A self-determination theory analysis of reflective debrief themes about dietetic student placement experiences in hospital: implications for education.

BACKGROUND: Healthcare placements in dietetics education contribute significantly to student learning. Exploring students' self-conceptualisation of placement experiences may provide insights to better support learning. Self-determination theory (SDT) has been used to seek insight into clinical and educational settings but has not yet been applied to dietetic placement learning. The present study investigated dietetics students' reflections of key influences on placement learning experiences and their alignment with an SDT framework. METHODS: A post-placement two-stage critical incident debrief was conducted with seven successive cohorts (168 students) of dietetic undergraduate students on final placement. In debriefs, students' anonymous themes were collected and discussed, inductively analysed, and then mapped against an SDT framework of psychological and motivational constructs. RESULTS: Nine key themes were identified that impacted upon placement experiences. Four themes related to framework constructs: (1) Supervisor (and Peer) Autonomy Support; (2) Perceived Competence; (3) Relatedness; and (4) Autonomy and Intrinsic Motivation. Non-SDT themes were also present, including: (5) Learning Environment and Experience; as well as themes about professional behaviours and identity: (6) Teamwork and Interactions; (7) Managing Emotions and Self-Care; (8) Dietetic Communications and Behaviours; and (9) Developing a Professional Identity. CONCLUSIONS: Embedding a structured debrief in the curriculum and using a psychological motivational SDT framework to analyse themes arising can provide valuable information about the learning needs of students on placement with potential for wider application in dietetic learning and teaching and workforce employability. The current findings may have application in university curricula before and after professional placement.

The tension between efficiency and effectiveness: a study of dietetic practice in primary care.

BACKGROUND: Primary healthcare dietitians have a vital role to play in the prevention and management of chronic disease. Working in primary care requires efficient and effective management of practice to ensure client and practitioner needs are met. The present study aimed to explore the way in which primary care dietitians in Australia view the constructs of efficiency and effectiveness within the context of their practice. METHODS: The study used an exploratory qualitative design within a pragmatist framework. Individual semi-structured telephone interviews were conducted with Australian primary care dietitians. All interviews were audio-recorded, transcribed verbatim and analysed using an inductive thematic approach. RESULTS: Twenty dietitians (17 females) working as private practitioners in primary care from three Australian states participated in the present study. Three themes emerged from the data. The first theme revealed that seeking efficiency and especially effectiveness were important to primary care dietitians and that there was a tension between the two. The second theme identified that efficiency and effectiveness are influenced by personal and structural factors. The final theme explored how dietitians are actively seeking ways to be more efficient and effective, including supportive networks, as well as the utilisation of technology. CONCLUSIONS: Achieving a balance between efficiency and effectiveness in primary care dietetics is challenging to practitioners, who may require further training and support to enhance productivity, time management and resource utilisation. Structured issues exist for the workface. Further studies are required to quantify these findings and to explore whether it is possible to optimise efficiency and effectiveness and achieve sustainability of the dietetic workforce in primary care.

Quality of development and reporting of dietetic intervention studies in primary care: a systematic review of randomised controlled trials.

BACKGROUND: High-quality research methodologies and clear reporting of studies are essential to facilitate confidence in research findings. The aim of the present study was to conduct an in-depth examination of the methodological quality and reporting of studies included in a recent systematic review of dietitians' effectiveness at providing individualised nutrition care to adult patients. METHODS: The methodological quality and reporting of 27 Randomised Controlled Trials (RCTs) were appraised using the UK Medical Research Council (MRC) Guidelines for complex interventions and the CONSORT checklist for reporting RCTs. A quality appraisal checklist was developed for each guideline/assessment tool aiming to evaluate the extent to which each study met the designated criteria. Excerpts from studies that best addressed criteria were collated to provide exemplary accounts of how criteria may be achieved in future studies. RESULTS: None of the reviewed studies met more than half of the MRC Guidance criteria, indicating that there is clear room for improvement in reporting the methodological underpinnings of these studies. Similarly, no studies met all criteria of the CONSORT checklist, suggesting that there is also room for improvement in the design and reporting of studies in this field. CONCLUSIONS: Dietitians, researchers and journal editors are encouraged to use the results and exemplary accounts from this review to identify key aspects of studies that could be improved in future research. Improving future research will enhance the quality of the evidence-base that investigates the outcomes of dietary interventions involving dietitians.

Is it possible to enhance the confidence of student dietitians prior to professional placements? A design-based research model.

BACKGROUND: Student confidence is an important contributor to a successful professional placement experience. The present study aimed to evaluate a placement preparation program for student dietitians and to assess the impact on self-rated confidence with respect to commencing placements. METHODS: The present study is part of a design-based research approach that involves students in a cyclic enquiry to evaluate and improve curricula. Nutrition and Dietetics students at an Australian university participated in a 1-week mandatory workshop - Pre-Placement week (PrePW), N = 98 students: in 2015 (n = 54) and 2016 (n = 44). An online survey was conducted before and after PrePW using a five-point Likert scale (1 = not confident; 5 = very confident) to assess self-rated confidence to commence placements. Mean (SD) scores were calculated. Paired and independent t-tests evaluated within- and between-group differences, respectively. RESULTS: Before PrePW, the mean (SD) for student confidence to commence placements overall (in all areas of practise) was 'somewhat confident' [2.9 (0.6) in 2015 and 3.0 (0.7) in 2016]. Students were least confident to commence Clinical Practice [2015: 2.5 (0.6); 2016: 2.8 (0.6)] compared to Food Service Management (FSM) [2015: 3.2 (0.9); 2016: 3.1 (0.9)] and Community and Public Health Nutrition (CPHN) [2015: 3.3 (0.9); 2016: 3.2 (0.8)]. Student feedback from PrePW 2015 was used to change the curriculum and PrePW program. The 2016 students reported significantly greater confidence within all areas of practice: Clinical Practice [3.4 (0.6)], FSM [3.7 (0.6)] and CPHN [3.8 (0.6)], including confidence to commence placements overall [3.6 (0.6)] (P < 0.05). CONCLUSIONS: Design-based research provides a useful framework for improvement to curricula and, in this case, was successful in enhancing student confidence in preparation for professional placement.

Weekend days are not required to accurately measure oral intake in hospitalised patients.

BACKGROUND: Nutrition studies in patients admitted to hospital frequently disregard oral intake because measurement is time-intensive and logistically challenging. In free-living populations, weighed food records (WFR) are the gold-standard and are conducted on weekend and weekdays to capture variations in intake, although this may not translate during hospitalisation. The present study aimed to determine whether oral intake differs between weekends and weekdays in hospitalised patients. METHODS: For adult patients initially admitted to the intensive therapy unit with a moderate-severe head injury over a 12-month period, WFR were conducted each week on Tuesday, Thursday and Saturday throughout hospitalisation. Meal components were weighed before and after consumption, and energy and protein intakes were calculated using specialised software. Data are reported as the mean (SD). Differences were assessed using paired t-tests and agreement using Bland-Altman plots. RESULTS: Thirty-two patients had WFR collected on 220 days, 68% (n = 149) on weekdays and 32% (n = 71) on weekends. Overall, daily intakes were 5.72 (3.67) MJ [1367 (877) kcal] and 62 (40) g protein. There were no differences in intake across all days (P = 0.937 energy, P = 0.797 protein), nor between weekdays and weekends, in weeks 1-3 of oral intake (all P > 0.1). Limits of agreement between mean intakes across days were wide for energy [range -11.20 to 9.55 MJ (-2680 to 2283 kcal)] and protein (range -125 to 110 g). CONCLUSIONS: Grouped energy and protein intakes from WFR in hospitalised patients are similar on weekdays and weekends, although large intra-patient variations occur. Future quantification of oral intake during hospitalisation should include as many days as feasible, although not necessarily weekend days, to reflect true intake.

The Family Diet Study: a cross-sectional study into the associations between diet, food habits and body weight status in Malay families.

BACKGROUND: Childhood obesity is becoming more common as Malaysia experiences rapid nutrition transition. Current evidence related to parental influences on child dietary intake and body weight status is limited. The present study aimed to report, among Malay families, the prevalence of energy mis-reporting and dietary relationships within family dyads. METHODS: The cross-sectional Family Diet Study (n = 236) was conducted at five primary schools in central of Peninsular Malaysia. Each family consisted of a Malay child, aged 8-12 years, and their main caregiver(s). Information on socio-demographics, dietary intake and anthropometry were collected. Correlations and regression analyses were used to assess dietary relationships within family dyads. RESULTS: Approximately 29.6% of the children and 75.0% parents were categorised as being overweight or obese. Intakes of nutrients and food groups were below the national recommended targets for majority of children and adults. A large proportion of energy intake mis-reporters were identified: mothers (55.5%), fathers (40.2%) and children (40.2%). Children's body mass index (BMI) was positively associated with parental BMI (fathers, r = 0.37; mothers, r = 0.34; P < 0.01). For dietary intakes, moderate-to-strong (0.35-0.72) and weak-to-moderate (0.16-0.35) correlations were found between mother-father and child-parent dyads, respectively. Multiple regression revealed that maternal percentage energy from fat (ß = 0.09, P < 0.01) explained 81% of the variation in children's fat intake. CONCLUSIONS: Clear parental dietary relationships, especially child-mother dyads, were found. Despite a significant proportion of families with members who were overweight or obese, the majority reported dietary intakes below recommended levels, distorted by energy mis-reporting. The findings of the present study can inform interventions targeting parent-child relationships to improve family dietary patterns in Malaysia.

The paradoxical psychological effects of lysergic acid diethylamide (LSD).

BACKGROUND: Lysergic acid diethylamide (LSD) is a potent serotonergic hallucinogen or psychedelic that modulates consciousness in a marked and novel way. This study sought to examine the acute and mid-term psychological effects of LSD in a controlled study. METHOD: A total of 20 healthy volunteers participated in this within-subjects study. Participants received LSD (75 µg, intravenously) on one occasion and placebo (saline, intravenously) on another, in a balanced order, with at least 2 weeks separating sessions. Acute subjective effects were measured using the Altered States of Consciousness questionnaire and the Psychotomimetic States Inventory (PSI). A measure of optimism (the Revised Life Orientation Test), the Revised NEO Personality Inventory, and the Peter's Delusions Inventory were issued at baseline and 2 weeks after each session. RESULTS: LSD produced robust psychological effects; including heightened mood but also high scores on the PSI, an index of psychosis-like symptoms. Increased optimism and trait openness were observed 2 weeks after LSD (and not placebo) and there were no changes in delusional thinking. CONCLUSIONS: The present findings reinforce the view that psychedelics elicit psychosis-like symptoms acutely yet improve psychological wellbeing in the mid to long term. It is proposed that acute alterations in mood are secondary to a more fundamental modulation in the quality of cognition, and that increased cognitive flexibility subsequent to serotonin 2A receptor (5-HT2AR) stimulation promotes emotional lability during intoxication and leaves a residue of 'loosened cognition' in the mid to long term that is conducive to improved psychological wellbeing.

Can a relatively low-intensity intervention by health professionals prevent weight gain in mid-age women? 12-Month outcomes of the 40-Something randomised controlled trial.

BACKGROUND: Weight gain in perimenopausal women results in increased visceral adipose tissue, leading to metabolic syndrome and associated comorbidities. Despite a high prevalence of weight gain at this life stage, interventions to prevent menopausal obesity are lacking. AIM: To test the effectiveness of an intervention delivered by health professionals using a motivational interviewing (MI) counselling style in preventing weight gain in non-obese (body mass index (BMI) 18.5 and 29.9 kg m(-2)) women in late premenopause. METHODS: In a randomised controlled trial, 54 women (mean (s.d.) age 47.3 (1.8) years; BMI 25.1 (2.4) kg m(-2)) who had menstruated within the preceding 3 months were randomly assigned to an MI intervention (n=28) (five health professional MI counselling sessions) or a self-directed intervention (SDI) (print materials only) (n=26). The primary outcome, body weight (kg) and secondary outcomes (blood lipids, glucose, body fat %, lean mass % and waist circumference) were measured at baseline and postintervention (12 months), and intention-to-treat analysis was conducted. RESULTS: Forty women completed all measures and adhered to all protocols. The weight at 12 months for the MI group of 65.6 kg (95% CI: 64.5; 66.8) was significantly different (P=0.034) from the SDI group of 67.4 kg (95% CI: 66.2; 68.6). When stratified by baseline BMI category, the MI group lost significantly more weight (-2.6 kg; 95% CI: -3.9; -1.2) than the SDI group (-0.1 kg; 95% CI: -1.2; 1.0, P=0.002) for the healthy weight women. The overweight women lost weight regardless of the intervention group, with no between-group difference (-3.5 kg; 95% CI: -6.1, -1.0 and -2.3; 95% CI: -4.1, -0.5, P=0.467). CONCLUSION: This relatively low-intensity intervention, incorporating MI into health professional counselling, not only effectively prevented weight gain but also achieved significant weight loss and decreased diastolic blood pressure. Further refinements are required to optimise outcomes for overweight women.

Client satisfaction and weight loss outcomes of student centred dietetic outpatient clinics.

AIM: Evaluation of health care services and providers is essential in determining effectiveness and quality. The aim of this study was to assess the client satisfaction and weight loss outcomes of student focussed dietetic outpatient weight loss clinics. METHODS: The outpatient clinics were conducted by the University as part of student education. Sixty-one clients attended a new appointment during 2008. Anthropometric and demographic details were extracted from clients' clinic records. Clients were mailed a 30-item satisfaction survey adapted from an existing instrument. RESULTS: Twenty-six surveys were returned (43% response rate). Respondents were less likely to be satisfied with appointment wait times and availability of parking (65%, 70%, respectively) compared with other factors. Dietitians were seen as polite and courteous, and the presence of students did not lessen the attention from the dietitian. Mean (SD) weight change was -3.3 (3.2) kg over 12 months (P < 0.05, n = 20). CONCLUSION: It was found that clients were satisfied with services and while statistically significant weight loss was achieved, results did not reach the clinically significant weight loss of 5% of initial weight.

Developing dietetic positions in rural areas: what are the key lessons?

INTRODUCTION: Rural and remote communities in Australia are typically underserviced by dietitians. The recruitment of dietitians to rural areas has improved in recent years; however, retention remains an issue. Key factors that lead to an increase in funding and the development of more dietetic positions in rural areas are unknown. The purpose of this study was to describe dietetic services in rural areas and to determine the drivers for and barriers to the development of dietetic positions in rural areas. METHODS: A sequential explanatory mixed methods approach was used to examine six case study sites of dietetic service delivery in rural northern New South Wales (NSW) Australia between 1991 and 2006. The six sites represented different models of dietetic service delivery from the study area. Data sources included workforce documents and in-depth individual interviews on position development with 40 key informants, including past and present dietitians, dietetic managers and health service managers. Interview data were thematically analysed with the aid of NVivo7 (www.qsrinternational.com). Themes were coded into common categories, using a constant comparison inductive approach. RESULTS: Forty key informants agreed to participate in the in-depth, semi-structured interview. Participants included 28 dietitians (past and present), three dietetics managers and nine managers. The majority of participants were female (87.5%). Document analysis showed that the dietetic workforce had a 5.6-fold increase across the six sites over the 15 years. Themes that emerged from the interviews indicated that new positions were established through ad hoc and opportunistic funding, a gradual increase in funding or due to concerted efforts by champions advocating for increased funding. CONCLUSION: The findings from this study have important implications for the development of dietetic staffing in rural areas. There is an inconsistent approach to the development of dietetic positions in rural areas of Australia. Factors that inhibited the development of positions included a general lack of funds and competing priorities. A systematic, planned approach to the development of dietetic positions is needed in rural Australia. Champions for the development of positions were effective in increasing positions, particularly when they have management support.

Weight gained in two years by a population of mid-aged women: how much is too much?

OBJECTIVE: To establish the prevalence of weight change in mid-aged women over a 2-year period, and to assess the relationship between weight change and physical and mental well-being (SF36) in order to begin debate about the need for quantified standards of weight gain. DESIGN: Prospective study of weight change and well-being over a 2-year period among mid-aged women participating in a large national survey. SUBJECTS: Seven thousand two hundred and seventy women without surgical menopause aged between 45 and 50 years (termed mid-aged), enrolled in the Australian Longitudinal Study on Women's Health. MEASUREMENTS: Weight change (self-reported weight at two time points) and physical and mental well-being (SF-36) explored using linear regression, while adjusting for potential confounders. RESULTS: Only half the women maintained their weight within 2.25 kg, and one-third gained more than this amount in a 2-year period. While weight gain (> or = 2.25 kg) was negatively associated with physical well-being, both weight loss and weight gain were associated with poorer mental well-being. CONCLUSION: This is the first prospective study using a large, population-based cohort to demonstrate that small changes in weight are associated with changes in well-being in mid-aged Australian women. It provides further evidence of the need for public health messages to specify the actual amount that constitutes weight gain, but further research is needed to establish these standards for the entire population.

A receptor for vascular endothelial growth factor that stimulates endothelial apoptosis.

Vascular endothelial growth factor (VEGF) is a dimeric angiogenic factor that is overexpressed by many tumors and stimulates tumor angiogenesis. VEGF initiates signaling by dimerizing the receptors VEGFR-1 and VEGFR-2. The Fas receptor stimulates apoptosis, and artificial dimerization of the Fas cytoplasmic domain has been shown to induce apoptosis. We constructed a chimeric receptor (VEGFR2Fas) combining the extracellular and transmembrane domains of VEGFR-2 with the cytoplasmic domain of Fas receptor. When VEGFR2Fas was stably expressed in endothelial cells in vitro, treatment with VEGF rapidly induced cell death with features characteristic of Fas-mediated apoptosis. These findings demonstrate that VEGFR2Fas functions as a VEGF-triggered death receptor and raise the possibility that introduction of VEGFR2Fas into tumor endothelium or tumor cells in vivo may convert tumor-derived VEGF from an angiogenic factor into an antiangiogenesis agent.

Elevated expression of axin2 and hnkd mRNA provides evidence that Wnt/beta -catenin signaling is activated in human colon tumors.

Genetic studies have identified mutations in key regulators of the Wnt/beta-catenin pathway in a variety of cancers, most frequently in colon cancers. However, whether the pathway is activated in clinical cancer samples is not easily determined, and therefore it is useful to find markers that could be surrogates to show activation of the Wnt/beta-catenin pathway. Gene expression profiles were analyzed in SW620, a colon cancer cell line in which beta-catenin levels are stabilized as a consequence of truncated adenomatous polyposis coli and were compared with profiles of the same cells transfected with antisense oligodeoxynucleotides. Treatment of cells with beta-catenin antisense oligodeoxynucleotides resulted in a decrease in the levels of axin2 and human naked cuticle (hnkd) mRNAs. Interestingly, the proteins encoded by both of these mRNAs are known inhibitors of the beta-catenin pathway. In 30 human cell lines derived from different origins, axin2 and hnkd were expressed only in human colon cancer cell lines that are known to have activating mutations in the Wnt/beta-catenin pathway. Further, levels of both axin2 and hnkd mRNA were also found to be elevated in about 65% of laser microdissected cells from human colon tumors compared with laser microdissected cells of normal morphology from the same patient samples. The increased expression of axin2 and hnkd correlated with truncations in adenomatous polyposis coli in the same patient samples. These results reveal that it is possible to detect activation of a carcinogenic pathway in human cancer samples with specific markers.

PAR-1 is a Dishevelled-associated kinase and a positive regulator of Wnt signalling.

Wnt signalling regulates beta-catenin-dependent developmental processes through the Dishevelled protein (Dsh). Dsh regulates two distinct pathways, one mediated by beta-catenin and the other by Jun kinase (JNK). We have purified a Dsh-associated kinase from Drosophila that encodes a homologue of Caenorhabditis elegans PAR-1, a known determinant of polarity during asymmetric cell divisions. Treating cells with Wnt increases endogenous PAR-1 activity coincident with Dsh phosphorylation. PAR-1 potentiates Wnt activation of the beta-catenin pathway but blocks the JNK pathway. Suppressing endogenous PAR-1 function inhibits Wnt signalling through beta-catenin in mammalian cells, and Xenopus and Drosophila embryos. PAR-1 seems to be a positive regulator of the beta-catenin pathway and an inhibitor of the JNK pathway. These findings show that PAR-1, a regulator of polarity, is also a modulator of Wnt-beta-catenin signalling, indicating a link between two important developmental pathways.

Cell autonomous regulation of multiple Dishevelled-dependent pathways by mammalian Nkd.

Genetic studies have identified Drosophila Naked Cuticle (Nkd) as an antagonist of the canonical Wnt/beta-catenin signaling pathway, but its mechanism of action remains obscure [Zeng, W., Wharton, K. A., Jr., Mack, J. A., Wang, K., Gadbaw, M., et al. (2000) Nature (London) 403, 789--795]. Here we have cloned a cDNA encoding a mammalian homolog of Drosophila Nkd, mNkd, and demonstrated that mNkd interacts directly with Dishevelled. Dishevelled is an intracellular mediator of both the canonical Wnt pathway and planar cell polarity (PCP) pathway. Activation of the c-Jun-N-terminal kinase has been implicated in the PCP pathway. We showed that mNkd acts in a cell-autonomous manner not only to inhibit the canonical Wnt pathway but also to stimulate c-Jun-N-terminal kinase activity. Expression of mNkd disrupted convergent extension in Xenopus, consistent with a role for mNkd in the PCP pathway. These data suggest that mNkd may act as a switch to direct Dishevelled activity toward the PCP pathway, and away from the canonical Wnt pathway.

Drosophila par-1 is required for oocyte differentiation and microtubule organization.

BACKGROUND: Drosophila oocyte determination involves a complex process by which a single cell within an interconnected cyst of 16 germline cells differentiates into an oocyte. This process requires the asymmetric accumulation of both specific messenger RNAs and proteins within the future oocyte as well as the proper organization of the microtubule cytoskeleton, which together with the fusome provides polarity within the developing germline cyst. RESULTS: In addition to its previously described late oogenic role in the establishment of anterior-posterior polarity and subsequent embryonic axis formation, the Drosophila par-1 gene is required very early in the germline for establishing cyst polarity and for oocyte specification. Germline clonal analyses, for which we used a protein null mutation, reveal that Drosophila par-1 (par-1) is required for the asymmetric accumulation of oocyte-specific factors as well as the proper organization of the microtubule cytoskeleton. Similarly, somatic clonal analyses indicate that par-1 is required for microtubule stabilization in follicle cells. The PAR-1 protein is localized to the fusome and ring canals within the developing germline cyst in direct contact with microtubules. Likewise, in the follicular epithelium, PAR-1 colocalizes with microtubules along the basolateral membrane. However, in either case PAR-1 localization is independent of microtubules. CONCLUSIONS: The Drosophila par-1 gene plays at least two essential roles during oogenesis; it is required early in the germline for organization of the microtubule cytoskeleton and subsequent oocyte determination, and it has a second, previously described role late in oogenesis in axis formation. In both cases, par-1 appears to exert its effects through the regulation of microtubule dynamics and/or stability, and this finding is consistent with the defined role of the mammalian PAR-1 homologs.

New steps in the Wnt/beta-catenin signal transduction pathway.

Wnt regulates developmental and oncogenic processes through its downstream effector, beta-catenin, and a set of other intracellular regulators that are largely conserved among species. Wnt family genes encode secreted glycoproteins that act as ligands for membrane receptors belonging to the Frizzled family of proteins. Wnt-1 originally was found as a proto-oncogene that was upregulated in tumors caused by the mouse mammary tumor virus. The Drosophila homologue of Wnt-1, wingless, is a segment polarity gene that regulates body patterning of the fly embryo. In Xenopus, the Wnt pathway regulates formation of the ventral-dorsal axis. Although Wnt proteins are expressed widely in mammals, the function of the Wnt signaling pathway in normal adult mammalian tissues is not understood. Downstream components of the Wnt pathway, APC (adenomatous polyposis coli) and beta-catenin, clearly are involved in human cancer. There are also several reports that Wnt ligands are highly expressed in tumors. Wnt stabilizes cytoplasmic beta-catenin and activates beta-catenin/Lef-1 (lymphoid enhancer factor), Tcf (T-cell factor)-dependent gene transcription. This regulation of cytosolic beta-catenin is mediated by glycogen synthase kinase-3 (GSK-3) activity but in neither case is the mechanism known. The mechanism by which Wnt inhibits GSK-3 is unknown. Recent studies have shown that some of the intracellular signaling molecules that mediate the Wnt pathway are in complexes, including Dishevelled (Dsh or Dvl), GSK-3beta, and APC protein. However, little is known about how Wnt or other upstream stimuli regulate these complexes to stabilize beta-catenin. We took a variety of approaches to identify new components of the Wnt pathway. Using an expression-cloning technique, we isolated casein kinase I (CKI)epsilon as a positive regulator of beta-catenin in the Wnt pathway. Overexpression of CKIepsilon mimics Wnt by stabilizing beta-catenin, thereby increasing expression of beta-catenin-dependent genes. Inhibition of endogenous CKIepsilon attenuated gene transcription stimulated by Wnt or by Dsh. CKIepsilon forms a complex with Axin and the other downstream components of the Wnt pathway. CKIepsilon is a positive regulator of the Wnt pathway and a possible functional link between upstream signals and the intracellular Axin signaling complex that regulates beta-catenin. In separate experiments, we have identified a Dishevelled-associated kinase (DAK) that binds to Dsh and regulates its functions. Dsh is required for two different pathways, the Wnt pathway and planar polarity pathway in Drosophila. DAK dramatically enhances the function of Dsh in the Wnt pathway and inhibits its function in the planar polarity pathway. This chapter will discuss these newly identified components of the Wnt pathway.

Regulation of cyclooxygenase-2 and periostin by Wnt-3 in mouse mammary epithelial cells.

Wnt family members are critical in developmental processes and have been shown to promote carcinogenesis when ectopically expressed in the mouse mammary gland. The gene expression pattern mediated by Wnt is pivotal for these diverse responses. The Wnt pathway has been conserved among different species. Genetic studies have shown that Wnt effects are mediated, at least in part, by beta-catenin, which regulates transcription of "downstream genes." Wnt stimulation inactivates glycogen-synthase kinase-3beta (GSK-3) with subsequent stabilization of beta-catenin, which after heterodimerizing with lymphocyte enhancer factor-1/T-cell factor cofactors stimulates transcription. To establish whether Wnt-stimulated transcription is mediated solely by beta-catenin, a comparison was made of gene expression profiles in response to Wnt-3, overexpression of beta-catenin, and inhibition of GSK-3. Infection of cells with Wnt-3 and inhibition of GSK-3 regulate a set of genes that include cyclooxygenase-2 and periostin. Interestingly, overexpression of beta-catenin or reducing beta-catenin levels with antisense oligonucleotide transfection did not have any effect on cyclooxygenase-2 or periostin expression, thereby defining a Wnt pathway, which cannot be mimicked by beta-catenin overexpression.

Casein kinase iepsilon in the wnt pathway: regulation of beta-catenin function.

Wnt and its intracellular effector beta-catenin regulate developmental and oncogenic processes. Using expression cloning to identify novel components of the Wnt pathway, we isolated casein kinase Iepsilon (CKIepsilon). CKIepsilon mimicked Wnt in inducing a secondary axis in Xenopus, stabilizing beta-catenin, and stimulating gene transcription in cells. Inhibition of endogenous CKIepsilon by kinase-defective CKIepsilon or CKIepsilon antisense-oligonucleotides attenuated Wnt signaling. CKIepsilon was in a complex with axin and other downstream components of the Wnt pathway, including Dishevelled. CKIepsilon appears to be a positive regulator of the pathway and a link between upstream signals and the complexes that regulate beta-catenin.

Functional domains of axin. Importance of the C terminus as an oligomerization domain.

To understand the mechanism of how Axin acts as an inhibitory molecule in the Wnt pathway, we generated a series of mutated forms of Axin. From the binding experiments, we defined the domains of Axin that bind glycogen synthase kinase-3beta (GSK-3beta) and beta-catenin. We also examined the ability of each Axin mutant to inhibit lymphoid enhancer factor-1 (Lef-1) reporter activity in a cell line expressing high levels of beta-catenin. Axin mutants that did not bind GSK-3beta or beta-catenin were ineffective in suppressing Lef-1 reporter activity. Binding GSK-3beta and beta-catenin was not sufficient for this inhibitory effect of Axin. Axin mutants with C-terminal truncations lacked the ability to inhibit Lef-1 reporter activity, even though they bound GSK-3beta and beta-catenin. The C-terminal region was required for binding to Axin itself. Substitution of the C-terminal region with an unrelated dimerizing molecule, the retinoid X receptor restored its inhibitory effect on Lef-1-dependent transcription. The oligomerization of Axin through its C terminus is important for its function in regulation of beta-catenin-mediated response.