Case report: The CCDC103 variant causes ultrastructural sperm axonemal defects and total sperm immotility in a professional athlete without primary ciliary diskinesia

Primary ciliary dyskinesia (PCD) is an inherited autosomal-recessive disorder characterized by abnormal ciliary motion, due to a defect in ciliary structure and/or function. This genetic condition leads to recurrent upper and lower respiratory infections, bronchiectasis, laterality defect, and subfertility. Male infertility is often associated with PCD, since the ultrastructure of the axoneme in the sperm tail is similar to that of the motile cilia of respiratory cells. We present the first reported case of a male patient from a non-consanguineous Italian family who exhibited a severe form of asthenozoospermia factor infertility but no situs inversus and absolutely no signs of the clinical respiratory phenotype, the proband being a professional basketball player. Whole-exome sequencing (WES) has identified a homozygote mutation (CCDC103 c.461 A>C, p.His154Pro) in the proband, while his brother was a heterozygous carrier for this mutation. Morphological and ultrastructural analyses of the axoneme in the sperm flagellum demonstrated the complete loss of both the inner and outer dynein arms (IDA and ODA, respectively). Moreover, immunofluorescence of DNAH1, which is used to check the assembly of IDA, and DNAH5, which labels ODA, demonstrated that these complexes are absent along the full length of the flagella in the spermatozoa from the proband, which was consistent with the IDA and ODA defects observed. Noteworthy, TEM analysis of the axoneme from respiratory cilia showed that dynein arms, although either IDAs and/or ODAs seldom missing on some doublets, are still partly present in each observed section. This case reports the total sperm immotility associated with the CCDC103 p.His154Pro mutation in a man with a normal respiratory phenotype and enriches the variant spectrum of ccdc103 variants and the associated clinical phenotypes in PCD, thus improving counseling of patients about their fertility and possible targeted treatments.

Intracellular Cl- Regulation of Ciliary Beating in Ciliated Human Nasal Epithelial Cells: Frequency and Distance of Ciliary Beating Observed by High-Speed Video Microscopy

Small inhaled particles, which are entrapped by the mucous layer that is maintained by mucous secretion via mucin exocytosis and fluid secretion, are removed from the nasal cavity by beating cilia. The functional activities of beating cilia are assessed by their frequency and the amplitude. Nasal ciliary beating is controlled by intracellular ions (Ca²⁺, H⁺ and Cl^-), and is enhanced by a decreased concentration of intracellular Cl^- ([Cl^-]_i) in ciliated human nasal epithelial cells (cHNECs) in primary culture, which increases the ciliary beat amplitude. A novel method to measure both ciliary beat frequency (CBF) and ciliary beat distance (CBD, an index of ciliary beat amplitude) in cHNECs has been developed using high-speed video microscopy, which revealed that a decrease in [Cl^-]_i increased CBD, but not CBF, and an increase in [Cl^-]_i decreased both CBD and CBF. Thus, [Cl^-]_i inhibits ciliary beating in cHNECs, suggesting that axonemal structures controlling CBD and CBF may have Cl^- sensors and be regulated by [Cl^-]_i. These observations indicate that the activation of Cl^- secretion stimulates ciliary beating (increased CBD) mediated via a decrease in [Cl^-]_i in cHNECs. Thus, [Cl^-]_i is critical for controlling ciliary beating in cHNECs. This review introduces the concept of Cl^- regulation of ciliary beating in cHNECs.

Ultrastructure of human nasal epithelium during an episode of coronavirus infection

The nasal epithelium from a young girl was examined by electron microscopy and found to be infected by coronavirus. Virions are seen within and outside the ciliated cells, but not outside or within the goblet cells or other cells of the nasal mucosa. Some virions are located near the microvilli, others in pockets in the apical cell membrane. The cytoplasm contains many small vesicles with a single virion, large apical vesicles containing hundreds of virions, and lysosome-like cytosomes with a moderate number of virions. Some virus-like particles devoid of an electron-dense interior are seen both in the cytosomes and extracellularly. Virus budding was observed in the Golgi apparatus but nowhere else in the cell. The ciliated cells seem not to be destroyed by the viruses, although in many cases the cilia are withdrawn into the cell body. The loss of cilia is likely to cause rhinorrhoea.