Insulinoma-associated antigen-1 zinc-finger transcription factor promotes pancreatic duct cell trans-differentiation.
Insulinoma-associated antigen-1 (INSM1/IA-1) is a unique zinc-finger transcription factor restrictedly expressed in pancreatic beta-cells during early pancreas development. INSM1 is transiently activated by the islet-specific endocrine factor neurogenin 3, and it subsequently regulates downstream target genes NeuroD1 and insulin during beta-cell maturation. Here, we examined how the INSM1 transcription factor contributes to endocrine cell differentiation using a defined serum-free medium-primed pancreatic duct cell model. We showed that ectopic expression of INSM1 can promote Panc-1 cell trans-differentiation. INSM1 up-regulates two islet transcription factors (ITFs), paired box 6 and homeodomain transcription factor 6.1, whereas other ITFs, including pancreatic duodenal homeobox-1 (Pdx-1), homeodomain transcription factor 2.2, NeuroD1, paired box 4, and neurogenin 3, were either down-regulated or absent. The result suggests that INSM1 is capable of regulating multiple ITFs and the insulin gene either directly or indirectly. When we overexpressed three ITFs, INSM1/Pdx-1/NeuroD1, in the Panc-1 differentiation model, higher insulin expression was observed in parallel with the activation of an additional ITF, neurogenin 3, signifying endocrine cell activation. Insulin expression from the three ITFs stimulation was readily detected by immunostaining and increased 40% as compared with the insulin-transferrin-selenium-LacZ control. Furthermore, we examined the differential chromatin acetylation patterns within the insulin promoter region using the chromatin immunoprecipitation assay. INSM1 alone can selectively enhance acetylation of histone H4, whereas NeuroD1 and Pdx-1 favor the acetylation of histone H3. Both H3 and H4 histone acetylations facilitate insulin gene expression. The consistent functional effect of INSM1, either with or without other ITFs, promotes pancreatic duct cell differentiation as well as induces Panc-1 cell cycle arrest.
Zhang
Tao
T
Children's Hospital, Research and Education Building, New Orleans, Louisiana 70118, USA.
Wang
Hongwei
H
Saunee
Nicolle A
NA
Breslin
Mary B
MB
Lan
Michael S
MS
D000107:Acetylation; D051792:Basic Helix-Loop-Helix Proteins / Q000235:genetics / Q000378:metabolism; D015153:Blotting, Western; D002453:Cell Cycle; D045744:Cell Line, Tumor; D054338:Cell Transdifferentiation; D005136:Eye Proteins / Q000235:genetics / Q000378:metabolism; D005434:Flow Cytometry; D006657:Histones / Q000378:metabolism; D018398:Homeodomain Proteins / Q000235:genetics / Q000378:metabolism; D006801:Humans; D007150:Immunohistochemistry; D007328:Insulin / Q000378:metabolism; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000378:metabolism; D000071841:PAX6 Transcription Factor; D051761:Paired Box Transcription Factors / Q000235:genetics / Q000378:metabolism; D010183:Pancreatic Ducts / Q000378:metabolism / Q000473:pathology; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D014162:Transfection; D016335:Zinc Fingers
D051792:Basic Helix-Loop-Helix Proteins; D005136:Eye Proteins; D006657:Histones; D018398:Homeodomain Proteins; D007328:Insulin; D009419:Nerve Tissue Proteins; D000071841:PAX6 Transcription Factor; D051761:Paired Box Transcription Factors; D012097:Repressor Proteins; D015534:Trans-Activators; D014157:Transcription Factors; C105201:NKX6-1 protein, human; C000605730:PAX6 protein, human; C084010:pancreatic and duodenal homeobox 1 protein; C087342:INSM1 protein, human; C093564:Neurogenic differentiation factor 1