Regulation of an acetylcholine receptor LacZ transgene by muscle innervation.

The role of motor innervation in the expression of beta-galactosidase targeted to the nucleus (nls beta gal) under the control of a chicken muscle acetylcholine receptor alpha-subunit promoter of 850 bp was investigated using two lines of transgenic mice. After birth, nls beta gal was transiently expressed in the endplate areas of extensor digitorum longus, tibialis anterior and diaphragm muscles. In the adult, denervation of several fast twitch muscles caused a burst of transgene expression which started at endplates and displayed defined though transient spatio-temporal patterns; in the slow soleus muscle, no regular patterns were observed. Thus, in vivo, the 850 bp promoter confers preferential expression of nls LacZ in the motor endplates of newborn mice and, in addition, directs expression of nls LacZ in denervated adult muscles.