EN
Mammary gland-specific expression of human genes and secretion of human proteins into the milk of transgenic farm animals provides an important tool for manufacturing of many valuable pharmaceuticals. More recently, attention has focused on urine-based expression systems as a much more cost-effective technology. Successful application of this technology, however, requires the definition of several crucial regulatory elements that direct production of the protein into the urinary tract. To date, the 5? flanking region of either the uroplakin II (UPII) or uromodulin (THP) genes were used to drive the expression of heterologous proteins in the bladder or kidney epithelium of the transgenic mice, respectively. Herein, the progress and current limitations in this field are presented. Other currently known urine-specific protein genes are also described.