Identification and characterization of a novel Schwann and outflow tract endocardial cushion lineage-restricted periostin enhancer.

Periostin is a fasciclin-containing adhesive glycoprotein that facilitates the migration and differentiation of cells that have undergone epithelial-mesenchymal transformation during embryogenesis and in pathological conditions. Despite the importance of post-transformational differentiation as a general developmental mechanism, little is known how periostin's embryonic expression is regulated. To help resolve this deficiency, a 3.

periostin null mice exhibit dwarfism, incisor enamel defects, and an early-onset periodontal disease-like phenotype.

Periostin was originally identified as an osteoblast-specific factor and is highly expressed in the embryonic periosteum, cardiac valves, placenta, and periodontal ligament as well as in many adult cancerous tissues. To investigate its role during development, we generated mice that lack the periostin gene and replaced the translation start site and first exon with a lacZ reporter gene. Surprisingly, although periostin is widely expressed in many developing organs, periostin-deficient (peri(lacZ)) embryos are grossly normal.

Periostin is expressed within the developing teeth at the sites of epithelial-mesenchymal interaction.

Periostin was originally isolated as an osteoblast-specific factor that functions as a cell adhesion molecule for preosteoblasts and is thought to be involved in osteoblast recruitment, attachment, and spreading. The protein was renamed "periostin" because of its expression in the periosteum and periodontal ligament, indicating a potential role in bone and maintenance of tooth structure. Periostin has structural similarity to insect fasciclin-I and can be induced by TGF-beta and Bmp2.

Role of sodium-calcium exchanger (Ncx1) in embryonic heart development: a transgenic rescue?

Na(+)/Ca(2+) exchanger (Ncx-1) is highly expressed in cardiomyocytes, is thought to be required to maintain a low intracellular Ca(2+) concentration, and may play a role in excitation-contraction coupling. Significantly, targeted deletion of Ncx-1 results in Ncx1-null embryos that do not have a spontaneously beating heart and die in utero. Ultrastructural analysis revealed gross anomalies in the Ncx1-null contractile apparatus, but physiologic analysis showed normal field-stimulated Ca(2+) transients, suggesting that Ncx-1 function may not be critical for Ca(2+) extrusion from the cytosol as previously thought.

What cardiovascular defect does my prenatal mouse mutant have, and why?

Since the advent of mouse targeted mutations, gene traps, an escalating use of a variety of complex transgenic manipulations, and large-scale chemical mutagenesis projects yielding many mutants with cardiovascular defects, it has become increasingly evident that defects within the heart and vascular system are largely responsible for the observed in utero lethality of the embryo and early fetus. If a transgenically altered embryo survives implantation but fails to be born, it usually indicates that there is some form of lethal cardiovascular defect present. A number of embryonic organ and body systems, including the central nervous system, gut, lungs, urogenital system, and musculoskeletal system appear to have little or no survival value in utero (Copp, 1995).