In vivo loss of function study reveals the short stature homeobox-containing (shox) gene plays indispensable roles in early embryonic growth and bone formation in zebrafish

Background: Congenital loss of the SHOX gene is considered to be a genetic cause of short stature phenotype in Turner syndrome and Leri-Weill dyschondrosteosis patients. Though SHOX expression initiates during early fetal development, little is known about the embryonic roles of SHOX. The evolutionary conservation of the zebrafish shox gene and the convenience of the early developmental stages for analyses make zebrafish a preferred model. Here, we characterized structure, expression, and developmental roles of zebrafish shox through a loss of function approach. Results: We found a previously undiscovered Shox protein that has both a homeodomain and an OAR-domain in zebrafish. The shox transcript emerged during the segmentation period and it increased in later stages. The predominant domains of shox expression were mandibular arch, pectoral fin, anterior notochord, rhombencephalon and mesencephalon, suggesting that Shox is involved in bone and neural development. Translational blockade of Shox mRNA by an antisense morpholino oligo delayed embryonic growth, which was restored by the co-overexpression of morpholino-resistant Shox mRNA. At later stages, impaired Shox expression markedly delayed the calcification process in the anterior vertebral column and craniofacial bones. Conclusions: Our data demonstrate evolutionarily-conserved Shox plays roles in early embryonic growth and in later bone formation.