Use of transgenic mice to define cis regulatory elements governing tissue specific expression
from Goldhamer, D. J., A. Faerman, M. Shani and C. P. Emerson, Jr. 1992. Regulatory elements that control the lineage-specific expression of myoD. Science. 256:538-542.
(A) Whole mount of transgenic embryo with -2.5 kb promoter element, lacking the distal enhancer. No staining of the somites, limb buds (forelimb bud designated with an asterisk) or visceral arches was detected. this embryo shows ectopic staining in the spinal cord (small arrows), mesencephalon (large arrow), and mesonephros(arrowheads).
(B) Whole mount of representative transgenic embryo showing experssion of the F3'/-2.5lacZ transgene, which includes the F3 distal enhancer fragment that lies 18-22 kb 5' of the human MyoD promoter.The lacZ expression in the somites is evident as a metameric pattern of staining along the rostro-caudal axis of the embryo. The lacZ expression is not evident in somites posterior to the level of the hind-limb bud. The proximal region of the fore-limb bud contains a large population of intensely stained cells (large arrow), whereas few lacZ-positive cells are present in the hind limb (small arrow). Intense staining is also observed in the mesoderm of the visceral arches (arrowheads). Weak staining in the head is probably associated with the developing extraocular muscles and nasal pits.
(C) Frontal section through othe somites (approximately somites 10-15) of the embryo shown in (B).
(D) Frontal section at the level of the forelimb bud of the embryo shown in (B). The beta-gal staining in the forelimb bud is restricted to cells of the dorsal and ventral premuscle masses.