Primary ciliary dyskinesia (PCD) is a genetically heterogeneous disorder of motile cilia. Most of the disease-causing mutations identified to date involve the heavy (DNAH5) or intermediate (DNAI1) chain dynein genes in ciliary outer dynein arms, although a few mutations have been noted in other genes. Clinical molecular genetic testing for PCD is available for the most common mutations. The respiratory manifestations of PCD (chronic bronchitis leading to bronchiectasis, chronic rhino-sinusitis and chronic otitis media) reflect impaired mucociliary clearance owing to defective axonemal structure. Ciliary ultrastructural analysis in most patients (>80%) reveals defective dynein arms, although defects in other axonemal components have also been observed. Approximately 50% of PCD patients have laterality defects (including situs inversus totalis and, less commonly, heterotaxy and congenital heart disease), reflecting dysfunction of embryological nodal cilia. Male infertility is common and reflects defects in sperm tail axonemes. Most PCD patients have a history of neonatal respiratory distress, suggesting that motile cilia play a role in fluid clearance during the transition from a fetal to neonatal lung. Ciliopathies involving sensory cilia, including autosomal dominant or recessive polycystic kidney disease, Bardet-Biedl syndrome, and Alstrom syndrome, may have chronic respiratory symptoms and even bronchiectasis suggesting clinical overlap with PCD.

Dilated intercellular spaces are a feature of reflux damage to human esophageal epithelium. As a morphological marker of increased paracellular permeability, its presence in patients without endoscopic abnormalities may help explain their development of heartburn.

Rationale: Several studies suggest that nasal nitric oxide (nNO) measurement could be a test for primary ciliary dyskinesia (PCD), but the procedure and interpretation have not been standardized.Objectives: To use a standard protocol for measuring nNO to establish a diseasespecific cutoff value at one site, and then validate at six other sites.Methods: At the lead site, nNO was prospectively measured in individuals later confirmed to have PCD by ciliary ultrastructural defects (n = 143) or DNAH11 mutations (n = 6); and in 78 healthy and 146 disease control subjects, including individuals with asthma (n = 37), cystic fibrosis (n = 77), and chronic obstructive pulmonary disease (n = 32). A disease-specific cutoff value was determined, using generalized estimating equations (GEEs). Six other sites prospectively measured nNO in 155 consecutive individuals enrolled for evaluation for possible PCD. Measurements and Main Results:At the lead site, nNO values in PCD (mean 6 standard deviation, 20.7 6 24.1 nl/min; range, 1.5-207.3 nl/min) only rarely overlapped with the nNO values of healthy control subjects (304.6 6 118.8; 125.5-867.0 nl/min), asthma (267.8 6 103.2; 125.0-589.7 nl/min), or chronic obstructive pulmonary disease (223.7 6 87.1; 109.7-449.1 nl/min); however, there was overlap with cystic fibrosis (134.0 6 73.5; 15.6-386.1 nl/min). The disease-specific nNO cutoff value was defined at 77 nl/minute (sensitivity, 0.98; specificity, .0.999). At six other sites, this cutoff identified 70 of the 71 (98.6%) participants with confirmed PCD.Conclusions: Using a standardized protocol in multicenter studies, nNO measurement accurately identifies individuals with PCD, and supports its usefulness as a test to support the clinical diagnosis of PCD.

Primary ciliary dyskinesia (PCD) is an autosomal recessive disorder of cilia structure, function, and biogenesis leading to chronic infections of the respiratory tract, fertility problems and disorders of organ laterality. The diagnosis can be challenging, using traditional tools such as characteristic clinical features, ciliary functional and ultra-structural defects; newer screening tools such as nasal nitric oxide levels and genetic testing add to the diagnostic algorithm. There are thirty-two known PCD causing genes, and in the future, comprehensive genetic testing may screen young infants prior to developing symptoms thus improving survival. Therapies include surveillance of pulmonary function and microbiology, in addition to airway clearance, antibiotics and ideally, early referral to bronchiectasis centers. As with CF, standardized care at specialized centers using a multidisciplinary approach likely improves outcomes. In conjunction with the CF foundation, the PCD foundation, and with lead investigators and clinicians, is developing a network of PCD clinical centers to coordinate the effort in North America and Europe. As the network grows, care and knowledge will improve.

Airway epithelial tight junctions (TJs) serve to separate the external and internal environments of the lung. However, the members of the claudin family that mediate this function have not been fully delineated. We characterized the claudin expression in normal airways removed from human donors during lung transplantation and determined the contribution of each claudin to airway barrier function. Stable cell lines in NIH/3T3 and human airway (IB3.1) cells were constructed expressing the claudin components found in the human airway, claudin-1, -3, or -5. The effects of claudin expression on transepithelial resistance, permeability coefficients, and claudin-claudin interactions were assessed. Claudin-1 and -3 decreased solute permeability, whereas claudin-5 increased permeability. We also detected oligomerization of claudin-5 in cell lines and in freshly excised human airways. Coimmunoprecipitation studies revealed heterophilic interactions between claudin species in both cell lines and human airway epithelium. These suggest that airway TJs are regulated by claudinclaudin interactions that confer the selectivity of the junction.

SUMMARY Dyx1c1 has been associated with dyslexia and neuronal migration in the developing neocortex. Unexpectedly, we found that deletion of Dyx1c1 exons 2–4 in mice caused a phenotype resembling primary ciliary dyskinesia (PCD), a genetically heterogeneous disorder characterized by chronic airway disease, laterality defects, and male infertility. This phenotype was confirmed independently in mice with a Dyx1c1c.T2A start codon mutation recovered from an ENU mutagenesis screen. Morpholinos targeting dyx1c1 in zebrafish also created laterality and ciliary motility defects. In humans, recessive loss-of-function DYX1C1 mutations were identified in twelve PCD individuals. Ultrastructural and immunofluorescence analyses of DYX1C1-mutant motile cilia in mice and humans revealed disruptions of outer and inner dynein arms (ODA/IDA). DYX1C1 localizes to the cytoplasm of respiratory epithelial cells, its interactome is enriched for molecular chaperones, and it interacts with the cytoplasmic ODA/IDA assembly factor DNAAF2/KTU. Thus, we propose that DYX1C1 is a newly identified dynein axonemal assembly factor (DNAAF4).

Exposure to complex mixtures of air pollutants produces in ammation in the upper and lower respiratory tract. Because the nasal cavity is a common portal of entry, respiratory and olfactory epithelia are vulnerable targets for toxicological damage. This study has evaluated, by light and electron microscopy and immunohistochemica l expression of nuclear factor-kappa beta (NF-j B) and inducible nitric oxide synthase (iNOS), the olfactory and respiratory nasal mucosae, olfactory bulb, and cortical and subcortical structures from 32 healthy mongrel canine residents in Southwest Metropolitan Mexico City (SWMMC), a highly polluted urban region. Findings were compared to those in 8 dogs from Tlaxcala, a less polluted, control city. In SWMMC dogs, expression of nuclear neuronal NF-j B and iNOS in cortical endothelial cells occurred at ages 2 and 4 weeks; subsequen t damage included alterations of the blood-brain barrier (BBB), degenerating cortical neurons, apoptotic glial white matter cells, deposition of apolipoprotein E (apoE)-positive lipid droplets in smooth muscle cells and pericytes, nonneuritic plaques, and neuro brillary tangles. Persistent pulmonary in ammation and deteriorating olfactory and respiratory barriers may play a role in the neuropatholog y observed in the brains of these highly exposed canines. Neurodegenerativ e disorders such as Alzheimer's may begin early in life with air pollutants playing a crucial role.

Rationale: The relationship between clinical phenotype of childhood primary ciliary dyskinesia (PCD) and ultrastructural defects and genotype is poorly defined.Objectives: To delineate clinical features of childhood PCD and their associations with ultrastructural defects and genotype.Methods: A total of 118 participants younger than 19 years old with PCD were evaluated prospectively at six centers in North America using standardized procedures for diagnostic testing, spirometry, chest computed tomography, respiratory cultures, and clinical phenotyping.Measurements and Main Results: Clinical features included neonatal respiratory distress (82%), chronic cough (99%), and chronic nasal congestion (97%). There were no differences in clinical features or respiratory pathogens in subjects with outer dynein arm (ODA) defects (ODA alone; n = 54) and ODA plus inner dynein arm (IDA) defects (ODA 1 IDA; n = 18) versus subjects with IDA and central apparatus defects with microtubular disorganization (IDA/ CA/MTD; n = 40). Median FEV 1 was worse in the IDA/CA/MTD group (72% predicted) versus the combined ODA groups (92% predicted; P = 0.003). Median body mass index was lower in the IDA/ CA/MTD group (46th percentile) versus the ODA groups (70th percentile; P = 0.003). For all 118 subjects, median number of lobes with bronchiectasis was three and alveolar consolidation was two. However, the 5-to 11-year-old IDA/CA/MTD group had more lobes of bronchiectasis (median, 5; P = 0.0008) and consolidation (median, 3; P = 0.0001) compared with the ODA groups (median, 3 and 2, respectively). Similar findings were observed when limited to participants with biallelic mutations.Conclusions: Lung disease was heterogeneous across all ultrastructural and genotype groups, but worse in those with IDA/ CA/MTD ultrastructural defects, most of whom had biallelic mutations in CCDC39 or CCDC40.