Improved Experimental Procedures for Achieving Efficient Germ Line Transmission of Nonobese Diabetic (NOD)-Derived Embryonic Stem Cells

The manipulation of a specific gene in NOD mice, thebest animal model for insulin-dependent diabetes mellitus(IDDM), must allow for the precise characterization of thefunctional involvement of its encoded molecule in the pathogenesisof the disease. Although this has been attempted bythe cross-breeding of NOD mice with many gene knockoutmice originally created on the 129 or C57BL/6 strain background,the interpretation of the resulting phenotype(s) hasoften been confusing due to the possibility of a known orunknown disease susceptibility locus (e.g., Idd locus) cosegregatingwith the targeted gene from the diabetes-resistantstrain. Therefore, it is important to generate mutant miceon a pure NOD background by using NOD-derived embryonicstem (ES) cells. By using the NOD ES cell line establishedby Nagafuchi and colleagues in 1999 (FEBSLett., 455,101–104), the authors reexamined various conditions in thecontext of cell culture, DNA transfection, and blastocyst injection,and achieved a markedly improved transmissionefficiency of these NOD ES cells into the mouse germ line.These modifications will enable gene targeting on a “pure” NOD background with high efficiency, and contribute toclarifying the physiological roles of a variety of genes in thedisease course of IDDM.