NFAT4 deficiency results in incomplete liver regeneration following partial hepatectomy.
BACKGROUND
Liver regeneration following partial hepatectomy requires the orchestration of highly regulated molecular pathways; a change in the abundance or activity of a specific gene product has the potential to adversely affect this process. The nuclear factor of activated T-cells (NFAT) transcription factors represent a family of gene transcription signaling intermediates that translate receptor-dependent signaling events into specific transcriptional responses using the Ras/Raf pathway.


METHODS
Eight-week old NFAT4 knockout (KO) mice and their wild type counterparts (Balb-c) underwent two-thirds partial hepatectomy. The animals were sacrificed and their livers were harvested at specific time points during regeneration. Recovery of liver mass was measured for each time point. PCR analysis was used to analyze expression levels of the immediate early genes c-fos, c-jun and c-myc as well as downstream effectors of NFAT4 including FGF-18 and BMP-4.


RESULTS
Hepatocyte proliferation and thus liver regeneration following hepatectomy was suppressed in NFAT4 knockout (KO) mice. Statistical significance was reached at 1 h, 7 d, and 10 d (P < 0.05) with a 22% median reduction in regeneration of liver mass in the NFAT4 KO mice by 10 d, at which time liver regeneration should be complete in mice. The immediate early gene c-fos was elevated in NFAT4 KO mice during early regeneration with a median value at 1 h and 1 d of 1.60E-08 and 1.09E-08 versus 6.10E-09 and 1.55E-09 in the Balb-c mice. C-jun, in contrast, was elevated during late regeneration in the NFAT4 KO mice (3.40E-09 and 5.67E-09 at 7 and 10 d, respectively) in comparison with the Balb-c mice (7.76E-10 and 1.24E-09, respectively.). NFAT2 was also up-regulated in the NFAT4 KO mice; however, no changes were detected in its downstream effectors, CCR1 and CCL3.


CONCLUSIONS
We demonstrated that NFAT4 deficiency impairs hepatic regeneration in a murine model proving that NFAT4 plays an important yet unclear role in liver regeneration; its absence may be compensated by c-fos, c-jun, and NFAT2 expression changes.
Pierre
Ketsia B
KB
Section of Surgical Sciences, Vanderbilt University Medical Center, Nashville, Tennessee 37232-4753, USA.
Jones
Christopher M
CM
Pierce
Janene M
JM
Nicoud
Ian B
IB
Earl
T Mark
TM
Chari
Ravi S
RS
D000818:Animals; D017209:Apoptosis / Q000502:physiology; D055415:Bone Morphogenetic Protein 4 / Q000235:genetics; D002455:Cell Division / Q000502:physiology; D005346:Fibroblast Growth Factors / Q000235:genetics; D006498:Hepatectomy; D048031:JNK Mitogen-Activated Protein Kinases / Q000378:metabolism; D008099:Liver / Q000166:cytology / Q000502:physiology* / Q000601:surgery; D008115:Liver Regeneration / Q000502:physiology*; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D018345:Mice, Knockout; D050778:NFATC Transcription Factors / Q000235:genetics* / Q000378:metabolism*; D018809:Proliferating Cell Nuclear Antigen / Q000378:metabolism; D016760:Proto-Oncogene Proteins c-fos / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology; D015854:Up-Regulation / Q000502:physiology
C525810:Bmp4 protein, mouse; D055415:Bone Morphogenetic Protein 4; D050778:NFATC Transcription Factors; C494009:Nfatc3 protein, mouse; D018809:Proliferating Cell Nuclear Antigen; D016760:Proto-Oncogene Proteins c-fos; C113569:fibroblast growth factor 18; D005346:Fibroblast Growth Factors; D048031:JNK Mitogen-Activated Protein Kinases