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Dilated cardiomyopathy (DCM) and hypertrophic cardiomyopathy (HCM) are genetically and phenotypically heterogeneous. Cardiac function is improved after treatment in some cardiomyopathy patients, but little is known about genetic predictors of long-term outcomes and myocardial recovery following medical treatment. To elucidate the genetic basis of cardiomyopathy in Japan and the genotypes involved in prognosis and left ventricular reverse remodeling (LVRR), we performed targeted sequencing on 120 DCM (70 sporadic and 50 familial) and 52 HCM (15 sporadic and 37 familial) patients and integrated their genotypes with clinical phenotypes. Among the 120 DCM patients, 20 (16.7%) had TTN truncating variants and 13 (10.8%) had LMNA variants. TTN truncating variants were the major cause of sporadic DCM (21.4% of sporadic cases) as with Caucasians, whereas LMNA variants, which include a novel recurrent LMNA E115M variant, were the most frequent in familial DCM (24.0% of familial cases) unlike Caucasians. Of the 52 HCM patients, MYH7 and MYBPC3 variants were the most common (12 (23.1%) had MYH7 variants and 11 (21.2%) had MYBPC3 variants) as with Caucasians. DCM patients harboring TTN truncating variants had better prognosis than those with LMNA variants. Most patients with TTN truncating variants achieved LVRR, unlike most patients with LMNA variants.

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Congenital heart defects (CHD) are very common in patients with trisomy 18 (T18) and trisomy 13 (T13). The surgical indication of CHD remains controversial since the natural history of these trisomies is documented to be poor. To investigate the outcome of CHD in patients with T18 and T13, we collected and evaluated clinical data from 134 patients with T18 and 27 patients with T13 through nationwide network of Japanese Society of Pediatric Cardiology and Cardiac Surgery. In patients with T18, 23 (17%) of 134 were alive at this survey. One hundred twenty-six (94%) of 134 patients had CHDs. The most common CHD was ventricular septal defect (VSD, 59%). Sixty-five (52%) of 126 patients with CHD developed pulmonary hypertension (PH). Thirty-two (25%) of 126 patients with CHD underwent cardiac surgery and 18 patients (56%) have survived beyond postoperative period. While palliative surgery was performed in most patients, six cases (19%) underwent intracardiac repair for VSD. Operated patients survived longer than those who did not have surgery (P < 0.01). In patients with T13, 5 (19%) of 27 patients were alive during study period. Twenty-three (85%) of 27 patients had CHD and 13 (57%) of 27 patients had PH. Atrial septal defect was the most common form of CHD (22%). Cardiac surgery was done in 6 (26%) of 23 patients. In this study, approximately a quarter of patients underwent surgery for CHD in both trisomies. Cardiac surgery may improve survival in selected patients with T18.

Heterotaxy, a birth defect involving left-right patterning defects, and primary ciliary dyskinesia (PCD), a sinopulmonary disease with dyskinetic/immotile cilia in the airway are seemingly disparate diseases. However, they have an overlapping genetic etiology involving mutations in cilia genes, a reflection of the common requirement for motile cilia in left-right patterning and airway clearance. While PCD is a monogenic recessive disorder, heterotaxy has a more complex, largely non-monogenic etiology. In this study, we show mutations in the novel dynein gene DNAH6 can cause heterotaxy and ciliary dysfunction similar to PCD. We provide the first evidence that trans-heterozygous interactions between DNAH6 and other PCD genes potentially can cause heterotaxy. DNAH6 was initially identified as a candidate heterotaxy/PCD gene by filtering exome-sequencing data from 25 heterotaxy patients stratified by whether they have airway motile cilia defects. dnah6 morpholino knockdown in zebrafish disrupted motile cilia in Kupffer’s vesicle required for left-right patterning and caused heterotaxy with abnormal cardiac/gut looping. Similarly DNAH6 shRNA knockdown disrupted motile cilia in human and mouse respiratory epithelia. Notably a heterotaxy patient harboring heterozygous DNAH6 mutation was identified to also carry a rare heterozygous PCD-causing DNAI1 mutation, suggesting a DNAH6/DNAI1 trans-heterozygous interaction. Furthermore, sequencing of 149 additional heterotaxy patients showed 5 of 6 patients with heterozygous DNAH6 mutations also had heterozygous mutations in DNAH5 or other PCD genes. We functionally assayed for DNAH6/DNAH5 and DNAH6/DNAI1 trans-heterozygous interactions using subthreshold double-morpholino knockdown in zebrafish and showed this caused heterotaxy. Similarly, subthreshold siRNA knockdown of Dnah6 in heterozygous Dnah5 or Dnai1 mutant mouse respiratory epithelia disrupted motile cilia function. Together, these findings support an oligogenic disease model with broad relevance for further interrogating the genetic etiology of human ciliopathies.