Ventricular septal defect and cardiomyopathy in mice lacking the transcription factor CHF1/Hey2

Abstract

Ventricular septal defects are common in human infants, but the genetic programs that control ventricular septation are poorly understood. Here we report that mice with a targeted disruption of the cardiovascular basic helix-loop-helix factor (CHF)1͞Hey2 gene show isolated ventricular septal defects. These defects result primarily in failure to thrive. Mice often succumbed within the first 3 wk after birth and showed pulmonary and liver congestion. The penetrance of this phenotype varied, depending on genetic background, suggesting the presence of modifier genes. Expression patterns of other cardiac-specific genes were not affected. Of the few animals on a mixed genetic background that survived to adulthood, most developed a cardiomyopathy but did not have ventricular septal defects. Our results indicate that CHF1 plays an important role in regulation of ventricular septation in mammalian heart development and is important for normal myocardial contractility. These mice provide a useful model for the study of the ontogeny and natural history of ventricular septal defects and cardiomyopathy. V entricular septal defects (VSD) are the most common congenital cardiac defects in human infants, if bicuspid aortic valve is excluded (1). The ontogeny of atrioventricular septation is complex (2). Multiple primordia contribute to the formation of the interatrial and interventricular septa, including endocardial cushion tissue and myocardium. The muscular portion of the interventricular septum arises from ingrowth and folding of the myocardial wall of the developing ventricle, whereas the membranous portion of the interventricular septum is derived primarily from endocardial cushion tissue. The genetics of ventricular septation are poorly understood, and in human populations, no single gene disorder primarily causing isolated VSD exists. Isolated VSD can occur in patients heterozygous for mutations in Nkx2.5 (3) or Tbx5 (4); however, this phenotype is less common. In mice, a number of gene disruptions have been shown to cause VSDs, but all of these occur in the context of anomalies involving other cardiac structures such as the semilunar valves, ventricular outflow, compaction of myocardium, etc. (5-11). To our knowledge, no genes in mice or humans have been linked primarily to isolated ventricular septal defects without other associated anatomic findings.Members of the cardiovascular basic helix-loop-helix factor (CHF) family of hairy-related transcription factors (also called gridlock, Hey, Hesr, Hrt, and HERP) have been suggested to play important roles in cardiovascular development (12)(13)(14)(15)(16)(17). In zebrafish, the gridlock mutation is associated with coarctation of the aorta (13). Loss-of-function and gain-of-function studies using morpholino-antisense oligonucleotides or microinjected RNA showed that gridlock expression favors the development of arteries instead of veins from undifferentiated vascular precursors (18). CHF1 (also called Hesr2, Hey2, Hrt2, and HERP1, henceforth to be referred to as CHF1) is ex...

Microarray analysis of Tbx5‐induced genes expressed in the developing heart

“…However, it is unclear whether Tbx5 can directly regulate the expression of these genes in the developing heart in vivo. The microarray data listed in Table 1 includes two Tbx5-induced genes, hey2, and odd-skipped related 1, that are also associated with septal defects (Donovan et al, 2002;Gessler et al, 2002;Sakata et al, 2002;Wang et al, 2005). Loss of either gene in mice results in atrial or ventricular septal defects similar to those found in tbx5ϩ/Ϫ mice (Donovan et al, 2002;Gessler et al, 2002;Sakata et al, 2002;Wang et al, 2005).…”

TGF-β and epithelial-to-mesenchymal transitions

“…Inhibition of HEY1 activity by RNAi approaches or by pharmacological inhibition of Notch receptor signals prevents major features of TGF-b-directed EMT such as disassembly of E-cadherin adherens junctions, disassembly of cortical actin and cell motility (Zavadil et al, 2004). The significance of H/Espl as direct targets of TGF-b signaling pathway in the context of EMT is further underscored by Tgfb2 and Hey2 gene ablation experiments in mice, revealing overlapping defects in cardiogenesis, suggesting that these proteins may be components of a functional pathway directing EMT in endothelial cushion remodeling during cardiac development (Camenisch et al, 2002;Donovan et al, 2002;Sakata et al, 2002). While TGF-b-induced expression of H/Espl repressors is reminiscent of the rapid recruitment of other transcriptional regulators (Slug, Snail, dEF or Twist) in order to silence epithelial-specific genes such as E-cadherin and contribute to the overall pattern of TGF-b-induced gene repression, the targets of H/Espl function in the specific context of EMT in development as well as disease pathogenesis remain to be identified.…”

Identification of BOIP, a novel cDNA highly expressed during spermatogenesis that encodes a protein interacting with the orange domain of the hairy‐related transcription factor HRT1/Hey1 in Xenopus and mouse

“…Like HES, HRT proteins function as transcriptional repressors and have been identified as effectors of the Notch signaling pathway. They have been shown to be involved in cardiovascular development (Chin et al, 2000;Zhong et al, 2000;Henderson et al, 2001;Gessler et al, 2002;Sakata et al, 2002) and are also likely to play a crucial role in somitogenesis (Leimeister et al, 2000), myogenesis (Sun et al, 2001), and gliogenesis (Satow et al, 2001).…”