DYX1C1 is required for axonemal dynein assembly and ciliary motility

DYX1C1 has been associated with dyslexia and neuronal migration in the developing neocortex. Unexpectedly, we found that deleting exons 2–4 of Dyx1c1 in mice caused a phenotype resembling primary ciliary dyskinesia (PCD), a disorder characterized by chronic airway disease, laterality defects and male infertility. This phenotype was confirmed independently in mice with a Dyx1c1 c.T2A start-codon mutation recovered from an N-ethyl-N-nitrosourea (ENU) mutagenesis screen. Morpholinos targeting dyx1c1 in zebrafish also caused laterality and ciliary motility defects. In humans, we identified recessive loss-of-function DYX1C1 mutations in 12 individuals with PCD. Ultrastructural and immunofluorescence analyses of DYX1C1-mutant motile cilia in mice and humans showed disruptions of outer and inner dynein arms (ODAs and IDAs, respectively). DYX1C1 localizes to the cytoplasm of respiratory epithelial cells, its interactome is enriched for molecular chaperones, and it interacts with the cytoplasmic ODA and IDA assembly factor DNAAF2 (KTU). Thus, we propose that DYX1C1 is a newly identified dynein axonemal assembly factor (DNAAF4)

The Role of DYX1C1 in Motile Cilia and Axonemal Dynein Assembly

Motile cilia and flagella are essential to many biological functions that require cellular or fluid movement. The motility of cilia and flagella in turn is dependent upon the action of large protein complexes that serve as molecular motors. Such axonemal motors are composed of multiple dyneins assembled in the cytoplasm of cells with motile cilia. The mechanisms underlying this assembly are not fully understood. Fortuitously, we found that genetic deletion of exons 2–4 of Dyx1c1 in mice caused a phenotype resembling Primary Ciliary Dyskinesia (PCD), a disorder characterized by chronic airway disease, laterality defects and male infertility. Ultrastructural and immunofluorescence analyses of Dyx1c1-mutant motile cilia in mice showed disruptions of outer and inner dynein arms (ODAs and IDAs, respectively). Dyx1c1 localizes to the cytoplasm of respiratory epithelial cells. Its interactome is enriched for molecular chaperones, and it interacts with the cytoplasmic axonemal motor assembly factor DNAAF2 (KTU) as well as transition zone protein Septin2. Additionally, a missense mutation in DYX1C1 found to lead to PCD in humans exhibits a weaker interaction of DYX1C1 with Sept2 and KTU and has reduced activity in promoting association of dyneins. These findings suggest that Dyx1c1 (DNAAF4) plays a role in dynein arm assembly or trafficking and when mutated leads to primary ciliary dyskinesia with laterality defects. Dyx1c1 interacts with intermediate and light chain subunits of the dynein arm complex in the cytoplasm of tracheal epithelial cells. Light and intermediate chains fail to form complexes in the cytoplasm of tracheal epithelial cells of Dyx1c1 mutants. Dyx1c1 increases by four fold the association of light chain subunits Dnal1 and Dnal4 in heterologously expressing HEK 293-T cells. Finally, a missense mutation in Dyx1c1 (p.L19Q) which cause PCD in humans is impaired in its ability to assembly Dnal1 and Dnal4. In conclusion, we identify a step in axonemal dynein pre-assembly in which Dyx1c1 facilitates formation of light and intermediate chain dynein complexes

Niraparib and dostarlimab for the treatment of recurrent platinum-resistant ovarian cancer: results of a Phase II study (MOONSTONE/GOG-3032)

This study assessed the efficacy, safety, and health-related quality of life (HRQoL) of the treatment regimen of dostarlimab, a programmed death-1 inhibitor, combined with niraparib, a poly (ADP-ribose) polymerase inhibitor, in patients with BRCA wild type (BRCAwt) recurrent platinum-resistant ovarian cancer (PROC) who had previously received bevacizumab treatment. This Phase II, open-label, single-arm, multicenter study, conducted in the USA, enrolled patients with recurrent PROC to receive niraparib and dostarlimab until disease progression or unacceptable toxicity (up to 3 years). A preplanned interim futility analysis was performed after the first 41 patients had undergone ≥1 radiographic evaluation (approximately 9 weeks from the first treatment). The prespecified interim futility criterion was met and the study was therefore terminated. For the 41 patients assessed, the objective response rate (ORR) was 7.3% (95% confidence interval: 1.5–19.9); no patients achieved a complete response, 3 patients (7.3%) achieved a partial response (duration of response; 3.0, 3.8, and 9.2 months, respectively), and 9 patients (22.0%) had stable disease. In total, 39 patients (95.1%) experienced a treatment-related adverse event, but no new safety issues were observed. HRQoL, assessed using FOSI, or Functional Assessment of Cancer Therapy – Ovarian Symptom Index scores, worsened over time compared with baseline scores. The study was terminated due to the observed ORR at the interim futility analysis. This highlights a need for effective therapies in treating patients with recurrent BRCAwt PROC. [Display omitted] •Overall response rate did not improve with niraparib and dostarlimab in recurrent BRCAwt platinum-resistant ovarian cancer (124/125).•Low objective response rate versus standard of care triggered prespecified futility criteria and early study termination (122/125).•No new safety signals were reported for niraparib and dostarlimab combination therapy (87/125).•Health-related quality of life measures worsened over time from baseline, with no control group for comparison (112/125)

DYX1C1 is required for axonemal dynein assembly and ciliary motility

DYX1C1 has been associated with dyslexia and neuronal migration in the developing neocortex. Unexpectedly, we found that deleting exons 2–4 of Dyx1c1 in mice caused a phenotype resembling primary ciliary dyskinesia (PCD), a disorder characterized by chronic airway disease, laterality defects and male infertility. This phenotype was confirmed independently in mice with a Dyx1c1 c.T2A start-codon mutation recovered from an N-ethyl-N-nitrosourea (ENU) mutagenesis screen. Morpholinos targeting dyx1c1 in zebrafish also caused laterality and ciliary motility defects. In humans, we identified recessive loss-of-function DYX1C1 mutations in 12 individuals with PCD. Ultrastructural and immunofluorescence analyses of DYX1C1-mutant motile cilia in mice and humans showed disruptions of outer and inner dynein arms (ODAs and IDAs, respectively). DYX1C1 localizes to the cytoplasm of respiratory epithelial cells, its interactome is enriched for molecular chaperones, and it interacts with the cytoplasmic ODA and IDA assembly factor DNAAF2 (KTU). Thus, we propose that DYX1C1 is a newly identified dynein axonemal assembly factor (DNAAF4)