Congenital heart disease (CHD) is the leading cause of mortality from birth defects. Exome sequencing of a single cohort of 2,871 CHD probands including 2,645 parent-offspring trios implicated rare inherited mutations in 1.8%, including a recessive founder mutation in GDF1 accounting for ~5% of severe CHD in Ashkenazim, recessive genotypes in MYH6 accounting for ~11% of Shone complex, and dominant FLT4 mutations accounting for 2.3% of Tetralogy of Fallot. De novo mutations (DNMs) accounted for 8% of cases, including ~3% of isolated CHD patients and ~28% with both neurodevelopmental and extra-cardiac congenital anomalies. Seven genes surpassed thresholds for genome-wide significance and 12 genes not previously implicated in CHD had > 70% probability of being disease-related; DNMs in ~440 genes are inferred to contribute to CHD. There was striking overlap between genes with damaging DNMs in probands with CHD and autism.

Congenital heart disease (CHD) is the most frequent birth defect, affecting 0.8% of live births1. Many cases occur sporadically and impair reproductive fitness, suggesting a role for de novo mutations. By analysis of exome sequencing of parent-offspring trios, we compared the incidence of de novo mutations in 362 severe CHD cases and 264 controls. CHD cases showed a significant excess of protein-altering de novo mutations in genes expressed in the developing heart, with an odds ratio of 7.5 for damaging mutations. Similar odds ratios were seen across major classes of severe CHD. We found a marked excess of de novo mutations in genes involved in production, removal or reading of H3K4 methylation (H3K4me), or ubiquitination of H2BK120, which is required for H3K4 methylation2–4. There were also two de novo mutations in SMAD2; SMAD2 signaling in the embryonic left-right organizer induces demethylation of H3K27me5. H3K4me and H3K27me mark `poised' promoters and enhancers that regulate expression of key developmental genes6. These findings implicate de novo point mutations in several hundred genes that collectively contribute to ~10% of severe CHD.

Congenital heart disease (CHD) patients have increased prevalence of extra-cardiac congenital anomalies (CA) and risk of neurodevelopmental disabilities (NDD). Exome sequencing of 1,213 CHD parent-offspring trios identified an excess of protein-damaging de novo mutations, especially in genes highly expressed in developing heart and brain. These mutations accounted for 20% of patients with CHD, NDD and CA but only 2% with isolated CHD. Mutations altered genes involved in morphogenesis, chromatin modification, and transcriptional regulation, including multiple mutations in RBFOX2, an mRNA splice regulator. Genes mutated in other cohorts ascertained for NDD were enriched in CHD cases, particularly those with coexisting NDD. These findings reveal shared genetic contributions to CHD, NDD, and CA and provide opportunities for improved prognostic assessment and early therapeutic intervention in CHD patients.

The current model of apoptosis holds that upstream signals lead to activation of downstream effector caspases. We generated mice deficient in the two effectors, caspase 3 and caspase 7, which died immediately after birth with defects in cardiac development. Fibroblasts lacking both enzymes were highly resistant to both mitochondrial and death receptor-mediated apoptosis, displayed preservation of mitochondrial membrane potential, and had defective nuclear translocation of apoptosis-inducing factor (AIF). Furthermore, the early apoptotic events of Bax translocation and cytochrome c release were also delayed. We conclude that caspases 3 and 7 are critical mediators of mitochondrial events of apoptosis.Mitochondria play a central role in apoptosis. Mitochondrial outer membrane permeabilization (MOMP) leads to release of proapoptotic factors such as cytochrome c and AIF (1). Furthermore, loss of mitochondrial membrane potential (Δψ m ) is thought to contribute to cell death by disruption of normal mitochondrial function (2, 3). Interaction of members of the Bcl-2 family of proteins regulates MOMP, the key event of cytochrome c release into the cytoplasm (3, 4). What is less clear, however, is the precise role of caspase proteases in mitochondrial events of apoptosis. Although upstream caspases, such as caspase 2 and caspase 8, affect mitochondrial events in both death-receptor and mitochondrial pathways of apoptosis, either directly or through interaction with Bcl-2 family members, the role of presumed downstream "effector" caspases in this process is less clear (5, 6). Therefore, we studied the two highly related effectors, caspase 3 and caspase 7, to elucidate their functions in apoptosis.* To whom correspondence should be addressed. richard.flavell@yale.edu. We generated caspase 7 −/− mice ( fig. S1), which were born in ratios consistent with Mendelian inheritance. They had normal appearance, organ morphology, and lymphoid development. When caspase 7 −/− mouse embryonic fibroblasts (MEFs) were treated with inducers of apoptosis, they exhibited a slight survival advantage as compared with wild-type MEFs. Apoptosis caused by a range of insults in other caspase 7 −/− cells proceeded normally, however, including the death of activated T cells following stimulation of the T cell receptor, thymocyte apoptosis, Fas-mediated death of B cells, and Fas-mediated death of hepatocytes ( fig. S2). Supporting Online MaterialCaspase 3, which is structurally similar to caspase 7, might compensate for the lack of caspase 7, which would lead to this relatively mild antiapoptotic phenotype (7,8). Thus, we bred caspase 7 −/− mice to caspase 3 −/− mice previously described by our laboratory (9). The embryonic stem cells containing the mutation were from the 129/SvJ genetic background. Mice derived from these embryonic stem cells were backcrossed six generations onto the C57BL/6 background. We obtained no live caspase 3 −/− /caspase 7 −/− double-knockout (DKO) mice when progeny were genotyped at an age of 10 to 14 days. DKO mic...

Mitochondria maintain tight regulation of inner mitochondrial membrane (IMM) permeability to sustain ATP production. Stressful events cause cellular calcium (Ca 2+ ) dysregulation followed by rapid loss of IMM potential known as permeability transition (PT), which produces osmotic shifts, metabolic dysfunction, and cell death. The molecular identity of the mitochondrial PT pore (mPTP) was previously unknown. We show that the purified reconstituted c-subunit ring of the F O of the F 1 F O ATP synthase forms a voltage-sensitive channel, the persistent opening of which leads to rapid and uncontrolled depolarization of the IMM in cells. Prolonged high matrix Ca 2+ enlarges the c-subunit ring and unhooks it from cyclophilin D/cyclosporine A binding sites in the ATP synthase F 1 , providing a mechanism for mPTP opening. In contrast, recombinant F 1 beta-subunit applied exogenously to the purified c-subunit enhances the probability of pore closure. Depletion of the c-subunit attenuates Ca 2+ -induced IMM depolarization and inhibits Ca 2+ and reactive oxygen species-induced cell death whereas increasing the expression or single-channel conductance of the c-subunit sensitizes to death. We conclude that a highly regulated c-subunit leak channel is a candidate for the mPTP. Beyond cell death, these findings also imply that increasing the probability of c-subunit channel closure in a healthy cell will enhance IMM coupling and increase cellular metabolic efficiency.metabolism | necrosis | apoptosis | ion channel | excitotoxicity M itochondria produce ATP by oxidative phosphorylation (OXPHOS). Leak currents in the inner mitochondrial membrane (IMM) reduce the efficiency of this process by uncoupling the electron transport system from ATP synthase activity. Many studies have described the biophysical and pharmacological features of an IMM pore [the mitochondrial permeability transition pore (mPTP)] that is responsible for a rapid IMM uncoupling, causing osmotic shifts within the mitochondrial matrix in the setting of cellular Ca 2+ dysregulation and adenine nucleotide depletion (1-4). Some studies suggest that such uncoupling also functions during physiological events and that the mPTP may transiently operate as a Ca 2+ -release channel (5-7). Although models for the molecular identity of the mPTP have been proposed (8), deletions of putative components, such as adenine nucleotide translocase (ANT) and the voltagedependent anion channel (VDAC), have failed to prevent rapid depolarizations (9). In the meantime, nonpore forming regulatory components of the mPTP, such as cyclophilin D (CypD), have been extensively investigated (10, 11).We recently reported a leak conductance sensitive to ATP/ ADP and the Bcl-2 family member B-cell lymphoma-extra large (Bcl-x L ) within the membrane of isolated submitochondrial vesicles (SMVs) enriched in ATP synthase (12, 13). We demonstrated binding of Bcl-x L within F 1 to the beta-subunit of the ATP synthase, suggesting that the channel responsible for the leak conductance lies within the memb...