IN UTERO MURINE EMBRYO CV PHENOTYPE SCREENING

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DESCRIPTION (Adapted from the applicant's abstract) All major structural cardiovascular (CV) malformations occur in utero and the genetic "risk" for developing serious CV disease is present at the time of birth. Trained fetal sonographers can now detect major structural defects in the human fetus after 16 weeks gestation in utero. These CV defects then present clinically at varying ages dependent on the degree of functional impairment. The investigators propose to develop, validate, and apply accurate and efficient screening technology to define murine embryo CV phenotype in utero. They also propose to provide an annual workshop for investigators and students to learn basic CV developmental morphology, integrated physiology, and murine embryo screening techniques for use in their laboratories. Most of the technology and applications to define embryonic CV performance in chick and mouse embryos has been developed in their labs. These invasive in vivo and in vitro protocols have provided detailed information on normal CV performance (blood pressure, blood flow, chamber dimensions, vascular impedance), the functional reserve of the normal embryo, and the relationship between altered structure and functional adaptation (Keller 1997, review). Most of these techniques cannot be applied as "screening" technologies, however, they provide the critical foundation for determining "normal" CV structure and function in utero. In addition to their focus on embryonic CV performance, they are now defining the normal hemodynamics and impact of anesthesia and experimental protocols on the pregnant mouse due to the direct effect of altered maternal hemodynamic and metabolic state on embryonic CV function. A wide range of altered CV phenotypes have already been produced using targeted genetic and mutagenesis techniques. The most severely affected embryos die in utero from failed vasculogenesis starting at embryo day (ED) 8.5 or failed CV function starting at ED 9.0. Some of these altered CV phenotypes have been detected in utero, however, the accuracy of these studies has varied and there has been no uniform approach to maternal sedation, technical measurement of embryo CV function, or interpretation of hemodynamic results (Dyson 1995, Gui 1966, Huang 1998). It is important to note that heterozygous embryos can also have altered CV phenotype, thus it is critical to detect these embryos during primary screening. They propose to develop standardized methods for embryonic CV phenotype screening in utero and to then train investigators to perform these screens at individual labs or regional centers. (End of Abstract.)