Recessive DNAH9 Loss-of-Function Mutations Cause Laterality Defects and Subtle Respiratory Ciliary-Beating Defects

Abstract

Dysfunction of motile monocilia, altering the leftward flow at the embryonic node essential for determination of left-right body asymmetry, is a major cause of laterality defects. Laterality defects are also often associated with reduced mucociliary clearance caused by defective multiple motile cilia of the airway and are responsible for destructive airway disease. Outer dynein arms (ODAs) are essential for ciliary beat generation, and human respiratory cilia contain different ODA heavy chains (HCs): the panaxonemally distributed γ-HC DNAH5, proximally located β-HC DNAH11 (defining ODA type 1), and the distally localized β-HC DNAH9 (defining ODA type 2). Here we report loss-of-function mutations in DNAH9 in five independent families causing situs abnormalities associated with subtle respiratory ciliary dysfunction. Consistent with the observed subtle respiratory phenotype, high-speed video microscopy demonstrates distally impaired ciliary bending in DNAH9 mutant respiratory cilia. DNAH9 -deficient cilia also lack other ODA components such as DNAH5, DNAI1, and DNAI2 from the distal axonemal compartment, demonstrating an essential role of DNAH9 for distal axonemal assembly of ODAs type 2. Yeast two-hybrid and co-immunoprecipitation analyses indicate interaction of DNAH9 with the ODA components DNAH5 and DNAI2 as well as the ODA-docking complex component CCDC114. We further show that during ciliogenesis of respiratory cilia, first proximally located DNAH11 and then distally located DNAH9 is assembled in the axoneme. We propose that the β-HC paralogs DNAH9 and DNAH11 achieved specific functional roles for the distinct axonemal compartments during evolution with human DNAH9 function matching that of ancient β-HCs such as that of the unicellular Chlamydomonas reinhardtii .

The Zebrafish Kupffer’s Vesicle: A Special Organ in a Model Organism to Study Human Diseases

“…Primary ciliary dyskinesia (PCD) is a rare congenital and heterogeneous disorder (OMIM: 244400) with an estimated prevalence of around 1:10 ,000 according to Rubbo and Lucas [16], which is thought to be higher in consanguineous populations [17]. However, other references in the literature consider a much lower prevalence, affecting approximately 1 in 20,000 individuals [18]. It is thought that the correct prevalence of the disease is unknown because many patients remain undiagnosed.…”

“…To date, mutations in more than 35 genes were identified to cause PCD. These genes are mainly coding for axonemal proteins that are required for cilia motility or for proteins that are needed for the assembly or transport of axonemal components [18,[21][22][23].…”

A DNAH17 missense variant causes flagella destabilization and asthenozoospermia

“…Heavy chains, also known as dynein axonemal heavy chains (DNAHs), comprise 13 members (5)(6)(7)(8)(9)(10)(11)(12)14,and 17) in humans (Pazour et al, 2006). Disruptions in DNAHs, such as DNAH5 (Hornef et al, 2006;Olbrich et al, 2002), DNAH6 (Li et al, 2016), DNAH9 (Fassad et al, 2018;Loges et al, 2018), and DNAH11 (Bartoloni et al, 2002;Knowles et al, 2012;Lucas et al, 2012;Schwabe et al, 2008), are known to cause, or are associated with, primary ciliary dyskinesia (PCD), a genetically heterogeneous disorder that is characterized by chronic airway diseases, left-right laterality disturbances, and male infertility (Leigh et al, 2009). So far, mutations in only DNAH1 or DNAH9 have been described in patients with asthenozoospermia.…”

Rare Human Diseases: Model Organisms in Deciphering the Molecular Basis of Primary Ciliary Dyskinesia

“…In the epithelial cells lining respiratory tracts, the γ DHC is encoded only by DNAH5 [MIM: 603335], while β DHC is encoded by one of two genes: DNAH11 [MIM: 603339] or DNAH9 [MIM: 603330]. ODAs containing DNAH11 β DHC are present in a more proximal part of cilia (ODA type 1), while ODAs containing DNAH9 are docked in the distal part of cilia (ODA type 2) [83,84]. Out of these three DHCs, mutations in DNAH5 cause the most severe alterations in cilia beating patterns, while mutations in DNAH9 result in the mildest alterations [84].…”

“…ODAs containing DNAH11 β DHC are present in a more proximal part of cilia (ODA type 1), while ODAs containing DNAH9 are docked in the distal part of cilia (ODA type 2) [83,84]. Out of these three DHCs, mutations in DNAH5 cause the most severe alterations in cilia beating patterns, while mutations in DNAH9 result in the mildest alterations [84]. Cilia of the respiratory epithelial cells from patients with mutations in DNAH5 are either immotile or exhibit residual twitching movement [85,86].…”