Expression and regulation of a proenkephalin β-galactosidase fusion gene in the reproductive system of transgenic mice

A fusion gene containing 3 kilobases of human proenkephalin 5′-flanking sequences and 1 kilobase of human proenkephalin 3′-flanking sequence and the easily visualized histochemical marker, Escherichia coll β-galactosidase, was used to study the function of cis-regulatory elements within the human proenkephalin gene in transgenic mice. Here data are presented on expression and regulation of this fusion gene in the reproductive system of three independent lines of transgenic mice. Within the male reproductive system, the fusion gene is expressed in the proximal epididymis and in developing germinal cells but not in mature or elongating spermatids. In the female reproductive system, the transgene was expressed at low basal levels, but expression was dramatically stimulated in the ovary and oviduct by hormonal stimulation and pregnancy; additionally, expression was induced at the uteroplacental junction in pregnant mice. Taken together these observations suggest that critical sequences for expression and regulation of the proenkephalin gene within the reproductive system are contained within sequences of the construct.