The Role of Tofacitinib in the Treatment of Acute Severe Colitis in Children.

Objectives: Acute severe colitis (ASC) occurs in up to 15 percent of children with ulcerative colitis, with a high index of morbidity and mortality. Treatment includes high-dose steroids, infliximab, and salvage therapies. Unfortunately, up to 20 percent of patients may need an urgent colectomy due to treatment failure. We report our experience using tofacitinib for the treatment of six patients. Methods: A retrospective review of our medical electronic records was conducted. We included every patient with ASC and treatment failure, in whom tofacitinib was used as a salvage therapy. Response, complications, and disease course were noted. Results: Six patients were included with Pediatric Ulcerative Colitis Activity Index (PUCAI) scores ranging from 65 to 85 on admission, and 35 to 85 before tofacitinib was started (P 0.07). Median response time was 72 h. A median decrease of 40 points in PUCAI was noted (P 0.00001). Mean length of stay was 18 days with discharge 9 days after tofacitinib introduction. Haemoglobin, albumin, fecal calprotectin, and CRP improved after tofacitinib (P 0.02, P 0.02, P 0.025, and P 0.01, respectively). The mean follow-up was 8.5 months, four patients achieved complete remission and only one had a recrudescence of symptoms (P 0.01). One patient had a systemic Epstein-Barr virus infection prior to tofacitinib therapy, which resolved with rituximab treatment. No other complications were noted. Conclusions: Tofacitinib response is rapid and impressive in children suffering from ASC, and the safety profile appears comparable to or better than other available treatments. In the future, tofacitinib should be integrated into pediatric protocols.

Transition care to adolescent hepatology in a tertiary center for rare adult-child liver disease.

AIMS: This study analyzed the results of a transition program in a patient population with a rare liver disease of pediatric onset. METHOD: Data were collected on the clinical course of an adolescent population with a rare disease of pediatric onset and enrolled in a transition program between 1994 and 2022. RESULTS: A total of 238 adolescents (including 34 having undergone a liver transplant on enrolling in the program) were included. Eight patients were lost to follow-up before the first transition consultation and 16 families requested follow-up in an adult hepatology department closer to their home. Overall, 214 initial transition consultations were carried out; 29 patients were subsequently lost to follow-up and 13 switched center. Overall, 15.4 % of the patients enrolled in our program were lost to follow-up. Five adult patients underwent a liver transplantation during this 28-year period. Overall mortality was 3.2 %, graft survival was 91.5 %, and posttransplant survival was 92 %. In total, the current active file represents 183 patients with a median age of 24.3 years (18-51) and a median follow-up period of 5.8 years (6 months to 28 years). CONCLUSION: The implementation of a transition program to adult medicine for adolescents with a rare liver disease should follow the recommendations but must be adapted in line with local practice conditions. This process requires close collaboration between the pediatric and adult medicine teams based on a mutual desire to constantly improve practices and enhance knowledge.

Accuracy of Serological Screening for the Diagnosis of Celiac Disease in Type 1 Diabetes Children.

Background and Objectives: Patients with type 1 diabetes (T1D) are considered at high-risk for developing celiac disease (CD). The purpose of our study was to determine the prevalence of CD among children who were followed in our unit for T1D using the latest ESPGHAN guidelines, and avoiding intestinal biopsies in some of the children. Materials and Methods: We performed a prospective monocentric study, which included 663 T1D children between June 2014 and June 2016. We considered CD according to serological (tissue transglutaminase (TGAs) and endomysium antibodies) results. Children were included either at the time of T1D diagnosis or during their follow up. We looked for clinical and biochemical signs of CD, and for T1D characteristics. Results: The children's ages ranged from 11 months to 18 years. CD was confirmed in 32 out of 663 patients with T1D, with a prevalence of 4.8%. CD was excluded in 619 children and remained uncertain for 12 children, who had positive TGAs without the required criteria. We found that 95% of T1D children express HLA-DQ2 and/or -DQ8, which was 2.4 times higher than in the general population. Conclusions: An intestinal biopsy could be avoided to confirm CD in the majority of T1D children. Silent forms of CD are frequent and screening is recommended for all patients. Importantly, repeated TGA assessment is required in HLA genetically predisposed T1D patients, while it is unnecessary in the 5% who are HLA-DQ2 and -DQ8 negative.

The regulation of meiotic crossover distribution: a coarse solution to a century-old mystery?

Meiotic crossovers, which are exchanges of genetic material between homologous chromosomes, are more evenly and distantly spaced along chromosomes than expected by chance. This is because the occurrence of one crossover reduces the likelihood of nearby crossover events - a conserved and intriguing phenomenon called crossover interference. Although crossover interference was first described over a century ago, the mechanism allowing coordination of the fate of potential crossover sites half a chromosome away remains elusive. In this review, we discuss the recently published evidence supporting a new model for crossover patterning, coined the coarsening model, and point out the missing pieces that are still needed to complete this fascinating puzzle.

Porto-Sinusoidal Vascular Disease: A Pediatric Study of 30 Patients.

OBJECTIVES: Porto-sinusoidal vascular disease (PSVD) refers to a broad spectrum of histological lesions and phenotypic expressions. There are only a few reported pediatric cases in the literature. The primary outcomes of this study were to describe the phenotype of children with PSVD, to specify their mode of presentation and their clinical, biological, histological, and radiological characteristics as well as to identify their underlying etiologies. METHODS: This is a descriptive, retrospective, and monocentric study of children followed at our reference center for rare vascular liver diseases. RESULTS: Our study included 30 children ages 2months to 17.4years at the time of diagnosis. in most cases, the diagnosis was made incidentally without manifestation of any clinical symptom but rather on the finding of splenomegaly on physical examination (n = 9) or biological abnormalities (n = 13). In the other cases, the main presenting symptom was an upper gastrointestinal bleeding (n = 6). At the first visit, liver laboratory values were either normal (37%) or slightly disturbed. Anemia and/or thrombocytopenia associated with hypersplenism were found in 60% of patients. Liver biopsy was necessary for diagnosis. A total of 80% of cases had no identified etiology. After a median follow-up of 4.5 years, 33% had not developed portal hypertension (PHT) and we reported the first pediatric case of hepatocellular carcinoma in PSVD children. CONCLUSIONS: PSVD is responsible for nonspecific symptomatology with variable evolution sometimes marked by serious complications requiring invasive treatments or even liver transplantation. Regular monitoring is essential to prevent, detect, and treat complications.

Risk Factors of Clinical Relapses in Pediatric Luminal Crohn's Disease: A Retrospective Cohort Study.

INTRODUCTION: There is currently little knowledge on factors associated with the relapse of Crohn's disease (CD) in children. The aims of this study were to describe the risk factors associated with relapse in pediatric CD and the changes in the relapse rate over the past decade. METHODS: Patients younger than 18 years and diagnosed between 2009 and 2019 were included in this retrospective cohort study. Clinical, endoscopic, histological, and laboratory data, as well as induction and maintenance treatments, were collected from the medical records. Survival analyses and Cox regression models were used to assess the impact of these risk factors on relapse. RESULTS: Six hundred thirty-nine patients were included. There was a decrease in the clinical relapse rate over the past decade: 70.9% of the patients diagnosed between 2009 and 2014 relapsed as compared with 49.1% of the patients diagnosed between 2015 and 2019 (P < 0.0001). The following variables were associated with clinical relapse: female sex (adjusted hazard ratio [aHR] = 1.52, P = 0.0007), exposure to oral 5-ASA (aHR = 1.44, P = 0.04), use of immunomodulatory agents compared with tumor necrosis factor-alpha inhibitors (methotrexate aHR = 1.73, P = 0.003; thiopurines aHR = 1.63, P = 0.002), presence of granulomas (aHR = 1.34, P = 0.02) and increased eosinophils on intestinal biopsies (aHR = 1.36, P = 0.02), high levels of C-reactive protein (aHR = 1.01, P < 0.0001) and fecal calprotectin (aHR = 1.08, P < 0.0001), and low serum infliximab levels (aHR = 2.32, P = 0.001). DISCUSSION: Relapse of pediatric CD has decreased in the past decade. The risk of relapse is significantly associated with clinical, endoscopic, histological, and laboratory variables and treatment strategies.

Changes in the clinical phenotype and behavior of pediatric luminal Crohn's disease at diagnosis in the last decade.

BACKGROUND AND AIMS: The aims of this study were to describe the trends in the behavior of pediatric CD during the last decade and to describe the seasonal variation of disease presentation. METHODS: Patients under 18 years old and diagnosed between 2009 and 2019 were included. The clinical, endoscopic, histological, and laboratory data were collected from the medical records. We analyzed the trends of these parameters according to the year and season of diagnosis. RESULTS: 654 patients were included in the study. The number of incident CD cases increased yearly. Patients diagnosed between 2015 and 2019 were younger at diagnosis (OR 2.53, p = 0.02), had more perianal diseases (OR: 2.30, p < 0.0001) and more granulomas (OR: 1.61, p = 0.003), but fewer eosinophils (OR: 0.35, p < 0.0001) and less chronic lymphoplasmacytic infiltrate (OR: 0.56, p = 0.008) as compared to the 2009-2014 cohort. There was fewer CD diagnosis during winter. Patients diagnosed in the fall had lower PCDAIs, less failure to thrive and less extensive digestive involvement. Colonic disease was significantly more frequent during summer and fall. CONCLUSION: The clinical and histological phenotype of CD has changed over time and there are important seasonal trends in the frequency and severity on disease behavior suggesting possible disease triggers.

Tofacitinib to Treat Severe Acute Refractory Colitis in a Teenager: Case Report and Review of the Literature.

Acute severe colitis (ASC) may occur within 3 months of ulcerative colitis diagnosis in 9%-15% of children and the rate of colectomy is up to 40%-50% within 5 years after an ASC. The aim of this publication is to present recent and relevant data on the success of medical treatment with tofacitinib in ASC. Methods: We report a challenging case of a teenage boy with ASC at diagnosis and conduct a discussion after a review of the literature regarding the use of tofacitinib in inflammatory bowel disease, especially in pediatric patients and in ASC. Results: The patient was hospitalized for 10 weeks and was refractory to conventional therapies: intravenous corticosteroids, infliximab, methotrexate, and vedolizumab. He received 7 blood transfusions and also presented with a severe malnutrition requiring a total parenteral nutrition. Tofacitinib was considered as a medical last resort before colectomy and was started at week 8. Thirteen days after starting tofacitinib, he was asymptomatic and was discharged on tofacitinib as sole treatment. By week 9 of tofacitinib, a colonoscopy showed both endoscopic and histological remission. He has remained in clinical remission at 6-month follow-up. Conclusions: Tofacitinib may be an alternative medical treatment to avoid colectomy in ASC. It is a small molecule with a rapid onset and few severe adverse events. It has been used for ASC in adult patients, allowing to avoid colectomy in more than 60%. To our knowledge, this is one of the few pediatric patients with refractory ASC at initial diagnosis who responded to tofacitinib.

Factors associated with time to clinical remission in pediatric luminal Crohn's disease: A retrospective cohort study.

BACKGROUND AND AIM: Data on factors influencing time to remission in pediatric Crohn's disease (CD) are very limited in the literature. The aim of this retrospective cohort study was to describe the trends of time to clinical remission over the past decade and to identify factors associated with time to clinical remission in children with luminal CD. METHODS: Patients under 18 years old diagnosed between 2009 and 2019 were included. All data were collected from the patients' medical records. Survival analyses and linear regression models were used to assess the impact of clinical, laboratory, endoscopic, histological, and therapeutic factors on time to clinical remission. RESULTS: A total of 654 patients were included in the study. There was no change in the time to clinical remission over the decade. Female sex in adolescents (adjusted bêta regression coefficient [aß] = 31.8 days, P = 0.02), upper digestive tract involvement (aß = 46.4 days, P = 0.04) perianal disease (aß = 32.2 days, P = 0.04), presence of active inflammation on biopsies at diagnosis (aß = 46.7 days, P = 0.01) and oral 5-aminosalicylates (5-ASA) exposure (aß = 56.6 days, P = 0.002) were associated with longer time to clinical remission. Antibiotic exposure (aß = -29.3 days, P = 0.04), increased eosinophils (aß = -29.6 days, P = 0.008) and combination of exclusive enteral nutrition with tumor-necrosis-factor-alpha (TNF-alpha) inhibitors as induction therapy (aß = -36.8 days, P = 0.04) were associated with shorter time to clinical remission. CONCLUSION: In children with newly diagnosed Crohn's disease, time to clinical remission did not shorten during the decade. It was associated with baseline clinical and histological data and treatment strategies. Combination of enteral nutrition and TNF-alpha inhibitors was associated with faster clinical remission.

Suppression of him-14(it44ts) by a transgene insertion expressing GFP::COSA-1.

Meiotic crossover formation requires the activity of multiple pro-crossover factors, including the MutSγ complex and the cyclin-related protein COSA-1, that become concentrated together at the sites of crossover recombination intermediates. Here we show that a transgene insertion expressing GFP::COSA-1 can suppress the crossover deficit caused by a partial reduction in MutSγ function. Our data, combined with previous findings, support a model in which COSA-1 promotes crossover formation, at least in part, through positive regulation of MutSγ function.

RNAi-Related Dicer and Argonaute Proteins Play Critical Roles for Meiocyte Formation, Chromosome-Axes Lengths and Crossover Patterning in the Fungus Sordaria macrospora.

RNA interference (RNAi) is a cellular process involving small RNAs that target and regulate complementary RNA transcripts. This phenomenon has well-characterized roles in regulating gene and transposon expression. In addition, Dicer and Argonaute proteins, which are key players of RNAi, also have functions unrelated to gene repression. We show here that in the filamentous Ascomycete Sordaria macrospora, genes encoding the two Dicer (Dcl1 and Dcl2) and the two Argonaute (Sms2 and Qde2) proteins are dispensable for vegetative growth. However, we identified roles for all four proteins in the sexual cycle. Dcl1 and Sms2 are essential for timely and successful ascus/meiocyte formation. During meiosis per se, Dcl1, Dcl2, and Qde2 modulate, more or less severely, chromosome axis length and crossover numbers, patterning and interference. Additionally, Sms2 is necessary both for correct synaptonemal complex formation and loading of the pro-crossover E3 ligase-protein Hei10. Moreover, meiocyte formation, and thus meiotic induction, is completely blocked in the dcl1 dcl2 and dcl1 sms2 null double mutants. These results indicate complex roles of the RNAi machinery during major steps of the meiotic process with newly uncovered roles for chromosomes-axis length modulation and crossover patterning regulation.

Spatial Regulation of Polo-Like Kinase Activity During Caenorhabditis elegans Meiosis by the Nucleoplasmic HAL-2/HAL-3 Complex.

Proper partitioning of homologous chromosomes during meiosis relies on the coordinated execution of multiple interconnected events: Homologs must locate, recognize, and align with their correct pairing partners. Further, homolog pairing must be coupled to assembly of the synaptonemal complex (SC), a meiosis-specific tripartite structure that maintains stable associations between the axes of aligned homologs and regulates formation of crossovers between their DNA molecules to create linkages that enable their segregation. Here, we identify HAL-3 (Homolog Alignment 3) as an important player in coordinating these key events during Caenorhabditis elegans meiosis. HAL-3, and the previously identified HAL-2, are interacting and interdependent components of a protein complex that localizes to the nucleoplasm of germ cells. hal-3 (or hal-2) mutants exhibit multiple meiotic prophase defects including failure to establish homolog pairing, inappropriate loading of SC subunits onto unpaired chromosome axes, and premature loss of synapsis checkpoint protein PCH-2. Further, loss of hal function results in misregulation of the subcellular localization and activity of Polo-like kinases (PLK-1 and PLK-2), which dynamically localize to different defined subnuclear sites during wild-type prophase progression to regulate distinct cellular events. Moreover, loss of PLK-2 activity partially restores tripartite SC structure in a hal mutant background, suggesting that the defect in pairwise SC assembly in hal mutants reflects inappropriate PLK activity. Together, our data support a model in which the nucleoplasmic HAL-2/HAL-3 protein complex constrains both localization and activity of meiotic Polo-like kinases, thereby preventing premature interaction with stage-inappropriate targets.

Interdependent and separable functions of Caenorhabditis elegans MRN-C complex members couple formation and repair of meiotic DSBs.

Faithful inheritance of genetic information through sexual reproduction relies on the formation of crossovers between homologous chromosomes during meiosis, which, in turn, relies on the formation and repair of numerous double-strand breaks (DSBs). As DSBs pose a potential threat to the genome, mechanisms that ensure timely and error-free DSB repair are crucial for successful meiosis. Here, we identify NBS-1, the Caenorhabditis elegans ortholog of the NBS1 (mutated in Nijmegen Breakage Syndrome) subunit of the conserved MRE11-RAD50-NBS1/Xrs2 (MRN) complex, as a key mediator of DSB repair via homologous recombination (HR) during meiosis. Loss of nbs-1 leads to severely reduced loading of recombinase RAD-51, ssDNA binding protein RPA, and pro-crossover factor COSA-1 during meiotic prophase progression; aggregated and fragmented chromosomes at the end of meiotic prophase; and 100% progeny lethality. These phenotypes reflect a role for NBS-1 in processing of meiotic DSBs for HR that is shared with its interacting partners MRE-11-RAD-50 and COM-1 (ortholog of Com1/Sae2/CtIP). Unexpectedly, in contrast to MRE-11 and RAD-50, NBS-1 is not required for meiotic DSB formation. Meiotic defects of the nbs-1 mutant are partially suppressed by abrogation of the nonhomologous end-joining (NHEJ) pathway, indicating a role for NBS-1 in antagonizing NHEJ during meiosis. Our data further reveal that NBS-1 and COM-1 play distinct roles in promoting HR and antagonizing NHEJ. We propose a model in which different components of the MRN-C complex work together to couple meiotic DSB formation with efficient and timely engagement of HR, thereby ensuring crossover formation and restoration of genome integrity before the meiotic divisions.

FIGL1 and its novel partner FLIP form a conserved complex that regulates homologous recombination.

Homologous recombination is central to repair DNA double-strand breaks, either accidently arising in mitotic cells or in a programed manner at meiosis. Crossovers resulting from the repair of meiotic breaks are essential for proper chromosome segregation and increase genetic diversity of the progeny. However, mechanisms regulating crossover formation remain elusive. Here, we identified through genetic and protein-protein interaction screens FIDGETIN-LIKE-1 INTERACTING PROTEIN (FLIP) as a new partner of the previously characterized anti-crossover factor FIDGETIN-LIKE-1 (FIGL1) in Arabidopsis thaliana. We showed that FLIP limits meiotic crossover together with FIGL1. Further, FLIP and FIGL1 form a protein complex conserved from Arabidopsis to human. FIGL1 interacts with the recombinases RAD51 and DMC1, the enzymes that catalyze the DNA strand exchange step of homologous recombination. Arabidopsis flip mutants recapitulate the figl1 phenotype, with enhanced meiotic recombination associated with change in counts of DMC1 and RAD51 foci. Our data thus suggests that FLIP and FIGL1 form a conserved complex that regulates the crucial step of strand invasion in homologous recombination.

RMI1 and TOP3α limit meiotic CO formation through their C-terminal domains.

At meiosis, hundreds of programmed DNA double-strand breaks (DSBs) form and are repaired by homologous recombination. From this large number of DSBs, only a subset yields crossovers (COs), with a minimum of one CO per chromosome pair. All DSBs must be repaired and every recombination intermediate must be resolved to avoid subsequent entanglement and chromosome breakage. The conserved BLM-TOP3α-RMI1 (BTR) complex acts on early and late meiotic recombination intermediates to both limit CO outcome and promote chromosome integrity. In Arabidopsis, the BLM homologues RECQ4A and RECQ4B act redundantly to prevent meiotic extra COs, but recombination intermediates are fully resolved in their absence. In contrast, TOP3α is needed for both processes. Here we show through the characterization of specific mutants that RMI1 is a major anti-CO factor, in addition to being essential to prevent chromosome breakage and entanglement. Further, our findings suggest a specific role of the C-terminal domains of RMI1 and TOP3α, that respectively contain an Oligo Binding domain (OB2) and ZINC finger motifs, in preventing extra-CO. We propose that these domains of TOP3α and RMI1 define a sub-domain of the BTR complex which is dispensable for the resolution of recombination intermediates but crucial to limit extra-COs.

AAA-ATPase FIDGETIN-LIKE 1 and Helicase FANCM Antagonize Meiotic Crossovers by Distinct Mechanisms.

Meiotic crossovers (COs) generate genetic diversity and are critical for the correct completion of meiosis in most species. Their occurrence is tightly constrained but the mechanisms underlying this limitation remain poorly understood. Here we identified the conserved AAA-ATPase FIDGETIN-LIKE-1 (FIGL1) as a negative regulator of meiotic CO formation. We show that Arabidopsis FIGL1 limits CO formation genome-wide, that FIGL1 controls dynamics of the two conserved recombinases DMC1 and RAD51 and that FIGL1 hinders the interaction between homologous chromosomes, suggesting that FIGL1 counteracts DMC1/RAD51-mediated inter-homologue strand invasion to limit CO formation. Further, depleting both FIGL1 and the previously identified anti-CO helicase FANCM synergistically increases crossover frequency. Additionally, we showed that the effect of mutating FANCM on recombination is much lower in F1 hybrids contrasting from the phenotype of inbred lines, while figl1 mutation equally increases crossovers in both contexts. This shows that the modes of action of FIGL1 and FANCM are differently affected by genomic contexts. We propose that FIGL1 and FANCM represent two successive barriers to CO formation, one limiting strand invasion, the other disassembling D-loops to promote SDSA, which when both lifted, leads to a large increase of crossovers, without impairing meiotic progression.

FANCM-associated proteins MHF1 and MHF2, but not the other Fanconi anemia factors, limit meiotic crossovers.

Genetic recombination is important for generating diversity and to ensure faithful segregation of chromosomes at meiosis. However, few crossovers (COs) are formed per meiosis despite an excess of DNA double-strand break precursors. This reflects the existence of active mechanisms that limit CO formation. We previously showed that AtFANCM is a meiotic anti-CO factor. The same genetic screen now identified AtMHF2 as another player of the same anti-CO pathway. FANCM and MHF2 are both Fanconi Anemia (FA) associated proteins, prompting us to test the other FA genes conserved in Arabidopsis for a role in CO control at meiosis. This revealed that among the FA proteins tested, only FANCM and its two DNA-binding co-factors MHF1 and MHF2 limit CO formation at meiosis.

Tinkering with meiosis.

Meiosis is at the heart of Mendelian heredity. Recently, much progress has been made in the understanding of this process, in various organisms. In the last 15 years, the functional characterization of numerous genes involved in meiosis has dramatically deepened our knowledge of key events, including recombination, the cell cycle, and chromosome distribution. Through a constantly advancing tool set and knowledge base, a number of advances have been made that will allow manipulation of meiosis from a plant breeding perspective. This review focuses on the aspects of meiosis that can be tinkered with to create and propagate new varieties. We would like to dedicate this review to the memory of Simon W. Chan (1974-2012) (http://www.plb.ucdavis.edu/labs/srchan/).