Biallelic missense mutations in MARS are responsible for rare but severe cases of pulmonary alveolar proteinosis (PAP) prevalent on the island of La Réunion. MARS encodes cytosolic methionyl‐tRNA ...synthetase (MetRS), an essential translation factor. The multisystemic effects observed in patients with this form of PAP are consistent with a loss‐of‐function defect in an ubiquitously expressed enzyme. The pathophysiological mechanisms involved in MARS‐related PAP are currently unknown. In this work, we analyzed the effect of the PAP‐related mutations in MARS on the thermal stability and on the catalytic parameters of the MetRS mutants, relative to wild‐type. The effect of these mutations on the structural integrity of the enzyme as a member of the cytosolic multisynthetase complex was also investigated. Our results establish that the PAP‐related substitutions in MetRS impact the tRNAMet‐aminoacylation reaction especially at the level of methionine recognition, and suggest a direct link between the loss of activity of the enzyme and the pathological disorders in PAP.
Mutations in MARS that are recovered in human pulmonary alveolar proteinosis alter aminoacylation activity of cytoplasmic methionyl‐tRNA synthetase, but do not prevent its association within the multisynthetase complex.
Paediatric airway endoscopy is accepted as a diagnostic and therapeutic procedure, with an expanding number of indications and applications in children. The aim of this European Respiratory Society ...task force was to produce a statement on interventional bronchoscopy in children, describing the evidence available at present and current clinical practice, and identifying areas deserving further investigation. The multidisciplinary task force panel performed a systematic review of the literature, focusing on whole lung lavage, transbronchial and endobronchial biopsy, transbronchial needle aspiration with endobronchial ultrasound, foreign body extraction, balloon dilation and occlusion, laser-assisted procedures, usage of airway stents, microdebriders, cryotherapy, endoscopic intubation, application of drugs and other liquids, and caregiver perspectives. There is a scarcity of published evidence in this field, and in many cases the task force had to resort to the collective clinical experience of the committee to develop this statement. The highlighted gaps in knowledge underline the need for further research and serve as a call to paediatric bronchoscopists to work together in multicentre collaborations, for the benefit of children with airway disorders.
Methionyl-tRNA synthetase (MARS) catalyzes the ligation of methionine to tRNA and is critical for protein biosynthesis. We identified biallelic missense mutations in MARS in a specific form of ...pediatric pulmonary alveolar proteinosis (PAP), a severe lung disorder which is prevalent on the Island of Réunion and whose molecular basis is unresolved. Mutations were found in 26 individuals from Réunion and nearby islands and 2 families from other countries. Functional consequences of the mutated alleles were assessed by growth and methionine incorporation assays in yeast. Enzyme activity was attenuated in liquid medium without methionine, but could be restored by methionine supplementation. In summary, identification of a founder mutation in MARS led to the molecular definition of a specific type of PAP and will enable carrier screening in the affected community and possibly opens new treatment opportunities.
Primary ciliary dyskinesia (PCD) is a group of autosomal-recessive disorders resulting from cilia and sperm-flagella defects, which lead to respiratory infections and male infertility. Most ...implicated genes encode structural proteins that participate in the composition of axonemal components, such as dynein arms (DAs), that are essential for ciliary and flagellar movements; they explain the pathology in fewer than half of the affected individuals. We undertook this study to further understand the pathogenesis of PCD due to the absence of both DAs. We identified, via homozygosity mapping, an early frameshift in LRRC6, a gene that encodes a leucine-rich-repeat (LRR)-containing protein. Subsequent analyses of this gene mainly expressed in testis and respiratory cells identified biallelic mutations in several independent individuals. The situs inversus observed in two of them supports a key role for LRRC6 in embryonic nodal cilia. Study of native LRRC6 in airway epithelial cells revealed that it localizes to the cytoplasm and within cilia, whereas it is absent from cells with loss-of-function mutations, in which DA protein markers are also missing. These results are consistent with the transmission-electron-microscopy data showing the absence of both DAs in cilia or flagella from individuals with LRRC6 mutations. In spite of structural and functional similarities between LRRC6 and DNAAF1, another LRR-containing protein involved in the same PCD phenotype, the two proteins are not redundant. The evolutionarily conserved LRRC6, therefore, emerges as an additional player in DA assembly, a process that is essential for proper axoneme building and that appears to be much more complex than was previously thought.
Interstitial lung disease in children (chILD) is rare, and most centres will only see a few cases/year. There are numerous possible underlying diagnoses, with specific and non-specific treatment ...possibilities. The chILD-EU collaboration has brought together centres from across Europe to advance understanding of these considerations, and as part of this process, has created standard operating procedures and protocols for the investigation of chILD. Where established consensus documents exist already, for example, for the performance of bronchoalveolar lavage and processing of lung biopsies, these have been adopted. This manuscript reports our proposals for a staged investigation of chILD, starting from when the condition is suspected to defining the diagnosis, using pathways dependent on the clinical condition and the degree of illness of the child. These include the performance of genetic testing, echocardiography, high-resolution CT, bronchoscopy when appropriate and the definitive investigation of lung biopsy, in order to establish a precise diagnosis. Since no randomised controlled trials of treatment have ever been performed, we also report a Delphi consensus process to try to harmonise treatment protocols such as the use of intravenous and oral corticosteroids, and add-on therapies such as hydroxychloroquine and azithromycin. The aim is not to dictate to clinicians when a therapeutic trial should be performed, but to offer the possibility to collaborators of having a unified approach when a decision to treat has been made.
Severe asthma (SA) affects less than 5% of the pediatric asthma population but is considered to account for approximately half of total pediatric asthma healthcare costs. Allergic comorbidities, ...including food allergies (FA) and allergic rhinitis (AR), are frequent in children with SA (1). The presence of FA and AR increases asthma severity (1-6) and medication use (4-6).
Primary ciliary dyskinesia (PCD) is a rare autosomal-recessive condition resulting from structural and/or functional defects of the axoneme in motile cilia and sperm flagella. The great majority of ...mutations identified so far involve genes whose defects result in dynein-arm anomalies. By contrast, PCD due to CC/RS defects (those in the central complex CC and radial spokes RSs), which might be difficult to diagnose, remains mostly unexplained. We identified non-ambiguous RSPH3 mutations in 5 of 48 independent families affected by CC/RS defects. RSPH3, whose ortholog in the flagellated alga Chlamydomonas reinhardtii encodes a RS-stalk protein, is mainly expressed in respiratory and testicular cells. Its protein product, which localizes within the cilia of respiratory epithelial cells, was undetectable in airway cells from an individual with RSPH3 mutations and in whom RSPH23 (a RS-neck protein) and RSPH1 and RSPH4A (RS-head proteins) were found to be still present within cilia. In the case of RSPH3 mutations, high-speed-videomicroscopy analyses revealed the coexistence of immotile cilia and motile cilia with movements of reduced amplitude. A striking feature of the ultrastructural phenotype associated with RSPH3 mutations is the near absence of detectable RSs in all cilia in combination with a variable proportion of cilia with CC defects. Overall, this study shows that RSPH3 mutations contribute to disease in more than 10% of PCD-affected individuals with CC/RS defects, thereby allowing an accurate diagnosis to be made in such cases. It also unveils the key role of RSPH3 in the proper building of RSs and the CC in humans.
Interplays between Mycobacterium tuberculosis, the etiological agent of tuberculosis (TB) in human and host professional phagocytes, namely macrophages (Mphis) and dendritic cells (DCs), are central ...to immune protection against TB and to TB pathogenesis. We and others have recently shown that the C-type lectin dendritic cell-specific intercellular adhesion molecule-3 grabbing nonintegrin (DC-SIGN; CD209) mediates important interactions between mycobacteria and human monocyte-derived DCs (MoDCs) in vitro.
In order to explore the possible role of DC-SIGN in M. tuberculosis infection in vivo, we have analysed DC-SIGN expression in broncho-alveolar lavage (BAL) cells from patients with TB (n = 40) or with other non-mycobacterial lung pathologies, namely asthma (n = 14) and sarcoidosis (n = 11), as well as from control individuals (n = 9). We show that in patients with TB, up to 70% of alveolar Mphis express DC-SIGN. By contrast, the lectin is barely detected in alveolar Mphis from all other individuals. Flow cytometry, RT-PCR, and enzyme-linked immunosorbent assay analyses of BAL-derived fluids and cells indicated that M. tuberculosis infection induces DC-SIGN expression in alveolar Mphis by a mechanism that is independent of Toll-like receptor-4, interleukin (IL)-4, and IL-13. This mechanism most likely relies on the secretion of soluble host and/or mycobacterial factors that have yet to be identified, as both infected and uninfected bystander Mphis were found to express DC-SIGN in the presence of M. tuberculosis. Immunohistochemical examination of lung biopsy samples from patients with TB showed that the bacilli concentrate in pulmonary regions enriched in DC-SIGN-expressing alveolar Mphis in vivo. Ex vivo binding and inhibition of binding experiments further revealed that DC-SIGN-expressing alveolar Mphis constitute preferential target cells for M. tuberculosis, as compared to their DC-SIGN- counterparts. In contrast with what has been reported previously in MoDCs in vitro, ex vivo DC-SIGN ligation by mycobacterial products failed to induce IL-10 secretion by alveolar Mphis, and IL-10 was not detected in BALs from patients with TB.
Altogether, our results provide further evidence for an important role of DC-SIGN during TB in humans. DC-SIGN induction in alveolar Mphis may have important consequences on lung colonization by the tubercle bacillus, and on pulmonary inflammatory and immune responses in the infected host.
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Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
To describe the characteristics of pediatric cases of eosinophilic granulomatosis with polyangiitis (EGPA), a systemic necrotizing vasculitis rarely diagnosed in children, retrieved from the French ...Reference Center for rare pediatric lung diseases and compared with adult cases included in the French Vasculitis Study Group cohort.
We collected information on pediatric EGPA disease presentation, management, and outcome. Cases met the Lanham criteria and/or American College of Rheumatology classification criteria.
Fourteen cases of pediatric EGPA were included, from 1980 to 2012, with a median follow-up of 58.5 months. Median age at diagnosis was 12.3 years. All cases had respiratory involvement. The organ systems most frequently involved were the upper airway (85%), skin (71%), digestive tract (64%), and heart (57%). Neurological and renal involvement were rare. Four of the fourteen children were positive for ANCA (30.7%). During follow-up, three children required intensive care and one child died. The relapse rate was 64%. In comparison with an adult cohort, we found more ENT, heart, and digestive-tract involvement, and fewer neurological manifestations. In children, the delay between asthma onset and diagnosis was shorter, and biopsies showed fewer features of vasculitis.
This French cohort is the biggest pediatric EGPA series described to date, with a long follow-up period. The findings confirm that pediatric EGPA has specific clinical, radiological, and histological characteristics that differ from adult EGPA. Development of systemic symptoms, and consequently diagnosis, occur with a shorter delay in children, mainly during the eosinophilic phase and leading to a specific presentation.
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