ZIGIR, a Granule-Specific Zn2+ Indicator, Reveals Human Islet α Cell Heterogeneity

Cell Rep. 2020 Jul 14;32(2):107904. doi: 10.1016/j.celrep.2020.107904.


Numerous mammalian cells contain abundant Zn2+ in their secretory granules, yet available Zn2+ sensors lack the desired specificity and sensitivity for imaging granular Zn2+. We developed a fluorescent zinc granule indicator, ZIGIR, that possesses numerous desired properties for live cell imaging, including >100-fold fluorescence enhancement, membrane permeability, and selective enrichment to acidic granules. The combined advantages endow ZIGIR with superior sensitivity and specificity for imaging granular Zn2+. ZIGIR enables separation of heterogenous β cells based on their insulin content and sorting of mouse islets into pure α cells and β cells. In human islets, ZIGIR facilitates sorting of endocrine cells into highly enriched α cells and β cells, reveals unexpectedly high Zn2+ activity in the somatostatin granule of some δ cells, and uncovers variation in the glucagon content among human α cells. We expect broad applications of ZIGIR for studying Zn2+ biology and Zn2+-rich secretory granules and for engineering β cells with high insulin content for treating diabetes.

Keywords: FACS islet cell; TIRF imaging; ZIGIR; Zinc sensor; ZnT8; alpha cell heterogeneity; beta cell; delta cell; dense core granule; zinc imaging.

Publication types

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

MeSH terms

  • Adult
  • Aged
  • Animals
  • Cells, Cultured
  • Cytoplasmic Granules / metabolism*
  • Female
  • Fluorescence
  • Fluorescent Dyes / chemistry
  • Fluorescent Dyes / metabolism*
  • Glucagon-Secreting Cells / metabolism*
  • Humans
  • Insulin / metabolism
  • Insulin-Secreting Cells / metabolism
  • Islets of Langerhans / metabolism*
  • Male
  • Mice
  • Middle Aged
  • Staining and Labeling
  • Zinc / metabolism*


  • Fluorescent Dyes
  • Insulin
  • Zinc