Axonemal dynein intermediate-chain gene (DNAI1) mutations result in situs inversus and primary ciliary dyskinesia (Kartagener syndrome)

Abstract

Kartagener syndrome (KS) is a trilogy of symptoms (nasal polyps, bronchiectasis, and situs inversus totalis) that is associated with ultrastructural anomalies of cilia of epithelial cells covering the upper and lower respiratory tracts and spermatozoa flagellae. The axonemal dynein intermediate-chain gene 1 (DNAI1), which has been demonstrated to be responsible for a case of primary ciliary dyskinesia (PCD) without situs inversus, was screened for mutation in a series of 34 patients with KS. We identified compound heterozygous DNAI1 gene defects in three independent patients and in two of their siblings who presented with PCD and situs solitus (i.e., normal position of inner organs). Strikingly, these five patients share one mutant allele (splice defect), which is identical to one of the mutant DNAI1 alleles found in the patient with PCD, reported elsewhere. Finally, this study demonstrates a link between ciliary function and situs determination, since compound mutation heterozygosity in DNAI1 results in PCD with situs solitus or situs inversus (KS).

Figure 1

A, Pedigree tree of the families of patients 1 and 2. Below symbols of the family tree of patient 1 is the agarose gel of exon 1 amplicons after digestion with HpaI. On the left-hand side, the size marker: a 100-bp ladder. Bars on the right-hand side indicate the position of obtained bands (190, 127, and 63 bp). Band 190 bp is the uncut amplicon; bands 127 and 63 bp are the cut bands when there is a T insertion in the splicing site. Blackened symbols indicate patients with KS; oblique stripes indicate patients with PCD. P2 and P3 indicate patients 2 and 3 of this study. B, Electrophoregram of the normal and missense mutations of patient 1. C, Electrophoregram of the normal and the 12-bp deletion observed in patient 3. Both abnormal electrophoregrams were obtained after cloning the amplicons.

Figure 2

Electron-microscopic specimen of a normal case (A) and of the brother of patient 1 (B). The outer dynein arms are shortened or missing. Bar: 0.1 μm. Tracheal biopsies were fixed with 2.5% glutaraldehyde in 0.1M cacodylate buffer, pH 7.4, postfixed 1 h at 4°C in 1% osmium tetroxyde in 0.1 M cacodylate, and, after 1 h impregnation in 2% aqueous uranyl acetate, embedded in Epon. Ultrathin sections were stained with uranyl acetate and lead citrate and were examined at 80 KV with a JEOL 2000EX electron microscope.