Onoufriadis, A;
Shoemark, A;
Schmidts, M;
Patel, M;
Jimenez, G;
Liu, H;
Thomas, B;
... Mitchison, HM; + view all
(2014)
Targeted NGS gene panel identifies mutations in RSPH1 causing primary ciliary dyskinesia and a common mechanism for ciliary central-pair agenesis due to radial spoke defects.
Hum Mol Genet
, 23
(13)
pp. 3362-3374.
10.1093/hmg/ddu046.
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Abstract
Primary ciliary dyskinesia (PCD) is an inherited chronic respiratory obstructive disease with randomised body laterality and infertility, resulting from cilia and sperm dysmotility. PCD is characterised by clinical variability and extensive genetic heterogeneity, associated with different cilia ultrastructural defects and mutations identified in >20 genes. Next generation sequencing (NGS) technologies therefore present a promising approach for genetic diagnosis which is not yet in routine use. We developed a targeted panel-based NGS pipeline to identify mutations by mutational analysis of selected candidate genes in 70 genetically undefined PCD patients. This detected loss-of-function RSPH1 mutations in four individuals with isolated central pair loss and normal body laterality, from two unrelated families. Ultrastructural analysis in RSPH1-mutated cilia revealed transposition of peripheral outer microtubules into the 'empty' central pair space, accompanied by a distinctive intermittent loss of the central pair microtubules. We find that mutations in RSPH1, RSPH4A and RSPH9, which all encode homologs of components of the 'head' structure of ciliary radial spoke complexes identified in Chlamydomonas, cause clinical phenotypes indistinguishable except at the gene level. By high-resolution immunofluorescence we identified a loss of RSPH4A and RSPH9 along with RSPH1 from RSPH1-mutated cilia, suggesting RSPH1 mutations may result in loss of the entire spoke head structure. Central pair loss accounts for up to 28% of PCD cases, in whom laterality determination specified by central pair-less embryonic node cilia remains undisturbed. We propose this defect could arise from instability of the ciliary central microtubules due to loss of their normal radial spoke head tethering.
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