Genetic Regulation of Cilia Assembly and the Relationship to Human Disease

Identification of novel compound heterozygous variants in the DNAH1 gene of a Chinese family with left-right asymmetry disorder

Most internal organs in humans and other vertebrates exhibit striking left-right asymmetry in position and structure. Variation of normal organ positioning results in left-right asymmetry disorders and presents as internal organ reversal or randomization. Up to date, at least 82 genes have been identified as the causative genetic factors of left-right asymmetry disorders. This study sought to discover potential pathogenic variants responsible for left-right asymmetry disorder present in a Han-Chinese family using whole exome sequencing combined with Sanger sequencing. Novel compound heterozygous variants, c.5690A>G (p.Asn1897Ser) and c.7759G>A (p.Val2587Met), in the dynein axonemal heavy chain 1 gene (DNAH1), were found in the proband and absent in unaffected family members. Conservation analysis has shown that the variants affect evolutionarily conserved residues, which may impact the tertiary structure of the DNAH1 protein. The novel compound heterozygous variants may potentially bear responsibility for left-right asymmetry disorder, which results from a perturbation of left-right axis coordination at the earliest embryonic development stages. This study broadens the variant spectrum of left-right asymmetry disorders and may be helpful for genetic counseling and healthcare management for the diagnosed individual, and promotes a greater understanding of the pathophysiology.

Renal Amyloidosis Associated With Kartagener Syndrome in a Dog

A 4-year-old cocker spaniel, male, of 12kg body weight was presented because of the onset of polyuria or polydipsia. From the first months of its life, the dog had exhibited constant serous to mucopurulent nasal discharge, productive cough, sneezing, reverse sneezing, otitis, and recurrent episodes of fever. The respiratory signs had been treated several times with antibiotics, without ever achieving a complete resolution. Clinical examination revealed normal rectal temperature (38.3°C), increased respiratory rate (40breaths/min), a copious mucous nasal discharge and right deviation of the heart apex beat (ictus cordis). Increased respiratory sounds with moist rales and crackles were found on chest auscultation. An increase in serum creatinine, urea and phosphorus, hypoalbuminemia and proteinuria were found. Lateral and ventrodorsal radiographs of the thorax and of the abdomen showed the transposition of the heart, with the cardiac apex pointing toward the right (dextrocardia), bronchointerstitial lung pattern, areas of consolidation, lesions consistent with bronchiectasis caves and a mirror-image of abdominal organs, confirming the diagnosis of complete situs inversus (CSI). Respiratory signs, combined with CSI, suggested the diagnosis of Kartagener syndrome (KS). Abdominal ultrasound showed an increase in the echogenicity of the renal parenchyma, a loss of definition of the corticomedullary line, slight bilateral pyelectasis, and decreased cortical perfusion. The dog died 2 months later because of a further worsening of the clinical condition. Necroscopy demonstrated the existence of CSI, rhinosinusitis, bronchitis, and bronchiectasis, so confirming the diagnosis of KS, and renal amyloidosis. This is the first case reported in veterinary medicine of the presence of renal amyloidosis together with KS in a dog.

Expression of polycystins and fibrocystin on primary cilia of lung cells

Mutations in polycystin-1, polycystin-2, or fibrocystin account for autosomal dominant or recessive polycystic kidney disease. Renal cystogenesis is linked to abnormal localization and function of these cystoproteins in renal primary cilia. They are also expressed in extrarenal tissues in which their functions are unclear. Here we found that human type-II alveolar epithelial A549, airway submucosal Calu-3 cells, and rat bronchioles contain primary or multiple cilia in which we detected these cystoproteins. At sub-confluency, polycystin-1 was expressed on plasma membrane, while polycystin-2 was localized to the ER of resting cells. Both polycystins were detected on the spindle and mid-body of mitotic cells, while fibrocystin was on centrosome throughout cell cycle. Polycystins and fibrocystin may participate in regulating mucociliary sensing and transport within pulmonary airways.

RFX3 modulation of FOXJ1 regulation of cilia genes in the human airway epithelium

Background

Ciliated cells play a central role in cleansing the airways of inhaled contaminants. They are derived from basal cells that include the airway stem/progenitor cells. In animal models, the transcription factor FOXJ1 has been shown to induce differentiation to the ciliated cell lineage, and the RFX transcription factor-family has been shown to be necessary for, but not sufficient to induce, correct cilia development.

Methods

To test the hypothesis that FOXJ1 and RFX3 cooperatively induce expression of ciliated genes in the differentiation process of basal progenitor cells toward a ciliated cell linage in the human airway epithelium, primary human airway basal cells were assessed under conditions of in vitro differentiation induced by plasmid-mediated gene transfer of FOXJ1 and/or RFX3. TaqMan PCR was used to quantify mRNA levels of basal, secretory, and cilia-associated genes.

Results

Basal cells, when cultured in air-liquid interface, differentiated into a ciliated epithelium, expressing FOXJ1 and RFX3. Transfection of FOXJ1 into resting basal cells activated promoters and induced expression of ciliated cell genes as well as both FOXJ1 and RFX3, but not basal cell genes. Transfection of RFX3 induced expression of RFX3 but not FOXJ1, nor the expression of cilia-related genes. The combination of FOXJ1 + RFX3 enhanced ciliated gene promoter activity and mRNA expression beyond that due to FOXJ1 alone. Corroborating immunoprecipitation studies demonstrated an interaction between FOXJ1 and RFX3.

Conclusion

FOXJ1 is an important regulator of cilia gene expression during ciliated cell differentiation, with RFX3 as a transcriptional co-activator to FOXJ1, helping to induce the expression of cilia genes in the process of ciliated cell differentiation of basal/progenitor cells.

Hairy cell leukemia in a patient with situs inversus totalis: an extremely rare combination

Hairy cell leukemia is a rare cancer of the blood. The occurrence of hairy cell leukemia with another very rare genetic disorder makes us question whether it is just a coincidence. This article reports the first case of hairy cell leukemia in a patient with situs inversus totalis in western literature. There have been studies into the pathogenesis of situs inversus totalis that suggest it is caused by the failure of embryonic cells to properly rotate during embryogenesis. On the molecular level, the nodal cilia, which are responsible for embryonic rotation, are built by transport through the KIF3 complex - a kinesin superfamily of molecular motors. The KIF3 complex is also responsible for N-cadherin movement in cells. Furthermore, it is well known that these cell adhesion molecules play an important role in carcinogenesis and its progression. This report attempts to link the rare conditions and propose a possible genetic relationship between the two.

Autosomal dominant polycystic kidney disease is associated with an increased prevalence of radiographic bronchiectasis

BACKGROUND

Autosomal dominant polycystic kidney disease (ADPKD) is a common disease with several known extrarenal manifestations, although no known pulmonary features. The formation of renal cysts in ADPKD has been attributed to dysfunction of primary cilia and the primary cilia-related proteins polycystin-1 (in 85% of cases) and polycystin-2 in renal epithelial cells. The goals of this study were to characterize the normal expression of polycystin-1 in the motile cilia of airway epithelial cells and to evaluate lung structure in ADPKD patients.

METHODS

Airway epithelium from non-ADPKD patients was immunostained to localize polycystin-1 expression, and lung tissue from ADPKD patients was examined for pathologic changes. CT scans from ADPKD patients (n = 95) and a control group of non-ADPKD chronic kidney disease patients (n = 95) were retrospectively reviewed for the presence of bronchiectasis using defined criteria.

RESULTS

Immunostaining revealed polycystin-1 expression in the motile cilia of non-ADPKD airway epithelial cells. Lung tissue from one of five available ADPKD patient autopsies revealed histologic changes of bronchiectasis. Review of CT scans revealed a threefold-increased prevalence of bronchiectasis in the ADPKD group compared to the control group (37% vs 13%, p = 0.002).

CONCLUSIONS

ADPKD patients demonstrate an increased prevalence of radiographic bronchiectasis, a previously unrecognized manifestation of the disease. This association suggests that patients with primary cilia-associated diseases may be at risk for airway disease.

Aspiration, Bronchial Obstruction, Bronchiectasis, and Related Disorders

The conducting airways play a pivotal role in the spectrum of pulmonary pathology, not only as conduits for injurious agents to enter the lung, but also as an anatomic compartment that is affected by a diverse array of primary or secondary bronchocentric diseases. This chapter discusses aspiration and bronchial obstruction in detail, with emphasis on the aspiration of toxic, infective, or particulate matter. Lung abscess, a frequent complication of obstruction or aspiration, is also reviewed. Both aspiration and lung abscess are reconsidered within the context of pulmonary infectious disease mainly in Chapter 8 on bacterial infections, and to some extent in the chapters on mycobacterial (Chapter 9), fungal (Chapter 10), and parasitic diseases (Chapter 14).

Quantitative analysis of ciliary ultrastructure in patients with primary ciliary dyskinesia

The present study was designed to investigate dynein arm and microtubule defects quantitatively in patients with respiratory disease and to establish the clinical relevance of dynein arm deficiency and microtubule abnormalities. Thirty-four patients with recurrent upper and/or lower respiratory infections were included in the study. Nasal mucosal brushings were fixed in glutaraldehyde and routine electron microscopic procedures were carried out. At least 20 cross-sectioned cilia were examined from each subject. Dynein arm and microtubular abnormalities were quantified and a statistical analysis was performed. Twenty-nine percent of the patients showed dynein arm deficiency and a further 21% had possible deficiency (PD). Microtubule defects in patients with dynein arm deficiency and PD were found to be significantly increased compared to the patients with no dynein arm deficiency. The most prominent defect in the dynein arm deficiency group was a translocation of central and/or peripheral microtubules. The high percentage of translocation defect in this group of patients suggests that these defects are primary, rather than secondary to infection.

Absence of tektin 4 causes asthenozoospermia and subfertility in male mice

Sperm flagellar motion is the outcome of a dynamic interplay between the axonemal cytoskeleton, the peri-axonemal accessory structures, and multiple regulatory networks that coordinate to produce flagellar beat and waveform. Tektins are conserved components of the flagellar proteome in evolutionarily diverse species and are believed to play essential roles in the mechanics of sperm motility. Using database mining, we identified multiple new paralogs of previously annotated tektins, including tektin 4 (TEKT4), which shares 77.1% identity with its nearest human homologue. Mouse Tekt4 is a germ cell-enriched gene, most abundantly expressed in haploid round spermatids in the testis, and the protein is localized to the sperm flagella. Male mice lacking TEKT4 on a 129S5/SvEvBrd inbred background are subfertile. Tekt4-null sperm exhibit drastically reduced forward progressive velocity and uncoordinated waveform propagation along the flagellum. In Tekt4-null sperm, flagellar ultrastructure is grossly unaltered as revealed by transmission electron microscopy. However, the ineffective flagellar strokes lead to approximately 10-fold higher consumption of intracellular ATP in Tekt4-null sperm as compared to wild-type, and null spermatozoa rapidly lose progressive motility when incubated for > or = 1.5 h. Our studies demonstrate that TEKT4 is necessary for the proper coordinated beating of the sperm flagellum and male reproductive physiology.