Epiretinal membrane in uveitis: Rate, visual prognosis, complications and surgical outcomes.

BACKGROUND: Epiretinal membrane (ERM) is a common finding in patients with uveitis that contributes to visual impairment. We describe the long-term visual acuity (VA) and morphometric progression in patients with uveitis and epiretinal membrane (ERM). METHODS: Retrospective cohort study of patients with uveitic ERM from a tertiary centre database. Multivariate analysis of risk factors for ERM progression was calculated using a marginal Cox regression model to estimate hazard ratios (HR). RESULTS: Two hundred and sixteen eyes (4%) of a total 5450 eyes with uveitis were identified to have an ERM. The most common diagnosis was idiopathic uveitis in 45 patients (28.7%), followed by sarcoidosis in 21 (13.4%), HLAB27-related uveitis in 15 (9.6%) and toxoplasmosis in 15 (9.6%). Risk factors for ERM development include age (HR 1.03), intermediate uveitis (HR 2.33), posterior uveitis (HR 1.53) and ERM fellow eye (HR 18.28). Anterior uveitis (HR 0.53) and alternating disease (HR 0.53) were protective. Median VA was 20/40 at diagnosis of ERM and 20/40 at final follow up. Progression of ERM grade occurred in 17 eyes (7.9%) during the study period. ERM peel was performed in 44 eyes (20.4%). Median VA was 20/60 and 20/40 at baseline and 12 months after surgery, respectively. Improvement in visual acuity occurred in 23 eyes (60.5%) following surgery. CONCLUSIONS: In addition to intermediate and posterior uveitis, fellow eye involvement is a strong risk factor for ERM development. In treated uveitis, the majority maintain their long-term vision and rates of ERM progression are low.

Differential regulation of the anti-crossover and replication fork regression activities of Mph1 by Mte1.

We identified Mte1 (Mph1-associated telomere maintenance protein 1) as a multifunctional regulator of Saccharomyces cerevisiae Mph1, a member of the FANCM family of DNA motor proteins important for DNA replication fork repair and crossover suppression during homologous recombination. We show that Mte1 interacts with Mph1 and DNA species that resemble a DNA replication fork and the D loop formed during recombination. Biochemically, Mte1 stimulates Mph1-mediated DNA replication fork regression and branch migration in a model substrate. Consistent with this activity, genetic analysis reveals that Mte1 functions with Mph1 and the associated MHF complex in replication fork repair. Surprisingly, Mte1 antagonizes the D-loop-dissociative activity of Mph1-MHF and exerts a procrossover role in mitotic recombination. We further show that the influence of Mte1 on Mph1 activities requires its binding to Mph1 and DNA. Thus, Mte1 differentially regulates Mph1 activities to achieve distinct outcomes in recombination and replication fork repair.

BRCA1-BARD1 promotes RAD51-mediated homologous DNA pairing.

The tumour suppressor complex BRCA1-BARD1 functions in the repair of DNA double-stranded breaks by homologous recombination. During this process, BRCA1-BARD1 facilitates the nucleolytic resection of DNA ends to generate a single-stranded template for the recruitment of another tumour suppressor complex, BRCA2-PALB2, and the recombinase RAD51. Here, by examining purified wild-type and mutant BRCA1-BARD1, we show that both BRCA1 and BARD1 bind DNA and interact with RAD51, and that BRCA1-BARD1 enhances the recombinase activity of RAD51. Mechanistically, BRCA1-BARD1 promotes the assembly of the synaptic complex, an essential intermediate in RAD51-mediated DNA joint formation. We provide evidence that BRCA1 and BARD1 are indispensable for RAD51 stimulation. Notably, BRCA1-BARD1 mutants with weakened RAD51 interactions show compromised DNA joint formation and impaired mediation of homologous recombination and DNA repair in cells. Our results identify a late role of BRCA1-BARD1 in homologous recombination, an attribute of the tumour suppressor complex that could be targeted in cancer therapy.

Promotion of BRCA2-Dependent Homologous Recombination by DSS1 via RPA Targeting and DNA Mimicry.

The tumor suppressor BRCA2 is thought to facilitate the handoff of ssDNA from replication protein A (RPA) to the RAD51 recombinase during DNA break and replication fork repair by homologous recombination. However, we find that RPA-RAD51 exchange requires the BRCA2 partner DSS1. Biochemical, structural, and in vivo analyses reveal that DSS1 allows the BRCA2-DSS1 complex to physically and functionally interact with RPA. Mechanistically, DSS1 acts as a DNA mimic to attenuate the affinity of RPA for ssDNA. A mutation in the solvent-exposed acidic domain of DSS1 compromises the efficacy of RPA-RAD51 exchange. Thus, by targeting RPA and mimicking DNA, DSS1 functions with BRCA2 in a two-component homologous recombination mediator complex in genome maintenance and tumor suppression. Our findings may provide a paradigm for understanding the roles of DSS1 in other biological processes.

Loss of Brca1 and Trp53 in adult mouse mammary ductal epithelium results in development of hormone receptor-positive or hormone receptor-negative tumors, depending on inactivation of Rb family proteins.

BACKGROUND: Breast cancer is a heterogenous disease with several histological and molecular subtypes. Models that represent these subtypes are essential for translational research aimed at improving clinical strategy for targeted therapeutics. METHODS: Different combinations of genetic aberrations (Brca1 and Trp53 loss, and inhibition of proteins of the Rb family) were induced in the mammary gland by injection of adenovirus expressing Cre recombinase into the mammary ducts of adult genetically engineered mice. Mammary tumors with different genetic aberrations were classified into molecular subtypes based on expression of molecular markers and RNAseq analysis. In vitro potency assays and Western blots were used to examine their drug sensitivities. RESULTS: Induction of Brca1 and Trp53 loss in mammary ductal epithelium resulted in development of basal-like hormone receptor (HR)-negative mammary tumors. Inhibition of Rb and Trp53 loss or the combination of Rb, Trp53 and Brca1 aberrations resulted in development of luminal ductal carcinoma positive for ER, PR, and Her2 expression. HR positivity in tumors with Rb, Trp53 and Brca1 aberrations indicated that functionality of the Rb pathway rather than Brca1 status affected HR status in these models. Mammary tumor gene expression profiles recapitulated human basal-like or luminal B breast cancer signatures, but HR-positive luminal cancer models were endocrine resistant and exhibited upregulation of PI3K signaling and sensitivity to this pathway inhibition. Furthermore, both tumor subtypes were resistant to CDK4/6 inhibition. CONCLUSIONS: Examination of molecular expression profiles and drug sensitivities of tumors indicate that these breast cancer models can be utilized as a translational platform for evaluation of targeted combinations to improve chemotherapeutic response in patients that no longer respond to hormone therapy or that are resistant to CDK4/6 inhibition.

Association of germline rare pathogenic mutations in guideline-recommended genes with prostate cancer progression: A meta-analysis.

BACKGROUND: Germline mutations in several genes, mainly DNA repair genes, have been associated with prostate cancer (PCa) progression. However, primarily due to the rarity of mutations, statistical evidence for these associations is not consistently established. The objective of this study is to synthesize evidence from multiple studies using a meta-analysis. METHODS: Genes analyzed were chosen based on National Comprehensive Cancer Network guidelines recommendations (10 genes) and a commonly reported gene (NBN). PCa progression in this analysis was defined as either having metastases or PCa-specific mortality. We searched PubMed for papers published before April 26, 2021, using selected keywords. Pooled odds ratio (OR) was estimated in all races and Caucasians-only using both fixed- and random-effect models. RESULTS: The search identified 1028 papers and an additional five from a manual review of references. After a manual process that excluded noneligible studies, 11 papers remained, including a total of 3944 progressors and 20,054 nonprogressors. Combining results from these eligible studies, mutation carrier rates were significantly higher in progressors than nonprogressors for NBN, BRCA2, ATM (under both fixed- and random-effect models), for CHEK2 (under fixed-effect model only), and for PALB2 (under random-effect model only), p < 0.05. Pooled OR (95% confidence interval) was 6.38 (2.25-18.05), 3.41 (2.31; 5.03), 1.93 (1.17-3.20), and 1.53 (1.00-2.33) for NBN, BRCA2, ATM, and CHEK2, respectively, under fixed-effect model and 2.63 (1.12-6.13) for PALB2 under random-effect model. No significant association was found for the six remaining genes. Certainty of evidence was low for many genes due primarily to the limited number of eligible studies and mutation carriers. CONCLUSIONS: Statistical evidence for five genes was obtained in this first meta-analysis of germline mutations and PCa progression. While these results may help urologists and genetic counselors interpret germline testing results for PCa progression, more original studies are needed.

Observed evidence for guideline-recommended genes in predicting prostate cancer risk from a large population-based cohort.

BACKGROUND: Germline testing for prostate cancer (PCa) is now recommended by the National Comprehensive Cancer Network. While multi-gene testing has been proposed, evidence for their association with PCa risk is not well established. METHODS: We tested associations of pathogenic/likely pathogenic mutations in 10 guideline-recommended genes (ATM, BRCA1, BRCA2, CHEK2, PALB2, MLH1, MSH2, MSH6, PMS2, and HOXB13) with PCa risk in the UK Biobank, a population-based cohort. Mutations were annotated based on prostate-specific transcripts using the American College of Medical Genetics and Genomics standards. Associations were tested in 4399 PCa cases and 85,403 unaffected male controls using logistic regression adjusting for age and genetic background. p < .005 was considered significant based on Bonferroni correction. RESULTS: Among the 10 tested genes, significantly higher mutation carrier rates in PCa cases versus controls were found for four genes at p < .005; HOXB13, BRCA2, ATM, and CHEK2, with odds ratios (95% confidence interval) estimated at 4.96 (3.62-6.69), 3.23 (2.23-4.56), 2.95 (2.01-4.22), 1.94 (1.43-2.58), respectively. No significant association was found between mutation carrier status and age at PCa diagnosis or family history of PCa. Despite the large sample size of this study, statistical power remains limited, especially for genes where pathogenic mutation carrier rates are extremely rare (<0.03%). CONCLUSION: Observed evidence for PCa risk was found for four of the 10 guideline-recommended genes in this large population-based study. Mutations in these four genes can be interpreted with confidence in genetic counseling for PCa risk assessment. Evidence for the remaining six genes needs to be further evaluated in larger studies.

Sociality and migration predict hybridization across birds.

Hybridization represents a natural experiment that can provide insight into processes of speciation and diversification. Though considerable research has focused on hybrid zone dynamics, macroevolutionary investigations of the factors that influence hybridization are few. Here, we compile a database of avian hybrids and perform comparative analyses to determine whether several social and life-history variables influence broad patterns of hybridization. We perform three main analyses: phylogenetic logistic regression to examine variables that are associated with the presence of hybridization, phylogenetic Poisson regression of only those species exhibiting hybridization to determine which variables are associated with the extent of hybridization, and a phylogenetic logistic regression on a subset of data to assess potential pseudoreplication. After testing several social and life-history variables, we found that social bond duration is associated with the presence and extent of hybridization. Specifically, lengthy social bonds are negatively associated with the presence and extent of hybridization. In addition to social bond length, migration is positively linked with a greater likelihood of hybridization. The broad-scale correlations between species-specific traits and hybridization across diverse avian lineages suggest commonalities in the fine-scale processes involved in mating with heterospecifics, which in turn has implications for how we think about, study and understand hybridization processes and their influence on evolutionary trajectories.

Case Report: Successful Corneal Crosslinking in a Patient with Corneal Ectasia Associated with Stevens-Johnson Syndrome.

SIGNIFICANCE: Corneal ectasia can be a complication of Stevens-Johnson syndrome. When detected in a timely manner, corneal crosslinking can be a safe treatment. This is an important association to highlight that early diagnosis and treatment can prevent the need for invasive surgical procedures such as keratoplasty. PURPOSE: This study aimed to report a successful accelerated epithelium-off corneal crosslinking in a rare case of corneal ectasia secondary to Stevens-Johnson syndrome. CASE REPORT: A 25-year-old Indian man presented with a progressive visual acuity decline 5 years after an acute episode of Stevens-Johnson syndrome secondary to penicillin ingestion. Serial tomography scans confirmed the diagnosis of corneal ectasia. After the preparation of the ocular surface, which was deemed to have a mild degree of limbal stem cell deficiency, with frequent preservative-free lubrication and steroid use, accelerated epithelium-off crosslinking was performed with 4 minutes of continuous ultraviolet-A exposure at 30 mW/cm2 and a total energy dose of 7.2 J/cm2. Complete re-epithelialization was observed at 72 hours after crosslinking with no complications. Corneal tomography 15 months after treatment showed stabilization of ectasia, with improvement in visual acuity. CONCLUSIONS: Corneal ectasia is a rare but important complication of Stevens-Johnson syndrome. Accelerated epithelium-off crosslinking treatment can be considered in patients with a compromised ocular surface after Stevens-Johnson syndrome. Pre-operative optimization of the ocular surface and vigilant monitoring in the early post-operative period are recommended for the prevention of complications.

A Transplantable Syngeneic Allograft Mouse Model for Nongestational Choriocarcinoma of the Ovary.

Nongestational choriocarcinoma is a rare malignancy in humans with poor prognosis. Naturally occurring choriocarcinoma is also rare in laboratory mice, and no genetic mouse model accurately recapitulates the features of this cancer. Here we report development of a genetically engineered mouse (GEM) model with alterations in Brca2, Trp53, and RB that develops ovarian tumors. Most of the ovarian tumors displayed histological characteristics of nongestational choriocarcinoma of the ovary (NGCO) (47%) with abundant syncytiotrophoblasts and cytotrophoblasts, positive immunolabeling for human chorionic gonadotropin, and positive periodic acid-Schiff reaction. The rest of the ovarian tumors were serous epithelial ovarian carcinoma (SEOC) (26%) or mixed tumors consisting of NGCO and SEOC (26%). We further established syngeneic orthotopic mouse models for NGCO by in vivo passaging of GEM tumors. These metastatic models provide a platform for evaluating new treatment strategies in preclinical studies aimed at improving outcomes in choriocarcinoma patients.

Visual and ocular morbidity in severe open-globe injuries presenting to a regional eye centre in New Zealand.

IMPORTANCE: Open-globe injuries (OGI) are a leading cause of monocular blindness world-wide with considerable cost to the individual and society. BACKGROUND: To characterize the epidemiology, severity and outcomes of OGI treated at a major ophthalmology centre in New Zealand. DESIGN: Retrospective study. PARTICIPANTS: A total of 385 eyes of 381 patients over a 10-year period. METHODS: Eligible patients were identified using diagnosis and surgery codes on hospital discharge summaries. Clinical notes were reviewed to determine patient demographics, injury details, treatments and outcomes. MAIN OUTCOME MEASURES: Complications of injury, visual acuity at 3 months and final follow-up, and final status of the eye. RESULTS: The estimated annual incidence of OGI was 2.8 per 100 000. Working-age males predominated but age at injury ranged from 9 months to 90 years. Maori and Pacific peoples were over-represented. Injuries were severe with 58.7% presenting with vision of hand movements or worse. Penetrating injuries (56.4%) were most common, followed by globe ruptures (35.6%). Major complications included retinal detachment (15.8%), enucleation/evisceration (9.1%), phthisis bulbi (9.9%), endophthalmitis (2.6%) and sympathetic ophthalmia (0.26%). Despite the injury severity, 46% of eyes achieved final BCVA of ≥6/12. The Ocular Trauma Score (OTS) was a useful prognostic tool for stratifying severity of injury and predicting visual outcome (Fisher's exact test P < 0.001). CONCLUSIONS AND RELEVANCE: The incidence and severity of OGI in NZ are comparable to global statistics. Surgical repair can effectively recover vision, predicted well by the OTS. We identified at-risk groups to target with education and prevention strategies.

Repeat corneal transplantation in Auckland, New Zealand: Indications, visual outcomes and risk factors for repeat keratoplasty failure.

IMPORTANCE: In New Zealand, repeat keratoplasty has become the second leading indication for corneal transplantation. BACKGROUND: To report the indications, outcomes and survival of repeat keratoplasty and evaluate the risk factors for graft failure. DESIGN: Retrospective study in a public corneal service. PARTICIPANTS: Two hundred nineteen patients undergoing 279 repeat keratoplasty procedures during 1991-2017. METHODS: The New Zealand National Eye Bank prospectively collects data on all corneal transplants. This was utilized to identify patients undergoing repeat keratoplasty in Auckland. Clinical records were retrospectively reviewed. MAIN OUTCOME MEASURES: Graft survival and visual outcome. RESULTS: The repeat keratoplasty technique was penetrating keratoplasty (PK) in 242 cases (86.7%) and endothelial keratoplasty in 37 (13.3%). The most common primary indication was keratoconus (46.6%). The most common indication for repeat keratoplasty was endothelial decompensation (37.6%). For PK performed as a repeat keratoplasty, the median survival in years was 12.0 for first, 3.5 for second and 2.3 for third repeat keratoplasty. Keratoconus had the longest graft survival (median 13.0 years). In surviving grafts, median visual acuity was 6/15 at 1 year and 6/12 at 2 years. On multivariate analysis, regraft number (P = .022), non-European ethnicity (P = .007), concurrent surgical procedure (P < .0005), lower donor endothelial density (P = .028), previous glaucoma surgery (P < .0005), postoperative raised intraocular pressure (P = .001) and graft rejection (P = .032) were associated with keratoplasty failure. CONCLUSIONS AND RELEVANCE: Repeat keratoplasty survival is affected by multiple interacting factors and prognosis worsens with each subsequent regraft. These results will help guide clinicians in addressing patients' individual risk factors when embarking on repeat corneal transplant surgery.

Engineering Bifunctional Antibodies with Constant Region Fusion Architectures.

We report a method to generate bifunctional antibodies by grafting full-length proteins into constant region loops of a full-length antibody or an antigen-binding fragment (Fab). The fusion proteins retain the antigen binding activity of the parent antibody but have an additional activity associated with the protein insert. The engineered antibodies have excellent in vitro activity, physiochemical properties, and stability. Among these, a Her2 × CD3 bispecific antibody (BsAb) was constructed by inserting an anti-Her2 single-chain variable fragment (ScFv) into an anti-CD3 Fab. This bispecific antibody efficiently induces targeted cell lysis in the presence of effector cells at as low as sub-picomolar concentrations in vitro. Moreover, the Her2 × CD3 BsAb shows potent in vivo antitumor activity in mouse Her22+ and Her21+ xenograft models. These results demonstrate that insertion of a full-length protein into non-CDR loops of antibodies provides a feasible approach to generate multifunctional antibodies for therapeutic applications.

Mechanism of the ATP-dependent DNA end-resection machinery from Saccharomyces cerevisiae.

If not properly processed and repaired, DNA double-strand breaks (DSBs) can give rise to deleterious chromosome rearrangements, which could ultimately lead to the tumour phenotype. DSB ends are resected in a 5' to 3' fashion in cells, to yield single-stranded DNA (ssDNA) for the recruitment of factors critical for DNA damage checkpoint activation and repair by homologous recombination. The resection process involves redundant pathways consisting of nucleases, DNA helicases and associated proteins. Being guided by recent genetic studies, we have reconstituted the first eukaryotic ATP-dependent DNA end-resection machinery comprising the Saccharomyces cerevisiae Mre11-Rad50-Xrs2 (MRX) complex, the Sgs1-Top3-Rmi1 complex, Dna2 protein and the heterotrimeric ssDNA-binding protein RPA. Here we show that DNA strand separation during end resection is mediated by the Sgs1 helicase function, in a manner that is enhanced by Top3-Rmi1 and MRX. In congruence with genetic observations, although the Dna2 nuclease activity is critical for resection, the Mre11 nuclease activity is dispensable. By examining the top3 Y356F allele and its encoded protein, we provide evidence that the topoisomerase activity of Top3, although critical for the suppression of crossover recombination, is not needed for resection either in cells or in the reconstituted system. Our results also unveil a multifaceted role of RPA, in the sequestration of ssDNA generated by DNA unwinding, enhancement of 5' strand incision, and protection of the 3' strand. Our reconstituted system should serve as a useful model for delineating the mechanistic intricacy of the DNA break resection process in eukaryotes.

Mechanistic insights into the role of Hop2-Mnd1 in meiotic homologous DNA pairing.

The Hop2-Mnd1 complex functions with the DMC1 recombinase in meiotic recombination. Hop2-Mnd1 stabilizes the DMC1-single-stranded DNA (ssDNA) filament and promotes the capture of the double-stranded DNA partner by the recombinase filament to assemble the synaptic complex. Herein, we define the action mechanism of Hop2-Mnd1 in DMC1-mediated recombination. Small angle X-ray scattering analysis and electron microscopy reveal that the heterodimeric Hop2-Mnd1 is a V-shaped molecule. We show that the protein complex harbors three distinct DNA binding sites, and determine their functional relevance. Specifically, the N-terminal double-stranded DNA binding functions of Hop2 and Mnd1 co-operate to mediate synaptic complex assembly, whereas ssDNA binding by the Hop2 C-terminus helps stabilize the DMC1-ssDNA filament. A model of the Hop2-Mnd1-DMC1-ssDNA ensemble is proposed to explain how it mediates homologous DNA pairing in meiotic recombination.

Multifunctional Antibody Agonists Targeting Glucagon-like Peptide-1, Glucagon, and Glucose-Dependent Insulinotropic Polypeptide Receptors.

Glucagon-like peptide-1 (GLP-1) receptor (GLP-1R), glucagon (GCG) receptor (GCGR), and glucose-dependent insulinotropic polypeptide (GIP, also known as gastric inhibitory polypeptide) receptor (GIPR), are three metabolically related peptide hormone receptors. A novel approach to the generation of multifunctional antibody agonists that activate these receptors has been developed. Native or engineered peptide agonists for GLP-1R, GCGR, and GIPR were fused to the N-terminus of the heavy chain or light chain of an antibody, either alone or in pairwise combinations. The fusion proteins have similar in vitro biological activities on the cognate receptors as the corresponding peptides, but circa 100-fold longer plasma half-lives. The GLP-1R mono agonist and GLP-1R/GCGR dual agonist antibodies both exhibit potent effects on glucose control and body weight reduction in mice, with the dual agonist antibody showing enhanced activity in the latter.

Deliveries from trophectoderm biopsied, fresh and vitrified blastocysts derived from polar body biopsied, vitrified oocytes.

This longitudinal study reports preliminary findings of six patients who underwent first polar body biopsy followed by oocyte vitrification. All oocytes were warmed, inseminated by intracytoplasmic sperm injection and cultured to blastocyst. All suitable blastocysts underwent trophectoderm biopsy for aneuploidy screening, and supernumerary blastocysts were vitrified. Euploid blastocysts were transferred either fresh or in a subsequent programmed cycle. Of the 91 metaphase II oocytes, 30 had euploid first polar bodies. Development to blastocyst was more likely in oocytes with a euploid first polar body (66.7% versus 24.6%; P < 0.001). Nineteen euploid blastocysts were produced: 10 from oocytes with a euploid first polar body and nine from oocytes with an aneuploid first polar body. Five out of six patients (83%) had a live birth or ongoing pregnancy at the time of analysis. Eleven euploid blastocysts have been transferred and seven implanted (64%). Although the chromosomal status of the first polar body was poorly predictive of embryonic ploidy, an association was found between chromosomal status of the first polar body and development to blastocyst. Further study is required to characterize these relationships, but proof of concept is provided that twice biopsied, twice cryopreserved oocytes and embryos can lead to viable pregnancies.

Multisite phosphoregulation of Cdc25 activity refines the mitotic entrance and exit switches.

Cyclin-dependent kinase 1 (Cdk1) kinase dephosphorylation and activation by Cdc25 phosphatase are essential for mitotic entry. Activated Cdk1 phosphorylates Cdc25 and other substrates, further activating Cdc25 to form a positive feedback loop that drives the abrupt G2/mitosis switch. Conversely, mitotic exit requires Cdk1 inactivation and reversal of Cdk1 substrate phosphorylation. This dephosphorylation is mediated, in part, by Clp1/Cdc14, a Cdk1-antagonizing phosphatase, which reverses Cdk1 phosphorylation of itself, Cdc25, and other Cdk1 substrates. Thus, Cdc25 phosphoregulation is essential for proper G2-M transition, and its contributions to cell cycle control have been modeled based on studies using Xenopus and human cell extracts. Because cell extract systems only approximate in vivo conditions where proteins interact within dynamic cellular environments, here, we use Schizosaccharomyces pombe to characterize, both experimentally and mathematically, the in vivo contributions of Cdk1-mediated phosphorylation of Cdc25 to the mitotic transition. Through comprehensive mapping of Cdk1 phosphosites on Cdc25 and characterization of phosphomutants, we show that Cdc25 hyperphosphorylation by Cdk1 governs Cdc25 catalytic activation, the precision of mitotic entry, and unvarying cell length but not Cdc25 localization or abundance. We propose a mathematical model that explains Cdc25 regulation by Cdk1 through a distributive and disordered phosphorylation mechanism that ultrasensitively activates Cdc25. We also show that Clp1/Cdc14 dephosphorylation of Cdk1 sites on Cdc25 controls the proper timing of cell division, a mechanism that is likely due to the double negative feedback loop between Clp1/Cdc14 and Cdc25 that controls the abruptness of the mitotic exit switch.

Pathophysiology, diagnosis, and management of hepatic encephalopathy.

Hepatic encephalopathy (HE) is a common complication of cirrhosis of the liver. It is also extremely debilitating, with an untreated 3-year survival of only 23 %. While the exact pathophysiology of HE has yet to be elucidated, a number of contributing factors have been described. Abnormal levels and altered metabolism of ammonia play a central role. Recently, inflammation has also been identified as a contributor to HE. Improved understanding of the pathophysiology of HE is crucial, as current therapy centers on reduction of the body's ammonia load. Lactulose is the first-line therapy for HE, with some antibiotics recently showing promise for improved outcomes in patients with HE. The role of anti-inflammatory therapies has yet to be evaluated.