Abstract 17947: Large Scale Mouse Mutagenesis Screen Using Fetal Echocardiography Indicates Genetic Contribution to Hypoplastic Left Heart Syndrome and Wide Spectrum of Other Congenital Heart Defects

Abstract

Introduction: Large scale forward genetic screens with ethyl-nitroso-urea (ENU) mutagenesis can provide a non-gene biased approach to elucidate the genetic etiology of congenital heart disease (CHD). We are using noninvasive fetal echocardiography to elucidate the genetic etiology of CHD with scanning of 100,000 mouse fetuses to achieve 5 fold genome coverage. Methods: C57BL/6J mice (G0) are ENU mutagenized and the resulting G1 males and their G2 daughters are backcrossed to generate G3 fetuses for ultrasound scanning. Primary screening used the clinical Acuson Sequoia ultrasound system with a 15 MHz transducer. Fetuses with CHD were further scanned at 40 MHz with the Vevo 2100 ultra-high frequency biomicroscope (UBM). CHD diagnoses were susbsequently confirmed by necropsy, microCT, and/or histopathology. Results: Ultrasound scanning of >20,000 G3 fetuses from >600 G1 pedigrees revealed 4% of fetuses with cardiac defects. A wide spectrum of CHD was observed, including DORV, TGA, PTA, pulmonary/aortic atresia, coarctation, arch anomalies, atrioventricular septal defects (AVSD) and other defects. The most common CHD found was ventricular septal defect. In contrast, hypoplastic left heart syndrome was found in only one mutant line (Figure). We also recovered 10 lines with laterality defects. Heterotaxy mutants exhibited complex CHD, but no heart disease was seen with situs inversus totalis. Overall, the UBM had higher detection sensitivity for cardiac situs (P<0.01), AVSD (P<0.01) and outflow tract malalignment (P<0.01), with 98.3% of the cardiac situs, 91% of the AVSD and 70% of the outflow defects identified by UBM. Conclusions: Our studies showed the integration of conventional ultrasound with the UBM for fetal mouse cardiovascular phenotyping can maximize the recovery of CHD mutants. The wide spectrum of CHD observed in our large scale screen indicates the importance of genetic contribution in all varieties of structural heart disease.