FOXJ1 Variants Causing Primary Ciliary Dyskinesia with Hydrocephalus: A Case Report from Japan

Primary Ciliary Dyskinesia Due to Compound Heterozygous Variants in CFAP221 with Obstructive Azoospermia: Young's Syndrome May Be a Phenotype of Primary Ciliary Dyskinesia

We report the case of a 42-year-old man with bronchiectasis who had a history of infertility treatment for obstructive azoospermia. Young's syndrome was suspected based on the triad of obstructive azoospermia, sinusitis, and bronchiectasis. He had normal electron microscopy findings, normal nasal nitric oxide levels (116 nL/min), and no situs inversus. However, we found compound heterozygous variants considered pathogenic in CFAP221. This led to a diagnosis of primary ciliary dyskinesia (PCD). Distinguishing PCD from Young's syndrome in patients with the triad of obstructive azoospermia, sinusitis, and bronchiectasis is challenging. Young's syndrome may be a phenotype of PCD.

Application of copy number variation sequencing combined with whole exome sequencing in prenatal left-right asymmetry disorders

BACKGROUND

Left-right (LR) asymmetry disorders present a complex etiology, with genetic factors emerging as a primary contributor. This study aims to explore the genetic underpinnings of chromosomal variants and individual genes in fetuses afflicted with prenatal LR asymmetry disorder.

METHODS

Through a retrospective analysis conducted between 2020 and 2023 at Tongji Hospital, Huazhong University of Science and Technology, genetic outcomes of LR asymmetric disorder were scrutinized utilizing copy number variation sequencing (CNV-seq) and whole exome sequencing (WES) methodologies.

RESULTS

With a combination of CNV-seq and WES, 5 fetuses in 17 patients with LR asymmetry had chromosomal or genetic variants. CNV-seq revealed a 16p11.2 microdeletion syndrome in a situs inversus fetus presenting pathogenic and a 2q36.3 microduplication syndrome in a fetus with Heterotaxy presenting a variant of uncertain significance (VUS). WES identified NM_198075.4:c.755del in the LRRC56 gene and NM_001454.4:c.865_868dup in the FOXJ1 gene in two situs inversus cases, along with two variants in DNAH5 in two other fetuses. Further bioinformatics scrutiny was conducted to assess the protein structure and function prediction of these variants, ultimately indicating their potential pathogenicity.

CONCLUSION

The study highlights that fetuses with LR asymmetric disorders may have copy number variants, underscoring the significance of mutations in LRRC56 and FOXJ1 in the development of LR asymmetry disorders.

A 3000-year-old founder variant in the DRC1 gene causes primary ciliary dyskinesia in Japan and Korea

Primary ciliary dyskinesia (PCD) is a genetic disorder characterized by ciliary structural abnormalities and dysfunction, leading to chronic rhinosinusitis, otitis media with effusion, bronchiectasis, and infertility. Approximately half of Japanese PCD cases are attributed to variants in the dynein regulatory complex subunit 1 (DRC1) gene, predominantly featuring homogeneous deletions of exons 1-4 spanning 27,748 base pairs on chromosome 2. Here, we report 10 new PCD cases (9 families) in addition to 29 previously reported cases (24 families) caused by DRC1 variants. Among these 39 cases, biallelic DRC1 exon 1-4 deletions were detected in 38 (97.4%). These DRC1 deletions exhibited an identical breakpoint in all PCD cases in the Japanese and Korean populations, strongly suggesting a founder effect. In this study, we performed haplotype analysis, using a whole-exome sequencing dataset of 18 Japanese PCD patients harboring large biallelic DRC1 deletions. We estimated that the founder allele likely emerged 115.1 generations ago (95% confidence interval: 33.7-205.1), suggesting an origin of approximately 3050 years ago, coinciding with the transition from the Jomon period to the early Yayoi period in Japan. Considering the formation of the modern Japanese population, the founder with the DRC1 exon 1-4 deletion likely lived on the Korean peninsula, with the allele later transmitted to Japan through migration. This study provides insights into the origin of the DRC1 copy number variant, the most frequent PCD variant in the Japanese and Korean populations, highlighting the importance of understanding population-specific genetic variations in the context of human migration and disease prevalence.

Impact of primary ciliary dyskinesia: Beyond sinobronchial syndrome in Japan

Primary ciliary dyskinesia (PCD) is a rare genetic disorder characterized by impaired motile cilia function, particularly in the upper and lower airways. To date, more than 50 causative genes related to the movement, development, and maintenance of cilia have been identified. PCD mostly follows an autosomal recessive inheritance pattern, in which PCD symptoms manifest only in the presence of pathogenic variants in both alleles. Several genes causing PCD have been recently identified that neither lead to situs inversus nor cause definitive abnormalities in ciliary ultrastructure. Importantly, the distribution of disease-causing genes and pathogenic variants varies depending on ethnicity. In Japan, homozygosity for a ∼27.7-kb deletion of DRC1 is estimated to be the most common cause of PCD, presumably as a founder mutation. The clinical picture of PCD is similar to that of sinobronchial syndrome, thus making its differentiation from diffuse panbronchiolitis and other related disorders difficult. Given the diagnostic challenges, many cases remain undiagnosed or misdiagnosed, particularly in adults. While no fundamental cure is currently available, lifelong medical subsidies are provided in Japan, and proper respiratory management, along with continued prevention and treatment of infections, is believed to mitigate the decline in respiratory function. Timely action will be necessary when specific treatments for PCD become available in the future. This narrative review focuses on variations in the disease status of PCD in a non-Western country.