Zebrafish motile cilia as a model for primary ciliary dyskinesia
Funding Information: Funding: This work was a product of the Project LYSOCIL funded by the European Union Horizon 2020 research and innovation under grant agreement No 811087. It received funding from Fundação para a Ciencia e tecnologia, grant PTDC/BEX-BID/1411/2014; M.R. was funded by the fellowship PD/BD/136927/2018. P.S was funded by the fellowship SFRH/BD/111611/2015; C.B. was funded by the fellowship SFRH/BD/141034/2018; SSL was funded by FCT CEEC-IND 2018. Funding Information: Acknowledgments: The authors want to thank the Fish Facility from NMS. This work was developed with the support of the Fish Facility NMS|FCM that is part of CONGENTO, a Research Infrastructure co-financed by Lisboa Regional Operational Programme (Lisboa2020), under the PORTUGAL 2020 Partnership Agreement, through the European Regional Development Fund (ERDF) and Fundação para a Ciência e Tecnologia (Portugal) LISBOA-01-0145-FEDER-022170. A.P. wants to thank the Royal Brompton and Harefield hospital, part of the Guy's and St Thomas' foundation trust, London. Publisher Copyright: © 2021 by the authors. Licensee MDPI, Basel, Switzerland. ; Zebrafish is a vertebrate teleost widely used in many areas of research. As embryos, they develop quickly and provide unique opportunities for research studies owing to their transparency for at least 48 h post fertilization. Zebrafish have many ciliated organs that include primary cilia as well as motile cilia. Using zebrafish as an animal model helps to better understand human diseases such as Primary Ciliary Dyskinesia (PCD), an autosomal recessive disorder that affects cilia motility, currently associated with more than 50 genes. The aim of this study was to validate zebrafish motile cilia, both in mono and multiciliated cells, as organelles for PCD research. For this purpose, we obtained systematic high-resolution data in both the olfactory pit (OP) and the left–right organizer (LRO), a superficial organ and a deep organ embedded in the tail of the embryo, respectively. For the analysis of their axonemal ciliary structure, we used conventional transmission electron microscopy (TEM) and electron tomography (ET). We characterised the wild-type OP cilia and showed, for the first time in zebrafish, the presence of motile cilia (9 + 2) in the periphery of the pit and the presence of immotile cilia (still 9 + 2), with absent outer dynein arms, in the centre of the pit. In addition, we reported that a central pair of microtubules in the LRO motile cilia is common in zebrafish, contrary to mouse embryos, but it is not observed in all LRO cilia from the same embryo. We further showed that the outer dynein arms of the microtubular doublet of both the OP and LRO cilia are structurally similar in dimensions to the human respiratory cilia at the resolution of TEM and ET. We conclude that zebrafish is a good model organism for PCD research but investigators need to be aware of the specific physical differences to correctly interpret their results. ; publishersversion ; published