Knock-in of diphteria toxin A chain gene at Ins2 locus: effects on islet development and localization of Ins2 expression in the brain
- Cite this article as:
- Lamotte, L., Jackerott, M., Bucchini, D. et al. Transgenic Res (2004) 13: 463. doi:10.1007/s11248-004-9587-x
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We report here knock-in of diphteria toxin A chain (dta) gene at the Ins2 locus, using the strategy previously employed to insert lacZ under control of the Ins2 promoter. Mutant Ins2dta/+, Ins2dta/lacZ or Ins2lacZ/+ mouse pups were generated by breeding and analyzed to study the effects of toxigenetic β-cell ablation on islet development and to localize the extrapancreatic Ins2 expression site in the brain. Ins2dta/+ and Ins2dta/lacZ pups developed a severe diabetic ketoacidosis and died rapidly. Histological analysis of their pancreas revealed that β-cells completely disappeared in their islets as evidenced by loss of lacZ activity or insulin immunonostaining. β-cell ablation did not alter the size of other islet cell populations which were normal at birth, although the glucagon-cell population was reduced by 85% at embryonic day E12.5. In the brain, comparative analysis of lacZ expression in Ins2lacZ/+ and Ins2dta/lacZ mice identified the choroid plexus (CP) as a major Ins2 expression site. This finding was confirmed by RT-PCR analysis of insulin transcripts in RNAs prepared from microdissected wild-type CP. Transcripts for other key β-cell markers, with the notable exception of Pdx-1, were also found in CP RNAs. These results must revive interest in studies focused on extrapancreatic insulin gene expression.