PCD Genes-From Patients to Model Organisms and Back to Humans

The mechanism of UV accelerated aging of polyvinyl chloride in marine environment: The role of free radicals

This study systematically investigated the photo-aging of polyvinyl chloride (PVC) in deionized water, estuary water, and seawater. As the concentration of Cl- increases, the carbonyl index (CI) of PVC during photo aging also increases, indicating that Cl- plays a dominant role in PVC photoaging in the environment, which enhance carbonyl index and •OH radical accumulation. Unlike previous studies, this study discovered that halogen radicals were also generated during PVC aging. Compared to •OH radicals, halogen radicals exhibit stronger selectivity and are more conducive to the photo aging of PVC. Additionally, it was found that PVC shows specific toxicity to Paramecia caudatum at various concentrations both before and after aging, affecting the reproduction process of Paramecia caudatum. This study elucidates the mechanism by which anions in natural water bodies affect the rate of PVC aging, providing a scientific basis for understanding the photodegradation of MPs in the ocean.

Development and Initial Characterization of Pigs with DNAI1 Mutations and Primary Ciliary Dyskinesia

Mutations in more than 50 different genes cause primary ciliary dyskinesia (PCD) by disrupting the activity of motile cilia that facilitate mucociliary transport (MCT). Knowledge of PCD has come from studies identifying disease-causing mutations, characterizing structural cilia abnormalities, finding genotype-phenotype relationships, and studying the cell biology of cilia. Despite these important findings, we still lack effective treatments and people with PCD have significant pulmonary impairment. As with many other diseases, a better understanding of pathogenic mechanisms may lead to effective treatments. To pursue disease mechanisms, we used CRISPR-Cas9 to develop a PCD pig with a disrupted DNAI1 gene. PCD pig airway cilia lacked the outer dynein arm and had impaired beating. MCT was impaired under both baseline conditions and after cholinergic stimulation in PCD pigs. Neonatal PCD pigs developed neonatal respiratory distress with evidence of atelectasis, air trapping, and airway mucus obstruction. Despite airway mucus accumulation, lung bacterial counts were similar between neonatal wild-type and PCD pigs. Sinonasal disease was present in all neonatal PCD pigs. Older PCD pigs developed worsening airway mucus obstruction, inflammation, and bacterial infection. This pig model closely mimics the disease phenotype seen in people with PCD and can be used to better understand the pathophysiology of PCD airway disease.

Mutations in CFAP47, a previously reported MMAF causative gene, also contribute to the respiratory defects in patients with PCD

BACKGROUND

Primary ciliary dyskinesia (PCD) is a genetic ciliopathy characterized by dysfunction of motile cilia. Currently, approximately 50 causative genes accounting for 60%-70% of all PCD cases have been identified in PCD-affected individuals, but the etiology in approximately 30%-40% of PCD cases remains unknown.

METHODS

We analyzed the clinical and genetic data of two PCD individuals who were suspected of having PCD. Whole-exome sequencing and Sanger sequencing were performed to identify and verify the variants in CFAP47. We also evaluated the expression of CFAP47 by real-time quantitative PCR and immunofluorescence. Transmission electron microscopy in respiratory epithelial cells was also conducted to analyze ciliary function.

RESULTS

Two hemizygous missense variants of X-linked CFAP47 in two unrelated PCD individuals were identified. The expression of CFAP47 in two PCD individuals was significantly reduced in vivo and in vitro assays. A reduction in the amount of epithelial ciliary cells and basal bodies from PCD individuals was also observed.

CONCLUSIONS

We describe two hemizygous missense variants of X-linked CFAP47 in two unrelated PCD individuals and prove CFAP47 variants are related to a reduced number of epithelial ciliary cells. Therefore, we suggest that CFAP47 should be known as a novel pathogenic gene of human PCD.

Clinical and genetic analysis of two patients with primary ciliary dyskinesia caused by a novel variant of DNAAF2

BACKGROUND

The study describes the clinical manifestations and variant screening of two Chinese siblings with primary ciliary dyskinesia (PCD). They carry the same DNAAF2 genotype, which is an extremely rare PCD genotype in the Chinese population. In addition, the study illustrated an overview of published variants on DNAAF2 to date.

METHODS

A two-child family was recruited for the study. Clinical manifestations, laboratory tests, bronchoscopic and otoscopic images, and radiographic data were collected. Whole blood was collected from siblings and their parents for whole-exome sequencing (WES) and Sanger sequencing to screen variants.

RESULTS

The two siblings exhibited typical clinical manifestations of PCD. Two compound heterozygous variants in DNAAF2 were detected in both by WES. Nonsense variant c.156 C>A and frameshift variant c.177_178insA, which was a novel variant.

CONCLUSION

The study identified a novel variant of DNAAF2 in Chinese children with a typical phenotype of PCD, which may enrich our knowledge of the clinical, diagnostic and genetic information of DNAAF2-induced PCD in children.

Mapping the Most Common Founder Variant in RSPH9 That Causes Primary Ciliary Dyskinesia in Multiple Consanguineous Families of Bedouin Arabs

INTRODUCTION

Primary ciliary dyskinesia (PCD) is a congenital thoracic disorder caused by dysfunction of motile cilia, resulting in insufficient mucociliary clearance of the lungs. The overall aim of this study is to identify causative defective genes in PCD-affected individuals in the Kuwaiti population.

METHODS

A cohort of multiple consanguineous PCD families was identified from Kuwaiti patients and genomic DNA from the family members was isolated using standard procedures. The DNA samples from all affected individuals were analyzed by whole exome sequencing (WES). Transmission electron microscopy (TEM) and immunofluorescent analysis (IF) were performed on samples obtained by nasal brushings to identify specific structural abnormalities within ciliated cells.

RESULTS

Here, we present six multiplex families with 11 patients who all presented with typical PCD symptoms. Ten out of eleven patients inherited a 3 bp homozygous deletion of GAA in RSPH9, whereas the eleventh patients inherited this variant in trans with a frameshift deletion in RSPH9. Genetic results were confirmed by segregation analysis. The in-frame deletion of GAA in RSPH9 has previously been published as pathogenic in both annotated RSPH9 transcript variants (1 and 2). In contrast, the previously unpublished RSPH9 frameshift deletion identified in KU-15.IV2 impacts only RSPH9 transcript variant two. Regarding all 11 PCD individuals analyzed, IF results demonstrated absence of RSPH9 protein and TEM analysis showed the typical findings in RSPH9 mutant individuals.

CONCLUSIONS

We present the largest cohort of PCD individuals affected by the founder in-frame deletion GAA in RSPH9. This founder variant is the most common PCD-causing variant in Bedouin Arabs in Kuwait.

Schmidtea mediterranea as a Model Organism to Study the Molecular Background of Human Motile Ciliopathies

Cilia and flagella are evolutionarily conserved organelles that form protrusions on the surface of many growth-arrested or differentiated eukaryotic cells. Due to the structural and functional differences, cilia can be roughly classified as motile and non-motile (primary). Genetically determined dysfunction of motile cilia is the basis of primary ciliary dyskinesia (PCD), a heterogeneous ciliopathy affecting respiratory airways, fertility, and laterality. In the face of the still incomplete knowledge of PCD genetics and phenotype-genotype relations in PCD and the spectrum of PCD-like diseases, a continuous search for new causative genes is required. The use of model organisms has been a great part of the advances in understanding molecular mechanisms and the genetic basis of human diseases; the PCD spectrum is not different in this respect. The planarian model (Schmidtea mediterranea) has been intensely used to study regeneration processes, and-in the context of cilia-their evolution, assembly, and role in cell signaling. However, relatively little attention has been paid to the use of this simple and accessible model for studying the genetics of PCD and related diseases. The recent rapid development of the available planarian databases with detailed genomic and functional annotations prompted us to review the potential of the S. mediterranea model for studying human motile ciliopathies.

Prevalence and founder effect of DRC1 exon 1-4 deletion in Korean patients with primary ciliary dyskinesia

Primary ciliary dyskinesia (PCD) is a genetically heterogeneous disorder affecting ciliary structure and function. PCD exhibiting dynein regulatory complex subunit 1 (DRC1) exon 1-4 deletion has been reported in several Japanese PCD patients; however, no large scale studies have been performed. Here, we aimed to determine the prevalence and founder effect of this variant in the Korean population. Using an in-house copy number variation tool, we screened for DRC1 exon 1-4 deletion in 20 patients with PCD and exome data of 1435 patients in the Seoul National University Hospital repository. In cases of suspected DRC1 deletion, confirmatory gap-PCR was performed. In a PCD cohort, three of 20 (15%) patients were positive for DRC1 exon 1-4 deletion (NM_145038.5(DRC1): c.1-3952_540 + 1331del27748-bp) while pathogenic variants were found in CCDC39 (N = 1), DNAAF6 (N = 1), DNAH9 (N = 1). In the 1,435-sample exome data, seven patients (0.49%) were confirmed to have DRC1 exon 1-4 deletion. A chimeric sequence including the junction was searched from the 1000 Genomes Project data repository. One Japanese patient (0.96%) was found to have the same DRC1 exon 1-4 deletion, which was absent in other populations. This study demonstrated that the DRC1 exon 1-4 deletion is a founder mutation based on haplotype analysis. In summary, the prevalence of PCD based on DRC1 exon 1-4 deletion is particularly high in Korean and Japanese populations, which is attributed to the founder effect. Genetic testing for DRC1 exon 1-4 deletion should be considered as an initial screening tool for Korean and Japanese patients with PCD.

Paramecium bursaria as a Potential Tool for Evaluation of Microplastics Toxicity

Microplastics (MPs) are normally defined as small plastic wastes with a size of 1 μm to 5 mm in diameter. This tiny plastic debris is abundant in aquatic systems and poses a great threat to aquatic biota. To date, toxicological assessment of MPs is predominantly dependent on metazoan animals, although their applications are sometimes limited due to the high cost, narrow ecological niche, or ethical considerations. In this regard, unicellular eukaryotes (i.e., protozoa) that are ubiquitously present in nature represent a promising alternative for evaluating the toxicity of MPs. In this study, we selected Paramecium bursaria (P. bursaria) as a representative of protozoa and further investigated behavioral and molecular changes in MPs-exposed P. bursaria. Our results showed that following MPs uptake, P. bursaria exhibited various changes, including anomalies in swimming patterns, reduction in moving speed, impairment of avoidance behavior, elevation of oxidative stress, and potential disturbance of endosymbiosis. These elicited changes in P. bursaria in response to MPs exposure were pronounced and measurable. Overall, this study demonstrated that P. bursaria could serve as a promising alternative for the toxicological assessment of MPs and may be further applied to evaluate the toxicity of other environmental contaminants.