Conditional Deletion of Dnaic1 in a Murine Model of Primary Ciliary Dyskinesia Causes Chronic Rhinosinusitis

Abstract

Studies of primary ciliary dyskinesia (PCD) have been hampered by the lack of a suitable animal model because disruption of essential ciliary genes in mice results in a high incidence of lethal hydrocephalus. To develop a viable mouse model for long-term studies of PCD, we have generated a transgenic mouse line in which two conserved exons of the mouse intermediate dynein chain gene, Dnaic1, are flanked by loxP sites (Dnaic1(flox/flox)). Dnaic1 is the murine homolog of human DNAI1, which is mutated in approximately 10% of human PCD cases. These mice have been crossed with mice expressing a tamoxifen-inducible Cre recombinase (CreER). Treatment of adult Dnaic1(flox/flox)/CreER(+/-) mice with tamoxifen results in an almost complete deletion of Dnaic1 with no evidence of hydrocephalus. Treated animals have reduced levels of full-length Dnaic1 mRNA, and electron micrographs of cilia demonstrate a loss of outer dynein arm structures. In treated Dnaic1(flox/flox)/CreER(+/-) animals, mucociliary clearance (MCC) was reduced over time. After approximately 3 months, no MCC was observed in the nasopharynx, whereas in the trachea, MCC was observed for up to 6 months, likely reflecting a difference in the turnover of ciliated cells in these tissues. All treated animals developed severe rhinosinusitis, demonstrating the importance of MCC to the health of the upper airways. However, no evidence of lung disease was observed up to 11 months after Dnaic1 deletion, suggesting that other mechanisms are able to compensate for the lack of MCC in the lower airways of mice. This model will be useful for the study of the pathogenesis and treatment of PCD.

Overexpressing mouse model demonstrates the protective role of Muc5ac in the lungs

“…4A). Clearance rates were measured during deep anesthesia and immediately after death because ciliary beat, and hence clearance, continues several hours postmortem (21). No significant differences in clearance rates were detected between the WT (1.69 ± 0.10 mm/min, n = 13) and Muc5ac-Tg (1.49 ± 0.17 mm/ min, n = 11) animals, suggesting the presence of a sufficiently hydrated mucus that is removed efficiently from the surfaces.…”

Static respiratory cilia associated with mutations in Dnahc11/DNAH11: A mouse model of PCD

“…This mouse line has been constantly bred as a homozygous colony for over 50 years, demonstrating that it is robust, viable, and that it demands only normal husbandry, in contrast to the viability issues seen in other models including Dnahc5 [Tan et al, 2007], nm1054 [Lee et al, 2008] and the complex preparatory considerations associated with the Dnaic conditional mutant [Ostrowski et al, 2010]. We have not only confirmed that the iv model has static respiratory cilia at 37 • C, but that it develops PCD-related disease including rhinitis, sinusitis, and otitis media.…”

“…A significant proportion, including Dnahc5 (MIM# 603335) [Tan et al, 2007], Poll (MIM# 606343) [Kobayashi et al, 2002], and Dnaic1 (MIM# 604366) [Ostrowski et al, 2010], demonstrate additional defects, particularly hydrocephalus and cardiac anomalies, reducing their viability and raising significant animal welfare issues. The repeated demonstration that mutation of human PCD loci in the mouse results in hydrocephalus has led some to suggest an underlying difference in physiology [Ibanez-Tallon et al, 2002;Ostrowski et al, 2010]. The nm1054 mouse (MGI: Del(1)1Brk), a six-gene deletion, gives rise to PCD-like upper respiratory pathology, lacks cardiac defects, and only shows hydrocephalus on certain genetic backgrounds.…”

“…These data led Ostrowski and colleagues to engineer postnatal deletion of Dnaic1 (MIM# 604366); deletion at 8-12 weeks of age avoids hydrocephalus. This, however, requires additional experimental intervention and clearly cannot model the condition in juveniles, the stage at which the disease is first evident in humans [Ostrowski et al, 2010]. Whether an easy-to-use mouse model of the respiratory PCD phenotypes exists, lacking additional phenotypes, remains to be determined.…”

FoxJ1-dependent gene expression is required for differentiation of radial glia into ependymal cells and a subset of astrocytes in the postnatal brain

“…Recovered pups were returned to their mother and those that developed hydrocephalus were sacrificed at P6 and P21 for analysis of differentiation in the SCN. Dnaic1 -/-mice (Ostrowski et al, 2009) were used as a genetic model for assessing the effects of hydrocephalus on SCN development and postnatal neurogenesis in the OB. The developmental time course of hydrocephalus in Dnaic1 -/-mice was similar to that in FoxJ1 -/-mice, starting between P1 and P6 with a progressive increase in ventricular volume by P21.…”