ABSTRACT
Congenital scoliosis (CS) is a type of vertebral malformation for which the etiology remains elusive. The notochord is pivotal for vertebrae development, but its role in CS is still understudied. Here, we generated a zebrafish knockout of ptk7a, a planar cell polarity (PCP) gene that is essential for convergence and extension (C&E) of the notochord, and detected congenital scoliosis-like vertebral malformations (CVMs). Maternal zygotic ptk7a mutants displayed severe C&E defects of the notochord. Excessive apoptosis occurred in the malformed notochord, causing a significantly reduced number of vacuolated cells, and compromising the mechanical properties of the notochord. The latter manifested as a less-stiff extracellular matrix along with a significant reduction in the number of the caveolae and severely loosened intercellular junctions in the vacuolated region. These defects led to focal kinks, abnormal mineralization, and CVMs exclusively at the anterior spine. Loss of function of another PCP gene, vangl2, also revealed excessive apoptosis in the notochord associated with CVMs. This study suggests a new model for CS pathogenesis that is associated with defects in notochord C&E and highlights an essential role of PCP signaling in vertebrae development.
Footnotes
Author contributions
Conceptualization: M.W., S.Z., N.W., Z.K.; Methodology: M.W., C.S., M.-C.G., M.L., J.T.T., B.M.W., N.C., C.-É.A., E.K.-S., J.Z.; Validation: Z.K.; Formal analysis: M.W., C.S., J.Z.; Investigation: M.W., N.W., Z.K.; Resources: M.L., P.D.; Data curation: M.W., C.S., J.Z.; Writing - original draft: Z.K.; Writing - review & editing: Z.K.; Visualization: M.W., C.S., J.T.T., B.M.W., E.K.-S., J.Z.; Supervision: Z.K.; Funding acquisition: Z.K.
Funding
This work is supported by funds from the Centre de recherche Azrieli du CHU Sainte-Justine and from the Natural Sciences and Engineering Research Council of Canada (Z.K.); Fonds de Recherche du Québec – Santé (FRQS) (M.W.); Institut TransMedTech (Canada First Research Excellence Funds) and Canada Foundation for Innovation (C.-É.A.); National Institutes of Health (K25HD097288 to J.Z.); Richard Barber Interdisciplinary Research Program (to J.Z. and C.S.); and Shriners Hospitals for Children and FRQS Programme de Bourses de Chercheur (B.M.W.).
Data availability
All relevant data can be found within the article and its supplementary information.