Cell cycle-dependent and independent mating blocks ensure fungal zygote survival and ploidy maintenance.

To ensure genome stability, sexually reproducing organisms require that mating brings together exactly 2 haploid gametes and that meiosis occurs only in diploid zygotes. In the fission yeast Schizosaccharomyces pombe, fertilization triggers the Mei3-Pat1-Mei2 signaling cascade, which represses subsequent mating and initiates meiosis. Here, we establish a degron system to specifically degrade proteins postfusion and demonstrate that mating blocks not only safeguard zygote ploidy but also prevent lysis caused by aberrant fusion attempts. Using long-term imaging and flow-cytometry approaches, we identify previously unrecognized and independent roles for Mei3 and Mei2 in zygotes. We show that Mei3 promotes premeiotic S-phase independently of Mei2 and that cell cycle progression is both necessary and sufficient to reduce zygotic mating behaviors. Mei2 not only imposes the meiotic program and promotes the meiotic cycle, but also blocks mating behaviors independently of Mei3 and cell cycle progression. Thus, we find that fungi preserve zygote ploidy and survival by at least 2 mechanisms where the zygotic fate imposed by Mei2 and the cell cycle reentry triggered by Mei3 synergize to prevent zygotic mating.

Gamete fusion triggers bipartite transcription factor assembly to block re-fertilization.

The ploidy cycle, which is integral to sexual reproduction, requires meiosis to halve chromosome numbers as well as mechanisms that ensure zygotes are formed by exactly two partners1-4. During sexual reproduction of the fungal model organism Schizosaccharomyces pombe, haploid P and M cells fuse to form a diploid zygote that immediately enters meiosis5. Here we reveal that rapid post-fusion reconstitution of a bipartite transcription factor blocks re-fertilization. We first identify mutants that undergo transient cell fusion involving cytosol exchange but not karyogamy, and show that this drives distinct cell fates in the two gametes. The P partner undergoes lethal haploid meiosis, whereas the M cell persists in mating. The zygotic transcription that drives meiosis is rapidly initiated first from the P parental genome, even in wild-type cells. This asymmetric gene expression depends on a bipartite complex formed post-fusion between the cytosolic M-cell-specific peptide Mi and the nuclear P-cell-specific homeobox protein Pi6,7, which captures Mi in the P nucleus. Zygotic transcription is thus poised to initiate in the P nucleus as fast as Mi reaches it after fusion, a design that we reconstruct using two synthetic interactors localized to the nucleus and the cytosol of two respective partner cells. Notably, delaying zygotic transcription-by postponing Mi expression or deleting its transcriptional target in the P genome-leads to zygotes fusing with additional gametes, thus forming polyploids and eventually aneuploid progeny. The signalling cascade to block re-fertilization shares components with, but bifurcates from, meiotic induction8-10. Thus, a cytoplasmic connection upon gamete fusion leads to asymmetric reconstitution of a bipartite transcription factor to rapidly block re-fertilization and induce meiosis, ensuring genome maintenance during sexual reproduction.

Spatial focalization of pheromone/MAPK signaling triggers commitment to cell-cell fusion.

Cell fusion is universal in eukaryotes for fertilization and development, but what signals this process is unknown. Here, we show in Schizosaccharomyces pombe that fusion does not require a dedicated signal but is triggered by spatial focalization of the same pheromone-GPCR (G-protein-coupled receptor)-MAPK signaling cascade that drives earlier mating events. Autocrine cells expressing the receptor for their own pheromone trigger fusion attempts independently of cell-cell contact by concentrating pheromone release at the fusion focus, a dynamic actin aster underlying the secretion of cell wall hydrolases. Pheromone receptor and MAPK cascade are similarly enriched at the fusion focus, concomitant with fusion commitment in wild-type mating pairs. This focalization promotes cell fusion by immobilizing the fusion focus, thus driving local cell wall dissolution. We propose that fusion commitment is imposed by a local increase in MAPK concentration at the fusion focus, driven by a positive feedback between fusion focus formation and focalization of pheromone release and perception.

Optogenetics reveals Cdc42 local activation by scaffold-mediated positive feedback and Ras GTPase.

Local activity of the small GTPase Cdc42 is critical for cell polarization. Whereas scaffold-mediated positive feedback was proposed to break symmetry of budding yeast cells and produce a single zone of Cdc42 activity, the existence of similar regulation has not been probed in other organisms. Here, we address this problem using rod-shaped cells of fission yeast Schizosaccharomyces pombe, which exhibit zones of active Cdc42-GTP at both cell poles. We implemented the CRY2-CIB1 optogenetic system for acute light-dependent protein recruitment to the plasma membrane, which allowed to directly demonstrate positive feedback. Indeed, optogenetic recruitment of constitutively active Cdc42 leads to co-recruitment of the guanine nucleotide exchange factor (GEF) Scd1 and endogenous Cdc42, in a manner dependent on the scaffold protein Scd2. We show that Scd2 function is dispensable when the positive feedback operates through an engineered interaction between the GEF and a Cdc42 effector, the p21-activated kinase 1 (Pak1). Remarkably, this rewired positive feedback confers viability and allows cells to form 2 zones of active Cdc42 even when otherwise essential Cdc42 activators are lacking. These cells further revealed that the small GTPase Ras1 plays a role in both localizing the GEF Scd1 and promoting its activity, which potentiates the positive feedback. We conclude that scaffold-mediated positive feedback, gated by Ras activity, confers robust polarization for rod-shape formation.

SUFU haploinsufficiency causes a recognisable neurodevelopmental phenotype at the mild end of the Joubert syndrome spectrum.

BACKGROUND: Joubert syndrome (JS) is a recessively inherited ciliopathy characterised by congenital ocular motor apraxia (COMA), developmental delay (DD), intellectual disability, ataxia, multiorgan involvement, and a unique cerebellar and brainstem malformation. Over 40 JS-associated genes are known with a diagnostic yield of 60%-75%.In 2018, we reported homozygous hypomorphic missense variants of the SUFU gene in two families with mild JS. Recently, heterozygous truncating SUFU variants were identified in families with dominantly inherited COMA, occasionally associated with mild DD and subtle cerebellar anomalies. METHODS: We reanalysed next generation sequencing (NGS) data in two cohorts comprising 1097 probands referred for genetic testing of JS genes. RESULTS: Heterozygous truncating and splice-site SUFU variants were detected in 22 patients from 17 families (1.5%) with strong male prevalence (86%), and in 8 asymptomatic parents. Patients presented with COMA, hypotonia, ataxia and mild DD, and only a third manifested intellectual disability of variable severity. Brain MRI showed consistent findings characterised by vermis hypoplasia, superior cerebellar dysplasia and subtle-to-mild abnormalities of the superior cerebellar peduncles. The same pattern was observed in two out of three tested asymptomatic parents. CONCLUSION: Heterozygous truncating or splice-site SUFU variants cause a novel neurodevelopmental syndrome encompassing COMA and mild JS, which likely represent overlapping entities. Variants can arise de novo or be inherited from a healthy parent, representing the first cause of JS with dominant inheritance and reduced penetrance. Awareness of this condition will increase the diagnostic yield of JS genetic testing, and allow appropriate counselling about prognosis, medical monitoring and recurrence risk.

A toolbox of stable integration vectors in the fission yeast Schizosaccharomyces pombe.

Schizosaccharomyces pombe is a widely used model organism to study many aspects of eukaryotic cell physiology. Its popularity as an experimental system partially stems from the ease of genetic manipulations, where the innate homology-targeted repair is exploited to precisely edit the genome. While vectors to incorporate exogenous sequences into the chromosomes are available, most are poorly characterized. Here, we show that commonly used fission yeast vectors, which upon integration produce repetitive genomic regions, give rise to unstable genomic loci. We overcome this problem by designing a new series of stable integration vectors (SIVs) that target four different prototrophy genes. SIVs produce non-repetitive, stable genomic loci and integrate predominantly as single copy. Additionally, we develop a set of complementary auxotrophic alleles that preclude false-positive integration events. We expand the vector series to include antibiotic resistance markers, promoters, fluorescent tags and terminators, and build a highly modular toolbox to introduce heterologous sequences. Finally, as proof of concept, we generate a large set of ready-to-use, fluorescent probes to mark organelles and cellular processes with a wide range of applications in fission yeast research.This article has an associated First Person interview with the first author of the paper.

A systematic screen for morphological abnormalities during fission yeast sexual reproduction identifies a mechanism of actin aster formation for cell fusion.

In non-motile fungi, sexual reproduction relies on strong morphogenetic changes in response to pheromone signaling. We report here on a systematic screen for morphological abnormalities of the mating process in fission yeast Schizosaccharomyces pombe. We derived a homothallic (self-fertile) collection of viable deletions, which, upon visual screening, revealed a plethora of phenotypes affecting all stages of the mating process, including cell polarization, cell fusion and sporulation. Cell fusion relies on the formation of the fusion focus, an aster-like F-actin structure that is marked by strong local accumulation of the myosin V Myo52, which concentrates secretion at the fusion site. A secondary screen for fusion-defective mutants identified the myosin V Myo51-associated coiled-coil proteins Rng8 and Rng9 as critical for the coalescence of the fusion focus. Indeed, rng8Δ and rng9Δ mutant cells exhibit multiple stable dots at the cell-cell contact site, instead of the single focus observed in wildtype. Rng8 and Rng9 accumulate on the fusion focus, dependent on Myo51 and tropomyosin Cdc8. A tropomyosin mutant allele, which compromises Rng8/9 localization but not actin binding, similarly leads to multiple stable dots instead of a single focus. By contrast, myo51 deletion does not strongly affect fusion focus coalescence. We propose that focusing of the actin filaments in the fusion aster primarily relies on Rng8/9-dependent cross-linking of tropomyosin-actin filaments.

Impact of 21-Gene Breast Cancer Assay on Treatment Decision for Patients with T1-T3, N0-N1, Estrogen Receptor-Positive/Human Epidermal Growth Receptor 2-Negative Breast Cancer: Final Results of the Prospective Multicenter ROXANE Study.

BACKGROUND: The ROXANE Italian prospective study evaluated the impact of the 21-gene Recurrence Score (RS) results on adjuvant treatment decision for patients with early breast cancer. MATERIALS AND METHODS: Nine centers participated. Physicians used the RS test whenever unsure about adjuvant treatment recommendation for patients with estrogen receptor-positive/human epidermal growth receptor 2-negative, T1-T3, N0-N1 early breast cancer. Pre-RS and post-RS treatment recommendations were collected. RESULTS: A total of 251 patients were included. N0 patients (61%) showed higher grade (p < .001) and higher Ki67 (p = .001) and were more frequently progesterone receptor negative (p = .012) as compared with N1 patients. RS results were as follows: <11, n = 63 (25.1%); 11-25, n = 143 (57%); and ≥26, n = 45 (17.9%). Higher RS was found in N0 vs. N1 patients (p = .001) and in cases of G3 (p < .001) and higher Ki67 (p < .001). The rate of change in treatment decision was 30% (n = 75), mostly from chemotherapy (CT) plus hormone therapy (CT + HT) to hormone therapy (HT; 76%, n = 57/75). The proportion of patients recommended to CT + HT was significantly reduced from pre-RS to post-RS (52% to 36%, p < .0001). CT use reduction was more evident for N1 patients (55% to 27%) than for N0 patients (50% to 42%) and was observed only in cases of RS ≤17. CONCLUSION: Physicians predominantly used the 21-gene assay in N0 patients with a more aggressive biology or in N1 patients showing more indolent biology. In this selected patient population, the use of RS testing led to a 30% rate of change in treatment decision. In the N1 patient subgroup, the use of RS testing contributed to reduce CT use by more than half. IMPLICATIONS FOR PRACTICE: This study shows that, even in a context in which physicians recommend a high proportion of patients to endocrine treatment alone before knowing the results of the Recurrence Score (RS) assay, the use of the RS test, whenever uncertainty regarding adjuvant treatment recommendation is present, significantly contributes in further reducing the use of chemotherapy, especially for N1 patients.

Exploration and stabilization of Ras1 mating zone: A mechanism with positive and negative feedbacks.

In mating fission yeast cells, sensing and response to extracellular pheromone concentrations occurs through an exploratory Cdc42 patch that stochastically samples the cell cortex before stabilizing towards a mating partner. Active Ras1 (Ras1-GTP), an upstream regulator of Cdc42, and Gap1, the GTPase-activating protein for Ras1, localize at the patch. We developed a reaction-diffusion model of Ras1 patch appearance and disappearance with a positive feedback by a Guanine nucleotide Exchange Factor (GEF) and Gap1 inhibition. The model is based on new estimates of Ras1-GDP, Ras1-GTP and Gap1 diffusion coefficients and rates of cytoplasmic exchange studied by FRAP. The model reproduces exploratory patch behavior and lack of Ras1 patch in cells lacking Gap1. Transition to a stable patch can occur by change of Gap1 rates constants or local increase of the positive feedback rate constants. The model predicts that the patch size and number of patches depend on the strength of positive and negative feedbacks. Measurements of Ras1 patch size and number in cells overexpressing the Ras1 GEF or Gap1 are consistent with the model.

Activated Phosphoinositide 3 Kinase Delta Syndrome (APDS): A Primary Immunodeficiency Mimicking Lymphoma.

Malignant or nonmalignant lymphoproliferative disorders together with repeated ear, nose, and throat infections should strongly motivate immunologic investigations. Indeed, we report a 7-year-old patient with a history of persistent abdominal symptoms along with recurrent ear, nose, and throat infections, who presented with intra-abdominal masses highly suggestive of a diagnostic of lymphoma, and who was diagnosed with activated-PI3K-delta syndrome, a recently described primary immunodeficiency prone to lymphoproliferation.

First Prospective Multicenter Italian Study on the Impact of the 21-Gene Recurrence Score in Adjuvant Clinical Decisions for Patients with ER Positive/HER2 Negative Breast Cancer.

BACKGROUND: The Breast DX Italy prospective study evaluated the impact of the 21-gene recurrence score (RS) result on adjuvant treatment decisions for patients with early breast cancer. MATERIALS AND METHODS: Nine centers (two Hub and seven Spoke centers of the Veneto Oncology Network) participated. Consecutive patients with estrogen receptor positive, human epidermal growth receptor negative, T1-T3, N0-N1 early breast cancer were prospectively registered; only those meeting protocol-defined clinicopathological "intermediate risk" criteria were eligible for the RS test. Pre-RS and post-RS physicians' treatment recommendations and treatment actually received were collected. RESULTS: A total of n = 124 N0 and n = 126 N1 patients underwent the RS assay. The majority had Grade 2 tumors (71%); median age was 55 years, median tumor size was 16 mm, and median Ki67 expression was 20%. Patients enrolled at Hub centers presented higher-risk features. The distribution of RS results was <18 (60.8%), 18-30 (32.4%), and >30 (6.8%). The indication before RS was hormonal therapy (HT) alone in 52% of cases. An indication before RS of chemotherapy (CT)+HT was more frequent for patients with N1 versus N0 tumors (57% vs. 39%, p = .0035) and for patients enrolled at Hub versus Spoke centers (54% vs. 36%, p = .007).The overall rate of change in treatment decision was 16% (n = 40), mostly from CT+HT to HT (n = 30). According to nodal status, rate of change in treatment decision was 12% for the N0 cohort and 20% for the N1 cohort. The proportion of patients recommended to CT+HT was significantly reduced from before to after RS (48% to 40%, p < .0016), especially in the N1 cohort (57% to 45%, p = .0027) and at Hub centers (54% to 44%, p = .001). CONCLUSION: Despite frequent indication of HT before RS, the use of the RS assay further contributed to sparing CT, especially for patients with N1 tumors and at Hub centers. IMPLICATIONS FOR PRACTICE: This study shows that, although a high proportion of patients were recommended to receive endocrine treatment alone before knowing the recurrence score (RS) assay, the RS test further contributed in sparing chemotherapy for some of these patients, especially in case of the N1 stage or for patients enrolled at referral centers. These data highlight the need for further work in collaboration with health authorities and companies in order to define strategies for the implementation of the use of RS testing in clinical practice in the Italian setting.

The Contemporary Bacteriologic Epidemiology of Osteoarticular Infections in Children in Switzerland.

OBJECTIVES: To assess the contemporary bacteriologic epidemiology of pediatric osteoarticular infection with particular regard to children's ages, because Kingella kingae has gained increasing recognition as the predominant pathogen for osteoarticular infection in young children. STUDY DESIGN: Retrospective file review of enrolled children from 0 to 15 years of age, admitted to our institution from 2007 to 2015 for suspected osteoarticular infection (217 cases). Information on age, sex, the bone or joint infected, imaging studies, and laboratory data (including bacterial investigations) were collected for analysis. RESULTS: Microorganism identification was possible for 138 infected children (63.6%), through blood (cultures or polymerase chain reaction [PCR]) and/or operative samples (cultures or PCR). Thirty-one patients (14.3%) were found to both have positive blood cultures and operative samples. The results of positive bacteriology specimens identified the most common causative pathogen for osteoarticular infection as K kingae (47.8% of microbiologically confirmed osteoarticular infections of all ages, and 87.7% in children between the ages of 6 and 48 months), significantly more common than Staphylococcus aureus (35.5% of microbiologically confirmed osteoarticular infections of all ages, and 78.2% in children >4 years of age). CONCLUSIONS: Use of the appropriate PCR assays demonstrated that K kingae currently is the major bacterial cause of pediatric osteoarticular infection, especially in children <4 years of age in whom K kingae is more common than S aureus. PCR assays should be used in routine microbiologic laboratory evaluation to improve diagnostic performance. However, despite the use of molecular methods, there are many osteoarticular infections in which no microorganism is detected, which suggests that these infections may be caused by other as yet unrecognized fastidious microorganisms.

A simple, precocious, and reliable way to assess future clinical outcome in children with Perthes disease and mild femoral head involvement: correlation between MRI with diffusion-weighted and dynamic gadolinium-enhanced subtraction and Catterall and Herring classifications.

BACKGROUND: In children older than 5 years with a mild form of Legg-Calvé-Perthes disease, the outcome is difficult to predict. In this study, we retrospectively correlated gadolinium-enhanced subtracted (DGS) and diffusion (DWI) MRI findings to the radiographic assessment according to the Catterall and Herring et al. classifications and to the final score according to Stulberg et al.: the aim was to identify a precocious, simple, and objective criterion to differentiate between forms evolving favourably and forms requiring an early surgical treatment in order to avoid femoral head deformity and subsequent osteoarthritis. METHODS: Twelve boys with unilateral mild femoral head involvement (Catterall grade 2 or grade 3) underwent DSG and DWI MR during the early phase of the disease. The absence of enhancement of the external pillar on DSG MRI and the presence of metaphyseal hyperintensity on DWI were considered to be the signs of poor outcome. These findings were correlated with the Catterall and Herring et al. classifications at the initial sclerotic stage and early fragmentation phase and with the Stulberg et al. classifications at least 5 years after the onset of the disease. RESULTS: DSG MRI findings correctly discriminated three out of four patients with a good outcome but underestimated two out of eight patients with a poor outcome. DWI findings correlated with the Catterall and Herring et al. classifications in 12 out of 12 cases. In only one case, DWI findings did not correlate with the Stulberg et al. classification. CONCLUSION: DWI MR provides an objective and accurate prognostic criterion that is relatively easy to recognise. DGS MR findings are less accurate, thus underestimating the gravity of the disease in one-fourth of the patients with a poor outcome.

Globus pallidus MR signal abnormalities in children with chronic liver disease and/or porto-systemic shunting.

OBJECTIVES: Detection of subclinical hepatic encephalopathy in children is difficult. We aimed to assess the changes in imaging of the central nervous system in children with chronic liver disease using MR imaging, diffusion, and 1H -spectroscopy. METHODS: Forty three children with chronic liver disease and/or porto-systemic shunting (111.4±56.9 months) and 24 controls (72.0±51.8 months) underwent brain MRI/spectroscopy on a 1.5T to examine T1, T2, ADC, Cho/Cr, ml/Cr, Glx/Cr ratio spectroscopy in the globus pallidus. Patients were divided into 3 groups according to the ratios of globus pallidus/putamen T1 signal : isointense (i), hyperintense (h), much more hyperintense (h+). The relationship with clinical and biological data was analyzed. RESULTS: T1 signal intensity and ml/Cr were significantly different between controls and group h+ (p=0.001). ADC did not differ significantly between groups. Age correlated strongly with the presence of a T1 signal ratio (p > 0.001). There was no correlation between imaging findings and biological parameters. CONCLUSIONS: In children with chronic liver disease and/or porto-systemic shunting, the presence of a hyperintense T1 signal in the globus pallidus correlated strongly with age. Biological and clinical parameters were not predictive of these changes. MRI may become a useful screening tool for hepatic encephalopathy in children. KEY POINTS: • Children with chronic liver disease should undergo brain MRI during their follow-up • T1 hyperintensity of globus pallidus is suggestive of liver-related CNS involvement • MRS mI/Cr is decreased in children with chronic liver disease • Biological parameters (ammonium) were not predictive of hepatic encephalopathy • Duration of chronic liver disease may be causative the hepatic encephalopathy.

Kappa statistic to measure agreement beyond chance in free-response assessments.

BACKGROUND: The usual kappa statistic requires that all observations be enumerated. However, in free-response assessments, only positive (or abnormal) findings are notified, but negative (or normal) findings are not. This situation occurs frequently in imaging or other diagnostic studies. We propose here a kappa statistic that is suitable for free-response assessments. METHOD: We derived the equivalent of Cohen's kappa statistic for two raters under the assumption that the number of possible findings for any given patient is very large, as well as a formula for sampling variance that is applicable to independent observations (for clustered observations, a bootstrap procedure is proposed). The proposed statistic was applied to a real-life dataset, and compared with the common practice of collapsing observations within a finite number of regions of interest. RESULTS: The free-response kappa is computed from the total numbers of discordant (b and c) and concordant positive (d) observations made in all patients, as 2d/(b + c + 2d). In 84 full-body magnetic resonance imaging procedures in children that were evaluated by 2 independent raters, the free-response kappa statistic was 0.820. Aggregation of results within regions of interest resulted in overestimation of agreement beyond chance. CONCLUSIONS: The free-response kappa provides an estimate of agreement beyond chance in situations where only positive findings are reported by raters.

Non-odontogenic tumors of the facial bones in children and adolescents: role of multiparametric imaging.

Tumors of the pediatric facial skeleton represent a major challenge in clinical practice because they can lead to functional impairment, facial deformation, and long-term disfigurement. Their treatment often requires a multidisciplinary approach, and radiologists play a pivotal role in the diagnosis and management of these lesions. Although rare, pediatric tumors arising in the facial bones comprise a wide spectrum of benign and malignant lesions of osteogenic, fibrogenic, hematopoietic, neurogenic, or epithelial origin. The more common lesions include Langerhans cell histiocytosis and osteoma, while rare lesions include inflammatory myofibroblastic and desmoid tumors; juvenile ossifying fibroma; primary intraosseous lymphoma; Ewing sarcoma; and metastases to the facial bones from neuroblastoma, Ewing sarcoma, or retinoblastoma. This article provides a comprehensive approach for the evaluation of children with non-odontogenic tumors of the facial skeleton. Typical findings are discussed with emphasis on the added value of multimodality multiparametric imaging with computed tomography (CT), magnetic resonance imaging (MRI) with diffusion-weighted imaging (DWI), positron emission tomography CT (PET CT), and PET MRI. Key imaging findings and characteristic histologic features of benign and malignant lesions are reviewed and the respective role of each modality for pretherapeutic assessment and post-treatment follow-up. Pitfalls of image interpretation are addressed and how to avoid them.

Wallenberg Syndrome: An Exceptional Cause of Acute Vertigo in Children.

The assessment of acute vertigo in childhood is often challenging, but fortunately a central cause is rarely identified. We present the case of a 7-year-old boy who developed, after a mild head trauma, a rotary vertigo associated with nausea and vomiting. A posttraumatic peripheral vestibular dysfunction was first suspected but not confirmed by an otoneurological evaluation. When subtle neurological signs were elicited, a brain magnetic resonance imaging was promptly requested. This showed a small infarct on the lateral posterior left part of the medulla oblongata of the brainstem, typical of Wallenberg syndrome. Vascular imaging was normal and no defined etiology was found. The child was started on prophylactic acetylsalicylic acid. The rapid disappearance of vertigo was noted. On follow-up at 6 months, there has been no recurrence and neurological examination was fully normal. Our case extends the differential diagnosis of acute vertigo in childhood that rarely includes the possibility of a brainstem infarct whose recognition through appropriate clinical examination is nevertheless capital for appropriate investigations and management.

Acoustic radiation force impulse sonography in assessing children with biliary atresia for liver transplantation.

BACKGROUND: Children with biliary atresia are prone to developing progressive hepatic fibrosis and biliary cirrhosis following the Kasai operation. The only treatment is liver transplantation. OBJECTIVE: To assess liver fibrosis by acoustic radiation force impulse elastography (ARFI) in children who had Kasai operation, with the goal of identifying an ARFI value cut-off for children requiring liver transplantation. MATERIALS AND METHODS: Of the 32 post-Kasai children included, 19 were transplanted or listed for transplantation (group A), while 13 were not on the list during their follow-up (group B). We recorded biopsies, blood samples and ARFI values over time, including at Kasai operation and at transplantation. We estimated an association between groups and continuous variables using generalized estimating equations, and we compared categorical variables using the Fisher exact test. RESULTS: Portal hypertension signs were similar in both groups, whereas ARFI values were higher in group A (mean±standard deviation=3.3±1.2 m/s) than in group B (2.0±0.7 m/s; P=.0003). Eighteen of 19 (94.7%) children in group A and 6/13 (46.2%) children in group B presented with two consecutive ARFI values ≥2 m/s (sensitivity=7%, specificity=53.8%; P=0.003). CONCLUSION: We found that children who were transplanted had two consecutive ARFI values ≥2 m/s during follow-up. ARFI for evaluation of post-Kasai liver fibrosis may assist the long-term assessment of biliary atresia and may even guide treatment decisions.

State-of-the-art MRI techniques in neuroradiology: principles, pitfalls, and clinical applications.

This article reviews the most relevant state-of-the-art magnetic resonance (MR) techniques, which are clinically available to investigate brain diseases. MR acquisition techniques addressed include notably diffusion imaging (diffusion-weighted imaging (DWI), diffusion tensor imaging (DTI), and diffusion kurtosis imaging (DKI)) as well as perfusion imaging (dynamic susceptibility contrast (DSC), arterial spin labeling (ASL), and dynamic contrast enhanced (DCE)). The underlying models used to process these images are described, as well as the theoretic underpinnings of quantitative diffusion and perfusion MR imaging-based methods. The technical requirements and how they may help to understand, classify, or follow-up neurological pathologies are briefly summarized. Techniques, principles, advantages but also intrinsic limitations, typical artifacts, and alternative solutions developed to overcome them are discussed. In this article, we also review routinely available three-dimensional (3D) techniques in neuro MRI, including state-of-the-art and emerging angiography sequences, and briefly introduce more recently proposed 3D quantitative neuro-anatomy sequences, and new technology, such as multi-slice and multi-transmit imaging.

Concomitant septic arthritis and osteomyelitis of the hip in young children; a new pathophysiological hypothesis suggested by MRI enhancement pattern.

BACKGROUND: In children, septic arthritis (SA) of the hip is either primary or concomitant with acute haematogenous osteomyelitis (AHO). However, seldom, patients with isolated SA at presentation, may later show osteomyelitis in the metaphysis. The aim of this study was to elaborate a physiopathological hypothesis based on the peculiar MRI findings to explain the onset of AHO after SA. METHODS: Cases of acute infection of the hip admitted between January 2010 and December 2013 were retrospectively reviewed to assess radiographic and MRI features, as well as bacteriological findings. Only children with isolated SA were included in this study, whereas cases of concomitant SA and AHO at presentation were excluded. RESULTS: Ten patients met the inclusion criteria. Six (1-11 months) demonstrated, on the initial MRI, decreased perfusion on gadolinium enhanced fat-suppressed T1-weighted sequence of the femoral epiphysis and developed one month later metaphyseal AHO. Four (5-14 years) did not show decreased perfusion and did not develop AHO on follow-up. The type of germ involved influenced neither the type of enhancement pattern nor the outcome. CONCLUSIONS: Age under one year and decreased perfusion of the affected femoral epiphysis increases the risk of secondary AHO. Our study is the first report in human medicine supporting the physiopathological hypothesis described by Alderson et al. in an animal model: primary infection can originally affect the joint, then penetrate the epiphyseal cartilage, and finally spread into the metaphyseal region through transphyseal vessels present only in the first 12/18 months of life.