<http://purl.org/dc/terms/description>
"Skeletogenesis is associated with the aggregation of mesenchymal cells into condensations that prefigure the mature skeleton under the influence of numerous signaling molecules. In the developing murine limb, Fibroblast growth factors (FGFs)\n(principally 4 and 8) are expressed in the apical ectodermal ridge (AER) and signal to the underlying distal mesenchymal cells. In this manner, FGFs are thought to influence the proliferation of chondroprogenitors, thereby modulating the growth of pre-cartilage condensations. To study these effects the chondrogenic program can be effectively modeled in vitro using high-density cultures of primary cells isolated from the murine limb bud (El 1.5). Treatment of distal mesenchymal cultures with\nFGF4 leads to a transient increase in proliferation and expansion of prechondrogenic condensations. Using transcriptional profiling with DNA microarrays we observed that consistent with the changes observed in cell proliferation, FGF4 treatment resulted in an \u223C 18 fold increase in the expression of Cdkn2b \u2014 a cyclin dependent kinase inhibitor. SiRNA knockdown of Cdkn2b resulted in sustained mesenchymal proliferation. Further, we determined that FGF4 regulates\nCdkn2b through a MEKI/ERK-dependent pathway. Additionally, we show that FGF4 promotes cell survival through the regulation of NFiB via upregulation of its activator RIPK4.\nTo enhance our studies of chondrogenesis, a high throughput reporter gene based assay was developed. Using this technology we performed a chemical genetic screen of \u223C1500 chemical compounds to assess their ability to regulate\nreporter gene activity. Of these compounds, 28 yielded a &gt;2.5 fold increase in S0X5/6/9 reporter gene activity. Secondary histological screens confirmed increased cartilage formation in response to treatment of primary limb cultures with\nseveral of these newly identified chemical enhancers of chondrogenesis. Through\nbioinformatic analysis of microarray data in comparison with the known targets of the\nscreened chemical compounds, we have shown that inhibition of potassium channel KCND2 (Kv4.2) promotes chondrogenesis. Additionally, it was found that prochondrogenic bone morphogenetic protein 4 (BMP4) downregulated the\nexpression of Kcnd2. These data have revealed an unanticipated role of potassium channels during chondrogenesis. Thus by using a combined approach of microarray analysis and chemical genetics we have further characterized the intricacies of the\nchondrogenic program."@en
<https://open.library.ubc.ca/cIRcle/collections/ubctheses/24/items/1.0069926>