A Unique Role for Nonmuscle Myosin Heavy Chain IIA in Regulation of Epithelial Apical Junctions

The integrity and function of the epithelial barrier is dependent on the apical junctional complex (AJC) composed of tight and adherens junctions and regulated by the underlying actin filaments. A major F-actin motor, myosin II, was previously implicated in regulation of the AJC, however direct evidence of the involvement of myosin II in AJC dynamics are lacking and the molecular identity of the myosin II motor that regulates formation and disassembly of apical junctions in mammalian epithelia is unknown. We investigated the role of nonmuscle myosin II (NMMII) heavy chain isoforms, A, B, and C in regulation of epithelial AJC dynamics and function. Expression of the three NMMII isoforms was observed in model intestinal epithelial cell lines, where all isoforms accumulated within the perijunctional F-actin belt. siRNA-mediated downregulation of NMMIIA, but not NMMIIB or NMMIIC expression in SK-CO15 colonic epithelial cells resulted in profound changes of cell morphology and cell-cell adhesions. These changes included acquisition of a fibroblast-like cell shape, defective paracellular barrier, and substantial attenuation of the assembly and disassembly of both adherens and tight junctions. Impaired assembly of the AJC observed after NMMIIA knock-down involved dramatic disorganization of perijunctional actin filaments. These findings provide the first direct non-pharmacological evidence of myosin II-dependent regulation of AJC dynamics in mammalian epithelia and highlight a unique role of NMMIIA in junctional biogenesis

MicroRNA-206 is differentially expressed in Brca1-deficient mice and regulates epithelial and stromal cell compartments of the mouse mammary gland

Depletion of Brca1 leads to defects in mouse mammary gland development and mammary tumors in humans and mice. To explore the role of microRNAs (miRNAs) in this process, we examined the mammary glands of MMTV-Cre Brca1(Co/Co) mice for differential miRNA expression using a candidate approach. Several miRNAs were differentially expressed in mammary tissue at day 1 of lactation and in mammary epithelial cell lines in which Brca1 messenger RNA (mRNA) levels have been reduced. Functional studies revealed that several of these miRNAs regulate mammary epithelial cell function in vitro, including miR-206. Creation and analysis of MMTV-miR-206 transgenic mice showed no effect on lactational mammary development and no tumors, but indicates a role in mammary tissue remodeling in mature mice, potentially involving Igf-1 and Sfrp1. These results indicate the potential of miRNAs to mediate the consequences of Brca1 loss and suggest a novel function for miR-206

Creating what sort of professional? Master's level nurse education as a professionalising strategy

This paper reports on a detailed analysis of selected findings from a larger study of master’s level nurse education. It locates some features of such education within the contemporary situation of nursing as a profession and interprets the role of master’s level nurse education as a professionalising strategy. In-depth interviews were undertaken with a purposive sample of 18 nurse lecturers drawn from eight universities in the United Kingdom. The interview agenda explored participants’ perspectives of the characteristics of master’s level performance in practice. Interview transcripts were interpreted by drawing upon hermeneutic methodology. The following themes emerged. (a) The credibility of the master’s level nurse was of central importance. In terms of the literature of professionalisation, this may be interpreted as a factor in enhancing the legitimacy of nursing as an occupation. (b) The clinical capability attributed to the nurse is interpreted as leading to an increase in the authority commanded by the expert professional. Thus, the individual capability of the master’s level nurse enhances the attribution of autonomous skill to the occupation as a whole. (c) The master’s level nurse is seen to exercise influence and leadership and this strengthens the power and status of nursing. Nursing does not have the appearance of a ‘traditional’ profession, neither has it a clear stance as a ‘new profession’. Rather it appears to be especially responsive to the tide of public opinion manifest through government edicts. While nursing is employing rhetoric that espouses both positions, the direction of master’s level education is anomalous.</p

The RhoGAP protein Deleted in Liver Cancer 3 (DLC3) is essential for adherens junctions integrity

Epithelial cell–cell contacts are mediated by E-cadherin interactions, which are regulated by the balanced local activity of Rho GTPases. Despite the known function of Rho at adherens junctions (AJs), little is known about the spatial control of Rho activity at these sites. Here we provide evidence that in breast epithelial cells the Deleted in Liver Cancer 3 (DLC3) protein localizes to AJs and is essential for E-cadherin function. DLC3 is a still poorly characterized RhoA-specific GTPase-activating protein that is frequently downregulated in various types of cancer. We demonstrate that DLC3 depletion leads to mislocalization of E-cadherin and catenins, which was associated with impaired cell aggregation and increased migration. This is explained by aberrant local Rho signaling because ROCK inhibition restored cell–cell contacts in DLC3 knockdown cells. We thus identify DLC3 as a novel negative regulator of junctional Rho and propose that DLC3 loss contributes to carcinogenesis by compromising epithelial integrity