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Detection of chromosomal structural abnormalities using conventional cytogenetic methods poses a challenge for prenatal genetic counseling due to unpredictable clinical outcomes and risk of recurrence. Of the 1,726 prenatal cases in a 3-year period, we performed oligonucleotide array comparative genomic hybridization (aCGH) analysis on 11 cases detected with various structural chromosomal abnormalities. In nine cases, genomic aberrations and gene contents involving a 3p distal deletion, a marker chromosome from chromosome 4, a derivative chromosome 5 from a 5p/7q translocation, a de novo distal 6q deletion, a recombinant chromosome 8 comprised of an 8p duplication and an 8q deletion, an extra derivative chromosome 9 from an 8p/9q translocation, mosaicism for chromosome 12q with added material of initially unknown origin, an unbalanced 13q/15q rearrangement, and a distal 18q duplication and deletion were delineated. An absence of pathogenic copy number changes was noted in one case with a de novo 11q/14q translocation and in another with a familial insertion of 21q into a 19q. Genomic characterization of the structural abnormalities aided in the prediction of clinical outcomes. These results demonstrated the value of aCGH analysis in prenatal cases with subtle or complex chromosomal rearrangements. Furthermore, a retrospective analysis of clinical indications of our prenatal cases showed that approximately 20% of them had abnormal ultrasound findings and should be considered as high risk pregnancies for a combined chromosome and aCGH analysis.

Background: Familial hypertrophic cardiomyopathy (HCM) is the most common inherited cardiac disease and is typically caused by mutations in genes encoding sarcomeric proteins that regulate cardiac contractility. HCM manifestations include left ventricular hypertrophy and heart failure, arrythmias, and sudden cardiac death. How dysregulated sarcomeric force production is sensed and leads to pathological remodeling remains poorly understood in HCM, thereby inhibiting the efficient development of new therapeutics. Methods: Our discovery was based on insights from a severe phenotype of an individual with HCM and a second genetic alteration in a sarcomeric mechanosensing protein. We derived cardiomyocytes from patient-specific induced pluripotent stem cells (iPSC-CMs) and developed robust engineered heart tissues (EHTs) by seeding iPSC-CMs into a laser-cut scaffold possessing native cardiac fiber alignment in order to study human cardiac mechanobiology at both cellular and tissue levels. Coupled with computational modeling for muscle contraction and rescue of disease phenotype via gene editing and pharmacological interventions, we have identified a new mechanotransduction pathway in HCM, shown to be essential in modulating the phenotypic expression of HCM in five families bearing distinct sarcomeric mutations. Results: Enhanced actomyosin crossbridge formation caused by sarcomeric mutations in cardiac myosin heavy chain ( MYH7 ) led to increased force generation, which when coupled with slower twitch relaxation, destabilized the muscle LIM protein (MLP) stretch-sensing complex at the Z-disc. Subsequent reduction in the sarcomeric MLP level caused disinhibition of calcineurin-nuclear factor of activated T-cells (NFAT) signaling, which promoted cardiac hypertrophy. We demonstrate that the common MLP-W4R variant is an important modifier, exacerbating the phenotypic expression of HCM, but alone may not be a disease-causing mutation. By mitigating enhanced actomyosin crossbridge formation through either genetic or pharmacological means, we alleviated stress at the Z-disc, preventing the development of hypertrophy associated with sarcomeric mutations. Conclusions: Our studies have uncovered a novel biomechanical mechanism through which dysregulated sarcomeric force production is sensed and leads to pathological signaling, remodeling, and hypertrophic responses. Together, these establish the foundation for developing innovative mechanism-based treatments for HCM that stabilize the Z-disc MLP mechanosensory complex.

BACKGROUND The prevalence and clinical characteristics of familial dilated cardiomyopathy (FDCM) among patients with end stage heart failure (ESHF) has yet to be elucidated. We sought to determine the prevalence of FDCM in ESHF in the United Network for Organ Sharing (UNOS) registry and compare this with center specific data from a large tertiary teaching hospital. Patients with a banked UNOS diagnosis of dilated cardiomyopathy (DCM) whose care originated at our center then underwent detailed pedigree analysis in order to determine the true prevalence of FDCM. METHODS AND RESULTS A total of 16,091 patients with DCM from all centers were identified in the UNOS registry of whom 492 carried the diagnosis of FDCM (3.1%). Patients with the diagnosis of FDCM tended to be younger (42 versus 49 years old in idiopathic dilated cardiomyopathy (IDCM), p=0.001), were less likely to have diabetes (7.8% versus 16.5% in IDCM, p<0.0001), had slightly lower creatinine (1.2 versus 1.4 in IDCM, p=0.0001) and were more likely to have a panel reactive antibody level ≥ 20% (62.1% versus 44.7% in IDCM, p<0.0001). Consecutive living adult patients with ESHF were identified from the UNOS registry that had been treated at the Yale Center for Advanced Heart Failure (YCAHF). After excluding all diagnoses that did not include any form of non-ischemic DCM, 73 patients met the inclusion criteria. Center-specific UNOS data showed pre-pedigree analysis diagnosis of FDCM in 4.12% of patients (3 out of 73), consistent with that found in the UNOS database for all centers. However, after detailed family history and pedigree analysis, 19 (26%) of 73 patients were found to have FDCM, while the remaining 54 were found to have IDCM. Echocardiographic findings including mitral regurgitation, mitral valve annulus and left ventricular end diastolic dimension were not significantly different between groups when adjusting for multiple testing. CONCLUSIONS The diagnosis of FDCM was missed in the majority of patients with end stage heart failure enrolled in the UNOS database, as sampled from a large, tertiary care teaching hospital in the United States. Echocardiographic findings are unlikely to aid in the differentiation between DCM and FDCM. Detailed pedigree analysis can successfully identify undiagnosed FDCM and should be encouraged prior to transplant listing as it has important implications for early detection and treatment of disease in family members.

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