Spatio-temporal distribution of chondromodulin-I mRNA in the chicken embryo: Expression during cartilage development and formation of the heart and eye

To define genes specifically expressed in cartilage and during chondrogenes is, we compared by differential display-polymerase chain reaction (DD-PCR) the mRNA populations of differentiated sternal chondrocytes from chicken em bryos with mRNA species modulated in vitro by retinoic acid (RA), Chondrocy te-specific gene expression is downregulated by RA, and PCR-amplified cDNAs from both untreated and RA-modulated cells were differentially displayed. Amplification products only from RNA of untreated chondrocytes were further analyzed, and a cDNA-fragment of the chondromodulin-I (ChM-I) mRNA was iso lated, After obtaining full length cDNA clones, we have analyzed the mRNA e xpression patterns at different developmental stages by RNase protection as say and in situ hybridization, Analysis of different tissues and cartilage from 17-day-old chicken embryos showed ChM-I mRNA only in chondrocytes. Dur ing somitogenesis of the chicken embryo, ChM-I transcripts were detected in the notochord, the floor and the roof plate of the neural tube, and in car tilage precursor tissues such as the sclerotomes of the somites, the develo ping limbs, the pharyngeal arches, the otic vesicle, and the sclera, ChM-I continued to be expressed in differentiated cartilages derived from these t issues and also in noncartilaginous domains of the developing heart and ret ina. Thus, in the chicken, the expression of ChM-I is not restricted to mat ure cartilage but is already present during early development in precartila ginous tissues as well as in heart and eye, Dev Dyn 1999; 216:233-243. (C) 1999 Wiley-Liss, Inc.