CHF1/Hey2 Regulates Hypertrophy A surprising finding of our study is that many genes as- sociated with autophagy and apoptosis demonstrate in- creased expression in the transgenic cells after serum stimu- lation. Autophagy has recently been reported to promote heart failure [30], although this finding is controversial and directly contradicted by other studies which suggests a pro- tective role for autophagy in cardiac hypertrophy and pro- gression to heart failure [26, 27]. Our data is more consistent with the latter studies. Increased expression of apoptosis related genes is surprising, as we have found that the trans- genic cells are resistant to apoptosis induced by pressure overload or hydrogen peroxide treatment [28]. One possible interpretation for this paradoxical finding is that apoptosis is inhibited downstream of these molecules, resulting in a ho- meostatic feedback loop that leads to enhanced expression of these proximal genes. Examination of the components of these apoptosis related gene sets reveals that the proapoptotic gene BAX is downregulated, even though the majority of the components are upregulated (Fig. 8). As BAX is a down- stream effector of mitochondrion-dependent apoptosis, such a scenario is plausible. Further experimentation will be re- quired to explore this hypothesis. One limitation of our study is that we do not have a clear idea of the relationship of CHF1/Hey2 to these other genes within the context of a gene network. Although we have considered performing network analysis on our microarray data, we have refrained, as our sample size may not be suffi- cient in size to conduct a rigorous network analysis with cur- rent algorithms. In addition, current algorithms make more assumptions than are present in our current analysis, which may lead to spurious conclusions. In the future, we hope to address this important question as algorithms improve and as we collect more data. CONCLUSIONS We have previously analyzed transcriptional pathways in smooth muscle cells lacking CHF1/Hey2 after growth factor stimulation to gain insight into CHF1/Hey2-dependent genes that determine neointimal formation after vascular injury [16, 31]. We have also previously reported that CHF1/Hey2 can attenuate the hypertrophic response of cardiac myocytes to phenylephrine in vivo and in vitro [1]. More recently, we have found that CHF1/Hey2 suppresses the development of pathological hypertrophy and promotes physiological hyper- trophy through suppression of apoptosis [28]. Our current study examines transcriptional pathways altered in trans- genic myocytes treated with serum, a potent hypertrophic stimulus, and reveals associations between CHF1/Hey2 tran- scriptional regulation, fluid transport, adenylate cyclase, phosphatase activity and a number of other important path- ways. These aggregate findings underscore the importance of CHF1/Hey2 in cardiac hypertrophy, and suggest that future therapies based on CHF1/Hey2 may have important thera- peutic implications in preventing hypertrophy and heart fail- ure. ACKNOWLEDGEMENTS This work was supported by NIH grant HL081088 to MTC. This work was also supported in part by the UW NIEHS sponsored Center for Ecogenetics and Environmental Health, Grant #: NIEHS P30ES07033. REFERENCES Current Genomics, 2010, Vol. 11, No. 4 295 [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] [14] [15] [16] [17] [18] Xiang, F.; Sakata, Y.; Cui, L.; Youngblood, J. M.; Nakagami, H.; Liao, J. K.; Liao, R.; Chin, M. T. Transcription factor CHF1/Hey2 suppresses cardiac hypertrophy through an inhibitory interaction with GATA4. Am. J. Physiol. Heart Circ. Physiol., 2006, 290(5), H1997-H2006. Kathiriya, I. S.; King, I. N.; Murakami, M.; Nakagawa, M.; Astle, J. M.; Gardner, K. A.; Gerard, R. D.; Olson, E. N.; Srivastava, D.; Nakagawa, O. 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