The Drosophila tumour suppressor Lgl and Vap33 activate the Hippo pathway through a dual mechanism.

The tumour suppressor, Lethal (2) giant larvae [Lgl; also known as L(2)gl], is an evolutionarily conserved protein that was discovered in the vinegar fly Drosophila, where its depletion results in tissue overgrowth and loss of cell polarity. Lgl links cell polarity and tissue growth through regulation of the Notch and the Hippo signalling pathways. Lgl regulates the Notch pathway by inhibiting V-ATPase activity via Vap33.

Leveraging gains from African Center for Integrated Laboratory Training to combat HIV epidemic in sub-Saharan Africa.

Background: In sub-Saharan Africa, there is dearth of trained laboratorians and strengthened laboratory systems to provide adequate and quality laboratory services for enhanced HIV control. In response to this challenge, in 2007, the African Centre for Integrated Laboratory Training (ACILT) was established in South Africa with a mission to train staffs from countries with high burdens of diseases in skills needed to strengthen sustainable laboratory systems. This study was undertaken to assess the transference of newly gained knowledge and skills to other laboratory staff, and to identify enabling and obstructive factors to their implementation.

A New Role for Neuropeptide F Signaling in Controlling Developmental Timing and Body Size in .

As juvenile animals grow, their behavior, physiology, and development need to be matched to environmental conditions to ensure they survive to adulthood. However, we know little about how behavior and physiology are integrated with development to achieve this outcome. Neuropeptides are prime candidates for achieving this due to their well-known signaling functions in controlling many aspects of behavior, physiology, and development in response to environmental cues.

Transcriptional repression of Myc underlies the tumour suppressor function of AGO1 in .

Here, we report novel tumour suppressor activity for the Argonaute family RNA-binding protein AGO1, a component of the miRNA-dependent RNA-induced silencing complex (RISC). The mechanism for growth inhibition does not, however, involve canonical roles as part of the RISC; rather, AGO1 controls cell and tissue growth by functioning as a direct transcriptional repressor of the master regulator of growth, Myc. AGO1 depletion in wing imaginal discs drives a significant increase in ribosome biogenesis, nucleolar expansion and cell growth in a manner dependent on Myc abundance.

Using Mouse and Models to Investigate the Mechanistic Links between Diet, Obesity, Type II Diabetes, and Cancer.

Many of the links between diet and cancer are controversial and over simplified. To date, human epidemiological studies consistently reveal that patients who suffer diet-related obesity and/or type II diabetes have an increased risk of cancer, suffer more aggressive cancers, and respond poorly to current therapies. However, the underlying molecular mechanisms that increase cancer risk and decrease the response to cancer therapies in these patients remain largely unknown.

Lgl reduces endosomal vesicle acidification and Notch signaling by promoting the interaction between Vap33 and the V-ATPase complex.

Epithelial cell polarity is linked to the control of tissue growth and tumorigenesis. The tumor suppressor and cell polarity protein lethal-2-giant larvae (Lgl) promotes Hippo signaling and inhibits Notch signaling to restrict tissue growth in Notch signaling is greater in mutant tissue than in wild-type tissue because of increased acidification of endosomal vesicles, which promotes the proteolytic processing and activation of Notch by γ-secretase. We showed that the increased Notch signaling and tissue growth defects of mutant tissue depended on endosomal vesicle acidification mediated by the vacuolar adenosine triphosphatase (V-ATPase).

mediates the role of Lethal giant larvae as an epithelial growth inhibitor in .

() encodes a conserved tumor suppressor with established roles in cell polarity, asymmetric division, and proliferation control. Lgl's human orthologs, HUGL1 and HUGL2, are altered in human cancers, however, its mechanistic role as a tumor suppressor remains poorly understood. Based on a previously established connection between Lgl and Fragile X protein (FMRP), a miRNA-associated translational regulator, we hypothesized that Lgl may exert its role as a tumor suppressor by interacting with the miRNA pathway.

A Kinome RNAi Screen in Identifies Novel Genes Interacting with Lgl, aPKC, and Crb Cell Polarity Genes in Epithelial Tissues.

In both and mammalian systems, epithelial structure and underlying cell polarity are essential for proper tissue morphogenesis and organ growth. Cell polarity interfaces with multiple cellular processes that are regulated by the phosphorylation status of large protein networks. To gain insight into the molecular mechanisms that coordinate cell polarity with tissue growth, we screened a boutique collection of RNAi stocks targeting the kinome for their capacity to modify "cell polarity" eye and wing phenotypes.

Defective Hfp-dependent transcriptional repression of dMYC is fundamental to tissue overgrowth in Drosophila XPB models.

Nucleotide excision DNA repair (NER) pathway mutations cause neurodegenerative and progeroid disorders (xeroderma pigmentosum (XP), Cockayne syndrome (CS) and trichothiodystrophy (TTD)), which are inexplicably associated with (XP) or without (CS/TTD) cancer. Moreover, cancer progression occurs in certain patients, but not others, with similar C-terminal mutations in the XPB helicase subunit of transcription and NER factor TFIIH. Mechanisms driving overproliferation and, therefore, cancer associated with XPB mutations are currently unknown.

Regulation of Notch signaling and endocytosis by the Lgl neoplastic tumor suppressor.

The evolutionarily conserved neoplastic tumor suppressor protein, Lethal (2) giant larvae (Lgl), plays roles in cell polarity and tissue growth via regulation of the Hippo pathway. In our recent study, we showed that in the developing Drosophila eye epithelium, depletion of Lgl leads to increased ligand-dependent Notch signaling. lgl mutant tissue also exhibits an accumulation of early endosomes, recycling endosomes, early-multivesicular body markers and acidic vesicles.

Lgl regulates Notch signaling via endocytosis, independently of the apical aPKC-Par6-Baz polarity complex.

Background: The Drosophila melanogaster junctional neoplastic tumor suppressor, Lethal-2-giant larvae (Lgl), is a regulator of apicobasal cell polarity and tissue growth. We have previously shown in the developing Drosophila eye epithelium that, without affecting cell polarity, depletion of Lgl results in ectopic cell proliferation and blockage of developmental cell death due to deregulation of the Hippo signaling pathway.

Results: Here, we show that Notch signaling is increased in lgl-depleted eye tissue, independently of Lgl's function in apicobasal cell polarity.

lgl Regulates the Hippo Pathway Independently of Fat/Dachs, Kibra/Expanded/Merlin and dRASSF/dSTRIPAK.

In both Drosophila and mammalian systems, the Hippo (Hpo) signalling pathway controls tissue growth by inhibiting cell proliferation and promoting apoptosis. The core pathway consists of a protein kinase Hpo (MST1/2 in mammals) that is regulated by a number of upstream inputs including Drosophila Ras Association Factor, dRASSF. We have previously shown in the developing Drosophila eye epithelium that loss of the apico-basal cell polarity regulator lethal-(2)-giant-larvae (lgl), and the concomitant increase in aPKC activity, results in ectopic proliferation and suppression of developmental cell death by blocking Hpo pathway signalling.

Global health: Integrating national laboratory health systems and services in resource-limited settings.

Laboratory systems worldwide are challenged not only by the need to compete for scarce resources with other sections of national health care programmes, but also with the lack of understanding of the critical role that laboratories play in the accurate diagnosis and monitoring of patients suffering from high-burdens of disease. An effective approach to establishing cost-effective laboratory systems that provide rapid and accurate test results for optimal impact on patient care is to move away from disease-specific programmes and establish integrated laboratory services. An integrated laboratory network provides all primary diagnostic services needed for care and treatment without requiring patients to go to different laboratory facilities for specific tests.

Laboratory diagnosis of tuberculosis in resource-poor countries: challenges and opportunities.

With an estimated 9.4 million new cases globally, tuberculosis (TB) continues to be a major public health concern. Eighty percent of all cases worldwide occur in 22 high-burden, mainly resource-poor settings.

A quality management systems approach for CD4 testing in resource-poor settings.

Quality assurance (QA) is a systematic process to monitor and improve clinical laboratory practices. The fundamental components of a laboratory QA program include providing a functional and safe laboratory environment, trained and competent personnel, maintained equipment, adequate supplies and reagents, testing of appropriate specimens, internal monitoring of quality, accurate reporting, and external quality assessments. These components are necessary to provide accurate and precise CD4 T-cell counts, an essential test to evaluate start of and monitor effectiveness of antiretroviral therapy for HIV-infected patients.

Lgl/aPKC and Crb regulate the Salvador/Warts/Hippo pathway.

A key goal of developmental biology is to understand the mechanisms that coordinate organ growth. It has long been recognized that the genes that control apico-basal cell polarity also regulate tissue growth. How loss of cell polarity contributes to tissue overgrowth has been the subject of much speculation.

Lgl, the SWH pathway and tumorigenesis: It's a matter of context & competition!

Loss of function of the neoplastic tumors suppressors, lgl, scrib and dlg or overexpression of the apical polarity components, Crumbs and atypical protein kinase C (aPKC), are associated with polarity loss and tissue overgrowth, however, the mechanism behind these effects is poorly understood. In our recent study, we showed that Lgl, aPKC and Crumbs mediate their effects on proliferation and survival via the Salvador/Warts/Hippo (SWH) tumor suppressor pathway. Loss of lgl can lead to substantial overgrowth, however the lgl mutant phenotype can be quite variable and the amount of overgrowth of the mutant tissue, its survival and ultimate fate is strongly determined by context and competition.

Geminin and Brahma act antagonistically to regulate EGFR-Ras-MAPK signaling in Drosophila.

Geminin was identified in Xenopus as a dual function protein involved in the regulation of DNA replication and neural differentiation. In Xenopus, Geminin acts to antagonize the Brahma (Brm) chromatin-remodeling protein, Brg1, during neural differentiation. Here, we investigate the interaction of Geminin with the Brm complex during Drosophila development.

Lgl, aPKC, and Crumbs regulate the Salvador/Warts/Hippo pathway through two distinct mechanisms.

Background: The Drosophila neoplastic tumor suppressor Lethal (2) giant larvae (Lgl) controls apicobasal cell polarity and proliferation. We have previously shown that lgl(-) clones in the developing eye exhibit ectopic proliferation and suppress apoptosis without affecting apicobasal cell polarity. Ectopic expression of the apical polarity regulators atypical protein kinase C (aPKC) and Crumbs also leads to increased cell proliferation and/or survival.

Concentration-dependent Mycobacterium tuberculosis killing and prevention of resistance by rifampin.

Rifampin is a cornerstone of modern antituberculosis therapy. However, rifampin's half-life of 3 h is believed to limit its utility for intermittent therapy, so new congeners with long half-lives are being developed. Using an in vitro pharmacokinetic-pharmacodynamic model of tuberculosis, we examined the relationships between rifampin exposure, microbial killing of log-phase-growth Mycobacterium tuberculosis, and suppression of resistance.

Sequencing of the pncA gene in members of the Mycobacterium tuberculosis complex has important diagnostic applications: Identification of a species-specific pncA mutation in "Mycobacterium canettii" and the reliable and rapid predictor of pyrazinamide resistance.

Testing for susceptibility to pyrazinamide (PZA) and analysis of the pncA gene sequences of 423 Mycobacterium tuberculosis complex isolates have revealed a unique silent nucleotide substitution that enables the rapid identification of "M. canettii" (proposed name). Moreover, the lack of a defined mutation within the pncA gene strongly suggests that an alternative mechanism is responsible for PZA resistance.

Phenotypic and molecular characterization of Mycobacterium tuberculosis isolates resistant to both isoniazid and ethambutol.

In performing radiometric susceptibility testing on over 2,000 patient isolates of Mycobacterium tuberculosis during the past 6 years, we found that resistance to 7.5 microg/ml ethambutol (EMB) occurred only in isolates that are also resistant to 0.4 microg/ml isoniazid (INH).

Characterization of novel Mycobacterium tuberculosis and Mycobacterium smegmatis mutants hypersusceptible to beta-lactam antibiotics.

Our laboratory previously constructed mutants of Mycobacterium tuberculosis and Mycobacterium smegmatis with deletions in the genes for their major beta-lactamases, BlaC and BlaS, respectively, and showed that the mutants have increased susceptibilities to most beta-lactam antibiotics, particularly the penicillins. However, there is still a basal level of resistance in the mutants to certain penicillins, and the susceptibilities of the mutants to some cephalosporin-based beta-lactams are essentially the same as those of the wild types. We hypothesized that characterizing additional mutants (derived from beta-lactamase deletion mutants) that are hypersusceptible to beta-lactam antibiotics might reveal novel genes involved with other mechanisms of beta-lactam resistance, peptidoglycan assembly, and cell envelope physiology.