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Submitted on February 1, 2006
Accepted on March 15, 2006
Departments of Medicineand Molecular Physiology and Biophysics, and Program in Developmental Biology, Vanderbilt University Medical Center, 2220 Pierce Avenue 746 PRB, Nashville, TN, and Department of Biochemistry and Molecular Genetics, University of Illinois at Chicago, 900 S. Ashland Avenue 2220 MBRB, Chicago, IL
* To whom correspondence should be addressed. E-mail: Maureen.gannon{at}vanderbilt.edu.
The FoxM1 transcription factor is highly expressed in proliferating cells and activates several cell cycle genes, although its requirement appears to be limited to certain tissue types. Embryonic hepatoblast-specific inactivation of Foxm1 results in a dramatic reduction in liver outgrowth and subsequent late gestation lethality, while inactivation of Foxm1 in adult liver impairs regeneration following partial hepatectomy. These results prompted us to examine whether FoxM1 functions similarly in embryonic outgrowth of the pancreas and
cell proliferation in the adult. We found that FoxM1 is highly expressed in embryonic and neonatal endocrine cells, when many of these cells are proliferating. Using a Cre-lox strategy, we generated mice in which Foxm1 was inactivated throughout the developing pancreatic endoderm by e15.5 (Foxm1
panc). Mice lacking Foxm1 in their entire pancreas were born with normal pancreatic and
cell mass, however, they displayed a gradual decline in
cell mass with age. Failure of postnatal
cell mass expansion resulted in impaired islet function by six weeks of age and overt diabetes by nine weeks. The decline in
cell mass in Foxm1
panc animals is due to a dramatic decrease in postnatal
cell replication and a corresponding increase in nuclear localization of the cyclin-dependent kinase inhibitor, p27Kip1, a known target of FoxM1 inhibition. We conclude that Foxm1 is essential to maintain normal
cell mass and regulate postnatal
cell turnover. These results suggest that mechanisms regulating embryonic
cell proliferation differ from those used postnatally to maintain the differentiated cell population.
This article has been cited by other articles:
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A. M Ackermann and M. Gannon Molecular regulation of pancreatic {beta}-cell mass development, maintenance, and expansion J. Mol. Endocrinol., February 1, 2007; 38(2): 193 - 206. [Abstract] [Full Text] [PDF] |
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L. C. Murtaugh Pancreas and beta-cell development: from the actual to the possible Development, February 1, 2007; 134(3): 427 - 438. [Abstract] [Full Text] [PDF] |
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