Human Ikaros function in activated T cells is regulated by coordinated expression of its largest isoforms

The Ikaros gene is alternately spliced to generate multiple zinc finger proteins involved in gene regulation and chromatin remodeling. Whereas murine studies have provided important information regarding the role of Ikaros in the mouse, little is known of Ikaros function in human. We report functional analyses of the two largest human Ikaros (hIK) isoforms, hIK-VI and hIK-H, in T cells. Abundant expression of hIK-H, the largest described isoform, is restricted to human hematopoietic cells. We find that the DNA binding affinity of hIK-H differs from that of hIK-VI. Co-expression of hIk-H with hIk-VI alters the ability of Ikaros complexes to bind DNA motifs found in pericentromeric heterochromatin (PC-HC). In the nucleus, hIK-VI is localized solely in PC-HC, whereas the hIK-H protein exhibits dual centromeric and non-centromeric localization. Mutational analysis defined the amino acids responsible for the distinct DNA binding ability of hIK-H, as well as the sequence required for the specific subcellular localization of this isoform. In proliferating cells, the binding of hIK-H to the upstream regulatory region of known Ikaros target genes correlates with their positive regulation by Ikaros. Results suggest that expression of hIK-H protein restricts affinity of Ikaros protein complexes toward specific PC-HC repeats. We propose a model, whereby the binding of hIK-H-deficient Ikaros complexes to the regulatory sequence of target genes would recruit these genes to the restrictive pericentromeric compartment, resulting in their repression. The presence of hIK-H in the Ikaros complex would alter its affinity for PC-HC, leading to chromatin remodeling and activation of target genes.     

Effects of FGF2 and oxygen in the BMP4-driven differentiation of trophoblast from human embryonic stem cells

Human embryonic stem cells (hESC) differentiate into trophoblast when treated with BMP4. Here we studied the effects of either low (4% O₂, L) or atmospheric O₂ (20% O₂, A) in the presence and absence of FGF2 on H1 hESC cultured in the presence of BMP4. Differentiation progressed from the periphery toward the center of colonies. It occurred most quickly in the absence of FGF2 and under A and was slowest in the presence of FGF2 and under L. Chorionic gonadotropin (CG) production required A, while FGF2 suppressed progesterone synthesis under both A and L. FGF2 was then omitted while we examined the trophoblast markers SSEA-1 and cytokeratin-7 and-8, whose expression also progressed inward from the periphery of colonies and occurred more rapidly under A than under L. By day 5, most cells outside central islands of Oct4-positive cells were positive for these antigens under both conditions and many also expressed HLA-G, a marker of extravillous cytotrophoblast. Under A, but not L, CG and CGβ became prominent in GATA2-positive, peripherally located, multinucleated cells. In conclusion, BMP4 induced conversion of hESC exclusively toward trophoblast; FGF2 slowed differentiation, while O₂ accelerated this process and promoted syncytiotrophoblast formation.     

Designer schools: the role of school space and architecture in obesity prevention

Spatial features of obesogenic environments studied on a broad community level have been associated with childhood overweight and obesity, but little research has focused on the effects of the design of micro spaces, such as schools, on individual health behaviors. This article aims to generate thinking and research on the link between school space and architecture and obesity prevention by reviewing and synthesizing available literature in architecture, environmental psychology, and obesity research, in an effort to propose promising ideas for school space design and redesign. The school environment is defined through 5 dimensions: physical, legal, policy, social, and cultural domains. Theories underlying environmental interventions and documented associations between the environment and health behaviors and outcomes are reviewed to illustrate how existing environmental research could translate to obesity prevention. Design strategies aimed at promoting physical activity and healthful eating are proposed, with particular emphasis on the design of cafeterias, activity spaces, connectivity with the larger community, and student health centers.     

DNA methylation in the human cerebral cortex is dynamically regulated throughout the life span and involves differentiated neurons

The role of DNA cytosine methylation, an epigenetic regulator of chromatin structure and function, during normal and pathological brain development and aging remains unclear. Here, we examined by MethyLight PCR the DNA methylation status at 50 loci, encompassing primarily 5' CpG islands of genes related to CNS growth and development, in temporal neocortex of 125 subjects ranging in age from 17 weeks of gestation to 104 years old. Two psychiatric disease cohorts--defined by chronic neurodegeneration (Alzheimer's) or lack thereof (schizophrenia)--were included. A robust and progressive rise in DNA methylation levels across the lifespan was observed for 8/50 loci (GABRA2, GAD1, HOXA1, NEUROD1, NEUROD2, PGR, STK11, SYK) typically in conjunction with declining levels of the corresponding mRNAs. Another 16 loci were defined by a sharp rise in DNA methylation levels within the first few months or years after birth. Disease-associated changes were limited to 2/50 loci in the Alzheimer's cohort, which appeared to reflect an acceleration of the age-related change in normal brain. Additionally, methylation studies on sorted nuclei provided evidence for bidirectional methylation events in cortical neurons during the transition from childhood to advanced age, as reflected by significant increases at 3, and a decrease at 1 of 10 loci. Furthermore, the DNMT3a de novo DNA methyl-transferase was expressed across all ages, including a subset of neurons residing in layers III and V of the mature cortex. Therefore, DNA methylation is dynamically regulated in the human cerebral cortex throughout the lifespan, involves differentiated neurons, and affects a substantial portion of genes predominantly by an age-related increase.     

Homology of ciliary bands in Spiralian Trochophores

A number of hypotheses have been presented regarding the originsof the metazoans and, more specifically, the Bilateria. Usingvarious phylogenetic analyses, characteristics have been mappedon phylogenetic trees to infer ancestral body plans and lifehistory strategies of those ancestors. Many arguments on theevolution of the Bilateria are based on the presumed homologyof certain characteristics of extant larva and adults, includingvarious ciliated bands involved in feeding and locomotion. Thisarticle considers a recent study indicating that the second,downstream-collecting, ciliated band in the veliger larva ofthe gastropod mollusc, Crepidula fornicata, is actually derivedfrom secondary trochoblasts (derived from second quartet micromeres),that normally form part of the prototrochal band found in otherspiralian phyla (Hejnol et al. 2007). Despite previous arguments,these new findings suggest that the second ciliated band inthe veliger larva is not homologous to the metatroch found inthe trochophore larva of some other spiralians, such as theannelid, Polygordius lacteus. In the latter case, the metatrochwas reported to be formed by a different set of lineage precursors(derived from third quartet micromeres) (Woltereck 1904). Thesefindings have important implications for the interpretationof various hypotheses related to the evolution of metazoan phyla.     

Megabase Length Hypermutation Accompanies Human Structural Variation at 17p11.2

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Evaluating seasonal patterns of female aggression: Case study in a cavity‐nesting bird with intense female–female competition

Seasonal plasticity in aggression is likely to be shaped by the contexts in which aggression is beneficial, as well as the constraints inherent in its underlying mechanisms. In males, seasonal plasticity in testosterone (T) secretion is thought to underlie seasonal plasticity in conspecific aggression, but it is less clear how and why female aggression may vary across different breeding stages. Here, we integrate functional and mechanistic perspectives to begin to explore seasonal patterns of conspecific aggression in female tree swallows (Tachycineta bicolor), a songbird with intense female–female competition and T‐mediated aggression. Female tree swallows elevate T levels during early breeding stages, coinciding with competition for nest boxes, after which time T levels are roughly halved. However, females need to defend ownership of their nesting territory throughout the breeding season, suggesting it may be adaptive to maintain aggressive capabilities, despite low T levels. We performed simulated territorial intrusions using 3D‐printed decoys of female tree swallows to determine how their aggressive response to a simulated intrusion changes across the breeding season. First, we found that 3D‐printed decoys produce data comparable to stage‐matched studies using live decoys, providing researchers with a new, more economical method of decoy construction. Further, female aggressiveness remained relatively high through incubation, a period of time when T levels are quite low, suggesting that other mechanisms may regulate conspecific female aggression during parental periods. By showing that seasonal patterns of female aggression do not mirror the established patterns of T levels in this highly competitive bird, our findings provide a unique glimpse into how behavioural mechanisms and functions may interact across breeding stages to regulate plasticity.