80 IDENTIFICATION OF NOVEL GH AND IGF-I RESPONSIVE GENES IN HUMAN CHONDROCYTES BY MICROARRAY ANALYSIS

Longitudinal bone growth is the result of chondrocyte proliferation followed by ossification in the growth plate. Both GH and IGF-I are known to have direct effect on the growth plate, but their mediating factors are not fully understood. In an attempt to find novel candidate genes for the regulation of longitudinal growth in children, (1) we have selected candidate genes by performing microarray analysis on human chondrocytes, (2) identified sequence variations in the candidates, and (3) will study those sequence variations in short and normal height populations. The microarray analysis was performed on primary cultured human chondrocytes treated with GH or insulin-like growth factor I (IGF-I) or saline (control) in duplicates using the U95 chips containing more than 12,000 genes (Affymetrix). The selection was based on signal intensity and quality. We identified several genes that have changed expression in response to GH (n=25), IGF-I (n=93), and both (n=11) compared to control. Of these 11 genes responding to both GH and IGF-I, CYR61 was particularly interesting for our purpose since it is involved in angiogenesis. A database searches identified 10 SNPs in the hCYR61 gene, and a cross species comparison reveals that CYR61 is highly conserved. Interestingly, some of SNPs are located in conserved regions. Sequence analysis will be used to identify additional SNPs and will also used to study the relationship between height and sequence variations in CYR6 1 in short and normal height populations.