Conditional expression of Wnt4 during chondrogenesis leads to dwarfism in mice

Wnts are expressed in the forming long bones, suggesting roles in skeletogenesis. To examine the action of Wnts in skeleton formation, we developed a genetic system to conditionally express Wnt4 in chondrogenic tissues of the mouse. A mouse Wnt4 cDNA was introduced into the ubiquitously expressed Rosa26 (R26) locus by gene targeting in embryonic stem (ES) cells. The expression of Wnt4 from the R26 locus was blocked by a neomycin selection cassette flanked by loxP sites (floxneo) that was positioned between the Rosa26 promoter and the Wnt4 cDNA, creating the allele designated R26(floxneoWnt4). Wnt4 expression was activated during chondrogenesis using Col2a1-Cre transgenic mice that express Cre recombinase in differentiating chondrocytes. R26(floxneoWnt4); Col2a1-Cre double heterozygous mice exhibited a growth deficiency, beginning approximately 7 to 10 days after birth, that resulted in dwarfism. In addition, they also had craniofacial abnormalities, and delayed ossification of the lumbar vertebrae and pelvic bones. Histological analysis revealed a disruption in the organization of the growth plates and a delay in the onset of the primary and secondary ossification centers. Molecular studies showed that Wnt4 overexpression caused decreased proliferation and altered maturation of chondrocytes. In addition, R26(floxneoWnt4); Col2a1-Cre mice had decreased expression of vascular endothelial growth factor (VEGF). These studies demonstrate that Wnt4 overexpression leads to dwarfism in mice. The data indicate that Wnt4 levels must be regulated in chondrocytes for normal growth plate development and skeletogenesis. Decreased VEGF expression suggests that defects in vascularization may contribute to the dwarf phenotype.     

Diseases of wild and cultured juvenile crustaceans: Insights from below the minimum landing size

Decapod crustaceans (i.e., lobsters, crabs, and shrimps) are all subject to disease, both in the wild and in culture. No life stage appears to be immune to some form of pathogen or parasite. However, juveniles appear to be the targets of some of the most pervasive and consequential diseases. It is therefore surprising, given the enormous economic value of adult decapods, that we know so little about the effects of pathogens on their vulnerable life stage. Here I review the significant diseases reported for juvenile decapods that support fisheries and aquaculture, and highlight research that demonstrates the advantage of incorporating juveniles and ecology in studies of disease.     

Expression, purification and structural analysis of the Pyrococcus abyssi RNA binding protein PAB1135

Background

Epistatic interactions of multiple single nucleotide polymorphisms (SNPs) are now believed to affect individual susceptibility to common diseases. The detection of such interactions, however, is a challenging task in large scale association studies. Ant colony optimization (ACO) algorithms have been shown to be useful in detecting epistatic interactions.

Findings

AntEpiSeeker, a new two-stage ant colony optimization algorithm, has been developed for detecting epistasis in a case-control design. Based on some practical epistatic models, AntEpiSeeker has performed very well.

Conclusions

AntEpiSeeker is a powerful and efficient tool for large-scale association studies and can be downloaded from http://nce.ads.uga.edu/~romdhane/AntEpiSeeker/index.html.     

A Promising Approach to Effectively Reduce Cramp Susceptibility in Human Muscles: A Randomized,Controlled Clinical Trial

Background

To investigate if the cramp threshold frequency (CTF) can be altered by electrical muscle stimulation in a shortened position.

Methods

A total of 15 healthy male sport students were randomly allocated to an intervention (IG, n = 10) and a non-treatment control group (CG, n = 5). Calf muscles of both legs in the IG were stimulated equally twice a week over 6 weeks. The protocol was 3×5 s on, 10 s off, 150 µs impulse width, 30 Hz above the individual CTF, and was at 85% of the maximal tolerated stimulation energy. One leg was stimulated in a shortened position, inducing muscle cramps (CT), while the opposite leg was fixated in a neutral position at the ankle, hindering muscle cramps (nCT). CTF tests were performed prior to the first and 96 h after the 6^th (3 w) and 12^th (6 w) training session.

Results

After 3 w, the CTF had significantly (p<0.001) increased in CT calves from 23.3±5.7 Hz to 33.3±6.9 Hz, while it remained unchanged in nCT (pre: 23.6±5.7 Hz, mid: 22.3±3.5 Hz) and in both legs of the CG (pre: 21.8±3.2 Hz, mid: 22.0±2.7 Hz). Only CT saw further insignificant increases in the CTF. The applied stimulation energy (mA² • µs) positively correlated with the effect on the CTF (r = 0.92; p<0.001).

Conclusions

The present study may be useful for developing new non-pharmacological strategies to reduce cramp susceptibility.

Trial Registry

German Clinical Trials Register DRKS00005312     

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.

     

A morphological and immunohistochemical comparison of mammary tissues from the short-tailed fruit bat (Carollia perspicillata) and the mouse

In the present study, mammary tissues from the fruit bat (Carollia perspicillata) and mouse (Mus musculus) were compared using histological and immunohistochemical methods. Because the female bat exhibits greater reproductive similarities to humans, it might provide a useful animal model for studying mammary physiology and disease with relevance to our own species. In lactating and recently lactating specimens, bat tissue had significantly fewer adipocytes and more collagenous connective tissue compared to the mouse. The proteins Stat5a, keratin 5, Npt2b, and E-cadherin were all similarly localized in mouse and bat mammary tissues taken from lactating animals. The present study demonstrates that whereas the epithelial compartment and the presence of differentiation markers are conserved between the mouse and bat, differences exist in the stromal compartment.     

Angiomotin regulates visceral endoderm movements during mouse embryogenesis

In pregastrula stage mouse embryos, visceral endoderm (VE) migrates from a distal to anterior position to initiate anterior identity in the adjacent epiblast. This anterior visceral endoderm (AVE) is then displaced away from the epiblast by the definitive endoderm to become associated with the extra-embryonic ectoderm and subsequently contributes to the yolk sac. Little is known about the molecules that regulate this proximal displacement. Here we describe a role for mouse angiomotin (amot) in VE movements. amot expression is initially detected in the AVE and subsequently in the VE associated with the extra-embryonic ectoderm. Most amot mutant mice die soon after gastrulation with distinct furrows of VE located at the junction of the embryonic and extra-embryonic regions. Mutant analysis suggests that VE accumulation in these furrows is caused by defects in cell migration into proximal extra-embryonic regions, although distal-to-anterior movements associated with the epiblast, definitive endoderm formation, and anterior specification of the epiblast appear to be normal. These results suggest that amot acts within subregions of the VE to regulate morphogenetic movements that are required for embryo viability.     

The early time course of the inhibition of stem growth of etiolated pea seedlings by fluorescent light

The stem elongation responses of etiolated peas (Pisum sativum L.) to fluorescent light (35–45 mol.m^t-2.s^-1) were recorded using high resolution position transducers. Continuous fluorescent light decreased growth by 70% within 9 min. The growth rate declined to 5% of the control over the next 2 h and remained at this level for 7 h. Pulses of fluorescent light ranging from 8 s to 34 min led to partial suppression of growth and resulted in a complex kinetic response. The distinctive kinetics of blue and red light inhibition were apparent as components of the responses to non-saturating levels of fluorescent light. The rapid suppression of growth by blue light was not affected by concomitant red light. The lag time for the onset of red light inhibition was not affected by concomitant blue, but the rate of inhibition appeared accelerated.