Novel dynein axonemal assembly factor 1 mutations identified using whole‑exome sequencing in patients with primary ciliary dyskinesia

Abstract

Primary ciliary dyskinesia (PCD) is a rare, genetically heterogeneous disorder caused by dysfunction of the cilia and flagella; however, causative genetic defects have not been detected in all patients with PCD. Seven Chinese Han patients with Kartagener syndrome were enrolled onto the present study. Transmission electron microscopy (TEM) was performed to evaluate the cilial defects and whole‑exome sequencing was used to analyze relevant genetic variations in all patients. In two of the seven patients with PCD, four novel dynein axonemal assembly factor 1 (DNAAF1) mutations were identified (NM_178452.6:c.3G>A, c.124+1G>C, c.509delG and c.943A>T) in three alleles. Both of these patients had long‑standing infertility. Their chest computed tomography results showed bronchiectasis, lung infections and situs inversus, and paranasal computed tomography revealed sinusitis. Semen analysis of the male patient showed poor sperm motility. TEM showed defects in the inner and outer dynein arms in both patients. The DNAAF1 sequences of family members were then analyzed. Bioinformatics analysis indicated that these mutations may be the cause of the cilial defects in these two probands. Thus, the present study identified novel PCD‑causing mutations in DNAAF1 in two patients with PCD. These genetic variations were predicted to alter DNAAF1 amino acid residues and lead to loss of function, thereby inhibiting cilia‑mediated motility. Accordingly, the two probands had PCD symptoms, and one of them died due to PCD‑associated complications.

Figure 1.

Chest and paranasal CT images of the two patients with dynein axonemal assembly factor 1 mutations. (A) Chest CT results revealed bronchiectasis and situs inversus and (B) paranasal CT results showed bilateral maxillary sinusitis in proband 1. (C) Chest CT results revealed bronchiectasis, a lung infection and situs inversus and (D) paranasal CT results showed bilateral ethmoid sinusitis in proband 2. White arrow, bronchiectasis. Red arrow, infection in the lung. Green arrow, cardiac situs inversus. Yellow arrow, maxillary sinusitis or ethmoid sinusitis. CT, computed tomography.

Figure 2.

Transmission electron microscopy image of sperm flagella in proband 1 illustrating that both inner and outer dynein arms were defective (black arrow).

Figure 3.

Schematic diagram of a cross-section of the ciliary axoneme with nine microtubule doublets surrounding the central pair of microtubules. The microtubules are interconnected via radial spokes, a nexin-dynein regulatory complex, and dynein arms.

Figure 4.

Sanger sequencing revealed mutations in two patients. (A) Exon 4: c.509delG (reverse complementary sequence), (B) exon 1: c.124+1G>C and (C) exon 1: c.3G>A in proband 1. (D) Exon 7: c.943A>T in proband 2.

Figure 5.

Proband 1 inherited exon 1: c.3G>A and exon 1: c.124+1G>C from his father and exon 4: c.509delG from his mother and had no children. Proband 2 inherited a homozygous dynein axonemal assembly factor 1 mutation, exon 7: c.943A>T, from her heterozygous parents and had two daughters by artificial fertilization. The double bar indicates that the proband's parents have the same grandfather.

Figure 6.

Dynein axonemal assembly factor 1 protein mutation positions.