Changes in the expression of myosins during postnatal development of masseter muscle in the microphthalmic mouse

Effect of Cadmium and Nickel Exposure on Early Development in Zebrafish (Danio rerio) Embryos

Exposure to even low concentrations of heavy metals can be toxic to aquatic organisms, especially during embryonic development. Thus, this study aimed to investigate the toxicity of nickel and cadmium in zebrafish (Danio rerio) embryos exposed to environmentally relevant concentrations of each metal alone or in combination from 4 h through to 72 h postfertilization. Neither metal altered survival, but individual and combined exposures decreased hatching rate. Whereas cadmium did not affect total body length, trunk area, eye diameter, or eye area, nickel alone and in combination with cadmium decreased each morphological parameter. Yolk sac area, an index of metabolic rate, was not affected by nickel, but was larger in embryos exposed to high cadmium concentrations or nickel and cadmium combined at high concentrations. Nickel decreased spontaneous movement, whereas cadmium alone or nickel and cadmium combined had no effect. Neither metal altered elicited movement, but nickel and cadmium combined decreased elicited movement. Myosin protein expression in skeletal muscle was not altered by cadmium exposure. However, exposure to nickel at low concentrations and combined exposure to nickel and cadmium decreased myosin expression. Overall, nickel was more toxic than cadmium. In conclusion, we observed that combined exposures had a greater effect on movement than gross morphology, and no significant additive or synergistic interactions were present. These results imply that nickel and cadmium are toxic to developing embryos, even at very low exposure concentrations, and that these metals act via different mechanisms.

Tfe3 and Tfeb Transcriptionally Regulate Peroxisome Proliferator-Activated Receptor γ2 Expression in Adipocytes and Mediate Adiponectin and Glucose Levels in Mice

Members of the MiT transcription factor family are pivotal regulators of several lineage-selective differentiation programs. We show that two of these, Tfeb and Tfe3, control the regulator of adipogenesis, peroxisome proliferator-activated receptor γ2 (Pparγ2). Knockdown of Tfeb or Tfe3 expression during in vitro adipogenesis causes dramatic downregulation of Pparγ2 expression as well as adipogenesis. Additionally, we found that these factors regulate Pparγ2 in mature adipocytes. Next, we demonstrated that Tfeb and Tfe3 act directly by binding to consensus E-boxes within the Pparγ transcriptional regulatory region. This transcriptional control also exists in vivo, as we discovered that wild-type mice in the fed state increased their expression of Tfe3, Tf3b, and Pparγ in white adipose tissue. Furthermore, Tfe3 knockout (Tfe3KO) mice in the fed state failed to upregulate Pparγ and the adiponectin gene, a Pparγ-dependent gene, confirming the in vivo role for Tfe3. Lastly, we found that blood glucose is elevated and serum adiponectin levels are suppressed in the Tfe3KO mice, indicating that the Tfe3/Tfeb/Pparγ2 axis may contribute to whole-body energy balance. Thus, we offer new insights into the upstream regulation of Pparγ by Tfe3/Tf3b and propose that targeting these transcription factors may offer opportunities to complement existing approaches for the treatment of diseases that have dysregulated energy metabolism.

Muscle Logic: New Knowledge Resource for Anatomy Enables Comprehensive Searches of the Literature on the Feeding Muscles of Mammals

Background

In recent years large bibliographic databases have made much of the published literature of biology available for searches. However, the capabilities of the search engines integrated into these databases for text-based bibliographic searches are limited. To enable searches that deliver the results expected by comparative anatomists, an underlying logical structure known as an ontology is required.

Development and Testing of the Ontology

Here we present the Mammalian Feeding Muscle Ontology (MFMO), a multi-species ontology focused on anatomical structures that participate in feeding and other oral/pharyngeal behaviors. A unique feature of the MFMO is that a simple, computable, definition of each muscle, which includes its attachments and innervation, is true across mammals. This construction mirrors the logical foundation of comparative anatomy and permits searches using language familiar to biologists. Further, it provides a template for muscles that will be useful in extending any anatomy ontology. The MFMO is developed to support the Feeding Experiments End-User Database Project (FEED, https://feedexp.org/), a publicly-available, online repository for physiological data collected from in vivo studies of feeding (e.g., mastication, biting, swallowing) in mammals. Currently the MFMO is integrated into FEED and also into two literature-specific implementations of Textpresso, a text-mining system that facilitates powerful searches of a corpus of scientific publications. We evaluate the MFMO by asking questions that test the ability of the ontology to return appropriate answers (competency questions). We compare the results of queries of the MFMO to results from similar searches in PubMed and Google Scholar.

Results and Significance

Our tests demonstrate that the MFMO is competent to answer queries formed in the common language of comparative anatomy, but PubMed and Google Scholar are not. Overall, our results show that by incorporating anatomical ontologies into searches, an expanded and anatomically comprehensive set of results can be obtained. The broader scientific and publishing communities should consider taking up the challenge of semantically enabled search capabilities.

Microphthalmia-associated transcription factor is required for mature myotube formation

BACKGROUND

The roles of microphthalmia-associated transcription factor (Mitf) in the skeletal muscle and during myogenesis are unclear.

METHODS

Expression of Mitf in mouse tissues and during myogenesis was evaluated. Effects of Mitf knockdown on myogenesis and gene expression related to myogenesis were subsequently explored. Furthermore, effects of p21, a cyclin-dependent kinase inhibitor, and integrin α9 (Itga9) were examined.

RESULTS

Mitf was highly expressed in the skeletal muscle; Mitf-A and -J were expressed. Mitf expression increased after differentiation stimulation in C2C12 myogenic cells. Down-regulation of Mitf expression by transfection of siRNA for common Mitf inhibited myotube formation, which was reproduced by Mitf-A knockdown. Morphometric analyses indicated that both multinucleated cell number and the proportion of myotubes with more than 6 nuclei were decreased in Mitf-knockdown cells, suggesting that Mitf is required for not only the formation of nascent myotubes but also their maturation. Searching for genes positively regulated by Mitf revealed p21 and Itga9; decreasing Mitf expression inhibited up-regulation of p21 expression after differentiation stimulation and blocked the induction of Itga9 expression in response to differentiation. Knockdown of p21 decreased the number of multinucleated cells, whereas Itga9 knockdown did not affect the myotube number. Both p21 knockdown and Itga9 knockdown decreased the proportion of myotubes with more than 6 nuclei.

GENERAL SIGNIFICANCE

Mitf positively regulates skeletal muscle formation; Mitf is significantly expressed during myogenesis, and is required for efficient myotube formation through expression of p21 and Itga9.

Osteoimmunopathology in HIV/AIDS: A Translational Evidence-Based Perspective

Infection with the human immunodeficiency virus-1 (HIV) and the resulting acquired immune deficiency syndrome (AIDS) alter not only cellular immune regulation but also the bone metabolism. Since cellular immunity and bone metabolism are intimately intertwined in the osteoimmune network, it is to be expected that bone metabolism is also affected in patients with HIV/AIDS. The concerted evidence points convincingly toward impaired activity of osteoblasts and increased activity of osteoclasts in patients with HIV/AIDS, leading to a significant increase in the prevalence of osteoporosis. Research attributes these outcomes in part at least to the ART, PI, and HAART therapies endured by these patients. We review and discuss these lines of evidence from the perspective of translational clinically relevant complex systematic reviews for comparative effectiveness analysis and evidence-based intervention on a global scale.