International stem cell collaboration: how disparate policies between the United States and the United Kingdom impact research.

As the scientific community globalizes, it is increasingly important to understand the effects of international collaboration on the quality and quantity of research produced. While it is generally assumed that international collaboration enhances the quality of research, this phenomenon is not well examined. Stem cell research is unique in that it is both politically charged and a research area that often generates international collaborations, making it an ideal case through which to examine international collaborations. Furthermore, with promising medical applications, the research area is dynamic and responsive to a globalizing science environment. Thus, studying international collaborations in stem cell research elucidates the role of existing international networks in promoting quality research, as well as the effects that disparate national policies might have on research. This study examined the impact of collaboration on publication significance in the United States and the United Kingdom, world leaders in stem cell research with disparate policies. We reviewed publications by US and UK authors from 2008, along with their citation rates and the political factors that may have contributed to the number of international collaborations. The data demonstrated that international collaborations significantly increased an article's impact for UK and US investigators. While this applied to UK authors whether they were corresponding or secondary, this effect was most significant for US authors who were corresponding authors. While the UK exhibited a higher proportion of international publications than the US, this difference was consistent with overall trends in international scientific collaboration. The findings suggested that national stem cell policy differences and regulatory mechanisms driving international stem cell research in the US and UK did not affect the frequency of international collaborations, or even the countries with which the US and UK most often collaborated. Geographical and traditional collaborative relationships were the predominate considerations in establishing international collaborations.

Myogenin regulates exercise capacity but is dispensable for skeletal muscle regeneration in adult mdx mice.

Duchenne muscular dystrophy (DMD) is the most prevalent inherited childhood muscle disorder in humans. mdx mice exhibit a similar pathophysiology to the human disorder allowing for an in-depth investigation of DMD. Myogenin, a myogenic regulatory factor, is best known for its role in embryonic myogenesis, but its role in adult muscle maintenance and regeneration is still poorly understood. Here, we generated an mdx:Myog(flox/flox) mouse harboring a tamoxifen-inducible Cre recombinase transgene, which was used to conditionally delete Myog during adult life. After tamoxifen treatment, three groups of mice were created to study the effects of Myog deletion: mdx:Myog(flox/flox) mice (mdx), Myog(flox/flox) mice (wild-type), and mdx:Myog(floxΔ/floxΔ):Cre-ER mice (mdx:Myog-deleted). mdx:Myog-deleted mice exhibited no adverse phenotype and behaved normally. When run to exhaustion, mdx:Myog-deleted mice demonstrated an enhanced capacity for exercise compared to mdx mice, running nearly as far as wild-type mice. Moreover, these mice showed the same signature characteristics of muscle regeneration as mdx mice. Unexpectedly, we found that myogenin was dispensable for muscle regeneration. Factors associated with muscle fatigue, metabolism, and proteolysis were significantly altered in mdx:Myog-deleted mice, and this might contribute to their increased exercise capacity. Our results reveal novel functions for myogenin in adult muscle and suggest that reducing Myog expression in other muscle disease models may partially restore muscle function.

Myogenin regulates exercise capacity and skeletal muscle metabolism in the adult mouse.

Although skeletal muscle metabolism is a well-studied physiological process, little is known about how it is regulated at the transcriptional level. The myogenic transcription factor myogenin is required for skeletal muscle development during embryonic and fetal life, but myogenin's role in adult skeletal muscle is unclear. We sought to determine myogenin's function in adult muscle metabolism. A Myog conditional allele and Cre-ER transgene were used to delete Myog in adult mice. Mice were analyzed for exercise capacity by involuntary treadmill running. To assess oxidative and glycolytic metabolism, we performed indirect calorimetry, monitored blood glucose and lactate levels, and performed histochemical analyses on muscle fibers. Surprisingly, we found that Myog-deleted mice performed significantly better than controls in high- and low-intensity treadmill running. This enhanced exercise capacity was due to more efficient oxidative metabolism during low- and high-intensity exercise and more efficient glycolytic metabolism during high-intensity exercise. Furthermore, Myog-deleted mice had an enhanced response to long-term voluntary exercise training on running wheels. We identified several candidate genes whose expression was altered in exercise-stressed muscle of mice lacking myogenin. The results suggest that myogenin plays a critical role as a high-level transcriptional regulator to control the energy balance between aerobic and anaerobic metabolism in adult skeletal muscle.

Myogenin and class II HDACs control neurogenic muscle atrophy by inducing E3 ubiquitin ligases.

Maintenance of skeletal muscle structure and function requires innervation by motor neurons, such that denervation causes muscle atrophy. We show that myogenin, an essential regulator of muscle development, controls neurogenic atrophy. Myogenin is upregulated in skeletal muscle following denervation and regulates expression of the E3 ubiquitin ligases MuRF1 and atrogin-1, which promote muscle proteolysis and atrophy. Deletion of myogenin from adult mice diminishes expression of MuRF1 and atrogin-1 in denervated muscle and confers resistance to atrophy. Mice lacking histone deacetylases (HDACs) 4 and 5 in skeletal muscle fail to upregulate myogenin and also preserve muscle mass following denervation. Conversely, forced expression of myogenin in skeletal muscle of HDAC mutant mice restores muscle atrophy following denervation. Thus, myogenin plays a dual role as both a regulator of muscle development and an inducer of neurogenic atrophy. These findings reveal a specific pathway for muscle wasting and potential therapeutic targets for this disorder.

Stem cell research in the Greater Middle East: the importance of establishing policy and ethics interoperability to foster international collaborations.

While fossil fuel reserves have strengthened the economies of numerous countries in the Greater Middle East (GME) for decades, multiple nations within this region are now increasingly investing in internal science and engineering programs as a mechanism to develop more extensive knowledge-based economies. One of these newly pursued disciplines is stem cell research. Nations such as Saudi Arabia and Qatar have founded nascent programs while Iran, Turkey, and Israel are more established in the field. The extent to which these investments have been productive, as measured by publication quantity and impact, remains unknown. Here we assess the state of stem cell research in the GME, report on the policy and ethical considerations facing the region, and determine the impact of international research collaborations in this area. In the majority of the region, there is no legal framework regulating stem cell research. Instead, scientists often rely on religious decrees outlining acceptable practices. These guidelines do not provide the necessary structure to foster international collaborations with nations that have enacted formal laws recognized worldwide. Our results illustrate that international collaborations in the GME produce publications of greater impact despite the fact that political tensions and issues unrelated to science have the potential to dramatically hinder cross-border relationships in the region. Overall, we conclude that the national governments of countries within the GME have the unique opportunity to establish stem cell research policies which confer interoperability between nations to foster crucial international collaborations throughout the region.

Myogenin regulates a distinct genetic program in adult muscle stem cells.

In contrast to the detailed understanding we have for the regulation of skeletal muscle gene expression in embryos, similar insights into postnatal muscle growth and regeneration are largely inferential or do not directly address gene regulatory mechanisms. Muscle stem cells (satellite cells) are chiefly responsible for providing new muscle during postnatal and adult life. The purpose of this study was to determine the role that the myogenic basic helix-loop-helix regulatory factor myogenin has in postnatal muscle growth and adult muscle stem cell gene expression. We found that myogenin is absolutely required for skeletal muscle development and survival until birth, but it is dispensable for postnatal life. However, Myog deletion after birth led to reduced body size implying a role for myogenin in regulating body homeostasis. Despite a lack of skeletal muscle defects in Myog-deleted mice during postnatal life and the efficient differentiation of cultured Myog-deleted adult muscle stem cells, the loss of myogenin profoundly altered the pattern of gene expression in cultured muscle stem cells and adult skeletal muscle. Remarkably, these changes in gene expression were distinct from those found in Myog-null embryonic skeletal muscle, indicating that myogenin has separate functions during postnatal life.

Target gene selectivity of the myogenic basic helix-loop-helix transcription factor myogenin in embryonic muscle.

The myogenic regulatory factors MyoD and myogenin are crucial for skeletal muscle development. Despite their importance, the mechanisms by which these factors selectively regulate different target genes are unclear. The purpose of the present investigation was to compare embryonic skeletal muscle from myogenin(+/+) and myogenin(-/-) mice to identify genes whose expression was dependent on the presence of myogenin but not MyoD and to determine whether myogenin-binding sites could be found within regulatory regions of myogenin-dependent genes independent of MyoD. We identified a set of 140 muscle-expressed genes whose expression in embryonic tongue muscle of myogenin(-/-) mice was downregulated in the absence of myogenin, but in the presence of MyoD. Myogenin bound within conserved regulatory regions of several of the downregulated genes, but MyoD bound only to a subset of these same regions, suggesting that many downregulated genes were selective targets of myogenin. The regulatory regions activated gene expression in cultured myoblasts and fibroblasts overexpressing myogenin or MyoD, indicating that expression from exogenously introduced DNA could not recapitulate the selectivity for myogenin observed in vivo. The results identify new target genes for myogenin and show that myogenin's target gene selectivity is not based solely on binding site sequences.