No abstract

RPGR gene encodes retinitis pigmentosa guanosine triphosphatase regulator protein, mutations of which cause 70% of the X-linked retinitis pigmentosa (XLRP) cases. Rarely, RPGR mutations can also cause primary ciliary dyskinesia (PCD), a multisystem disorder characterized by recurrent respiratory tract infections, sinusitis, bronchiectasis, and male subfertility. Two patients with PCD_RP and their relatives were analyzed using DNA sequencing, transmission electron microscopy (TEM), immunofluorescence (IF), photometry, and high-speed videomicroscopy. The Polish patient carried a previously known c.154G>A substitution (p.Gly52Arg) in exon 2 (known to affect splicing); the mutation was co-segregating with the XLRP symptoms in his family. The c.824 G>T mutation (p. Gly275Val) in the Australian patient was a de novo mutation. In both patients, TEM and IF did not reveal any changes in the respiratory cilia structure. However, following ciliogenesis in vitro, in contrast to the ciliary beat frequency, the ciliary beat coordination in the spheroids from the Polish proband and his relatives carrying the c.154G>A mutation was reduced. Analysis of the ciliary alignment indicated severely disturbed orientation of cilia. Therefore, we confirm that defects in the RPGR protein may contribute to syndromic PCD. Lack of ultrastructural defects in respiratory cilia of the probands, the reduced ciliary orientation and the decreased coordination of the ciliary bundles observed in the Polish patient suggested that the RPGR protein may play a role in the establishment of the proper respiratory cilia orientation.

Cilia are small cellular projections that either act as sensors (primary cilia) or propel fluid over the epithelia of various organs (motile cilia). The organellum has gained much attention lately because of its involvement in a group of human diseases called ciliopathies. Primary ciliary dyskinesia (PCD) is an autosomal recessive ciliopathy caused by mutations in cilia motility genes. The disease is characterized by recurrent respiratory tract infections due to the lack of an efficient mucociliary clearance. We performed whole-genome gene expression profiling in bronchial biopsies from PCD patients. We used the quality threshold clustering algorithm to identify groups of genes that revealed highly correlated RNA expression patterns in the biopsies. The largest cluster contained 372 genes and was significantly enriched for genes related to cilia. The database and literature search showed that 164 genes in this cluster were known cilia genes, strongly indicating that the remaining 208 genes were likely to be new cilia genes. The tissue expression pattern of the 208 new cilia genes and the 164 known genes was consistent with the presence of motile cilia in a given tissue. The analysis of the upstream promotor sequences revealed evidence for RFX transcription factors binding site motif in both subgroups. Based on the correlated expression patterns in PCD-affected tissues, we identified 208 genes that we predict to be involved in cilia biology. Our predictions are based directly on the human material and not on model organisms. This list of genes provides candidate genes for PCD and other ciliopathies.