Abstract
Following the transfer into fertilized mouse eggs of recombinant genes composed of the upstream region of the rat insulin II gene linked to sequences coding for the large-T antigen of SV 40, large-T antigen was detected exclusively in the .beta.-cells of the endocrine pancrease of transgenic mice. The .alpha. and .delta.-cells normally found in the islets of Langerhans were rare and disordered. Well-vascularized .beta.-cell tumors arise in mice harboring and inheriting these hybrid oncogenes.