Effect of short interspersed element sequences on the integration and expression of a reporter gene in the preimplantation-stage mouse embryos

Based on the assumption that foreign DNA sequences may have increased chance of integration into the host genome if they are flanked by high copy‐numbered genomic sequences such as SINEs (short interspersed elements), we investigated the integration frequency of Lac Z reporter gene flanked by a fused B1/B2 in an in vivo system using pronuclear microinjection technique in the mouse. The SINE‐flanked DNA showed a 4‐fold increased integration frequency of the reporter gene than the control DNA (63% vs. 16%). Moreover, the level of β‐galactosidase expression, estimated from the X‐Gal staining intensity in transgenic embryos, was greatly higher in SINE‐carrying DNA. These results suggest that the SINE sequences can serve a very useful tool in improving the efficiency of current transgenic animal technology. Mol. Reprod. Dev. 56:366–371, 2000. © 2000 Wiley‐Liss, Inc.