Ins1 Gene Up-Regulated in a β-Cell Line Derived from Ins2 Knockout Mice

The authors have derived a new β-cell line (βIns2(−/−lacZ)) from Ins2(−/−) mice that carry the lacZ reporter gene under control of the Ins2 promoter. βIns2(−/−lacZ) cells stained positively using anti-insulin antibody, expressed β-cell–specific genes encoding the transcription factor PDX-1, glucokinase, and Glut-2, retained glucose-responsiveness for insulin secretion, and expressed the lacZ gene. Analysis of Ins1 expression by reverse transcriptase–polymerase chain reaction (RT-PCR) showed that Ins1 transcripts were significantly raised to compensate for the lack of Ins2 transcripts in βIns2(−/−lacZ) cells, as compared to those found in βTC1 cells expressing both Ins1/Ins2. Thus, transcriptional up-regulation of the remaining functional insulin gene in Ins2(−/−) mice could potentially contribute to the β-cell adaptation exhibited by these mutants, in addition to the increase in β-cell mass that we previously reported.We have also shown that lacZ expression, as analyzed by determining β-galactosidase activity, was up-regulated by incubating βIns2(−/−lacZ) cells with GLP-1 and/or IBMX, 2 known stimulators of insulin gene expression. These cells thus represent a new tool for testing of molecules capable of stimulating Ins2 promoter activity