A-kinase anchoring proteins (AKAPs) recruit signaling molecules and present them to downstream targets to achieve efficient spatial and temporal control of their phosphorylation state. In the heart, sympathetic nervous system (SNS) regulation of cardiac action potential duration (APD), mediated by ␤-adrenergic receptor (␤AR) activation, requires assembly of AKAP9 (Yotiao) with the I Ks potassium channel ␣ subunit (KCNQ1). KCNQ1 mutations that disrupt this complex cause type 1 long-QT syndrome (LQT1), one of the potentially lethal heritable arrhythmia syndromes. Here, we report identification of (i) regions on Yotiao critical to its binding to KCNQ1 and (ii) a single putative LQTS-causing mutation (S1570L) in AKAP9 (Yotiao) localized to the KCNQ1 binding domain in 1/50 (2%) subjects with a clinically robust phenotype for LQTS but absent in 1,320 reference alleles. The inherited S1570L mutation reduces the interaction between KCNQ1 and Yotiao, reduces the cAMP-induced phosphorylation of the channel, eliminates the functional response of the I Ks channel to cAMP, and prolongs the action potential in a computational model of the ventricular cardiocyte. These reconstituted cellular consequences of the inherited S1570L-Yotiao mutation are consistent with delayed repolarization of the ventricular action potential observed in the affected siblings. Thus, we have demonstrated a link between genetic perturbations in AKAP and human disease in general and AKAP9 and LQTS in particular. potassium channel ͉ protein kinase A

Hypertrophic Cardiomyopathy (HCM) is a common primary cardiac disorder defined by a hypertrophied left ventricle, is one of the main causes of sudden death in young athletes and has been associated with mutations in most sarcomeric proteins (tropomyosin, Troponin T and I, and actin, etc.). Many of these mutations appear to affect the functional properties of cardiac troponin C (cTnC), i.e., by increasing the Ca 2+ -sensitivity of contraction, a hallmark of HCM, and surprisingly, prior to this report, cTnC had not been classified as a HCM susceptibility gene. In this study, we show that mutations occurring in the human cTnC (HcTnC) gene (TNNC1) have the same prevalence (~0.4%) as well established HCM-susceptibility genes that encode other sarcomeric proteins. Comprehensive open reading frame/splice site mutation analysis of TNNC1 performed on 1025 unrelated HCM patients over the last 10 years revealed novel missense mutations in TNNC1: A8V, C84Y, E134D, and D145E. Functional studies with these recombinant HcTnC HCM mutations showed increased Ca 2+ sensitivity of force development (A8V, C84Y and D145E) and force recovery (A8V and D145E). These results are consistent with the HCM functional phenotypes seen with other sarcomeric HCM mutations (E134D showed no changes in these parameters). This is the largest cohort analysis of TNNC1 in HCM that details the discovery of at least three novel HCM-associated mutations and more strongly links TNNC1 to HCM along with functional evidence that supports a central role for its involvement in the disease. These types of studies may help to further define TNNC1 as an HCMsusceptibility gene that has already been established for the other members of the Troponin complex.

We report a low risk of clinically significant post-procedure arrhythmias after device placement. Clinically significant heart block occurred in only two patients (0.3%). Changes in several markers of atrial conduction were found, suggesting an effect of device closure on intra-atrial conduction.

Copper deficiency can cause bone lesions in infants, which might be confused with child abuse. Two extremely low birth weight preterm infants had complicated medical courses requiring prolonged parenteral nutrition for short-gut syndrome, which led to the development of cholestasis. Both had spent their entire lives in the hospital. They had been on prolonged ventilator support for chronic lung disease. They developed signs of copper deficiency between 5 and 6 months of age, initially raising child abuse concerns. Musculoskeletal discomfort led to the recognition of radiographic findings of metabolic bone disease. Included were osteoporosis, metaphyseal changes, and physeal disruptions. Copper levels were low; both low copper parenteral nutrition and gut losses from refeeding diarrhea likely contributed to their deficiency. Therapeutic supplementation with copper corrected their deficits and clinical and radiologic findings. The information from these cases, in particular, their radiologic findings, indicate the need to monitor copper status in at-risk premature infants. These findings may aid prevention and earlier recognition of copper deficiency. Their specific radiologic and clinical findings should aid differentiation of such children from abused infants.

A-Kinase Anchoring Protein 9 (AKAP9), or Yotiao, binds to the carboxy-terminus (C-T) of the IKs channel alpha subunit KCNQ1 and recruits cAMP-dependent protein kinase A (PKA) and protein phosphatase 1 (PP1) to the channel to control its phosphorylation state. Previously, an inherited LQT1-causing mutation in the KCNQ1 C-T/Yotiao binding domain was shown to disrupt the complex and render the channel functionally insensitive to cAMP-dependent regulation. Despite the critical role of Yotiao in mediating this fundamental physiological response, the large size of the Yotiao protein (over 200 kD) has hindered patient screens and, to date, no disease-linked mutations have been found in this adaptor protein. The objectives of the present study were first to locate reciprocal binding site(s) for KCNQ1 on Yotiao and to test whether mutation(s) in the binding module(s) might cause LQTS. Using GST fusion protein pull down and immunoprecipitation (IP) techniques, we identified two regions in Yotiao necessary for binding to KCNQ1: one within the Yotiao N-terminus (residues 29 – 46), and a second within its C-terminus (1574 –1643). Targeted sequence analysis was then carried out in fifty clinically diagnosed but genotype negative LQTS patients in the coding regions for these two KCNQ1 binding domains in AKAP9-encoded Yotiao. This analysis identified a novel missense mutation, S1570L-Yotiao, present in two siblings diagnosed with LQTS but absent in the normal population. We found that the S1570L mutation, located close to the Yotiao C-T binding motif for KCNQ1, disrupted the interaction between the two proteins and significantly reduced both basal and exogenous cAMP-induced KCNQ1 phosphorylation. Perforated patch experiments in CHO cells revealed that expression of S1570L-Yotiao significantly reduced basal IKS channel activity and completely ablated the response of the IKs channel to cAMP plus the phosphatase inhibitor okadaic acid. These reconstituted cellular consequences of the inherited S1570L-Yotiao mutation are consistent with delayed repolarization of the ventricular action potential observed in the affected siblings. Thus, we have demonstrated for the first time a link between an inherited AKAP mutation and human disease, LQTS.