Sequences 5' of the basement membrane laminin beta 1 chain gene (LAMB1) direct the expression of beta-galactosidase during development of the mouse testis and ovary.

The murine LAMB1 gene encoding laminin beta 1 is expressed in the developing male and female gonads and mesonephros. To identify the cis-acting elements regulating the expression of LAMB1, murine transgenic lines were generated by fusing regions of the LAMB1 gene to the Eschericia coli lacZ gene. The p3.9LAM beta gal construct contained approximately 4 kb of 5' flanking sequence and directed beta-galactosidase expression in many different organs including the kidney, mammary gland, and the male and female genital systems, the focus of this report. In male embryos, between gestational ages E 14.5 and birth beta-galactosidase was transiently expressed in the prospermatogonia cells of the testis and in the differentiating epithelial cells in the ductus deferens, ductus epididymis, and seminal vesicles. In female embryos, beta-galactosidase was not detected in the ovary until about 1 week after birth; at this time, beta-galactosidase was expressed by oocytes of primary and secondary follicles. In contrast, transgenic mice carrying the first 0.7 kb of LAMB1 fused to the lacZ gene expressed beta-galactosidase only in the prospermatogonia cells of the testis. Thus, the cis-acting element(s) necessary for the expression of the LAMB1 gene in prospermatogonia cells are located in the first 0.7 kb of LAMB1 5' flanking sequence; element(s) required for expression of the LAMB1 gene in oocytes and epithelial cells of the mesonephric ducts, mesonephric tubules, the ductus deferens, ductus epididymis, and seminal vesicles are located with 4 kb 5' of the transcription initiation site.