Inhibition of the ­ miR‐200 family results in cardiac developmental defects

Cardiac development is a multifaceted process involving a plethora of genes and pathways.Errors in cardiac development are classified under the umbrella of Congenital Cardiovascular Defects (CCDs), which occur in 6.9 of 1000 live births, making CCDs the most common birth defect.microRNAs (miRs) have been shown to contribute to proper cardiac development by regulating cardiomyocyte differentiation and mature cardiomyocyte function. Furthermore, ectopic expression of miRs have been found in patients with CCDs. In recent years the miR‐200 family, has been proposed to play a critical role in cardiac development and CCDs. Though miRs have a proposed role in cardiac development, current methods of miR inhibition cannot be studied ­ in vivo. Our lab has been able to overcome this obstacle by utilizing the Plasmid‐based MicroRNA Inhibitor System (PMIS) where we are able to inhibit the miR‐200 family in vivo. Analysis of hearts from PMIS miR‐200 inhibitor mice, show a range of defects including ventricle wall development and abnormal cardiomyocyte maturation.PMIS inhibitor mice present with imperfections in trabecular and compact myocardium development.Moreover, ultrasound analysis of PMIS inhibitor mice displayed a slower heart rate and hemorrhaging in the pericardial cavity.Immunofluorescent analysis of cardiac troponin showed PMIS cardiomyocytes have expression of sarcomere bands at earlier stages in development.Additionally, these mice have defects in the both non‐muscle layers of the heart, the epicardium and endocardium, which appear to have lack of EMT into the myocardium.Our model offers a unique and novel approach to studying the precise role of the ­ miR‐200 family in cardiac development and CCDs progression.