeletal defects observed in Gsc-null mice may reflect a regional reduction of precursor cells during embryonic development.     

DNA identification and characterization of Campylobacter jejuni and Campylobacter coli isolated from caecal samples of chickens in Grenada

Aims: To speciate Campylobacter strains from the caeca of chickens in Grenada using PCR and to evaluate DNA‐based typing methods for the characterization of these isolates. Methods and Results: Isolates were speciated with two multiplex PCR assays and were typed with flaA‐RFLP, pulsed‐field gel electrophoresis (PFGE) and multilocus sequence typing (MLST). Results confirmed that Campylobacter coli strains were more predominant than Campylobacter jejuni strains. From 56 isolates, 18 were misidentified using biochemical tests. PFGE typing gave the highest discriminatory power among the methods used (Simpson’s index of diversity, D = 0·9061). However, the combination of flaA‐RFLP, PFGE and MLST results gave the highest discrimination for subtyping of these isolates (D = 0·9857). A band position tolerance of 4% in Bio Numerics was the most appropriate for the analysis of this database. MLST profiles were generally concordant with PFGE and/or flaA‐RFLP types. Several isolates exhibited new MLST sequence types (STs), and 43 of the 49 Camp. coli strains belonged to the ST‐828 clonal complex. Conclusions: Campylobacter coli was the most prevalent species isolated from broilers and layers in Grenada, and a combination of restriction and sequence methods was most appropriate for the typing of Camp. coli isolates. Campylobacter coli STs clustered with described poultry‐associated Camp. coli STs by phylogenetic analysis. Significance and Impact of the Study: Further studies to understand the predominance of Camp. coli within Campylobacter spp. from chickens in Grenada may help elucidate the epidemiology of these pathogens in chickens.     

Fgf9 and Wnt4 Act as Antagonistic Signals to Regulate Mammalian Sex Determination

The genes encoding members of the wingless-related MMTV integration site (WNT) and fibroblast growth factor (FGF) families coordinate growth, morphogenesis, and differentiation in many fields of cells during development. In the mouse, Fgf9 and Wnt4 are expressed in gonads of both sexes prior to sex determination. Loss of Fgf9 leads to XY sex reversal, whereas loss of Wnt4 results in partial testis development in XX gonads. However, the relationship between these signals and the male sex-determining gene, Sry, was unknown. We show through gain- and loss-of-function experiments that fibroblast growth factor 9 (FGF9) and WNT4 act as opposing signals to regulate sex determination. In the mouse XY gonad, Sry normally initiates a feed-forward loop between Sox9 and Fgf9, which up-regulates Fgf9 and represses Wnt4 to establish the testis pathway. Surprisingly, loss of Wnt4 in XX gonads is sufficient to up-regulate Fgf9 and Sox9 in the absence of Sry. These data suggest that the fate of the gonad is controlled by antagonism between Fgf9 and Wnt4. The role of the male sex-determining switch— Sry in the case of mammals—is to tip the balance between these underlying patterning signals. In principle, sex determination in other vertebrates may operate through any switch that introduces an imbalance between these two signaling pathways.     

BMPs regulate multiple aspects of growth-plate chondrogenesis through opposing actions on FGF pathways

Bone morphogenetic protein (BMP) signaling pathways are essential regulators of chondrogenesis. However, the roles of these pathways in vivo are not well understood. Limb-culture studies have provided a number of essential insights, including the demonstration that BMP pathways are required for chondrocyte proliferation and differentiation. However, limb-culture studies have yielded contradictory results; some studies indicate that BMPs exert stimulatory effects on differentiation, whereas others support inhibitory effects. Therefore, we characterized the skeletal phenotypes of mice lacking Bmpr1a in chondrocytes (Bmpr1a(CKO)) and Bmpr1a(CKO);Bmpr1b+/- (Bmpr1a(CKO);1b+/-) in order to test the roles of BMP pathways in the growth plate in vivo. These mice reveal requirements for BMP signaling in multiple aspects of chondrogenesis. They also demonstrate that the balance between signaling outputs from BMP and fibroblast growth factor (FGF) pathways plays a crucial role in the growth plate. These studies indicate that BMP signaling is required to promote Ihh expression, and to inhibit activation of STAT and ERK1/2 MAPK, key effectors of FGF signaling. BMP pathways inhibit FGF signaling, at least in part, by inhibiting the expression of FGFR1. These results provide a genetic in vivo demonstration that the progression of chondrocytes through the growth plate is controlled by antagonistic BMP and FGF signaling pathways.     

Stable isotope analysis of production and trophic relationships in a tropical marine hard-bottom community

Seagrasses produce much of the organic carbon in the shallow waters of the Caribbean and it has long been assumed that a substantial portion of this carbon is exported to nearby habitats, contributing substantially to their food webs. In the shallow coastal waters of the Florida Keys (USA), seagrass intersperses with hard-bottom habitat where bushy, red macroalgae are the most prominent primary producers. However, the relative importance of seagrass-derived carbon versus autochthonous algal production or phytoplankton in supporting higher trophic levels within hard-bottom communities has never been investigated. We compared the carbon and nitrogen isotopic values of potential primary producers and representative higher trophic level taxa from hard-bottom sites on the bay-side and ocean-side of the Florida Keys. We also included in our study a set of bay-side sites that experienced significant ecological disturbances over the past decade (e.g., cyanobacteria blooms, seagrass die-off, and sponge die-offs) that may have altered trophic relationships in those regions. We did not detect any differences among regions in the trophic status of hard-bottom taxa that might be associated with ecosystem disturbance. However, our results suggest that autochthonous production of algal detritus is an important source of secondary production in these hard-bottom communities, with seagrass and phytoplankton contributing smaller fractions.