A transgenic construct containing GFP under the control of the Sox3 promoter was co-injected with a tyrosinase minigene at equimolar ratios. The hol (holstein) line contains 11 copies of the transgene inserted into chromosome 9 between Col6a4 and Glyctk and deletes 153 bp. GFP expression is not detected. FACS analysis confirmed increased expression of Col6a4 in the proximal and distal small intestine and cecum.