Publications

Common genetic variants 3' of MC4R within two large linkage disequilibrium (LD) blocks spanning 288 kb have been associated with common and rare forms of obesity. This large association region has not been refined and the relevant DNA segments within the association region have not been identified. In this study, we investigated whether common variants in the MC4R gene region were associated with adiposity-related traits in a biracial population-based study. Single nucleotide polymorphisms (SNPs) in the MC4R region were genotyped with a custom array and a genome-wide array and associations between SNPs and five adiposity-related traits were determined using race-stratified linear regression. Previously reported associations between lower BMI and the minor alleles of rs2229616/Val103Ile and rs52820871/Ile251Leu were replicated in white female participants. Among white participants, rs11152221 in a proximal 3' LD block (closer to MC4R) was significantly associated with multiple adiposity traits, but SNPs in a distal 3' LD block (farther from MC4R) were not. In a case-control study of severe obesity, rs11152221 was significantly associated. The association results directed our follow-up studies to the proximal LD block downstream of MC4R. By considering nucleotide conservation, the significance of association, and proximity to the MC4R gene, we identified a candidate MC4R regulatory region. This candidate region was sequenced in 20 individuals from a study of severe obesity in an attempt to identify additional variants, and the candidate region was tested for enhancer activity using in vivo enhancer assays in zebrafish and mice. Novel variants were not identified by sequencing and the candidate region did not drive reporter gene expression in zebrafish or mice. The identification of a putative insulator in this region could help to explain the challenges faced in this study and others to link SNPs associated with adiposity to altered MC4R expression.

The unfolded protein response (UPR) pathway, a stress-induced signaling cascade emanating from the endoplasmic reticulum (ER), regulates the expression and activity of molecules including BiP (HSPA5), IRE1 (ERN1), Blimp-1 (PRDM1), and X-box binding protein 1 (XBP1). These molecules are required for terminal differentiation of B cells into plasma cells and expressed at high levels in plasma cell-derived multiple myeloma. Although these molecules have no known role at early stages of B-cell development, here we show that their expression transiently peaks at the pre-B-cell receptor checkpoint. Inducible, Cre-mediated deletion of Hspa5, Prdm1, and Xbp1 consistently induces cellular stress and cell death in normal pre-B cells and in pre-B-cell acute lymphoblastic leukemia (ALL) driven by BCR-ABL1- and NRAS(G12D) oncogenes. Mechanistically, expression and activity of the UPR downstream effector XBP1 is regulated positively by STAT5 and negatively by the B-cell-specific transcriptional repressors BACH2 and BCL6. In two clinical trials for children and adults with ALL, high XBP1 mRNA levels at the time of diagnosis predicted poor outcome. A small molecule inhibitor of ERN1-mediated XBP1 activation induced selective cell death of patient-derived pre-B ALL cells in vitro and significantly prolonged survival of transplant recipient mice in vivo. Collectively, these studies reveal that pre-B ALL cells are uniquely vulnerable to ER stress and identify the UPR pathway and its downstream effector XBP1 as novel therapeutic targets to overcome drug resistance in pre-B ALL.

PURPOSE

Histology, the science of cells and tissues at the microscopic level, is an integral component of most dental and medical curricula and is often taught using both traditional and novel computer-based didactic approaches. The purpose of this study was to analyse the strategies used by dental and medical students when studying this very visual and challenging subject.

METHODS

Data were collected from 75 dental and 143 medical students, who had almost identical histology learning resources at their disposal.

RESULTS

When compared with their medical counterparts, dental students view histology as a more difficult subject and as less relevant for their future career. Whereas dental students, who are required to attend class unlike medical students, made more use of in-classroom learning opportunities, they did not take as much advantage of out-of-classroom resources. In addition, dental students reported a significantly higher tendency than medical students to work together, rather than to study alone.

DISCUSSION

Small differences in the dental versus the medical learning environment associate with several observed differences in learning strategies that are adopted by dental and medical students.

CONCLUSIONS

These differences should be considered when teaching the subject of histology to dental or to medical students.

Prostaglandin E2 (PGE2) promotes Th17 expansion while otherwise inhibiting other CD4+ T cell subsets. Here, we identified a PGE2-dependent pathway that induces pathogenic Th17 cells in autoimmune disease and is regulated by the transcription factor RORC. Compared with other CD4+ cell types from healthy subjects, there is a surprising lack of the prostaglandin receptor EP2 on Th17 cells; therefore, we examined the hypothesis that RORγt, which is highly expressed in Th17 cells, mediates EP2 downregulation. Chromatin immunoprecipitation followed by DNA sequencing revealed that RORγt binds directly to Ptger2 (the gene encoding EP2 receptor) in Th17 cells isolated from WT mice. In Th17 cells isolated from humans, RORC repressed EP2 by directly silencing PTGER2 transcription, and knock down of RORC restored EP2 expression in Th17 cells. Compared with Th17 cells from healthy individuals, Th17 cells from patients with MS exhibited reduced RORC binding to the PTGER2 promoter region, resulting in higher EP2 levels and increased expression of IFN-γ and GM-CSF. Finally, overexpression of EP2 in Th17 cells from healthy individuals induced a specific program of inflammatory gene transcription that produced a pathogenic Th17 cell phenotype. These findings reveal that RORC directly regulates the effects of PGE2 on Th17 cells, and dysfunction of this pathway induces a pathogenic Th17 cell phenotype.