Extensive characterization of genetic alterations in a series of human colorectal cancer cell lines

A number of genetic alterations have been described in colorectal cancers. They include allelic losses on specific chromosomal arms, mutations of oncogenes, tumor suppressor genes and mismatch repair genes, microsatellite instability in coding repeat sequences of target genes and methylation defects in gene promoters. Since these alterations have been reported by different groups on different tumors and cell lines, the complete repertoire of genetic alterations for any given tumor sample remains unknown. In the present study, we analysed a series of 22 colorectal cancer cell lines for 31 different genetic alterations. We found significant correlations between mutational profiles in these colorectal cell lines associated with differences in mismatch repair status. This panel of colon cancer cell lines is representative of the genetic heterogeneity occurring in sporadic colorectal carcinoma. Our results may prove to be very useful for understanding the different biological pathways involved in the development of colon cancer, and for groups studying cellular biology and pharmacology on the same cell lines.

Compromised Mitochondrial Protein Import Acts as a Signal for UPRmt

The induction of the mitochondrial unfolded protein response (UPR^mt) results in increased transcription of the gene encoding the mitochondrial chaperone HSP70. We systematically screened the C. elegans genome and identified 171 genes that, when knocked down, induce the expression of an hsp-6 HSP70 reporter and encode mitochondrial proteins. These genes represent many, but not all, mitochondrial processes (e.g., mitochondrial calcium homeostasis and mitophagy are not represented). Knockdown of these genes leads to reduced mitochondrial membrane potential and, hence, decreased protein import into mitochondria. In addition, it induces UPR^mt in a manner that is dependent on ATFS-1 but that is not antagonized by the kinase GCN-2. We propose that compromised mitochondrial protein import signals the induction of UPR^mt and that the mitochondrial targeting sequence of ATFS-1 functions as a sensor for this signal.

Evolution of instability at coding and non-coding repeat sequences in human MSI-H colorectal cancers

A number of human genes containing coding mononucleotide repeat sequences are particularly prone to mutations in tumors with defects in mismatch repair (MMR) genes (MSI-H cancers). In a large series of MSI-H colorectal tumors, we looked for mutations in 25 coding repeats contained in eight genes already known to be mutated in these cancers or in 17 other genes with an expected role in carcinogenesis. Mutations were found in 19 of the 25 candidate genes. Using a maximum likelihood statistical method, they were separated into two different groups that differed significantly in their mutation frequencies, and were likely to represent mutations that do or do not provide selective pressures during MSI-H tumoral progression, respectively. Three new target genes were found (GRB-14, RHAMM, RAD50). Our results provide evidence that MSI-H tumoral progression involves the cumulative mutations of a large number of genes. For each MSI-H tumor we calculated indexes representing the number of mutations found in genes of these groups. We also evaluated a shortening index at both the Bat-25 and Bat-26 non-coding mononucleotide tracts that are known to be almost always unstable in MSI-H cancers. A significant correlation was observed between instability at both coding and non-coding repeats, suggesting that Bat-25 and Bat-26 could be used as simple phenotypical markers of the tumoral evolution. A preferential order of mutations was deduced. During this process, hMSH3 alterations, a target gene encoding for a MMR protein, was found to play an important role by increasing the instability phenomenon characterizing these cancers.

Age-dependent changes in mitochondrial morphology and volume are not predictors of lifespan

Mitochondrial dysfunction is a hallmark of skeletal muscle degeneration during aging. One mechanism through which mitochondrial dysfunction can be caused is through changes in mitochondrial morphology. To determine the role of mitochondrial morphology changes in age-dependent mitochondrial dysfunction, we studied mitochondrial morphology in body wall muscles of the nematode C. elegans. We found that in this tissue, animals display a tubular mitochondrial network, which fragments with increasing age. This fragmentation is accompanied by a decrease in mitochondrial volume. Mitochondrial fragmentation and volume loss occur faster under conditions that shorten lifespan and occur slower under conditions that increase lifespan. However, neither mitochondrial morphology nor mitochondrial volume of five- and seven-day old wild-type animals can be used to predict individual lifespan. Our results indicate that while mitochondria in body wall muscles undergo age-dependent fragmentation and a loss in volume, these changes are not the cause of aging but rather a consequence of the aging process.

Agrobacterium-mediated transformation of Botrytis cinerea, simple purification of monokaryotic transformants and rapid conidia-based identification of the transfer-DNA host genomic DNA flanking sequences

The Agrobacterium tumefaciens-mediated transfer of foreign DNA to the phytopathogenic fungus Botrytis cinerea was investigated. Fifteen stable transformants per 10(6) conidia were consistently produced. Monokaryons were purified in a single step and their molecular analysis demonstrated the random integration of predominantly single or tandem copies of the foreign DNA into their genome. Thermal asymmetric interlaced PCR performed directly on conidia led to the rapid identification of the genomic DNA sequences that flanked the integration sites of the transfer-DNA. Transcriptional fusions of green fluorescent protein and beta-glucuronidase-encoding genes to the promoter of the secreted proteolytic enzyme ACP1 were realised to validate the system. We provide herein observations of B. cinerea hyphae producing green fluorescent protein or beta-glucuronidase under growth conditions similar to those known to induce transcription of the acp1 gene.

The BCL-2-like protein CED-9 of C. elegans promotes FZO-1/Mfn1,2- and EAT-3/Opa1-dependent mitochondrial fusion

The mammalian dynamin-related guanosine triphosphatases Mfn1,2 and Opa1 are required for mitochondrial fusion. However, how their activities are controlled and coordinated is largely unknown. We present data that implicate the BCL-2–like protein CED-9 in the control of mitochondrial fusion in Caenorhabditis elegans. We demonstrate that CED-9 can promote complete mitochondrial fusion of both the outer and inner mitochondrial membrane. We also show that this fusion is dependent on the C. elegans Mfn1,2 homologue FZO-1 and the C. elegans Opa1 homologue EAT-3. Furthermore, we show that CED-9 physically interacts with FZO-1 in vivo and that the ability of CED-9 to interact with FZO-1 is important for its ability to cause mitochondrial fusion. CED-9–induced mitochondrial fusion is not required for the maintenance of mitochondrial morphology during embryogenesis or in muscle cells, at least under normal conditions and in the absence of stress. Therefore, we propose that the BCL-2–like CED-9 acts through FZO-1/Mfn1,2 and EAT-3/Opa1 to promote mitochondrial fusion in response to specific cellular signals.

Eosinophilic esophagitis in children: symptoms, histology and pH probe results

AIM

To review the authors' experience with eosinophilic esophagitis.

METHODS

Between 1993 and 2001, the authors identified 12 patients with eosinophilic esophagitis defined on histologic criteria (> or = 20 eosinophils per high-power field in the distal esophageal epithelium). The authors reviewed medical records for details of clinical presentation; laboratory data; radiologic, endoscopic, and histologic findings; and the results of continuous esophageal pH probe monitoring.

RESULTS

Seventy-five percent of the patients were male. The median age at presentation was 10.8 years (range, 1-17 years). Commonly reported symptoms were dysphagia with solid food (66%), epigastric pain (42%), food impaction (50%), and vomiting (8%). Food allergy was reported in 50% and asthma in 33%. Peripheral eosinophilia (> 700/mm3) was found in 42%. Upper gastrointestinal series performed in eight patients, showed esophageal luminal narrowing in three. Computed tomography, performed in two patients, revealed thickening of the esophageal wall. Esophageal pH probe monitoring, performed in nine patients, revealed no abnormal acid reflux. All of the monitored patients had episodic alkalinization of the esophagus. Upper endoscopic analysis revealed white specks on the esophageal mucosa in 42%, esophageal narrowing in 33%, esophageal rings in 25%, and esophageal furrowing in 8%. The mean eosinophils per high-power field was 65 (range, 20-200). Histologic characteristics included juxtaluminar (33%) and peripapillary clusters of eosinophils (33%), increased papillary height (50%), and basal cell hyperplasia (34%).

CONCLUSION

Solid food dysphagia was the most common feature of eosinophilic esophagitis in our patients. Alkalinization of the esophagus was found in all nine pH probe recordings of eosinophilic esophagitis patients and may represent a previously unreported characteristic of the condition.

Impaired complex IV activity in response to loss of LRPPRC function can be compensated by mitochondrial hyperfusion

Mitochondrial morphology changes in response to various stimuli but the significance of this is unclear. In a screen for mutants with abnormal mitochondrial morphology, we identified MMA-1, the Caenorhabditis elegans homolog of the French Canadian Leigh Syndrome protein LRPPRC (leucine-rich pentatricopeptide repeat containing). We demonstrate that reducing mma-1 or LRPPRC function causes mitochondrial hyperfusion. Reducing mma-1/LRPPRC function also decreases the activity of complex IV of the electron transport chain, however without affecting cellular ATP levels. Preventing mitochondrial hyperfusion in mma-1 animals causes larval arrest and embryonic lethality. Furthermore, prolonged LRPPRC knock-down in mammalian cells leads to mitochondrial fragmentation and decreased levels of ATP. These findings indicate that in a mma-1/LRPPRC-deficient background, hyperfusion allows mitochondria to maintain their functions despite a reduction in complex IV activity. Our data reveal an evolutionary conserved mechanism that is triggered by reduced complex IV function and that induces mitochondrial hyperfusion to transiently compensate for a drop in the activity of the electron transport chain.

Meta-analysis: rectal indomethacin for the prevention of post-ERCP pancreatitis

BACKGROUND

Despite initial evidence in the literature, nonsteroidal anti-inflammatory drugs (NSAIDs) have not been widely used to prevent post-endoscopic retrograde cholangiopancreatography (ERCP) pancreatitis (PEP).

AIM

To complete a meta-analysis of high-quality RCTs that included the latest available literature published after past meta-analytical efforts

METHODS

A comprehensive electronic literature search was carried out for RCTs comparing peri-procedural rectal indomethacin and placebo in preventing PEP. Methodological quality was assessed by the Cochrane risk of bias tool. Fixed model Mantel-Haenszel meta-analysis, Q test and I(2) index were used. Several subgroup and sensitivity analyses were planned.

RESULTS

A total of four of 61 retrieved trials between 2007 and 2012 (n = 1470) were included. No significant publication bias existed. All studies used similar criteria to detect pancreatitis. The pooled proportion estimate of the rate of pancreatitis was 5.1% with indomethacin and 10.3% with placebo. After excluding the high-risk patients, the rates were 3.9% and 7.9% respectively. Fixed model meta-analysis showed that the rate of pancreatitis was significantly lower using indomethacin as compared with placebo [OR = 0.49(0.34-0.71); P = 0.0002]. Number needed to treat was 20. There was no significant statistical or clinical heterogeneity. In subgroup analysis, the difference remained unchanged for average-risk population [OR = 0.49(0.28-0.85); P = 0.01] or in preventing severe PEP [OR = 0.41(0.21-0.78); P = 0.007]. The result of the main outcome remained robust in multiple sensitivity analyses.

CONCLUSIONS

Rectal indomethacin used immediately before or after ERCP significantly reduces the risk of PEP to half in both low- and high-risk patients, and with both statistically and clinically significant conclusions. These results suggest that a possible change in routine practice for patients at both low and high risk of developing PEP should be advocated.

Characterization of a new, nonpathogenic mutant of Botrytis cinerea with impaired plant colonization capacity

Botrytis cinerea is a necrotrophic pathogen that attacks more than 200 plant species. Here, the nonpathogenic mutant A336, obtained via insertional mutagenesis, was characterized. Mutant A336 was nonpathogenic on leaves and fruits, on intact and wounded tissue, while still able to penetrate the host plant. It grew normally in vitro on rich media but its conidiation pattern was altered. The mutant did not produce oxalic acid and exhibited a modified regulation of the production of some secreted proteins (acid protease 1 and endopolygalacturonase 1). Culture filtrates of the mutant triggered an important oxidative burst in grapevine (Vitis vinifera) suspension cells, and the mutant-plant interaction resulted in the formation of hypersensitive response-like necrosis. Genetic segregation analyses revealed that the pathogenicity phenotype was linked to a single locus, but showed that the mutated gene was not tagged by the plasmid pAN7-1. Mutant A336 is the first oxalate-deficient mutant to be described in B. cinerea and it differs from all the nonpathogenic B. cinerea mutants described to date.

pH controls both transcription and post-translational processing of the protease BcACP1 in the phytopathogenic fungus Botrytis cinerea

During pathogenesis, the ascomycete Botrytis cinerea secretes a range of cell-wall-degrading enzymes such as polygalacturonases, glucanases and proteases. We report the identification of a new member of the G1 family of proteases, BcACP1, which is secreted by B. cinerea during infection. The production of BcACP1 correlates with the acidification of the plant tissue, and transcriptional analysis of the Bcacp1 gene showed that it is only expressed under acidic growth conditions. Using a transcriptional reporter system, we showed that pH regulation of Bcacp1 is not mediated by the canonical PacC transcription factor binding site. Like other G1 proteases, BcACP1 is produced as a pro-enzyme. Trapping of the zymogen form allowed investigation of its maturation process. Evidence is presented for an autocatalytic proteolysis of the enzyme that is triggered by acidic pH. Environmental pH therefore controls Bcacp1 production at both the transcriptional and post-translational level.

MitoSegNet: Easy-to-use Deep Learning Segmentation for Analyzing Mitochondrial Morphology

While the analysis of mitochondrial morphology has emerged as a key tool in the study of mitochondrial function, efficient quantification of mitochondrial microscopy images presents a challenging task and bottleneck for statistically robust conclusions. Here, we present Mitochondrial Segmentation Network (MitoSegNet), a pretrained deep learning segmentation model that enables researchers to easily exploit the power of deep learning for the quantification of mitochondrial morphology. We tested the performance of MitoSegNet against three feature-based segmentation algorithms and the machine-learning segmentation tool Ilastik. MitoSegNet outperformed all other methods in both pixelwise and morphological segmentation accuracy. We successfully applied MitoSegNet to unseen fluorescence microscopy images of mitoGFP expressing mitochondria in wild-type and catp-6 ATP13A2 mutant C. elegans adults. Additionally, MitoSegNet was capable of accurately segmenting mitochondria in HeLa cells treated with fragmentation inducing reagents. We provide MitoSegNet in a toolbox for Windows and Linux operating systems that combines segmentation with morphological analysis.

Clinical competency exercises: some student perceptions

Clinical competency assessments are an important part of dental curricula-to satisfy national requirements, maintain professionalism and ensure graduates are prepared for independent clinical practice. It has been observed within Newcastle Dental School (UK) that students tend to undertake the majority of their competency assessments at a very late stage. A questionnaire was designed to investigate student perceptions of two different competency assessment processes (formative structured clinical operative tests vs. summative grading), assess why they chose to undertake competency exercises at a particular time, investigate how well prepared they felt, and finally to evaluate potential barriers that students perceived within the competency process. Data regarding the timing of competency assessments and grades achieved were analysed. Fifty-nine per cent of students reported preferring the summative grading system. Most students felt that they undertook their competency assessments at about the right time (54%: conservation department, 66%: paediatric department) and the majority felt adequately prepared to undertake each exercise (68-98%). The greatest barrier stated to undertaking competency assessments was a lack of suitable patients both on which to practise and to undertake the exercise. No correlation was found between when students took summative assessments and the grades achieved. Therefore, we must encourage students to undertake their competency assessments once they have accrued sufficient clinical experience and reassure them that timing has little effect on the grade achieved. We should assist them to locate suitable patients wherever possible.

Autophagy compensates for defects in mitochondrial dynamics

Compromising mitochondrial fusion or fission disrupts cellular homeostasis; however, the underlying mechanism(s) are not fully understood. The loss of C. elegans fzo-1MFN results in mitochondrial fragmentation, decreased mitochondrial membrane potential and the induction of the mitochondrial unfolded protein response (UPRmt). We performed a genome-wide RNAi screen for genes that when knocked-down suppress fzo-1MFN(lf)-induced UPRmt. Of the 299 genes identified, 143 encode negative regulators of autophagy, many of which have previously not been implicated in this cellular quality control mechanism. We present evidence that increased autophagic flux suppresses fzo-1MFN(lf)-induced UPRmt by increasing mitochondrial membrane potential rather than restoring mitochondrial morphology. Furthermore, we demonstrate that increased autophagic flux also suppresses UPRmt induction in response to a block in mitochondrial fission, but not in response to the loss of spg-7AFG3L2, which encodes a mitochondrial metalloprotease. Finally, we found that blocking mitochondrial fusion or fission leads to increased levels of certain types of triacylglycerols and that this is at least partially reverted by the induction of autophagy. We propose that the breakdown of these triacylglycerols through autophagy leads to elevated metabolic activity, thereby increasing mitochondrial membrane potential and restoring mitochondrial and cellular homeostasis.

Msp1 cooperates with the proteasome for extraction of arrested mitochondrial import intermediates

The mitochondrial AAA ATPase Msp1 is well known for extraction of mislocalized tail-anchored ER proteins from the mitochondrial outer membrane. Here, we analyzed the extraction of precursors blocking the import pore in the outer membrane. We demonstrate strong genetic interactions of Msp1 and the proteasome with components of the TOM complex, the main translocase in the outer membrane. Msp1 and the proteasome both contribute to the removal of arrested precursor proteins that specifically accumulate in these mutants. The proteasome activity is essential for the removal as proteasome inhibitors block extraction. Furthermore, the proteasomal subunit Rpn10 copurified with Msp1. The human Msp1 homologue has been implicated in neurodegenerative diseases, and we show that the lack of the Caenorhabditis elegans Msp1 homologue triggers an import stress response in the worm, which indicates a conserved role in metazoa. In summary, our results suggest a role of Msp1 as an adaptor for the proteasome that drives the extraction of arrested and mislocalized proteins at the mitochondrial outer membrane.

Connection between the Rag4 glucose sensor and the KlRgt1 repressor in Kluyveromyces lactis

The RAG4 gene encodes for the sole transmembrane glucose sensor of Kluyveromyces lactis. A rag4 mutation leads to a fermentation-deficient phenotype (Rag- phenotype) and to a severe defect in the expression of the major glucose transporter gene RAG1. A recessive extragenic suppressor of the rag4 mutation has been identified. It encodes a protein (KlRgt1) 31% identical to the Saccharomyces cerevisiae Rgt1 regulator of the HXT genes (ScRgt1). The Klrgt1 null mutant displays abnormally high levels of RAG1 expression in the absence of glucose but still presents an induction of RAG1 expression in the presence of glucose. KlRgt1 is therefore only a repressor of RAG1. As described for ScRgt1, the KlRgt1 repressor function is controlled by phosphorylation in response to high glucose concentration and this phosphorylation is dependent on the sensor Rag4 and the casein kinase Rag8. However, contrary to that observed with ScRgt1, KlRgt1 is always bound to the RAG1 promoter. This article reveals that the key components of the glucose-signaling pathway are conserved between S. cerevisiae and K. lactis, but points out major differences in Rgt1 regulation and function that might reflect different carbon metabolism of these yeasts.

Wernicke-Korsakoff syndrome in Sydney hospitals after 6 years of thiamin enrichment of bread

OBJECTIVES

To estimate the incidence of Wernicke's encephalopathy (WE) and Korsakoff's psychosis (KP) before and after the introduction of thiamin enrichment of bread in Australia.

DESIGN AND SUBJECTS

Inpatient records were examined in 17 major public general hospitals in greater Sydney for the 4 years 1993-96 (inclusive) with the International Classification of Diseases (ICD) 9 diagnoses 265.1 (WE), 291.1 and 294.0 (KP). Relevant clinical data were recorded on a specially designed form so that cases could be classified as confirmed or probable WE, confirmed or probable KP, confirmed or probable Wernicke-Korsakoff syndrome (WE + KP) or not WE or KP. The average number of cases of WE + KP was 38 acute (new) cases and 69 total (acute + chronic) cases per annum for all the hospitals combined.

RESULTS

This study used the same methods as our earlier retrospective examination of Wernicke-Korsakoff cases in essentially the same hospitals for 1978-93. Records for 1993 were thus pulled twice and, while individual cases (using hospital index number) did not always coincide, the total numbers for 1993 were 69 and 70. For the 5 years after 1991 the number of acute cases of WE and KP in Sydney hospitals was 61% of the number for the 5 years before 1991 (P<0.01). There is, however, no continuing downward trend.

CONCLUSIONS

These results are consistent with a 40% reduction of the incidence of acute WE and KP since bread has been enriched with thiamin. The disease complex has, however, not been eliminated. To achieve this, further public health action would be needed, such as addition of thiamin to beer.

Sulphur and nitrogen regulation of the protease-encoding ACP1 gene in the fungus Botrytis cinerea: correlation with a phospholipase D activity

Sulphur and nitrogen catabolic repressions are regulations that have long been recognized in fungi, but whose molecular bases remain largely elusive. This paper shows that catabolic repression of a protease-encoding gene correlates with the modulation of a phosphatidylethanolamine (PE)-specific phospholipase D (PLD) activity in the pathogenic fungus Botrytis cinerea. Our results first demonstrate that the ACP1 gene is subject to sulphur catabolic repression, with sulphate and cysteine inhibiting its expression. Sulphate and cysteine also cause a decrease of the total cellular PLD activity and, reciprocally, the two PLD inhibitors AEBSF [4-(2-aminoethyl)benzenesulphonyl fluoride] and curcumin negatively affect ACP1 expression in vivo. Cysteine moreover inhibits the PE-specific PLD activity in cell extracts. ACP1 is regulated by nitrogen, but here we show that this regulation does not rely on the proximal AREA binding site in its promoter, and that glutamine does not play a particular role in the process. A decrease in the total cellular PLD activity is also observed when the cells are fed ammonia, but this effect is smaller than that produced by sulphur. RNA-interference experiments finally suggest that the enzyme responsible for the PE-specific PLD activity is encoded by a gene that does not belong to the known HKD gene family of PLDs.

Recombinant expression, biophysical characterization, and cardiolipin-induced changes of two Caenorhabditis elegans cytochrome c proteins

Cytochrome c (cyt c) is one of the most widely studied biomolecules, but not much is known about this protein from nematodes. Recombinant expression of Caenorhabditis elegans CYC-2.1 and CYC-2.2 allowed for detailed characterization of their structural features, redox properties, stabilities, and interactions with cardiolipin (CL)-containing liposomes. Using a variety of spectroscopic tools, we show that CYC-2.1 and CYC-2.2 adopt a globular α-helical fold with His/Met heme ligation. The longer CYC-2.2 has a lower thermodynamic stability than CYC-2.1 and lacks His residues to misligate to the heme in the protein's denatured state. Both C. elegans proteins bind to CL-containing liposomes, and these interactions promote the proteins' peroxidase activity but to a much greater degree for CYC-2.2. Dye-to-heme distance distributions from time-resolved fluorescence resonance energy transfer in bimane-labeled CYC-2.1 and CYC-2.2 revealed similar populations of extended and compact conformers for CL-bound proteins, suggesting that their distinct peroxidase activities in the presence of CL arise from differences in the local heme environments for the two polypeptide ensembles. Without inhibition from His misligation, a less stable and more prone to unfolding CYC-2.2 allows for better access of substrates to the heme and thus exhibits higher peroxidase activity. Similar features of the conformational ensembles of CYC-2.1 and CYC-2.2 to those of mammalian cyt c suggest that C. elegans proteins, particularly the former, could serve as useful models for examining the mechanism of cyt c-CL interactions in live organisms.

Three-dimensional computational model of a blood oxygenator reconstructed from micro-CT scans

Cardiopulmonary bypass procedures are one of the most common operations and blood oxygenators are the centre piece for the heart-lung machines. Blood oxygenators have been tested as entire devices but intricate details on the flow field inside the oxygenators remain unknown. In this study, a novel method is presented to analyse the flow field inside oxygenators based on micro Computed Tomography (μCT) scans. Two Hollow Fibre Membrane (HFM) oxygenator prototypes were scanned and three-dimensional full scale models that capture the device-specific fibre distributions are set up for computational fluid dynamics analysis. The blood flow through the oxygenator is modelled as a non-Newtonian fluid. The results were compared against the flow solution through an ideal fibre distribution and show the importance of a uniform distribution of fibres and that the oxygenators analysed are not susceptible to flow directionality as mass flow versus area remain the same. However the pressure drop across the oxygenator is dependent on flow rate and direction. By comparing residence time of blood against the time frame to fully saturate blood with oxygen we highlight the potential of this method as design optimisation tool. In conclusion, image-based reconstruction is found to be a feasible route to assess oxygenator performance through flow modelling. It offers the possibility to review a product as manufactured rather than as designed, which is a valuable insight as a precursor to the approval processes. Finally, the flow analysis presented may be extended, at computational cost, to include species transport in further studies.

How to analyze mitochondrial morphology in healthy cells and apoptotic cells in Caenorhabditis elegans

Mitochondria constantly undergo fusion and fission events. A proper balance of fusion and fission is essential in healthy cells, as disrupting this balance is associated with several neurodegenerative diseases. Mitochondrial fission has also been shown to play an important role during apoptosis. Hence, the machineries that control mitochondrial morphology have both nonapoptotic and apoptotic functions. Seminal work in yeast has identified some of the key components of these machineries. However, the list is certainly not complete and new factors that are specific to metazoans are being identified every year. In this review, we describe methodologies to test whether a particular candidate gene plays a role in the control of mitochondrial morphology in healthy cells and apoptotic cells using Caenorhabditis elegans.

Quality assurance, benchmarking, assessment and mutual international recognition of qualifications

The aim of this report is to provide guidance to assist in the international convergence of quality assurance, benchmarking and assessment systems to improve dental education. Proposals are developed for mutual recognition of qualifications, to aid international movement and exchange of staff and students including and supporting developing countries. Quality assurance is the responsibility of all staff involved in dental education and involves three levels: internal, institutional and external. Benchmarking information provides a subject framework. Benchmarks are useful for a variety of purposes including design and validation of programmes, examination and review; they can also strengthen the accreditation process undertaken by professional and statutory bodies. Benchmark information can be used by institutions as part of their programme approval process, to set degree standards. The standards should be developed by the dental academic community through formal groups of experts. Assessment outcomes of student learning are a measure of the quality of the learning programme. The goal of an effective assessment strategy should be that it provides the starting point for students to adopt a positive approach to effective and competent practice, reflective and lifelong learning. All assessment methods should be evidence based or based upon research. Mutual recognition of professional qualifications means that qualifications gained in one country (the home country) are recognized in another country (the host country). It empowers movement of skilled workers, which can help resolve skills shortages within participating countries. These proposals are not intended to be either exhaustive or prescriptive; they are purely for guidance and derived from the identification of what is perceived to be 'best practice'.

Reduced peroxisomal import triggers peroxisomal retrograde signaling

Maintaining organelle function in the face of stress is known to involve organelle-specific retrograde signaling. Using Caenorhabditis elegans, we present evidence of the existence of such retrograde signaling for peroxisomes, which we define as the peroxisomal retrograde signaling (PRS). Specifically, we show that peroxisomal import stress caused by knockdown of the peroxisomal matrix import receptor prx-5/PEX5 triggers NHR-49/peroxisome proliferator activated receptor alpha (PPARα)- and MDT-15/MED15-dependent upregulation of the peroxisomal Lon protease lonp-2/LONP2 and the peroxisomal catalase ctl-2/CAT. Using proteomic and transcriptomic analyses, we show that proteins involved in peroxisomal lipid metabolism and immunity are also upregulated upon prx-5(RNAi). While the PRS can be triggered by perturbation of peroxisomal β-oxidation, we also observed hallmarks of PRS activation upon infection with Pseudomonas aeruginosa. We propose that the PRS, in addition to a role in lipid metabolism homeostasis, may act as a surveillance mechanism to protect against pathogens.

Genome-wide RNAi screen for regulators of UPRmt in Caenorhabditis elegans mutants with defects in mitochondrial fusion

Mitochondrial dynamics plays an important role in mitochondrial quality control and the adaptation of metabolic activity in response to environmental changes. The disruption of mitochondrial dynamics has detrimental consequences for mitochondrial and cellular homeostasis and leads to the activation of the mitochondrial unfolded protein response (UPRmt), a quality control mechanism that adjusts cellular metabolism and restores homeostasis. To identify genes involved in the induction of UPRmt in response to a block in mitochondrial fusion, we performed a genome-wide RNAi screen in Caenorhabditis elegans mutants lacking the gene fzo-1, which encodes the ortholog of mammalian Mitofusin, and identified 299 suppressors and 86 enhancers. Approximately 90% of these 385 genes are conserved in humans, and one third of the conserved genes have been implicated in human disease. Furthermore, many have roles in developmental processes, which suggests that mitochondrial function and the response to stress are defined during development and maintained throughout life. Our dataset primarily contains mitochondrial enhancers and non-mitochondrial suppressors of UPRmt, indicating that the maintenance of mitochondrial homeostasis has evolved as a critical cellular function, which, when disrupted, can be compensated for by many different cellular processes. Analysis of the subsets 'non-mitochondrial enhancers' and 'mitochondrial suppressors' suggests that organellar contact sites, especially between the ER and mitochondria, are of importance for mitochondrial homeostasis. In addition, we identified several genes involved in IP3 signaling that modulate UPRmt in fzo-1 mutants and found a potential link between pre-mRNA splicing and UPRmt activation.