DISTINCT REGIONS CONTROL TRANSCRIPTIONAL ACTIVATION OF THE ALPHA-1(VI) COLLAGEN PROMOTER IN DIFFERENT TISSUES OF TRANSGENIC MICE

To identify regions involved in tissue specific regulation of transcri ption of the al(VI) collagen chain, transgenic mice were generated car rying various portions of the gene's 5'-flanking sequence fused to the E. coli p-galactosidase gene. Analysis of the transgene expression pa ttern by X-gal staining of embryos revealed that: (a) The proximal 0.6 kb of promoter sequence activated transcription in mesenchymal cells at sites of insertion of superficial muscular aponeurosis into the ski n; tendons were also faintly positive. (b) The region between -4.0 and -5.4 kb from the transcription start site was required for activation of the transgene in nerves. It also drove expression in joints, in in tervertebral disks, and in subepidermal and vibrissae mesenchyme. (c) The fragment comprised within -6.2 and -7.5 kb was necessary for high level transcription in skeletal muscle and meninges. Positive cells in muscle were mostly mononuclear and probably included connective tissu e elements, although staining of myoblasts was not ruled out. This fra gment also activated expression in joints, in intervertebral disks, an d in subepidermal and vibrissae mesenchyme, (d) beta-Galactosidase sta ining in vibrissae induced by the sequences -4.0 to -5.4 and -6.2 to - 7.5 was not coincident: with the latter sequence labeled nuclei were f ound mainly in the ventral and posterior quadrant, and, histologically , in the outer layers of mesenchyme surrounding and between the follic les, whereas with the former the remaining quadrants were positive and expressing cells were mostly in the inner layers of the dermal sheath . (e) Other tissues, notably lung, adrenal gland, digestive tract, whi ch produce high amounts of collagen type VI, did not stain for beta-ga lactosidase. (f) Central nervous system and retina, in which the endog enous gene is inactive, expressed the lacZ transgene in most lines. Th e data suggest that transcription of alpha 1(VI) in different tissues is regulated by distinct sequence elements in a modular arrangement, a mechanism which confers high flexibility in the temporal and spatial pattern of expression during development.