Insertional mutagenesis in transgenic mice generated by the pronuclear microinjection procedure.

Insertional mutagenesis in transgenic mice is a powerful method to study structure/function relationships between individual genes and complex developmental traits in the whole organism. Unlike spontaneous or chemical-induced mutations, insertional mutations have the advantage that the mutant locus is "tagged" with the transgene and, therefore, readily accessible at the molecular level. Starting with the work on the limb deformity locus, we describe here the characterization of several mouse mutants generated by insertional mutagenesis with the pronuclear microinjection procedure. These transgenic lines have proven to be ideal as models for human disease and for studying the function of novel genes during development. We also describe the unique features of insertional mutations that arise in transgenic mice produced with the pronuclear microinjection procedure and provide recommendations on how to clone and characterize these mutations at the molecular level. Finally, we discuss future prospects for the use of this unique form of germline mutagenesis in the mouse.