SIX2 and SIX3 coordinately regulate functional maturity and fate of human pancreatic β cells

Genes Dev. 2021 Feb 1;35(3-4):234-249. doi: 10.1101/gad.342378.120. Epub 2021 Jan 14.

Abstract

The physiological functions of many vital tissues and organs continue to mature after birth, but the genetic mechanisms governing this postnatal maturation remain an unsolved mystery. Human pancreatic β cells produce and secrete insulin in response to physiological cues like glucose, and these hallmark functions improve in the years after birth. This coincides with expression of the transcription factors SIX2 and SIX3, whose functions in native human β cells remain unknown. Here, we show that shRNA-mediated SIX2 or SIX3 suppression in human pancreatic adult islets impairs insulin secretion. However, transcriptome studies revealed that SIX2 and SIX3 regulate distinct targets. Loss of SIX2 markedly impaired expression of genes governing β-cell insulin processing and output, glucose sensing, and electrophysiology, while SIX3 loss led to inappropriate expression of genes normally expressed in fetal β cells, adult α cells, and other non-β cells. Chromatin accessibility studies identified genes directly regulated by SIX2. Moreover, β cells from diabetic humans with impaired insulin secretion also had reduced SIX2 transcript levels. Revealing how SIX2 and SIX3 govern functional maturation and maintain developmental fate in native human β cells should advance β-cell replacement and other therapeutic strategies for diabetes.

Keywords: diabetes mellitus; islet; pancreas; transcription factor; β cells.

Publication types

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

MeSH terms

  • Cell Differentiation / genetics*
  • Diabetes Mellitus, Type 2 / physiopathology
  • Eye Proteins / metabolism*
  • Gene Expression Regulation / genetics*
  • Homeodomain Proteins / metabolism*
  • Humans
  • Insulin Secretion / genetics
  • Insulin-Secreting Cells / cytology*
  • Nerve Tissue Proteins / metabolism*
  • RNA, Small Interfering / metabolism
  • Transcriptome

Substances

  • Eye Proteins
  • Homeodomain Proteins
  • Nerve Tissue Proteins
  • RNA, Small Interfering
  • SIX2 protein, human
  • Sine oculis homeobox homolog 3 protein