Cellular and developmental control of O2 homeostasis by hypoxia-inducible factor 1 alpha.

Hypoxia is an essential developmental and physiological stimulus that plays a key role in the pathophysiology of cancer, heart attack, stroke, and other major causes of mortality. Hypoxia-inducible factor 1 (HIF-1) is the only known mammalian transcription factor expressed uniquely in response to physiologically relevant levels of hypoxia. We now report that in Hif1a-/- embryonic stem cells that did not express the O2-regulated HIF-1alpha subunit, levels of mRNAs encoding glucose transporters and glycolytic enzymes were reduced, and cellular proliferation was impaired. Vascular endothelial growth factor mRNA expression was also markedly decreased in hypoxic Hif1a-/- embryonic stem cells and cystic embryoid bodies. Complete deficiency of HIF-1alpha resulted in developmental arrest and lethality by E11 of Hif1a-/- embryos that manifested neural tube defects, cardiovascular malformations, and marked cell death within the cephalic mesenchyme. In Hif1a+/+ embryos, HIF-1alpha expression increased between E8.5 and E9.5, coincident with the onset of developmental defects and cell death in Hif1a-/- embryos. These results demonstrate that HIF-1alpha is a master regulator of cellular and developmental O2 homeostasis

Alteration of gene expression by alcohol exposure at early neurulation

<p>Abstract</p> <p>Background</p> <p>We have previously demonstrated that alcohol exposure at early neurulation induces growth retardation, neural tube abnormalities, and alteration of DNA methylation. To explore the global gene expression changes which may underline these developmental defects, microarray analyses were performed in a whole embryo mouse culture model that allows control over alcohol and embryonic variables.</p> <p>Result</p> <p>Alcohol caused teratogenesis in brain, heart, forelimb, and optic vesicle; a subset of the embryos also showed cranial neural tube defects. In microarray analysis (accession number GSM9545), adopting hypothesis-driven Gene Set Enrichment Analysis (GSEA) informatics and intersection analysis of two independent experiments, we found that there was a collective reduction in expression of neural specification genes (neurogenin, <it>Sox5, Bhlhe22</it>), neural growth factor genes [<it>Igf1, Efemp1</it>, <it>Klf10 </it>(<it>Tieg), and Edil3</it>], and alteration of genes involved in cell growth, apoptosis, histone variants, eye and heart development. There was also a reduction of retinol binding protein 1 (<it>Rbp1</it>), and <it>de novo </it>expression of aldehyde dehydrogenase 1B1 (<it>Aldh1B1</it>). Remarkably, four key hematopoiesis genes (glycophorin A, adducin 2, beta-2 microglobulin, and ceruloplasmin) were absent after alcohol treatment, and histone variant genes were reduced. The down-regulation of the neurospecification and the neurotrophic genes were further confirmed by quantitative RT-PCR. Furthermore, the gene expression profile demonstrated distinct subgroups which corresponded with two distinct alcohol-related neural tube phenotypes: an open (ALC-NTO) and a closed neural tube (ALC-NTC). Further, the epidermal growth factor signaling pathway and histone variants were specifically altered in ALC-NTO, and a greater number of neurotrophic/growth factor genes were down-regulated in the ALC-NTO than in the ALC-NTC embryos.</p> <p>Conclusion</p> <p>This study revealed a set of genes vulnerable to alcohol exposure and genes that were associated with neural tube defects during early neurulation.</p

Self-assembly of synthetic collagen triple helices

Collagen is the most abundant protein in animals and the major component of connective tissues. Although collagen isolated from natural sources has long served as the basis for some biomaterials, natural collagen is difficult to modify and can engender pathogenic and immunological side effects. Collagen comprises a helix of three strands. Triple helices derived from synthetic peptides are much shorter (<10 nm) than natural collagen (≈300 nm), limiting their utility. Here, we describe the synthesis of short collagen fragments in which the three strands are held in a staggered array by disulfide bonds. Data from CD spectroscopy, dynamic light scattering, analytical ultracentrifugation, atomic force microscopy, and transmission electron microscopy indicate that these “sticky-ended” fragments self-assemble via intermolecular triple-helix formation. The resulting fibrils resemble natural collagen, and some are longer (>400 nm) than any known collagen. We anticipate that our self-assembly strategy can provide synthetic collagen-mimetic materials for a variety of applications

Research Ethics, Children, and Young People

Special considerations apply to the ethics of research with children and young people. The United Nations Convention on the Rights of the Child (United Nations, 1989) highlights the need to respect children’s autonomy and agency while also recognizing the need for protection and support. For researchers, this means that particular care should be taken to ensure that children are fully involved in consenting processes, which may involve difficult ethical decision making where local norms and values run counter to a rights-based approach. A rights-based approach also mandates a need to avoid excluding children from research that concerns them and to ensure that their voices are heard. The wide variations in how childhood is socially constructed around the world and the increasing use of social media and the Internet by children challenge researchers to adopt ethically sound practices. While children are widely seen as especially vulnerable, this should not mean that the protection and care imprimatur must dominate and override concern for autonomy. Research with teenagers is very different from research with younger children, and children’s capacities for understanding and relating to adults develop and change massively through childhood. The ethics of research with children and young people involves tensions between competing views and interests, and achieving good outcomes requires careful reasoning. This chapter discusses these issues and offers suggestions for solutions