Molecular cloning and developmental expression of a hyaluronan and proteoglycan link protein gene, crtl1/hapln1, in zebrafish.

The proteoglycan aggregate of the cartilage is composed of aggrecan, link protein (LP), and hyaluronan, providing resistance to compression in joints and cartilage structures. To further understand the function of LP during the process of chondrogenesis and bone formation in zebrafish, we cloned the zebrafish cDNA for hyaluronan and proteoglycan link protein 1 (crtl1/hapln1) and examined the expression of the gene during embryogenesis using in-situ hybridization. crtl1/hapln1 expression is first observed in the adaxial cells at the bud- stage. Throughout somitogenesis, crtl1/hapln1 is expressed in the sclerotomes, floor plate, and hypochord. In addition, crtl1/hapln1 is expressed in rhombomeres 3 and 5, pharyngeal arches, telecephalon, otic vesicles, and pectral fins. During chondrocranial/skull formation, crtl1/hapln1 expression is highest at around 4 dpf and is colocalized with aggrecan in the cartilaginous arches and with dermacan in the dermal bones.