LENS COMPLEMENTATION SYSTEM FOR THE GENETIC-ANALYSIS OF GROWTH, DIFFERENTIATION, AND APOPTOSIS IN-VIVO

A genetic approach has been established that combines the advantages o f blastocyst complementation with the experimental attributes of the d eveloping lens for the functional analysis of genes governing cellular proliferation, terminal differentiation, and apoptosis, This lens com plementation system (LCS) makes use of a mutant mouse strain, aphakia (ak), homozygotes of which fail to develop an ocular lens, We demonstr ate that microinjection of wild-type embryonic stem (ES) cells into ak /ak blastocysts produces chimeras with normal ES-cell-derived lenses a nd that microinjection of Rb-/- ES cells generates an aberrant lens ph enotype identical to that obtained through conventional gene targeting methodology, Our determination that a cell autonomous defect underlie s the aphakia condition assures that lenses generated through LCS are necessarily ES-cell-derived, LCS provides for the rapid phenotypic ana lysis of loss-of-function mutations, circumvents the need for germ-lin e transmission of null alleles, and, most significantly, facilitates t he study of essential genes whose inactivation is associated with earl y lethal phenotypes.