These remain concerns for the clinical use of nucleasebased approaches. Alternatively, traditional HR strategy is likely to be devoid of aberrant genomic mutations. Traditional HR has been used for targeted introduction of transgenes and loss-offunction mutations in mouse for decades and geneknockout pigs has been produced by traditional HR. Gene knockin by traditional HR can be achieved in embryonic stem cells and induced pluripotent stem cells, but has not succeeded in somatic cells. Due to unavailability of the germline-competent stem cells, gene-knockin pig by traditional HR is not obtained yet. Specific genomic site with high homologous combination frequency and ubiquitous transcriptional Levomefolic acid activity is also critical for success in gene targeting. The most preferred integration site used for gene targeting is the Rosa26 locus in mouse. The Rosa26 26Sor) gene was identified originally as a ubiquitous marker in a retroviral SCH 619734 gene-trapping screen in mouse ESCs. It expresses a non-coding RNA ubiquitously in embryo and adult tissue. As in mouse, the human and rat Rosa26 loci were identified and successfully targeted by traditional HR, suggesting gene targeting at this locus is efficient. Recently, the pRosa26 locus has been characterized by homology search with human Rosa26 sequences and targeted by a Credependent reporter gene. Now, hundreds of transgenic animals and cell lines expressing a variety of transgenes have been successfully created using the Rosa26 locus. Tissue-specific promoters are valuable for elucidating specific gene functions and for use in gene therapy. However, even in mouse, activity of tissue-specific promoters driving transgene expression at the locus has not been addressed. Manipulating gene expression in muscle is of interest for a wide array offundamental and applied research. In the study, the sequence of pRosa26 locus was further characterized, and Myostatin promoter, a muscle-specific promoter, was targeted into the locus. We demonstrate that Rosa26 locus supports tissue-specific promoter driving transgene expression in its own manner.