NKX6.1 Promotes PDX-1-Induced Liver to Pancreatic β-Cells Reprogramming

Abstract

Reprogramming adult mammalian cells is an attractive approach for generating cell-based therapies for degenerative diseases, such as diabetes. Adult human liver cells exhibit a high level of developmental plasticity and have been suggested as a potential source of pancreatic progenitor tissue. An instructive role for dominant pancreatic transcription factors in altering the hepatic developmental fate along the pancreatic lineage and function has been demonstrated. Here we analyze whether transcription factors expressed in mature pancreatic β-cells preferentially activate β-cell lineage differentiation in liver. NKX6.1 is a transcription factor uniquely expressed in β-cells of the adult pancreas, its potential role in reprogramming liver cells to pancreatic lineages has never been analyzed. Our results suggest that NKX6.1 activates immature pancreatic markers such as NGN-3 and ISL-1 but not pancreatic hormones gene expression in human liver cells. We hypothesized that its restricted capacity to activate a wide pancreatic repertoire in liver could be related to its incapacity to activate endogenous PDX-1 expression in liver cells. Indeed, the complementation of NKX6.1 by ectopic PDX-1 expression substantially and specifically promoted insulin expression and glucose regulated processed hormone secretion to a higher extent than that of PDX-1 alone, without increasing the reprogrammed cells. This may suggest a potential role for NKX6.1 in promoting PDX-1 reprogrammed cells maturation along the β-cell-like lineage. By contrast, NKX6.1 repressed PDX-1 induced proglucagon gene expression. The individual and concerted effects of pancreatic transcription factors in adult extra-pancreatic cells, is expected to facilitate developing regenerative medicine approaches for cell replacement therapy in diabetics.

Gastrin induces ductal cell dedifferentiation and β-cell neogenesis after 90% pancreatectomy

“…Specifically, continuous expression of NKX6-1 in the entire pancreatic progenitor pool significantly represses Ptf1a expression, preventing acinar cell differentiation, and favours an endocrine over a ductal cell fate choice (Schaffer et al 2010). In the post-natal pancreas, nuclear NKX6-1 expression is restricted to endocrine b-cells (Sander et al 2000), and it has been shown that induction of NKX6-1 expression in PDX1-expressing liver cells promotes endocrine cell reprogramming (Gefen-Halevi et al 2010). The presence of NEUROG3 and NKX6-1 expression in a subpopulation of ductal cells indicates that these cells have an endocrine progenitor-like phenotype.…”

Nkx2.2 repressor complex regulates islet β-cell specification and prevents β-to-α-cell reprogramming

“…In addition, recent studies have exploited the known islet transcriptional networks to transdifferentiate nonpancreatic or exocrine tissue into endocrine cells. Ectopic expression of different combinations of pancreatic transcription factors-including Pdx1, Ngn3, NeuroD, MafA, and Nkx6.1-promotes liver-to-pancreatic b-cell reprogramming Kojima et al 2003;Song et al 2007;Delisle et al 2009;Nagaya et al 2009;Gefen-Halevi et al 2010). Similarly, ectopic expression of a defined set of transcription factors in adult pancreatic acinar cells results in an acinar-to-b-cell conversion (Zhou et al 2008).…”

Diabetes reversal via gene transfer: building on successes in animal models

“…It has been demonstrated that ectopic expression of Nkx6.1 alone is not a strong inducer of upper-hierarchy β-cell transcription factor expression, and that only upon coexpression with Pdx-1 was it capable of substantial insulin expression and glucose-responsive secretion of insulin. 150 The lack of expression of the full hierarchy of β-cell transcription factors makes Nkx6.1 a mediocre choice for the generation of artificial β-cells for analysis in animal models of diabetes.…”