IFT46 Expression in the Nasal Mucosa of Primary Ciliary Dyskinesia Patients: Preliminary Study

Abstract

Background: Primary ciliary dyskinesia (PCD) is characterised by an imbalance in mucociliary clearance leading to chronic respiratory infections. Cilia length is considered to be a contributing factor in cilia movement. Recently, IFT46 protein has been related to cilia length. Therefore, this work aims to study IFT46 expression in a PCD patients cohort and analyse its relationship with cilia length and function, as it was not previously described.

Materials and methods: The expression of one intraflagellar transport (IFT46) and two regulating ciliary architecture (FOXJ1 and DNAI2) genes, as well as cilia length of 27 PCD patients, were measured. PCD patients were diagnosed based on clinical data, and cilia function and ultrastructure. Gene expression was estimated by real-time RT-PCR and cilia length by electron microscopy in nasal epithelium biopsies.Results and conclusions: While IFT46 expression was only diminished in patients with short cilia, FOXJ1, and DNAI2 expression were reduced in all PCD patient groups compared to controls levels. Among the PCD patients, cilia were short in 44% (5.9 ± 0.70 µm); nine of these (33% from the total) patients' cilia also had an abnormal ultrastructure. Cilia length was normal in 33% of patients (6.4 ± 0.39 µm), and only three patients' biopsies indicated decreased expression of dynein.

Keywords: IFT46; cilia length; ciliogenesis; ciliopathies; primary ciliary dyskinesia.

Figure 1.

Example of cilia measure (1A), normal length cilia (1B), normal at the lower limit (1C), and short ones (1D). Images were taken at 40× magnification with a Leica DM108 microscope. Scale bar equals to 5 μm.

Figure 2.

IFT46, DNAI2, and FOXJ1 gene expression analysis. Relative expression was calculated using 2^−ΔΔCt method. Fold change calculated with respect to control group is represented in Y-axis. Total RNA was extracted from nasal biopsies and analysed by real-time RT-PCR. 30 healthy volunteers (group C) and 27 primary ciliary dyskinesia well characterised (PCD group) patients were included. PCD patients were analysed together (panel A) or divided into three groups: NoC (non-ciliated; n = 3), SC (short cilia; patients showing a cilia length bellow 5.9 µM; n = 12) and NC (normal cilia; patients showing a cilia length above 5.9 µM; n = 9) for FOXJ1 (panel B), DNAI2 (panel C) and IFT46 (panel D) analysis. Results are represented as mean ± SEM. *p < 0.05 compared to healthy volunteers.