Seven-Pass Transmembrane Cadherins: Roles and Emerging Mechanisms in Axonal and Dendritic Patterning

The Flamingo/Celsr seven-transmembrane cadherins represent a conserved subgroup of the cadherin superfamily involved in multiple aspects of development. In the developing nervous system, Fmi/Celsr control axonal blueprint and dendritic morphogenesis from invertebrates to mammals. As expected from their molecular structure, seven-transmembrane cadherins can induce cell–cell homophilic interactions but also intracellular signaling. Fmi/Celsr is known to regulate planar cell polarity (PCP) through interactions with PCP proteins. In the nervous system, Fmi/Celsr can function in collaboration with or independently of other PCP genes. Here, we focus on recent studies which show that seven-transmembrane cadherins use distinct molecular mechanisms to achieve diverse functions in the development of the nervous system

Clues to Neuro-Degeneration in Niemann-Pick Type C Disease from Global Gene Expression Profiling

BACKGROUND: Niemann-Pick Type C (NPC) disease is a neurodegenerative disease that is characterized by the accumulation of cholesterol and glycosphingolipids in the late endocytic pathway. The majority of NPC cases are due to mutations in the NPC1 gene. The precise function of this gene is not yet known. METHODOLOGY/PRINCIPAL FINDINGS: Using cDNA microarrays, we analyzed the genome-wide expression patterns of human fibroblasts homozygous for the I1061T NPC1 mutation that is characterized by a severe defect in the intracellular processing of low density lipoprotein-derived cholesterol. A distinct gene expression profile was identified in NPC fibroblasts from different individuals when compared with fibroblasts isolated from normal subjects. As expected, NPC1 mutant cells displayed an inappropriate homeostatic response to accumulated intracellular cholesterol. In addition, a number of striking parallels were observed between NPC disease and Alzheimer's disease. CONCLUSIONS/SIGNIFICANCE: Many genes involved in the trafficking and processing of amyloid precursor protein and the microtubule binding protein, tau, were more highly expressed. Numerous genes important for membrane traffic and the cellular regulation of calcium, metals and other ions were upregulated. Finally, NPC fibroblasts exhibited a gene expression profile indicative of oxidative stress. These changes are likely contributors to the pathophysiology of Niemann-Pick Type C disease

The RHO-1 RhoGTPase Modulates Fertility and Multiple Behaviors in Adult C. elegans

The Rho family of small GTPases are essential during early embryonic development making it difficult to study their functions in adult animals. Using inducible transgenes expressing either a constitutively active version of the single C. elegans Rho ortholog, RHO-1, or an inhibitor of endogenous Rho (C3 transferase), we demonstrate multiple defects caused by altering Rho signaling in adult C. elegans. Changes in RHO-1 signaling in cholinergic neurons affected locomotion, pharyngeal pumping and fecundity. Changes in RHO-1 signaling outside the cholinergic neurons resulted in defective defecation, ovulation, and changes in C. elegans body morphology. Finally both increased and decreased RHO-1 signaling in adults resulted in death within hours. The multiple post-developmental roles for Rho in C. elegans demonstrate that RhoA signaling pathways continue to be used post-developmentally and the resulting phenotypes provide an opportunity to further study post-developmental Rho signaling pathways using genetic screens

Profile of Central and Effector Memory T Cells in the Progression of Chronic Human Chagas Disease

Chagas disease is a parasitic infection caused by protozoan Trypanosoma cruzi that affects approximately 11 million people in Latin America. The involvement of the host's immune response on the development of severe forms of Chagas disease has not been fully elucidated. Studies on the immune response against T. cruzi infection show that the immunoregulatory mechanisms are necessary to prevent the deleterious effect of excessive immune response stimulation and consequently the fatal outcome of the disease. A recall response against parasite antigens observed in in vitro peripheral blood cell culture clearly demonstrates that memory response is generated during infection. Memory T cells are heterogeneous and differ in both the ability to migrate and exert their effector function. This heterogeneity is reflected in the definition of central (TCM) and effector memory (TEM) T cells. Our results suggest that a balance between regulatory and effectors T cells may be important for the progression and development of the disease. Furthermore, the high percentage of central memory CD4+ T cells in indeterminate patients after stimulation suggests that these cells may modulate host's inflammatory response by controlling cell migration to tissues and their effector role during chronic phase of the disease

Memory CD4 T cell-derived IL-2 synergizes with viral infection to exacerbate lung inflammation.

Defining the most penetrating correlates of protective memory T cells is key for designing improved vaccines and T cell therapies. Here, we evaluate how interleukin (IL-2) production by memory CD4 T cells, a widely held indicator of their protective potential, impacts immune responses against murine influenza A virus (IAV). Unexpectedly, we show that IL-2-deficient memory CD4 T cells are more effective on a per cell basis at combating IAV than wild-type memory cells that produce IL-2. Improved outcomes orchestrated by IL-2-deficient cells include reduced weight loss and improved respiratory function that correlate with reduced levels of a broad array of inflammatory factors in the infected lung. Blocking CD70-CD27 signals to reduce CD4 T cell IL-2 production tempers the inflammation induced by wild-type memory CD4 T cells and improves the outcome of IAV infection in vaccinated mice. Finally, we show that IL-2 administration drives rapid and extremely potent lung inflammation involving NK cells, which can synergize with sublethal IAV infection to promote acute death. These results suggest that IL-2 production is not necessarily an indicator of protective CD4 T cells, and that the lung environment is particularly sensitive to IL-2-induced inflammation during viral infection