AbstractConnective tissue growth factor (CTGF) is reported to be a target gene of transforming growth factor β (TGFβ) and bone morphogenetic protein (BMP) in vitro. Its physiological role in angiogenesis and skeletogenesis during mouse development has been described recently. Here, we have mapped expression of CTGF mRNA during mouse heart development, postnatal adult life, and after experimental myocardial infarction. Furthermore, we investigated the relationship between CTGF and the BMP/TGFβ signaling pathway in particular during heart development in mutant mice. Postnatally, CTGF expression in the heart became restricted to the atrium. Strikingly, 1 week after myocardial infarction, when myocytes have disappeared from the infarct zone, CTGF and TGFβ expression as well as activated forms of TGFβ but not BMP, Smad effector proteins are colocalized exclusively in the fibroblasts of the scar tissue, suggesting possible cooperation between CTGF and TGFβ during the pathological fibrotic response. Developmental Dynamics 231:542–550, 2004. © 2004 Wiley‐Liss, Inc.