Children with DS and single-ventricle anatomy have excellent survival when PVR is less than 3 WUm(2) in the first year of life, with minimal mortality beyond 2 years of age. When accounting for PVR, DS alone is not associated with increased mortality in patients with single-ventricle anatomy.

ZASP is a cytoskeletal PDZ-LIM protein predominantly expressed in striated muscle. It forms multiprotein complexes and plays a pivotal role in the structural integrity of sarcomeres. Mutations in the ZASP protein are associated with myofibrillar myopathy, left ventricular non-compaction and dilated cardiomyopathy. The ablation of its murine homologue Cypher results in neonatal lethality. ZASP has several alternatively spliced isoforms, in this paper we clarify the nomenclature of its human isoforms as well as their dynamics and expression pattern in striated muscle. Interaction is demonstrated between ZASP and two new binding partners both of which have roles in signalling, regulation of gene expression and muscle differentiation; the mechanosensing protein Ankrd2 and the tumour suppressor protein p53. These proteins and ZASP form a triple complex that appears to facilitate poly-SUMOylation of p53. We also show the importance of two of its functional domains, the ZM-motif and the PDZ domain. The PDZ domain can bind directly to both Ankrd2 and p53 indicating that there is no competition between it and p53 for the same binding site on Ankrd2. However there is competition for this binding site between p53 and a region of the ZASP protein lacking the PDZ domain, but containing the ZM-motif. ZASP is negative regulator of p53 in transactivation experiments with the p53-responsive promoters, MDM2 and BAX. Mutations in the ZASP ZM-motif induce modification in protein turnover. In fact, two mutants, A165V and A171T, were not able to bind Ankrd2 and bound only poorly to alpha-actinin2. This is important since the A165V mutation is responsible for zaspopathy, a well characterized autosomal dominant distal myopathy. Although the mechanism by which this mutant causes disease is still unknown, this is the first indication of how a ZASP disease associated mutant protein differs from that of the wild type ZASP protein.

Background Defects of cytoarchitectural proteins can cause left ventricular noncompaction (LVNC), which is often associated with conduction system diseases. We have previously identified a p.D117N mutation in the LDB3-encoding Z-band Alternatively Spliced PDZ motif gene (ZASP) in a patient with LVNC and conduction disturbances. We sought to investigate a role of p.D117N mutation in the LBD3 NM_001080114.1 isoform (ZASP1-D117N) in the regulation of cardiac sodium channel (Nav1.5) that plays an important role in the cardiac conduction system. Methods and Results Effects of ZASP1-wt and ZASP1-D117N on Nav1.5 were studied in HEK-293 cells and neonatal rat cardiomyocytes (NRCMs). Patch-clamp study demonstrated that ZASP1-D117N significantly attenuated INa by 27% in HEK-293 cells and by 32% in NRCMs. In addition, ZASP1-D117N rightward shifted the voltage-dependent activation and inactivation in both systems. In silico simulation using Luo-Rudy phase 1 model demonstrated that altered Nav1.5 function can reduce cardiac conduction velocity by 28% compared to the control. Pull-down assays showed that both wt and ZASP1-D117N can complex with Nav1.5 and telethonin/T-Cap, which required intact PDZ domains. Immunohistochemical staining in NRCMs demonstrates that ZASP1-D117N did not significantly disturb the Z-line structure. Disruption of cytoskeletal networks with ML-7 and cytochalasin D abolished the effects of ZASP1-D117N on the Nav1.5. Conclusions ZASP1 can form protein complex with telethonin/T-Cap and Nav1.5. The LVNC-specific ZASP1 mutation can cause loss-of-function of Nav1.5 without significant alteration of the cytoskeletal protein complex. Our study suggests that electrical remodeling can occur in LVNC subject due to a direct effect of mutant ZASP on Nav1.5.

Angiotensin-converting enzyme inhibitors (ACEi) are commonly used for pediatric cardiology patients. However, studies examining their safety for neonates with cardiac disease are scarce. The current study aimed to test the hypothesis that ACEi-mediated nephrotoxicity occurs in neonates and may be underappreciated in this population. A retrospective review of 243 neonates with cardiac disease between 2007 and 2010 was performed. Demographic data, weight, length, captopril and enalapril dosing, serum [K⁺], serum creatinine, and concomitant medications during ACEi therapy were recorded and analyzed. Body surface area (BSA), creatinine clearance (CrCl), and change in [K⁺] were calculated. The age range of neonates at ACEi initiation was 15.9-18.1 days. The inclusion criteria was met by 206 neonates: 168 term (82%) and 38 preterm (18%) newborns. Of these neonates, 42% were female, and all the patients had a BSA smaller than 0.33 m² (a group known to have relative renal insufficiency). The mean dose of enalapril was 0.08 ± 0.007 mg/kg for the preterm neonates and 0.08 ± 0.003 mg/kg for the term neonates. The mean dose of captopril was 0.07 ± 0.009 mg/kg for the preterm neonates and 0.13 ± 0.019 mg/kg for the term neonates. A significant decrease in CrCl occurred for both the preterm (p < 0.01) and term (p < 0.001) neonates while they were receiving ACEi. However, the two groups did not differ significantly (p = 0.183). Nearly 42% of all the patients showed renal risk, with approximately 30% demonstrating renal failure by modified pRIFLE (pediatric risk, injury, failure, loss, and end-stage renal disease) criteria. Despite the lack of significantly different CrCl, the premature neonates were more likely to experience ACEi-related renal failure by pRIFLE (55%) than their term counterparts (23%; p < 0.001). Despite its common use for term neonates with cardiac disease, ACEi should be used cautiously and only when indications are clear. These results also raise the question whether ACEi should be used at all for preterm neonates.