Loss-of-function mutations in RSPH1 cause primary ciliary dyskinesia with central-complex and radial-spoke defects.

Primary ciliary dyskinesia (PCD) is a rare autosomal-recessive respiratory disorder resulting from defects of motile cilia. Various axonemal ultrastructural phenotypes have been observed, including one with so-called central-complex (CC) defects, whose molecular basis remains unexplained in most cases. To identify genes involved in this phenotype, whose diagnosis can be particularly difficult to establish, we combined homozygosity mapping and whole-exome sequencing in a consanguineous individual with CC defects. This identified a nonsense mutation in RSPH1, a gene whose ortholog in Chlamydomonas reinhardtii encodes a radial-spoke (RS)-head protein and is mainly expressed in respiratory and testis cells. Subsequent analyses of RSPH1 identified biallelic mutations in 10 of 48 independent families affected by CC defects. These mutations include splicing defects, as demonstrated by the study of RSPH1 transcripts obtained from airway cells of affected individuals. Wild-type RSPH1 localizes within cilia of airway cells, but we were unable to detect it in an individual with RSPH1 loss-of-function mutations. High-speed-videomicroscopy analyses revealed the coexistence of different ciliary beating patterns-cilia with a normal beat frequency but abnormal motion alongside immotile cilia or cilia with a slowed beat frequency-in each individual. This study shows that this gene is mutated in 20.8% of individuals with CC defects, whose diagnosis could now be improved by molecular screening. RSPH1 mutations thus appear as a major etiology for this PCD phenotype, which in fact includes RS defects, thereby unveiling the importance of RSPH1 in the proper building of CCs and RSs in humans.

Psychological effects of false-positive results in cystic fibrosis newborn screening: a two-year follow-up.

OBJECTIVE: To evaluate parental stress after a false-positive result at the time of the cystic fibrosis (CF) newborn screening (NBS), attributable to heterozygotism or persistent hypertrypsinemia. STUDY DESIGN: A prospective study was conducted in 86 French families at 3, 12, and 24 months after NBS. A psychologist conducted interviews with a questionnaire, the Perceived Stress Scale, and the Vulnerable Child Scale. RESULTS: Overall, 96.5% of parents said they had been anxious at the time of the sweat test. However, 86% felt entirely reassured 3 months after the test. The mean Perceived Stress Scale score did not differ from that observed in the French population. Mean Vulnerable Child Scale scores were high, associated with a low Parental Perception of Child Vulnerability. These results did not differ significantly at 1 and 2 years. In total, 86% to 100% of families no longer worried about CF. All parents stated that they would have the test performed again for another child. CONCLUSIONS: CF NBS can lead to false-positive results, causing parental anxiety, which quickly decreases after a sweat test performed soon after the phone call.

Lung disease modifier genes in cystic fibrosis.

Cystic fibrosis (CF) is recognized as a single gene disorder. However, a considerable diversity in its clinical phenotype has been documented since the description of the disease. Identification of additional gene alleles, so called "modifier genes" that directly influence the phenotype of CF disease became a challenge in the late '90ies, not only for the insight it provides into the CF pathophysiology, but also for the development of new potential therapeutic targets. One of the most studied phenotype has been the lung disease severity as lung dysfunction is the major cause of morbidity and mortality in CF. This review details the results of two main genetic approaches that have mainly been explored so far: (1) an "a priori" approach, i.e. the candidate gene approach; (2) a "without a priori" approach, analyzing the whole genome by linkage and genome-wide association studies (GWAS), or the whole exome by exome sequencing.

Tufted angioma with Kasabach-Merritt syndrome mistaken for child abuse.

We report the case of a 2-month-old infant with a single apparently ecchymotic lesion on the shoulder that raised suspicions of abuse. The medicolegal examination concluded that the appearance of the lesion was only mildly suggestive of an ecchymosis. A second, temporally remote examination confirmed this doubt. The evolution of the lesion, notably an increase in its volume, allowed us to rule out a traumatic lesion and was suggestive of a vascular tumor. The histological type of the tumor was a tufted angioma. There was thrombocytopenia and consumptive coagulopathy. All these data confirmed the diagnosis of Kasabach-Merritt syndrome. In contrast to benign infantile hemangiomas, which are frequent and well-known in clinical practice, vascular tumors complicated by Kasabach-Merritt syndrome are rare. They deserve to be widely known because they mandate rapid medical management and because they are one of the only differential diagnoses of ecchymosis, especially in children. When there is doubt about the traumatic nature of a cutaneous lesion, a temporally remote examination is essential. The evolution of the lesion may then suggest a dermatologic origin.

AGER -429T/C is associated with an increased lung disease severity in cystic fibrosis.

The clinical course of cystic fibrosis (CF) varies between patients bearing identical CFTR mutations, suggesting the involvement of modifier genes. We assessed the association of lung disease severity with the variant AGER -429 T/C, coding for RAGE, a pro-inflammatory protein, in CF patients from the French CF Gene Modifier Study. We analyzed the lung function of 967 CF patients p.Phe508del homozygous. FEV(1) was analyzed as CF-specific percentile adjusted on age, height and mortality. AGER -429T/C polymorphism was genotyped and its function was evaluated in vitro by measurement of the luciferase activity. AGER -429 minor allele (C) was associated with poorer lung function (p = 0.03). In vitro, the promoter activity was higher in cells transfected with AGER -429C compared to cells transfected with the AGER -429T allele (p = 0.016 in BEAS-2B cells). AGER seems to be a modifier gene of lung disease severity in CF, and could be an interesting biomarker of CF airway inflammation. The functional promoter AGER -429C variant is associated with an increased RAGE expression that can lead to an increased lung inflammation and a more severe lung disease.

Ancestral haplotype 8.1 and lung disease severity in European cystic fibrosis patients.

BACKGROUND: The clinical course of cystic fibrosis (CF) lung disease varies between patients bearing identical CFTR mutations. This suggests that additional genetic modifiers may contribute to the pulmonary phenotype. The highly conserved ancestral haplotype 8.1 (8.1AH), carried by up to one quarter of Caucasians, comprises linked gene polymorphisms on chromosome 6 that play a key role in the inflammatory response: LTA +252A/G; TNF -308G/A, HSP70-2 +1267A/G and RAGE -429T/C. As inflammation is a key component inducing CF lung damage, we investigated whether the 8.1AH represents a lung function modifier in CF. METHODS: We analyzed the lung function of 404 European CF patients from France (n=230), Germany (n=95) and UK (n=79). FEV(1) differences between 8.1AH carriers and non-carriers were calculated in each country and pooled using a random effects model. RESULTS: The frequency of 8.1AH carriers was similar between French (22%), German (29%) and UK (27%) patients. We found that 8.1AH carriers had significantly lower FEV(1), adjusted for age classes and countries (P<0.04, mean FEV(1) difference -6.4% CI95% [-12.4%, -0.5%]). No difference was observed with respect to BMI Z-scores and chronic colonization with P. aeruginosa. CONCLUSIONS: These findings support the concept that 8.1AH is an important genetic modifier of lung disease in CF. To conclude, multiple linked genes outside the CF locus might explain some of the variability in lung phenotype.