DIFFERENT CIS-REGULATORY DNA ELEMENTS MEDIATE DEVELOPMENTAL STAGE-SPECIFIC AND TISSUE-SPECIFIC EXPRESSION OF THE HUMAN COL2A1 GENE IN TRANSGENIC MICE

Expression of the type II collagen gene (human COL2A1, mouse Col2a1) h eralds the differentiation of chondrocytes. It is also expressed in pr ogenitor cells of some nonchondrogenic tissues during embryogenesis. D NA sequences in the 5' flanking region and intron 1 are known to contr ol tissue-specific expression in vitro, but the regulation of COL2A1 e xpression in vivo is not clearly understood. We have tested the regula tory activity of DNA sequences from COL2A1 on the expression of a lacZ reporter gene in transgenic mice. We have found that type II collagen characteristic expression of the transgene requires the enhancer acti vity of a 309-bp fragment (+2,388 to +2,696) in intron 1 in conjunctio n with 6.1-kb 5' sequences. Different regulatory elements were found i n the 1.6-kb region (+701 to +2,387) of intron 1 which only needs 90-b p 5' sequences for tissue-specific expression in different components of the developing cartilaginous skeleton. Distinct positive and negati ve regulatory elements act together to control tissue-specific transge ne expression in the developing midbrain neuroepithelium. Positive ele ments affecting expression in the midbrain were found in the region fr om -90 to -1,500 and from +701 to +2.387. whereas negatively acting el ements were detected in the regions from -1,500 to -6,100 and +2,388 t o +2,855.