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Regulation of Murine Lactate Dehydrogenase C (Ldhc) Gene Expression¹

Department of Biochemistry, Molecular Biology and Cell Biology, Northwestern University, Evanston, Illinois 60208

ABSTRACT

Expression of Ldhc begins with the onset of meiosis in male germ cells and continues throughout spermatogenesis. Transcriptional regulatory mechanisms, especially in primary spermatocytes, are poorly described because of the lack of a reliable cell culture system. We constructed mouse transgenics and transfected germ cells in situ to study expression of the testis-specific isozyme of lactate dehydrogenase (LDH). From previous work, we determined that a 100-bp Ldhc core promoter contained potential cis regulatory elements, including a palindrome (–21 to +10), GC box (–70 to –65), and cAMP-responsive element (CRE) sites (–53 to –49, –39 to –35). We provide here the demonstration of a functional role for these sequences by expression of mutated transgenes in vivo. Our results reveal for the first time that mutation of the GC box does not abolish promoter activity, which remains testis-specific. Mutation of GC box or CRE sites resulted in a 73% and 74% reduction in promoter activity, respectively, in a transient transfection of germ cells in vivo by electroporation; the combination of GC box and CRE site mutations eliminates promoter activity. Therefore, we conclude that simultaneous occupancy of the GC box and CRE sites in the core promoter is necessary for full expression of Ldhc in the testis.

CRE, electroporation, gamete biology, GC box, gene regulation, Ldhc, mutation, promoter, spermatogenesis, testis, transgenic mice

¹Supported by NIH grant R01 HD005863-35. Core facilities used in this research were provided by the Lurie Cancer Center, Northwestern University.

Correspondence: ²Erwin Goldberg, Northwestern University, Department of Biochemistry, Molecular Biology and Cell Biology, 2205 Tech Drive, Evanston, IL 60208. FAX: 847 467 1380; e-mail: erv{at}northwestern.edu