Structural insights into the cause of human RSPH4A primary ciliary dyskinesia.

Cilia and flagella are evolutionarily conserved eukaryotic organelles involved in cell motility and signaling. In humans, mutations in Radial Spoke Head Component 4A (RSPH4A) can lead to primary ciliary dyskinesia (PCD), a life-shortening disease characterized by chronic respiratory tract infections, abnormal organ positioning, and infertility. Despite its importance for human health, the location of RSPH4A in human cilia has not been resolved, and the structural basis of RSPH4A-/- PCD remains elusive. Here, we present the native three-dimensional structure of RSPH4A-/- human respiratory cilia using samples collected noninvasively from a PCD patient. Using cryo-electron tomography (cryo-ET) and subtomogram averaging, we compared the structures of control and RSPH4A-/- cilia, revealing primary defects in two of the three radial spokes (RSs) within the axonemal repeat and secondary (heterogeneous) defects in the central pair complex. Similar to RSPH1-/- cilia, the radial spoke heads of RS1 and RS2, but not RS3, were missing in RSPH4A-/- cilia. However, RSPH4A-/- cilia also exhibited defects within the arch domains adjacent to the RS1 and RS2 heads, which were not observed with RSPH1 loss. Our results provide insight into the underlying structural basis for RSPH4A-/- PCD and highlight the benefits of applying cryo-ET directly to patient samples for molecular structure determination.

The Prevalence and Significance of Staphylococcus aureus in Patients with Non-Cystic Fibrosis Bronchiectasis.

RATIONALE: Staphylococcus aureus is commonly cultured from the sputum of patients with bronchiectasis; however, little is known about the prevalence of the organism in these patients, the characteristics of patients who have grown the organism, or its implications. OBJECTIVES: Determine the relationship between S. aureus and pulmonary function, frequency of exacerbations, and frequency of hospitalization in patients with bronchiectasis Methods: The Bronchiectasis Research Registry is a database of adults with non-cystic fibrosis bronchiectasis identified from 13 sites within the United States. Baseline and follow-up demographic, spirometric, microbiologic, and therapeutic data were entered into a central web-based database. Patients were grouped into three cohorts based on their previous respiratory cultures at the time of entry into the Registry: 1) no prior S. aureus or glucose-nonfermenting gram-negative bacilli (NF-GNB) (Pseudomonas, Stenotrophomonas, or Burkholderia spp.); 2) prior S. aureus at least once; or 3) no prior S. aureus but prior NF-GNB at least once. The association between S. aureus isolation and pulmonary function and frequency of exacerbations and hospital admissions was assessed, both at baseline and after 1 year of follow-up. RESULTS: S. aureus was cultured from 94 of 830 patients (11.3%) included in the analysis. Patients who had grown S. aureus before entry into the Registry had a frequency of prior exacerbations and baseline pulmonary function that was between that of patients who had grown NF-GNB and those who had grown neither NF-GNB or S. aureus. Similarly, at the first follow-up visit after study entry, patients who had grown S. aureus had a frequency of exacerbations and hospitalizations that was between those of patients who had grown NF-GNB and those who had grown neither NF-GNB nor S. aureus. However, in multivariate analysis, S. aureus was not associated with pulmonary function, frequency of exacerbation, or hospital admissions. There were no significant differences in patient characteristics or outcomes between patients who had methicillin-sensitive and methicillin-resistant S. aureus. CONCLUSIONS: Staphylococcus aureus does not appear to be an independent risk factor for severe disease in patients with bronchiectasis enrolled in the Bronchiectasis Research Registry.