A comparison of the expression pattern of five genes of the family of small leucine-rich proteoglycans during mouse development

For five members of the family of the small leucine-rich proteoglycans (SLR Ps), the expression pattern during fetal development was analyzed. RNA in s itu hybridization on whole body sections of mouse embryos was performed for biglycan (Bgn), decorin (Dcn), fibromodulin (Fmod), chondroadherin (Chad), and lumican (Lum), Special attention was given to the question of whether these patterns coincide only with sites of collagen secretion in connective tissue during tissue modeling or if expression can be observed at specific sites of organ differentiation also. In general, Fined, Lum, and Bgn are e xpressed at sites of cartilage and bone formation and interstitial tissue d eposition; Chad is expressed only at sites of cartilage; and Dcn is express ed only at sites of interstitial tissue deposition. However, there are some distinct developmental stages where no collagen secretion is known to occu r. For example, this applies for the expression of Fined in the forming som ites of stage 9.5 postconception (p.c.), for Dcn and Lum in later stage emb ryos in the pituitary gland and dorsal root ganglia, and for Bgn and Dcn du ring differentiation in the kidney. These studies provide further evidence for a role of these molecules during connective tissue organization but als o for an involvement at specific sites of organ differentiation.