Localization of connective tissue growth factor during the period of embryo implantation in the mouse

Cloning the full-length cDNA for rat connective tissue growth factor: implications for skeletal development

The mammalian osteopetroses represent a pathogenetically diverse group of skeletal disorders characterized by excess bone mass resulting from reduced osteoclastic bone resorption. Abnormalities involving osteoblast function and skeletal development have also been reported in many forms of the disease. In this study, we used the rat mutation, osteopetrosis (op), to examine differences in skeletal gene expression between op mutants and their normal littermates. RNA isolated from calvaria and long bones was used as a template for mRNA-differential display. Sequence information for one of the many cDNA that were selectively expressed in either normal or mutant bone suggested that it is the rat homologue of connective tissue growth factor (CTGF) previously cloned in the human, mouse, and other species. A consensus sequence was assembled from overlapping 5'-RACE clones and used to confirm the rat CTGF cDNA protein coding region. Northern blot analysis confirmed that this message was highly (8- to 10-fold) over-expressed in op versus normal bone; it was also upregulated in op kidney but none of the other tissues (brain, liver, spleen, thymus) examined. In primary rat osteoblast cultures, the CTGF message exhibits a temporal pattern of expression dependent on their state of differentiation. Furthermore, CTGF expression is regulated by prostaglandin E(2), a factor known to modulate osteoblast differentiation. Since members of the CTGF family regulate the expression of specific genes, such as collagen and fibronectin, we propose that CTGF may play a previously unreported role in normal skeletal modeling/remodeling. Its dramatic over-expression in the op mutant skeleton may be secondary to the uncoupling of bone resorption and bone formation resulting in dysregulation of osteoblast gene expression and function.

Immunohistochemical localization of connective tissue growth factor (CTGF) in the mouse embryo between days 7.5 and 14.5 of gestation

Connective tissue growth factor (CTGF) is a 38 kDa modular protein that is involved in processes such as cell proliferation, survival, migration, adhesion and extracellular matrix production. Target cells for CTGF include fibroblasts, smooth muscle cells and endothelial cells. Using a specific peptide antibody, CTGF was localized in tissue sections obtained from mouse embryos between days 7.5 and 14.5 of gestation. On day 7.5, CTGF was present at high levels in the embryonic ectoderm, mesoderm, and chorion, with weaker levels in the squamous endoderm. No CTGF was detected in Reichert's membrane, parietal endoderm, and visceral endoderm. Decidual cells of the maternal uterus stained strongly for CTGF. There was no specific staining for CTGF on day 11.5 but by day 13.5, the protein was detectable in a limited number of structures, most notably the liver, thymus, lung, and intestine. By day 14.5, staining for CTGF had become extensive and was present at high or moderate levels in the thymus, aorta, trachea, liver, lung, adrenal gland, kidney, iliac sinus, olfactory region, tongue, pharynx, esophagus, thyroglossal duct, choroid plexi, Rathke's pouch, stomach, pancreas, and midgut. Relatively weak staining was present in the heart and dorsal root ganglia. There was no staining in the vitelline duct or in the outer cortical or medullary regions of the brain. Among specific cell types, CTGF was localized at high levels in secretory and absorptive epithelial cells and liver parenchyma cells, at moderate levels in vascular endothelial cells and myoblasts and at low levels in mesenchymal and connective tissue cells. These data show that various tissues and organ systems produce CTGF in a specific temporo-spatial pattern during embryogenesis and support a role for CTGF in cellular differentiation and development during prenatal life.