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Endometrial cancers have high rates of phosphoinositide 3-kinase (PI3K) pathway alterations. MK-2206 is an allosteric inhibitor of AKT, an effector kinase of PI3K signals. We hypothesized patients with tumors harboring PIK3CA mutations would be more likely to benefit from MK-2206 than those without PIK3CA mutation. A Phase II study was performed in patients with recurrent endometrial cancer; all histologies except carcinosarcoma were eligible. Up to two prior chemotherapy lines were permitted, excluding prior treatment with PI3K pathway inhibitors. The first 18 patients were treated with MK-2206 200 mg weekly. Due to unacceptable toxicity, dose was reduced to 135 mg. Co-primary endpoints were objective response rate (ORR) and progression-free survival at 6 months (6moPFS). Thirty-seven patients were enrolled (one ineligible). By somatic PIK3CA mutation analysis, nine patients were mutant (MT) [one with partial response (PR)/6moPFS, two with 6moPFS]. Twenty-seven patients were wild-type (WT) (one PR and four 6moPFS). Most common toxicities were rash (44%), fatigue (41%), nausea (42%) and hyperglycemia (31%). Grade 3 and 4 toxicities occurred in 25 and 17% of patients, respectively. Exploratory analysis found serous histology had greater 6moPFS as compared to all other histologies (5/8 vs. 2/28, p = 0.003). PTEN expression was associated with median time to progression (p = 0.04). No other significant associations with PI3K pathway alterations were identified. There is limited single agent activity of MK-2206 in PIK3CA MT and PIK3CA WT endometrial cancer populations. Activity was detected in patients with serous histology and due to their poor outcomes warrants further study (NCT01307631)., (© 2019 UICC.)

Cationic antimicrobial peptides (CAMPs) have been known to act as multi-modal weapons against Gram-negative bacteria. As a new approach to investigate the nature of the interactions between CAMPs and the surfaces of bacteria, native mass spectrometry and two MS/MS strategies (ultraviolet photodissociation (UVPD) and higher energy collisional activation (HCD)) are used to examine formation and disassembly of saccharolipid·peptide complexes. Kdo2-lipid A (KLA) is used as a model saccharolipid to evaluate complexation with a series of cationic peptides (melittin and three analogs). Collisional activation of the KLA·peptide complexes results in the disruption of electrostatic interactions, resulting in apo-sequence ions with shifts in the distribution of ions compared to the fragmentation patterns of the apo-peptides. UVPD of the KLA·peptide complexes results in both apo- and holo-sequence ions of the peptides, the latter in which the KLA remains bound to the truncated peptide fragment despite cleavage of a covalent bond of the peptide backbone. Mapping both the N- and C-terminal holo-product ions gives insight into the peptide motifs (specifically an electropositive KRKR segment and a proline residue) that are responsible for mediating the electrostatic interactions between the cationic peptides and saccharolipid.

Background: Polypharmacy is common in hospitalized older adults. Deprescribing interventions are not well described in the acute-care setting. The objective of this study was to describe a hospital-based, patient-centered deprescribing protocol (Shed-MEDS) and report pilot results., Methods: This was a pilot study set in one academic medical center in the United States. Participants consisted of a convenience sample of 40 Medicare-eligible, hospitalized patients with at least five prescribed medications. A deprescribing protocol (Shed-MEDS) was implemented among 20 intervention and 20 usual care control patients during their hospital stay. The primary outcome was the total number of medications deprescribed from hospital enrollment. Deprescribed was defined as medication termination or dose reduction. Enrollment medications reflected all prehospital medications and active in-hospital medications. Baseline characteristics and outcomes were compared between the intervention and usual care groups using simple logistic or linear regression for categorical and continuous measures, respectively., Results: There was no significant difference between groups in mean age, sex or Charlson comorbidity index. The intervention and control groups had a comparable number of medications at enrollment, 25.2 (±6.3) and 23.4 (±3.8), respectively. The number of prehospital medications in each group was 13.3 (±4.6) and 15.3 (±4.6), respectively. The Shed-MEDS protocol compared with usual care significantly increased the mean number of deprescribed medications at hospital discharge and reduced the total medication burden by 11.6 versus 9.1 ( p = 0.032) medications. The deprescribing intervention was associated with a difference of 4.6 [95% confidence interval (CI) 2.5-6.7, p < 0.001] in deprescribed medications and a 0.5 point reduction (95% CI -0.01 to 1.1) in the drug burden index., Conclusions: A hospital-based, patient-centered deprescribing intervention is feasible and may reduce the medication burden in older adults., Competing Interests: Conflict of interest statement: Dr Kripalani has received stock/stock options from Bioscape Digital, LLC.

Background: More than half of the hospitalized older adults discharged to skilled nursing facilities (SNFs) have more than 3 geriatric syndromes. Pharmacotherapy may be contributing to geriatric syndromes in this population., Objectives: Develop a list of medications associated with geriatric syndromes and describe their prevalence in patients discharged from acute care to SNFs., Design: Literature review and multidisciplinary expert panel discussion, followed by cross-sectional analysis., Setting: Academic medical center in the United States PARTICIPANTS: One hundred fifty-four hospitalized Medicare beneficiaries discharged to SNFs., Measurements: Development of a list of medications that are associated with 6 geriatric syndromes. Prevalence of the medications associated with geriatric syndromes was examined in the hospital discharge sample., Results: A list of 513 medications was developed as potentially contributing to 6 geriatric syndromes: cognitive impairment, delirium, falls, reduced appetite or weight loss, urinary incontinence, and depression. Medications included 18 categories. Antiepileptics were associated with all syndromes, whereas antipsychotics, antidepressants, antiparkinsonism, and opioid agonists were associated with 5 geriatric syndromes. In the prevalence sample, patients were discharged to SNFs with an overall average of 14.0 (±4.7) medications, including an average of 5.9 (±2.2) medications that could contribute to geriatric syndromes, with falls having the most associated medications at discharge at 5.5 (±2.2)., Conclusions: Many commonly prescribed medications are associated with geriatric syndromes. Over 40% of all medications ordered upon discharge to SNFs were associated with geriatric syndromes and could be contributing to the high prevalence of geriatric syndromes experienced by this population. Journal of Hospital Medicine 2016;11:694-700. © 2016 Society of Hospital Medicine., Competing Interests: Each co-author contributed significantly to the manuscript. Dr. Kripalani has received stock/stock options from Bioscape Digital, LLC. None of the other authors have significant conflicts of interest to report related to this project or the results reported within this manuscript., (© 2016 Society of Hospital Medicine.)

Objective: Rapamycin analogs have reproducible but modest efficacy in endometrial cancer (EC). Identification of molecular biomarkers that predict benefit could guide clinical development., Methods: Fixed primary tissue and whole blood were collected prospectively from patients enrolled on GOG 248. DNA was isolated from macro-dissected tumors and blood; next-generation sequence analysis was performed on a panel of cancer related genes. Associations between clinical outcomes [response rate (RR) 20%; progression-free survival (PFS) median 4.9months] and mutations (PTEN, PIK3CA, PIK3R1, KRAS, CTNNB1, AKT1, TSC1, TSC2, NF1, FBXW7) were explored., Results: Sequencing data was obtained from tumors of 55 of the 73 enrolled pts. Mutation rates were consistent with published reports: mutations in PTEN (45%), PIK3CA (29%), PIK3R1 (24%), K-RAS (16%), CTNNB1 (18%) were common and mutations in AKT1 (4%), TSC1 (2%), TSC2 (2%), NF1 (9%) and FBXW7 (4%) were less common. Increased PFS (HR 0.16; 95% CI 0.01-0.78) and RR (response difference 0.83; 95% CI 0.03-0.99) were noted for AKT1 mutation. An increase in PFS (HR 0.46; 95% CI 0.20-0.97) but not RR (response difference 0.00, 95% CI -0.34-0.34) was identified for CTNNB1 mutation. Both patients with TSC mutations had an objective response. There were no statistically significant associations between mutations in PIK3CA, PTEN, PIK3R1, or KRAS and PFS or RR., Conclusions: Mutations in AKT1, TSC1 and TSC2 are rare, but may predict clinical benefit from temsirolimus. CTNNB1 mutations were associated with longer PFS on temsirolimus., (Copyright © 2016. Published by Elsevier Inc.)

Endometrial cancer incidence is increasing, due in part to a strong association with obesity. Mutations in the phosphatidylinositol 3-kinase (PI3K) pathway, the central relay pathway of insulin signals, occur in the majority of endometrioid adenocarcinomas, the most common form of endometrial cancer. We sought to determine the impact of PI3K pathway alterations on progression free survival in a cohort of endometrioid endometrial cancers. Prognostic utility of PIK3CA, PIK3R1, and PTEN mutations, as well as PTEN protein loss by immunohistochemistry, was explored in the context of patient body mass index. Reverse-phase protein arrays were utilized to assess protein expression based on PTEN status. Among 187 endometrioid endometrial cancers, there were no statistically significant associations between PFS and PIK3CA, PIK3R1, PTEN mutation or loss. When stratified by body mass index, PTEN loss was associated with improved progression free survival (P < 0.006) in obese (body mass index ≥ 30) patients. PTEN loss resulted in distinct protein changes: Canonical PI3K pathway activation was observed only in the non-obese population while decreased expression of β-CATENIN and phosphorylated FOXO3A was observed in obese patients. These data suggest the impact of PTEN loss on tumor biology and clinical outcomes must be interpreted in the context of body mass index, and provide a potential explanation for discrepant reports on the effect of PTEN status and obesity on prognosis in endometrial cancer. This reveals a clinically important interaction between metabolic state and tumor genetics that may unveil the biologic underpinning of obesity-related cancers and impact ongoing clinical trials with PI3K pathway inhibitors., (Copyright © 2015 Federation of European Biochemical Societies. Published by Elsevier B.V. All rights reserved.)

Urbanisation of the coastal zone represents a key threat to marine biodiversity, including rocky reef communities which often possess disproportionate ecological, recreational and commercial importance. The nature and magnitude of local urban impacts on reef biodiversity near three Australian capital cities were quantified using visual census methods. The most impacted reefs in urbanised embayments were consistently characterised by smaller, faster growing species, reduced fish biomass and richness, and reduced mobile invertebrate abundance and richness. Reef faunal distribution varied significantly with heavy metals, local population density, and proximity to city ports, while native fish and invertebrate communities were most depauperate in locations where invasive species were abundant. Our study adds impetus for improved urban planning and pollution management practises, while also highlighting the potential for skilled volunteers to improve the tracking of changes in marine biodiversity values and the effectiveness of management intervention., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

The likelihood of a drug reaction with lamotrigine is increased by dose escalation that is too rapid or drug interactions that increase the concentration of lamotrigine. There is a well-documented interaction between valproic acid and lamotrigine in which lamotrigine levels are increased, subsequently increasing the risk of a drug reaction with eosinophilia and systemic symptoms (DRESS) syndrome. This syndrome is characterized by fever, lymphadenopathy, diffuse maculopapular rash, multivisceral involvement, eosinophilia, and atypical lymphocytes and has a mortality rate of 10-40%. We describe the first case, to our knowledge, of DRESS syndrome that was probably induced by a drug interaction between lamotrigine and ginseng. A 44-year-old white man presented to the emergency department after experiencing a possible seizure. His medical history included two other lifetime events concerning for seizures at ages 14 and 29 years old. After referral to the neurology clinic, he was diagnosed with generalized tonic-clonic seizure disorder, and lamotrigine was started with up-titration according to the drug's package insert to a goal dosage of 150 mg twice/day. The patient had also been taking deer antler velvet and ginseng that he continued during his lamotrigine therapy. On day 43 of therapy, the patient presented to the emergency department with a pruritic rash that had started on his extremities and spread to his torso. He was thought to have experienced a drug reaction to lamotrigine, and the drug was discontinued. Thirteen days later, the patient was admitted from the acute care clinic for inpatient observation due to laboratory abnormalities in the setting of continued rash, headache, and myalgias. His admission laboratory results on that day were remarkable for leukocytosis, with a white blood cell count up to 17.6 × 10(3) /mm(3) , with a prominent eosinophilia of 3.04 × 10(3) /mm(3) ; his liver enzyme levels were also elevated, with an aspartate aminotransferase level of 191 U/L, alanine aminotransferase level 473 U/L, alkaline phosphatase level 465 U/L, and total bilirubin level 1.4 mg/dl. Use of the Drug Interaction Probability Scale indicated that a drug interaction between lamotrigine and ginseng was the probable cause (score of 5). The proposed mechanism of the interaction is ginseng inhibition of the uridine diphosphate glucuronosyltransferase 2B7 enzyme, similar to the mechanism of the interaction with valproic acid. Clinicians should be aware of this probable drug interaction and avoid coadministration of ginseng and lamotrigine or use a more conservative dose titration of lamotrigine for patients who are also taking ginseng., (© 2015 Pharmacotherapy Publications, Inc.)

Objective: To examine the association of patient- and medication-related factors with postdischarge medication errors., Patients and Methods: The Vanderbilt Inpatient Cohort Study includes adults hospitalized with acute coronary syndromes and/or acute decompensated heart failure. We measured health literacy, subjective numeracy, marital status, cognition, social support, educational attainment, income, depression, global health status, and medication adherence in patients enrolled from October 1, 2011, through August 31, 2012. We used binomial logistic regression to determine predictors of discordance between the discharge medication list and the patient-reported list during postdischarge medication review., Results: Among 471 patients (mean age, 59 years), the mean total number of medications reported was 12, and 79 patients (16.8%) had inadequate or marginal health literacy. A total of 242 patients (51.4%) were taking 1 or more discordant medication (ie, appeared on either the discharge list or patient-reported list but not both), 129 (27.4%) failed to report a medication on their discharge list, and 168 (35.7%) reported a medication not on their discharge list. In addition, 279 participants (59.2%) had a misunderstanding in indication, dose, or frequency in a cardiac medication. In multivariable analyses, higher subjective numeracy (odds ratio [OR], 0.81; 95% CI, 0.67-0.98) was associated with lower odds of having discordant medications. For cardiac medications, participants with higher health literacy (OR, 0.84; 95% CI, 0.74-0.95), with higher subjective numeracy (OR, 0.77; 95% CI, 0.63-0.95), and who were female (OR, 0.60; 95% CI, 0.46-0.78) had lower odds of misunderstandings in indication, dose, or frequency., Conclusion: Medication errors are present in approximately half of patients after hospital discharge and are more common among patients with lower numeracy or health literacy., (Copyright © 2014 Mayo Foundation for Medical Education and Research. Published by Elsevier Inc. All rights reserved.)

Signals from the tumor suppressors PTEN and LKB1 converge on mTOR to negatively regulate its function in cancer cells. Notably, both of these suppressors are attenuated in a significant fraction of human endometrial tumors. In this study, we generated a genetic mouse model of endometrial cancer driven by concomitant loss of these suppressors to gain pathophysiological insight into this disease. Dual loss of Pten and Lkb1 in the endometrial epithelium led to rapid development of advanced endometrioid endometrial tumors with 100% penetrance and short host survival. The tumors displayed dysregulated phosphatidylinositol 3-kinase (PI3K)/Akt and Lkb1/Ampk signaling with hyperactivation of mTOR signaling. Treatment with a dual PI3K/mTOR inhibitor, BEZ235, extended the time before tumor onset and prolonged overall survival. The PI3K inhibitor GDC-0941 used as a single agent reduced the growth rate of primary tumor implants in Pten/Lkb1-deficient mice, and the mTOR inhibitor RAD001 was unexpectedly as effective as BEZ235 in triggering tumor regression. In parallel, we also found that ectopic expression of LKB1 in PTEN/LKB1-deficient human endometrial cancer cells increased their sensitivity to PI3K inhibition. Together, our results demonstrated that Pten/Lkb1-deficient endometrial tumors rely strongly on deregulated mTOR signaling, and they provided evidence that LKB1 status may modulate the response of PTEN-deficient tumors to PI3K or mTOR inhibitors.

Unlabelled: The phosphoinositide 3-kinase (PI3K) pathway is one of the most frequently mutated pathways in cancer, and is actively being pursued as a therapeutic target. Despite the importance of the PI3K pathway in cancer, durable responses to PI3K pathway-targeted therapies are uncommon with monotherapy. Several in vitro and xenograft models have elucidated compensatory signaling and genomic changes which may limit the therapeutic effectiveness of PI3K inhibitors in the clinic. Future clinical trials with prospective evaluation of tumor signaling and genomic changes are likely to identify novel resistance mechanisms as well as subsets of patients who may derive maximal benefit from PI3K pathway inhibitors., Significance: There are multiple ongoing clinical trials targeting the PI3K pathway members in several malignancies. This review summarizes the known mechanisms of resistance to targeting the PI3K pathway. Understanding of resistance mechanisms will help to inform more rational clinical trial design to optimize the clinical impact of targeting the PI3K pathway in cancer., (©2013 AACR.)

Background: Cervical cancer is the second leading cause of cancer deaths among women worldwide. The objective of this study was to describe the most common oncogenic mutations in cervical cancers and to explore genomic differences between the 2 most common histologic subtypes: adenocarcinoma and squamous cell carcinoma., Methods: A high-throughput genotyping platform, termed Oncomap, was used to interrogate 80 cervical tumors for 1250 known mutations in 139 cancer genes. Samples were analyzed using a mass spectrometry-based genotyping platform and were validated using orthogonal chemistry. Epidermal growth factor receptor (EGFR) mutations were further validated by massive parallel sequencing. Human papilloma virus (HPV) genotyping also was performed., Results: Validated mutations were detected in 48 of 80 tumors (60%) examined. The highest mutation rates were in the genes phosphatidylinositol 3-kinase, catalytic subunit α (PIK3CA) (31.3%); Kirsten rat sarcoma viral oncogene homolog (KRAS) (8.8%); and EGFR (3.8%). PIK3CA mutation rates did not differ significantly between adenocarcinomas and squamous cell carcinomas (25% vs 37.5%, respectively; P = .33). In contrast, KRAS mutations were identified only in adenocarcinomas (17.5% vs 0%; P = .01), and a novel EGFR mutation was detected only in squamous cell carcinomas (0% vs 7.5%; P = .24). There were no associations between HPV-16 or HPV-18 and somatic mutations or overall survival. In adjusted analyses, PIK3CA mutations were associated with shorter survival (67.1 months vs 90.3 months; hazard ratio, 9.1; 95% confidence interval, 2.8-29.5 months; P < .001)., Conclusions: Cervical cancers harbor high rates of potentially targetable oncogenic mutations. In addition, cervical squamous cell carcinoma and adenocarcinoma have distinct molecular profiles, suggesting that clinical outcomes may be improved with the use of more tailored treatment strategies, including PI3K and MEK inhibitors., (© 2013 American Cancer Society.)

Introduction: Epithelial ovarian cancer (EOC) is the second most common gynecologic malignancy and the leading cause of death from gynecologic cancer in the USA. EOC is an exquisitely chemo-sensitive disease with response rates of over 75% in the upfront setting. Despite this, due to high rates of recurrence and development of chemo-resistance, the overall survival of EOC remains about 25%. Thus, there is a great need for new therapeutic approaches to render more durable responses. Based on preclinical and early phase clinical studies, key targeted pathways include targets that drive angiogenesis and chemo-resistance. Receptor tyrosine kinases and non-receptor tyrosine kinases play important roles in these processes and several small molecule tyrosine kinase inhibitors (TKIs) are in clinical development., Areas Covered: This review summarizes clinical rationale, mechanisms of action and clinical data for the TKIs under evaluation in the Phase III setting for EOC., Expert Opinion: Despite reasonable preclinical activity, small molecule TKIs are unlikely to improve patient survival as single agent therapies in an unselected EOC population. Incorporation of tissue evaluation during ongoing clinical trials is required to identify molecularly defined groups that respond to single agents and direct rational combination strategies based on mechanisms of resistance to improve outcomes in EOC.

Endometrial cancer is the most common gynecologic malignancy in the developed world and affects approximately 40,000 women in the United States each year. The phosphoinositide 3-kinase (PI3K) signaling pathway regulates key aspects of cancer biology including glucose uptake and metabolism, cellular growth, and survival. Endometrial cancers harbor the highest rates of PI3K pathway alterations reported to date. The PI3K pathway is highly druggable and several classes of agents are in clinical development including rapalogs, pan-PI3K inhibitors, PI3K isoform-specific inhibitors, dual PI3K/mTOR catalytic inhibitors, mTOR-specific catalytic inhibitors, and AKT inhibitors. It has been 10 years since the initiation of the first studies of rapalogs as anticancer agents. There are more than 20 registered clinical trials of PI3K/mTOR inhibitors as single agents or in therapeutic combinations for the treatment of endometrial cancers. What have we learned from the completed studies? What can we expect to learn from ongoing studies? What should we anticipate moving forward? Clin Cancer Res; 19(19); 5264-74. ©2013 AACR.

Prevention and early detection remain essential to decreasing cancer mortality. Screening DNA in Pap smears has the potential to increase the rate of early detection of endometrial and ovarian cancers. In this issue of Science Translational Medicine, Kinde and colleagues use advanced sequencing technology to evaluate DNA to screen for gynecologic malignancies.

We demonstrate that phosphatidylinositol 3-kinase (PI3K) pathway aberrations occur in >80% of endometrioid endometrial cancers, with coordinate mutations of multiple PI3K pathway members being more common than predicted by chance. PIK3R1 (p85α) mutations occur at a higher rate in endometrial cancer than in any other tumor lineage, and PIK3R2 (p85β), not previously demonstrated to be a cancer gene, is also frequently mutated. The dominant activation event in the PI3K pathway appears to be PTEN protein loss. However, in tumors with retained PTEN protein, PI3K pathway mutations phenocopy PTEN loss, resulting in pathway activation. KRAS mutations are common in endometrioid tumors activating independent events from PI3K pathway aberrations. Multiple PIK3R1 and PIK3R2 mutations demonstrate gain of function, including disruption of a novel mechanism of pathway regulation wherein p85α dimers bind and stabilize PTEN. Taken together, the PI3K pathway represents a critical driver of endometrial cancer pathogenesis and a novel therapeutic target.

In this issue of Science Translational Medicine, Wallin et al. have identified a subset of breast and ovarian cancer cell lines that show synergistic response to the combination of doxorubicin and GDC-0941, a class IA phosphatidylinositol 3-kinase (PI3K) inhibitor. Here, we discuss the potential implications of these data on the clinical development of PI3K pathway inhibitors as cancer therapeutics.

There is high morbidity associated with local recurrence of rectal cancer. However, the adjuvant therapies given to prevent such recurrences also have significant side effects and associated risks. The ability to select patients with the highest risk of recurrence and greatest therapeutic response will improve rectal cancer care.

Background: Knowledge of geography is integral to the study of insect-borne infectious disease such as malaria. This study was designed to evaluate whether geographic parameters are associated with malarial infection in the East Sepik province of Papua New Guinea (PNG), a remote area where malaria is a major cause of morbidity and mortality., Methods: A global positioning system (GPS) unit was used at each village to collect elevation, latitude and longitude data. Concurrently, a sketch map of each village was generated and the villages were sub-divided into regions of roughly equal populations. Blood samples were taken from subjects in each region using filter paper collection. The samples were later processed using nested PCR for qualitative determination of malarial infection. The area was mapped using the GPS-information and overlaid with prevalence data. Data tables were examined using traditional chi square statistical techniques. A logistic regression analysis was then used to determine the significance of geographic risk factors including, elevation, distance from administrative centre and village of residence., Results: Three hundred and thirty-two samples were included (24% of the total estimated population). Ninety-six were positive, yielding a prevalence of 29%. Chi square testing within each village found a non-random distribution of cases across sub-regions (p < 0.05). Multivariate logistic regression techniques suggested malarial infection changed with elevation (OR = 0.64 per 10 m, p < 0.05) and distance from administrative centre (OR = 1.3 per 100 m, p < 0.05)., Conclusion: These results suggest that malarial infection is significantly and independently associated with lower elevation and greater distance from administrative centre in a rural area in PNG. This type of analysis can provide information that may be used to target specific areas in developing countries for malaria prevention and treatment.

In Xenopus, Wnt signals and their transcriptional effector beta-catenin are required for the development of dorsal axial structures. In zebrafish, previous loss-of-function studies have not identified an essential role for beta-catenin in dorsal axis formation, but the maternal-effect mutation ichabod disrupts beta-catenin accumulation in dorsal nuclei and leads to a reduction of dorsoanterior derivatives. We have identified and characterized a second zebrafish beta-catenin gene, beta-catenin-2, located on a different linkage group from the previously studied beta-catenin-1, but situated close to the ichabod mutation on LG19. Although the ichabod mutation does not functionally alter the beta-catenin-2 reading frame, the level of maternal beta-catenin-2, but not beta-catenin-1, transcript is substantially lower in ichabod, compared with wild-type, embryos. Reduction of beta-catenin-2 function in wild-type embryos by injection of morpholino antisense oligonucleotides (MOs) specific for this gene (MO2) results in the same ventralized phenotypes as seen in ichabod embryos, and administration of MO2 to ichabod embryos increases the extent of ventralization. MOs directed against beta-catenin-1 (MO1), by contrast, had no ventralizing effect on wild-type embryos. beta-catenin-2 is thus specifically required for organizer formation and this function is apparently required maternally, because the ichabod mutation causes a reduction in maternal transcription of the gene and a reduced level of beta-catenin-2 protein in the early embryo. A redundant role of beta-catenins in suppressing formation of neurectoderm is revealed when both beta-catenin genes are inhibited. Using a combination of MO1 and MO2 in wild-type embryos, or by injecting solely MO1 in ichabod embryos, we obtain expression of a wide spectrum of neural markers in apparently appropriate anteroposterior pattern. We propose that the early, dorsal-promoting function of beta-catenin-2 is essential to counteract a later, dorsal- and neurectoderm-repressing function that is shared by both beta-catenin genes.

Receptor tyrosine kinase (RTK) signals regulate the specification of a varied array of tissue types by utilizing distinct modules of proteins to elicit diverse effects. The RSK proteins are part of the RTK signal transduction pathway and are thought to relay these signals by acting downstream of extracellular signal-regulated kinase (ERK). In this study we report the identification of ribosomal S6 kinase 4 (Rsk4) as an inhibitor of RTK signals. Among the RSK proteins, RTK inhibition is specific to RSK4 and, in accordance, is dependent upon a region of the RSK4 protein that is divergent from other RSK family members. We demonstrate that Rsk4 inhibits the transcriptional activation of specific targets of RTK signaling as well as the activation of ERK. Developmentally, Rsk4 is expressed in extraembryonic tissue, where RTK signals are known to have critical roles. Further examination of Rsk4 expression in the extraembryonic tissues demonstrates that its expression is inversely correlated with the presence of activated ERK 1/2. These studies demonstrate a new and divergent function for RSK4 and support a role for RSK proteins in the specification of RTK signals during early mouse development.