Morphology and development of a novel murine skeletal dysplasia

Marta Marchini; Elizabeth Silva Hernandez; Campbell Rolian

doi:10.7717/peerj.7180

Morphology and development of a novel murine skeletal dysplasia

PeerJ. 2019 Jul 4:7:e7180. doi: 10.7717/peerj.7180. eCollection 2019.

Authors

Marta Marchini^{1

2}, Elizabeth Silva Hernandez³, Campbell Rolian^{2

3}

Affiliations

¹ Department of Cell Biology and Anatomy, Cumming School of Medicine, University of Calgary, Calgary, Canada.
² McCaig Institute for Bone and Joint Health, University of Calgary, Calgary, Canada.
³ Department of Comparative Biology and Experimental Medicine, Faculty of Veterinary Medicine, University of Calgary, Calgary, Canada.

Abstract

Background: Limb bones develop and grow by endochondral ossification, which is regulated by specific cell and molecular pathways. Changes in one or more of these pathways can have severe effects on normal skeletal development, leading to skeletal dysplasias. Many skeletal dysplasias are known to result from mis-expression of major genes involved in skeletal development, but the etiology of many skeletal dysplasias remains unknown. We investigated the morphology and development of a mouse line with an uncharacterized mutation exhibiting a skeletal dysplasia-like phenotype (Nabo).

Methods: We used µCT scanning and histology to comprehensively characterize the phenotype and its development, and to determine the developmental stage when this phenotype first appears.

Results: Nabo mice have shorter limb elements compared to wildtype mice, while clavicles and dermal bones of the skull are not affected. Nabo embryos at embryonic stage E14 show shorter limb cartilage condensations. The tibial growth plate in Nabo mice is wider than in wildtype, particularly in the proliferative zone, however proliferative chondrocytes show less activity than wildtype mice. Cell proliferation assays and immunohistochemistry against the chondrogenic marker Sox9 suggest relatively lower, spatially-restricted, chondrocyte proliferation activity in Nabo. Bone volume and trabecular thickness in Nabo tibiae are also decreased compared to wildtype.

Discussion: Our data suggest that the Nabo mutation affects endochondral ossification only, with the strongest effects manifesting in more proximal limb structures. The phenotype appears before embryonic stage E14, suggesting that outgrowth and patterning processes may be affected. Nabo mice present a combination of skeletal dysplasia-like characteristics not present in any known skeletal dysplasia. Further genomic and molecular analysis will help to identify the genetic basis and precise developmental pathways involved in this unique skeletal dysplasia.

Keywords: Bone µCT; Dysplasia; Growth plate; Limb patterning.

Grants and funding

Marta Marchini and Campbell Rolian were supported by the University of Calgary Faculty of Veterinary Medicine. Campbell Rolian was also supported by Discovery Grant 4181932 from the Natural Sciences and Engineering Research Council of Canada. There was no additional external funding received for this study. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.