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High-speed Video Microscopy Analysis for First-line Diagnosis of Primary Ciliary Dyskinesia
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Recessive DNAH9 Loss-of-Function Mutations Cause Laterality Defects and Subtle Respiratory Ciliary-Beating Defects
Niki T Loges1, Dinu Antony2, Ales Maver3
1Department of General Pediatrics, University Hospital Muenster, 48149 Muenster, Germany.
American Journal of Human Genetics
|November 26, 2018
Summary
Mutations in DNAH9 cause laterality defects and subtle respiratory issues by impairing outer dynein arm assembly in cilia. This research highlights DNAH9's crucial role in ciliary function and development.
Area of Science:
- Cell Biology
- Genetics
- Developmental Biology
Background:
- Ciliary dysfunction, particularly of motile monocilia and multiple motile cilia, leads to laterality defects and impaired mucociliary clearance, causing airway diseases.
- Outer dynein arms (ODAs) are critical for ciliary beating, with distinct heavy chains (HCs) like DNAH5, DNAH11 (β-HC, ODA type 1), and DNAH9 (β-HC, ODA type 2) located in different ciliary compartments.
Purpose of the Study:
- To investigate the role of DNAH9 in ciliary function and its association with laterality defects and respiratory dysfunction.
- To elucidate the mechanism by which DNAH9 contributes to the assembly of ODAs type 2 in human respiratory cilia.
Main Methods:
- Analysis of loss-of-function mutations in DNAH9 in affected families.
- High-speed video microscopy to assess ciliary bending in DNAH9 mutant cilia.
- Biochemical assays including yeast two-hybrid and co-immunoprecipitation to study protein interactions.
- Investigation of ODA component assembly during ciliogenesis.
Main Results:
- Loss-of-function mutations in DNAH9 were identified in five families, causing situs abnormalities and subtle respiratory ciliary dysfunction.
- DNAH9 mutant cilia exhibited impaired distal ciliary bending and lacked other ODA components (DNAH5, DNAI1, DNAI2) in the distal axoneme.
- DNAH9 was found to interact with DNAH5, DNAI2, and CCDC114, and its assembly in the axoneme occurs after DNAH11 during ciliogenesis.
- These findings demonstrate DNAH9's essential role in the distal assembly of ODAs type 2.
Conclusions:
- DNAH9 is essential for the proper assembly of distal outer dynein arms (ODAs type 2) in human respiratory cilia.
- Mutations in DNAH9 lead to laterality defects and subtle respiratory phenotypes due to impaired ciliary function.
- The study suggests that DNAH9 and DNAH11 have evolved distinct roles in specific ciliary compartments, with DNAH9's function mirroring that of ancient β-HCs.
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