ROS-based lethality of Caenorhabditis elegans mitochondrial electron transport mutants grown on Escherichia coli siderophore iron release mutants.

Caenorhabditis elegans consumes bacteria, which can supply essential vitamins and cofactors, especially for mitochondrial functions that have a bacterial ancestry. Therefore, we screened the Keio Escherichia coli knockout library for mutations that induce the C. elegans hsp-6 mitochondrial damage response gene, and identified 45 E. coli mutations that induce hsp-6::gfp We tested whether any of these E. coli mutations that stress the C. elegans mitochondrion genetically interact with C. elegans mutations in mitochondrial functions. Surprisingly, 4 E. coli mutations that disrupt the import or removal of iron from the bacterial siderophore enterobactin were lethal in combination with a collection of C. elegans mutations that disrupt particular iron-sulfur proteins of the electron transport chain. Bacterial mutations that fail to synthesize enterobactin are not synthetic lethal with these C. elegans mitochondrial mutants; it is the enterobactin-iron complex that is lethal in combination with the C. elegans mitochondrial mutations. Antioxidants suppress this inviability, suggesting that reactive oxygen species (ROS) are produced by the mutant mitochondria in combination with the bacterial enterobactin-iron complex.

Lipid signalling couples translational surveillance to systemic detoxification in Caenorhabditis elegans.

Translation in eukaryotes is followed to detect toxins and virulence factors and coupled to the induction of defence pathways. Caenorhabditis elegans germline-specific mutations in translation components are detected by this system to induce detoxification and immune responses in distinct somatic cells. An RNA interference screen revealed gene inactivations that act at multiple steps in lipid biosynthetic and kinase pathways upstream of MAP kinase to mediate the systemic communication of translation defects to induce detoxification genes. Mammalian bile acids can rescue the defect in detoxification gene induction caused by C. elegans lipid biosynthetic gene inactivations. Extracts prepared from C. elegans with translation deficits but not from the wild type can also rescue detoxification gene induction in lipid-biosynthesis-defective strains. These eukaryotic antibacterial countermeasures are not ignored by bacteria: particular bacterial species suppress normal C. elegans detoxification responses to mutations in translation factors.

Dialogue between E. coli free radical pathways and the mitochondria of C. elegans.

The microbial world presents a complex palette of opportunities and dangers to animals, which have developed surveillance and response strategies to hints of microbial intent. We show here that the mitochondrial homeostatic response pathway of the nematode Caenorhabditis elegans responds to Escherichia coli mutations that activate free radical detoxification pathways. Activation of C. elegans mitochondrial responses could be suppressed by additional mutations in E. coli, suggesting that C. elegans responds to products of E. coli to anticipate challenges to its mitochondrion. Out of 50 C. elegans gene inactivations known to mediate mitochondrial defense, we found that 7 genes were required for C. elegans response to a free radical producing E. coli mutant, including the bZip transcription factor atfs-1 (activating transcription factor associated with stress). An atfs-1 loss-of-function mutant was partially resistant to the effects of free radical-producing E. coli mutant, but a constitutively active atfs-1 mutant growing on wild-type E. coli inappropriately activated the pattern of mitochondrial responses normally induced by an E. coli free radical pathway mutant. Carbonylated proteins from free radical-producing E. coli mutant may directly activate the ATFS-1/bZIP transcription factor to induce mitochondrial stress response: feeding C. elegans with H2O2-treated E. coli induces the mitochondrial unfolded protein response, and inhibition of a gut peptide transporter partially suppressed C. elegans response to free radical damaged E. coli.

Increasing cancer incidence in a tertiary care hospital in a developing country, India.

OBJECTIVE: Cancer is a major health problem in many countries including India. Since Cancer Registries are incomplete in India, only a few epidemiological studies have been done so far. The objective was to determine the leading causes of cancer in a tertiary care hospital and compare the incidences of different types of cancer with the incidences in India and developed countries. MATERIALS AND METHODS: An epidemiological study was done to collect data from pathology records of 1003 cancer cases during 6-month period in the year 2010. The data was collected in a computer and the data was utilized to make tables and histograms. RESULTS: Of the 1003 cases, the leading cancer site was breast, followed by colon and rectum, lymph node and stomach. The leading cancer site for men was colon and rectum and for women was breast. CONCLUSION: Cancer incidence is now low in India, a developing country, compared to developed Western countries. However, some cancers, like breast and colon and rectum cancers are increasing every year. IMPACT: The findings of this study support that cancer incidence is increasing in India and more epidemiological studies are needed.

Nephrogenic diabetes insipidus partially responsive to oral desmopressin in a subject with lithium-induced multiple endocrinopathy.

Lithium (Li) may cause multiple endocrinopathies, including hypercalcaemia, thyroid dysfunction and nephrogenic diabetes insipidus (NDI), but rarely in the same patient. The management of NDI remains a challenge. We report on a patient on long-term Li who had simultaneous NDI (paired serum and urine samples had abnormal osmolalities, typical of NDI, and treatment with parenteral desmopressin failed to affect urinary volume and serum osmolality), 'destructive' thyroiditis (hyperthyroidism, absent radioiodine uptake and absent thyrotrophin receptor antibodies) and primary hyperparathyroidism (compatible biochemistry, urine calcium excluding 'set point' anomalies and hypocalciuric hypercalcaemia, and normal parathyroid imaging). The thyroiditis resolved spontaneously and hypercalcaemia responded to reduction of Li dose. The NDI was unresponsive to amiloride, thiazides and ibuprofen in combination. However, urine output was reduced by 50% when a high dose of oral desmopressin was given. We conclude that Li-induced multiple endocrinopathy remains rare and, although NDI is difficult to manage, high dose oral desmopressin should be tried when other medications fail.

SACY-1 DEAD-Box helicase links the somatic control of oocyte meiotic maturation to the sperm-to-oocyte switch and gamete maintenance in Caenorhabditis elegans.

In sexually reproducing animals, oocytes arrest at diplotene or diakinesis and resume meiosis (meiotic maturation) in response to hormones. In Caenorhabditis elegans, major sperm protein triggers meiotic resumption through a mechanism involving somatic Gα(s)-adenylate cyclase signaling and soma-to-germline gap-junctional communication. Using genetic mosaic analysis, we show that the major effector of Gα(s)-adenylate cyclase signaling, protein kinase A (PKA), is required in gonadal sheath cells for oocyte meiotic maturation and dispensable in the germ line. This result rules out a model in which cyclic nucleotides must transit through sheath-oocyte gap junctions to activate PKA in the germ line, as proposed in vertebrate systems. We conducted a genetic screen to identify regulators of oocyte meiotic maturation functioning downstream of Gα(s)-adenylate cyclase-PKA signaling. We molecularly identified 10 regulatory loci, which include essential and nonessential factors. sacy-1, which encodes a highly conserved DEAD-box helicase, is an essential germline factor that negatively regulates meiotic maturation. SACY-1 is a multifunctional protein that establishes a mechanistic link connecting the somatic control of meiotic maturation to germline sex determination and gamete maintenance. Modulatory factors include multiple subunits of a CoREST-like complex and the TWK-1 two-pore potassium channel. These factors are not absolutely required for meiotic maturation or its negative regulation in the absence of sperm, but function cumulatively to enable somatic control of meiotic maturation. This work provides insights into the genetic control of meiotic maturation signaling in C. elegans, and the conserved factors identified here might inform analysis in other systems through either homology or analogy.

Exenatide therapy in insulin-treated type 2 diabetes and obesity.

BACKGROUND: Exenatide, a GLP-1 analogue, is used in combination with oral anti-diabetic agents in type 2 diabetes and obesity, and promotes weight loss. Exenatide use in combination with insulin in insulin-treated type 2 diabetes and obesity is unlicensed in the UK and outcomes are unclear. AIMS: To assess the effectiveness of exenatide in insulin-treated type 2 diabetes with obesity. DESIGN AND METHODS: This prospective study included 174 consecutive patients with insulin-treated type 2 diabetes and obesity initiated on exenatide in our out-patient, between October 2007 and November 2008. Weight, BMI, HbA1c, serum fructosamine, total cholesterol, HDL-cholesterol and insulin doses were recorded at baseline, 3, 6 and 12 months. Side effect profiles were recorded. RESULTS: Fourteen patients discontinued exenatide before 3 months of initiation, because of side effects, and were excluded. Data were analysed on remaining 160 people all of whom completed 6 months and 57 completed 12 months treatment. Mean weight loss was 10.7 +/- 5.7 kg and 12.8 +/- 7.5 kg (P < 0.001) at 6 and 12 months. Insulin doses dropped significantly (mean 144 +/- 90 U/day at baseline to 51 +/- 55 U/day and 55 +/- 53 U/day at 6 and 12 months). At 3 months, 25% came off insulin. There was little change in HbA1c. CONCLUSION: Exenatide therapy in insulin-treated type 2 diabetes and obesity was associated with very significant reductions in weight and insulin doses. Exenatide should be considered in people with type 2 diabetes on insulin and have obesity, weight gain and poor glycaemic control.

Somatic cAMP signaling regulates MSP-dependent oocyte growth and meiotic maturation in C. elegans.

Soma-germline interactions control fertility at many levels, including stem cell proliferation, meiosis and gametogenesis, yet the nature of these fundamental signaling mechanisms and their potential evolutionary conservation are incompletely understood. In C. elegans, a sperm-sensing mechanism regulates oocyte meiotic maturation and ovulation, tightly coordinating sperm availability and fertilization. Sperm release the major sperm protein (MSP) signal to trigger meiotic resumption (meiotic maturation) and to promote contraction of the follicle-like gonadal sheath cells that surround oocytes. Using genetic mosaic analysis, we show that all known MSP-dependent meiotic maturation events in the germline require Galpha(s)-adenylate cyclase signaling in the gonadal sheath cells. We show that the MSP hormone promotes the sustained actomyosin-dependent cytoplasmic streaming that drives oocyte growth. Furthermore, we demonstrate that efficient oocyte production and cytoplasmic streaming require Galpha(s)-adenylate cyclase signaling in the gonadal sheath cells, thereby providing a somatic mechanism that coordinates oocyte growth and meiotic maturation with sperm availability. We present genetic evidence that MSP and Galpha(s)-adenylate cyclase signaling regulate oocyte growth and meiotic maturation in part by antagonizing gap-junctional communication between sheath cells and oocytes. In the absence of MSP or Galpha(s)-adenylate cyclase signaling, MSP binding sites are enriched and appear clustered on sheath cells. We discuss these results in the context of a model in which the sheath cells function as the major initial sensor of MSP, potentially via multiple classes of G-protein-coupled receptors. Our findings highlight a remarkable similarity between the regulation of meiotic resumption by soma-germline interactions in C. elegans and mammals.

MSP and GLP-1/Notch signaling coordinately regulate actomyosin-dependent cytoplasmic streaming and oocyte growth in C. elegans.

Fertility depends on germline stem cell proliferation, meiosis and gametogenesis, yet how these key transitions are coordinated is unclear. In C. elegans, we show that GLP-1/Notch signaling functions in the germline to modulate oocyte growth when sperm are available for fertilization and the major sperm protein (MSP) hormone is present. Reduction-of-function mutations in glp-1 cause oocytes to grow abnormally large when MSP is present and Galpha(s)-adenylate cyclase signaling in the gonadal sheath cells is active. By contrast, gain-of-function glp-1 mutations lead to the production of small oocytes. Surprisingly, proper oocyte growth depends on distal tip cell signaling involving the redundant function of GLP-1 ligands LAG-2 and APX-1. GLP-1 signaling also affects two cellular oocyte growth processes, actomyosin-dependent cytoplasmic streaming and oocyte cellularization. glp-1 reduction-of-function mutants exhibit elevated rates of cytoplasmic streaming and delayed cellularization. GLP-1 signaling in oocyte growth depends in part on the downstream function of the FBF-1/2 PUF RNA-binding proteins. Furthermore, abnormal oocyte growth in glp-1 mutants, but not the inappropriate differentiation of germline stem cells, requires the function of the cell death pathway. The data support a model in which GLP-1 function in MSP-dependent oocyte growth is separable from its role in the proliferation versus meiotic entry decision. Thus, two major germline signaling centers, distal GLP-1 activation and proximal MSP signaling, coordinate several spatially and temporally distinct processes by which germline stem cells differentiate into functional oocytes.

Regulated trafficking of the MSP/Eph receptor during oocyte meiotic maturation in C. elegans.

BACKGROUND: In C. elegans, a sperm-sensing mechanism regulates oocyte meiotic maturation and ovulation, tightly coordinating sperm availability and embryo production; sperm release the major sperm protein (MSP) signal to trigger meiotic resumption. Meiotic arrest depends on the parallel function of the oocyte VAB-1 MSP/Eph receptor and somatic G protein signaling. MSP promotes meiotic maturation by antagonizing Eph receptor signaling and counteracting inhibitory inputs from the gonadal sheath cells. RESULTS: Here, we present evidence suggesting that in the absence of the MSP ligand, the VAB-1 Eph receptor inhibits meiotic maturation while either in or in transit to the endocytic-recycling compartment. VAB-1::GFP localization to the RAB-11-positive endocytic-recycling compartment is independent of ephrins but is antagonized by MSP signaling. Two negative regulators of oocyte meiotic maturation, DAB-1/Disabled and RAN-1, interact with the VAB-1 receptor and are required for its accumulation in the endocytic-recycling compartment in the absence of MSP or sperm (hereafter referred to as MSP/sperm). Inactivation of the endosomal recycling regulators rme-1 or rab-11.1 causes a vab-1-dependent reduction in the meiotic-maturation rate in the presence of MSP/sperm. Further, we show that Galpha(s) signaling in the gonadal sheath cells, which is required for meiotic maturation in the presence of MSP/sperm, affects VAB-1::GFP trafficking in oocytes. CONCLUSIONS: Regulated endocytic trafficking of the VAB-1 MSP/Eph receptor contributes to the control of oocyte meiotic maturation in C. elegans. Eph receptor trafficking in other systems may be influenced by the conserved proteins DAB-1/Disabled and RAN-1 and by crosstalk with G protein signaling in neighboring cells.

Embryogenesis: anchors away!

It has long been appreciated that the oocyte cortex plays a key role in regulating fertilization and establishing embryonic polarity. Recent studies have identified the anti-phosphatase EGG-3 as a cortical anchor for regulatory proteins required for launching embryogenesis in Caenhorhabditis elegans.

Major sperm protein signaling promotes oocyte microtubule reorganization prior to fertilization in Caenorhabditis elegans.

In most animals, female meiotic spindles assemble in the absence of centrosomes; instead, microtubule nucleation by chromatin, motor activity, and microtubule dynamics drive the self-organization of a bipolar meiotic spindle. Meiotic spindle assembly commences when microtubules gain access to chromatin after nuclear envelope breakdown (NEBD) during meiotic maturation. Although many studies have addressed the chromatin-based mechanism of female meiotic spindle assembly, it is less clear how signaling influences microtubule localization and dynamics prior to NEBD. Here we analyze microtubule behavior in Caenorhabditis elegans oocytes at early stages of the meiotic maturation process using confocal microscopy and live-cell imaging. In C. elegans, sperm trigger oocyte meiotic maturation and ovulation using the major sperm protein (MSP) as an extracellular signaling molecule. We show that MSP signaling reorganizes oocyte microtubules prior to NEBD and fertilization by affecting their localization and dynamics. We present evidence that MSP signaling reorganizes oocyte microtubules through a signaling network involving antagonistic G alpha(o/i) and G alpha(s) pathways and gap-junctional communication with somatic cells of the gonad. We propose that MSP-dependent microtubule reorganization promotes meiotic spindle assembly by facilitating the search and capture of microtubules by meiotic chromatin following NEBD.

Galphao/i and Galphas signaling function in parallel with the MSP/Eph receptor to control meiotic diapause in C. elegans.

BACKGROUND: A conserved biological feature of sexual reproduction in animals is that oocytes arrest in meiotic prophase and resume meiosis in response to extraovarian signals. In C. elegans, sperm trigger meiotic resumption by means of the major sperm protein (MSP) signal. MSP promotes meiotic resumption by functioning as an ephrin-signaling antagonist and by counteracting inhibitory inputs from the somatic gonadal sheath cells. RESULTS: By using a genome-wide RNAi screen in a female-sterile genetic background, we identified 17 conserved genes that maintain meiotic arrest in the absence of the MSP signal. In vitro binding experiments show that MSP promotes oocyte mitogen-activated protein kinase activation and meiotic maturation in part through direct interaction with the VAB-1 Eph receptor. Four conserved proteins, including a disabled protein (DAB-1), a vav family GEF (VAV-1), a protein kinase C (PKC-1), and a STAM homolog (PQN-19), function with the VAB-1 Eph/MSP receptor in oocytes. We show that antagonistic Galphao/i and Galphas signaling pathways function in the soma to regulate meiotic maturation in parallel to the VAB-1 pathway. Galphas activity is necessary and sufficient to promote meiotic maturation, which it does in part by antagonizing inhibitory sheath/oocyte gap-junctional communication. CONCLUSIONS: Our findings show that oocyte Eph receptor and somatic cell G protein signaling pathways control meiotic diapause in C. elegans, highlighting contrasts and parallels between MSP signaling in C. elegans and luteinizing hormone signaling in mammals.