MicroRNA 21 targets BCL2 mRNA to increase apoptosis in rat and human beta cells

Diabetologia. 2017 Jun;60(6):1057-1065. doi: 10.1007/s00125-017-4237-z. Epub 2017 Mar 9.


Aims/hypothesis: The role of beta cell microRNA (miR)-21 in the pathophysiology of type 1 diabetes has been controversial. Here, we sought to define the context of beta cell miR-21 upregulation in type 1 diabetes and the phenotype of beta cell miR-21 overexpression through target identification.

Methods: Islets were isolated from NOD mice and mice treated with multiple low doses of streptozotocin, as a mouse model of diabetes. INS-1 832/13 beta cells and human islets were treated with IL-1β, IFN-γ and TNF-α to mimic the milieu of early type 1 diabetes. Cells and islets were transfected with miR-21 mimics or inhibitors. Luciferase assays and polyribosomal profiling (PRP) were performed to define miR-21-target interactions.

Results: Beta cell miR-21 was increased in in vivo models of type 1 diabetes and cytokine-treated cells/islets. miR-21 overexpression decreased cell count and viability, and increased cleaved caspase 3 levels, suggesting increased cell death. In silico prediction tools identified the antiapoptotic mRNA BCL2 as a conserved miR-21 target. Consistent with this, miR-21 overexpression decreased BCL2 transcript and B cell lymphoma 2 (BCL2) protein production, while miR-21 inhibition increased BCL2 protein levels and reduced cleaved caspase 3 levels after cytokine treatment. miR-21-mediated cell death was abrogated in 828/33 cells, which constitutively overexpress Bcl2. Luciferase assays suggested a direct interaction between miR-21 and the BCL2 3' untranslated region. With miR-21 overexpression, PRP revealed a shift of the Bcl2 message towards monosome-associated fractions, indicating inhibition of Bcl2 translation. Finally, overexpression in dispersed human islets confirmed a reduction in BCL2 transcripts and increased cleaved caspase 3 production.

Conclusions/interpretation: In contrast to the pro-survival role reported in other systems, our results demonstrate that miR-21 increases beta cell death via BCL2 transcript degradation and inhibition of BCL2 translation.

Keywords: Animal – mouse; Basic science; Beta cell signal transduction; Cell lines; Islet degeneration and damage; Islets.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, U.S. Gov't, Non-P.H.S.
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Diabetes Mellitus, Type 1 / genetics*
  • Fluorescent Antibody Technique
  • Humans
  • Immunoblotting
  • Insulin-Secreting Cells / metabolism
  • Interferon-gamma / metabolism
  • Interleukin-1beta / metabolism
  • Male
  • Mice
  • Mice, Inbred NOD
  • MicroRNAs / genetics
  • MicroRNAs / metabolism*
  • Proto-Oncogene Proteins c-bcl-2 / genetics
  • Proto-Oncogene Proteins c-bcl-2 / metabolism
  • Rats
  • Tumor Necrosis Factor-alpha / metabolism


  • Interleukin-1beta
  • MIRN21 microRNA, human
  • MicroRNAs
  • Proto-Oncogene Proteins c-bcl-2
  • Tumor Necrosis Factor-alpha
  • mirn21 microRNA, rat
  • Interferon-gamma