Expression analysis of the Adam21 gene in mouse testis.

A number of members belonging to a disintegrin and metalloprotease (ADAM) family of cell surface proteins, including ADAM21, are expressed specifically or predominantly in the mammalian testis. Here, we investigated the transcriptional characteristics of the Adam21 gene. We found that Adam21 produces two types of transcripts with different developmental stages and cellular localizations. One type comprises germ cell-specific transcripts with both exons 1 and 2, while the other type corresponds to exon 2 and is expressed in testicular somatic cells. Further, regulatory and promoter regions responsible for the expression of Adam21 in testicular somatic cells were investigated using an in silico sequence analysis and an in vitro transient transfection assay. We identified an essential promoter and mapped regulatory regions that repress the transcription of Adam21. Finally, we confirmed the expression of Adam21 at the protein level in testicular somatic cells in which the promoter of the gene was found to be active. This is the first study to provide information regarding transcriptional regulation of a testicular ADAM family member, which will aid in elucidation of the transcriptional mechanisms of other testicular Adam genes.