Rationale: Familial recurrence studies provide strong evidence for a genetic component to the predisposition to sporadic, non-syndromic Tetralogy of Fallot (TOF), the most common cyanotic congenital heart disease (CHD) phenotype. Rare genetic variants have been identified as important contributors to the risk of CHD, but relatively small numbers of TOF cases have been studied to date. Objective: We used whole exome sequencing (WES) to assess the prevalence of unique, deleterious variants in the largest cohort of non-syndromic TOF patients reported to date. Methods and Results: 829 TOF patients underwent WES. The presence of unique, deleterious variants was determined; defined by their absence in the Genome Aggregation Database (gnomAD) and a scaled combined annotation-dependent depletion (CADD) score of ≥20. The clustering of variants in two genes, NOTCH1 and FLT4, surpassed thresholds for genome-wide significance (assigned as P<5x10-8) after correction for multiple comparisons. NOTCH1 was most frequently found to harbour unique, deleterious variants. 31 changes were observed in 37 probands (4.5%; 95% confidence interval [CI]:3.2-6.1%) and included seven loss-of-function variants 22 missense variants and two in-frame indels. Sanger-sequencing of the unaffected parents of seven cases identified five de novo variants. Three NOTCH1 variants (p.G200R, p.C607Y and p.N1875S) were subjected to functional evaluation and two showed a reduction in Jagged1-induced NOTCH signalling. FLT4 variants were found in 2.4% (95% CI:1.6-3.8%) of TOF patients, with 21 patients harbouring 22 unique, deleterious variants. The variants identified were distinct to those that cause the congenital lymphoedema syndrome Milroy Disease. In addition to NOTCH1, FLT4 and the well-established TOF gene, TBX1, we identified potential association with variants in several other candidates including RYR1, ZFPM1, CAMTA2, DLX6 and PCM1. Conclusions: The NOTCH1 locus is the most frequent site of genetic variants predisposing to nonsyndromic TOF, followed by FLT4. Together, variants in these genes are found in almost 7% of TOF patients.

The coordinated regulation of mitochondrial and nuclear activities is essential for cellular respiration and its disruption leads to mitochondrial dysfunction, a hallmark of ageing. Mitochondria communicate with nuclei via retrograde signalling pathways that modulate nuclear gene expression in order to maintain mitochondrial homeostasis. The monooxygenase CLK-1 was previously reported to be mitochondrial, with a role in respiration and longevity. We have uncovered a distinct nuclear form of CLK-1 that independently regulates lifespan. Nuclear CLK-1 mediates a retrograde signalling pathway that is conserved from Caenorhabditis elegans to humans and is responsive to mitochondrial reactive oxygen species, thus acting as a barometer of oxidative metabolism. We show that, through modulation of gene expression, the pathway regulates both mitochondrial reactive oxygen species metabolism and the mitochondrial unfolded protein response. Our results demonstrate that a respiratory enzyme acts in the nucleus to control mitochondrial stress responses and longevity.

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Vascular endothelial growth factor receptors (VEGFRs) are part of the evolutionarily conserved VEGF signalling pathways that regulate the development and maintenance of the body’s cardiovascular and lymphovascular systems. VEGFR3, encoded by the FLT4 gene, has an indispensable and well-characterised function in development and establishment of the lymphatic system. Autosomal dominant VEGFR3 mutations, that prevent the receptor functioning as a homodimer, cause one of the major forms of hereditary primary lymphoedema; Milroy disease. Recently, we and others have shown that FLT4 variants, distinct to those observed in Milroy disease cases, predispose individuals to Tetralogy of Fallot, the most common cyanotic congenital heart disease, demonstrating a novel function for VEGFR3 in early cardiac development. Here, we examine the familiar and emerging roles of VEGFR3 in the development of both lymphovascular and cardiovascular systems, respectively, compare how distinct genetic variants in FLT4 lead to two disparate human conditions, and highlight the research still required to fully understand this multifaceted receptor.

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The main effector of the renin angiotensin system (RAS), angiotensin II (AngII), is a key mediator of this remodelling. AngII has previously been shown to upregulate microRNA-132 (miR-132) expression in rat VSMC which may contrib-3 Konstantinos Stellos.