Combined NGS Approaches Identify Mutations in the Intraflagellar Transport Gene IFT140 in Skeletal Ciliopathies with Early Progressive Kidney Disease

Ciliopathies are genetically heterogeneous disorders characterized by variable expressivity and overlaps between different disease entities. This is exemplified by the short rib‐polydactyly syndromes, Jeune, Sensenbrenner, and Mainzer‐Saldino chondrodysplasia syndromes. These three syndromes are frequently caused by mutations in intraflagellar transport (IFT) genes affecting the primary cilia, which play a crucial role in skeletal and chondral development. Here, we identified mutations in IFT140, an IFT complex A gene, in five Jeune asphyxiating thoracic dystrophy (JATD) and two Mainzer‐Saldino syndrome (MSS) families, by screening a cohort of 66 JATD/MSS patients using whole exome sequencing and targeted resequencing of a customized ciliopathy gene panel. We also found an enrichment of rare IFT140 alleles in JATD compared with nonciliopathy diseases, implying putative modifier effects for certain alleles. IFT140 patients presented with mild chest narrowing, but all had end‐stage renal failure under 13 years of age and retinal dystrophy when examined for ocular dysfunction. This is consistent with the severe cystic phenotype of Ift140 conditional knockout mice, and the higher level of Ift140 expression in kidney and retina compared with the skeleton at E15.5 in the mouse. IFT140 is therefore a major cause of cono‐renal syndromes (JATD and MSS). The present study strengthens the rationale for IFT140 screening in skeletal ciliopathy spectrum patients that have kidney disease and/or retinal dystrophy.     

Anatomical Study on the Variations in the Branching Pattern of Internal Iliac Artery

The internal iliac artery (IIA) arises from the common iliac artery at the level of the sacroiliac joint. It descends as trunk, divides into anterior and posterior divisions. From the anterior division it gives superior vesical, obturator, middle rectal, inferior vesical, inferior gluteal, and internal pudendal arteries. In females, inferior vesical artery is replaced by vaginal artery and gives an additional branch, uterine artery. The branches from the posterior division are ilio lumbar, lateral sacral, and superior gluteal arteries. An accidental hemorrhage and neurovascular injuries are common due to erroneous interpretation of variant arteries during surgical procedures. Hence the present study has been undertaken with reference to highlight its clinical and surgical significances. The study included 50 human bisected pelvises irrespective of their side and sex. Formalin-fixed specimens were selected and the branching patterns of IIA were studied. The level of origin, length, and the branching pattern of the IIA were examined and tabulated. The present study highlighted the variation seen in the origin, division branches of the IIA. The detailed knowledge of morphology is essential for successful ligation of the IIA during acute hemorrhage. This will guide the interventional radiologist in intra-arterial procedures during arterial embolization for hemorrhage, control of pelvic fractures, during selective catheterization of the intra-arterial chemotherapy, and embolization of the pelvic tumors.     

G protein-gated IKACh channels as therapeutic targets for treatment of sick sinus syndrome and heart block

Dysfunction of pacemaker activity in the sinoatrial node (SAN) underlies “sick sinus” syndrome (SSS), a common clinical condition characterized by abnormally low heart rate (bradycardia). If untreated, SSS carries potentially life-threatening symptoms, such as syncope and end-stage organ hypoperfusion. The only currently available therapy for SSS consists of electronic pacemaker implantation. Mice lacking L-type Ca_v1.3 Ca²⁺ channels (Ca_v1.3^−/−) recapitulate several symptoms of SSS in humans, including bradycardia and atrioventricular (AV) dysfunction (heart block). Here, we tested whether genetic ablation or pharmacological inhibition of the muscarinic-gated K⁺ channel (I_KACh) could rescue SSS and heart block in Ca_v1.3^−/− mice. We found that genetic inactivation of I_KACh abolished SSS symptoms in Ca_v1.3^−/− mice without reducing the relative degree of heart rate regulation. Rescuing of SAN and AV dysfunction could be obtained also by pharmacological inhibition of I_KACh either in Ca_v1.3^−/− mice or following selective inhibition of Ca_v1.3-mediated L-type Ca²⁺ (I_Ca,L) current in vivo. Ablation of I_KACh prevented dysfunction of SAN pacemaker activity by allowing net inward current to flow during the diastolic depolarization phase under cholinergic activation. Our data suggest that patients affected by SSS and heart block may benefit from I_KACh suppression achieved by gene therapy or selective pharmacological inhibition.Pacemaker activity of the sinoatrial node (SAN) controls heart rate under physiological conditions. Abnormal generation of SAN automaticity underlies “sick sinus” syndrome (SSS), a pathological condition manifested when heart rate is not sufficient to meet the physiological requirements of the organism (1). Typical hallmarks of SSS include SAN bradycardia, chronotropic incompetence, SAN arrest, and/or exit block (1–3). SSS carries incapacitating symptoms, such as fatigue and syncope (1–3). A significant percentage of patients with SSS present also with tachycardia-bradycardia syndrome (3). SSS can also be associated with atrioventricular (AV) conduction block (heart block) (1–3). Although aging is a known intrinsic cause of SSS (4), this disease appears also in the absence of any associated cardiac pathology and displays a genetic legacy (1, 2). Heart disease or drug intake can induce acquired SSS (2). Symptomatic SSS requires the implantation of an electronic pacemaker. SSS accounts for about half of all pacemaker implantations in the United States (5, 6). The incidence of SSS has been forecasted to increase during the next 50 y, particularly in the elder population (7). Furthermore, it has been estimated that at least half of SSS patients will need to be electronically paced (7). Although pacemakers are continuously ameliorated, they remain costly and require lifelong follow-up. Moreover, the implantation of an electronic pacemaker remains difficult in pediatric patients (8). Development of alternative and complementary pharmacological or molecular therapies for SSS management could improve quality of life and limit the need for implantation of electronic pacemakers.Recently, the genetic bases of some inherited forms of SSS have been elucidated (recently reviewed in 1, 9) with the discovery of mutations in genes encoding for ion channels involved in cardiac automaticity (4, 9, 10). Notably, loss of function of L-type Ca_v1.3 Ca²⁺ channels is central in some inherited forms of SSS. For instance, loss of function in Ca_v1.3-mediated L-type Ca²⁺ (I_Ca,L) current causes the sinoatrial node dysfunction and deafness syndrome (SANDD) (10). Affected individuals with SANDD present with profound deafness, bradycardia, and dysfunction of AV conduction (10). Mutation in ankyrin-B causes SSS by reduced membrane targeting of Ca_v1.3 channels (11). The relevance of Ca_v1.3 channels to SSS is demonstrated also by work on the pathophysiology of congenital heart block, where down-regulation of Ca_v1.3 channels by maternal Abs causes heart block in infants (12). Additionally, recent data show that chronic iron overload induces acquired SSS via a reduction in Ca_v1.3-mediated I_Ca,L (13).In mice and humans, Ca_v1.3 channels are expressed in the SAN, atria, and the AV node but are absent in adult ventricular tissue (14, 15). Ca_v1.3-mediated I_Ca,L plays a major role in the generation of the diastolic depolarization in SAN and AV myocytes, thereby constituting important determinants of heart rate and AV conduction velocity (14, 16). The heart rate of mice lacking Ca_v1.3 channels (Ca_v1.3^−/− mice) fairly recapitulates the hallmarks of SSS and associated symptoms, including bradycardia and tachycardia-bradycardia syndrome (17, 18). In addition, severe AV dysfunction is recorded in Ca_v1.3^−/− mice to variable degrees. Typically, these mice show first- and second-degree AV block (16, 17, 19). Complete AV block with dissociated atrial and ventricular rhythms can also be observed in these animals. The phenotype of Ca_v1.3^−/− mice thus constitutes a unique model for developing new therapeutic strategies against SSS (10).The muscarinic-gated K⁺ channel (I_KACh) is involved in the negative chronotropic effect of the parasympathetic nervous system on heart rate (20, 21). Two subunits of the G-protein activated inwardly rectifying K⁺ channels (GIRK1 and GIRK4) of the GIRK/Kir3 subfamily assemble as heterotetramers to form cardiac I_KACh channels (22). Indeed, both Girk1^−/− and Girk4^−/− mice lack cardiac I_KACh (20, 21, 23). We recently showed that silencing of the hyperpolarization-activated current “funny” (I_f) channel in mice induces a complex arrhythmic profile that can be rescued by concurrent genetic ablation of Girk4 (24). In this study, we tested the effects of genetic ablation and pharmacological inhibition of I_KACh on the Ca_v1.3^−/− mouse model of SSS. We found that Girk4 ablation or pharmacological inhibition of I_KACh rescues SSS and AV dysfunction in Ca_v1.3^−/−. Thus, our study shows that I_KACh targeting may be pursued as a therapeutic strategy for treatment of SSS and heart block.     

EGF receptor family: twisting targets for improved cancer therapies

Abstract

The epidermal growth factor receptor (EGFR) undergoes a conformational change in response to ligand binding. The ligand-induced changes in cell surface aggregation and mobility have a profound effect on the function of all the family members. Ligand also activates the EGFR intracellular kinase, stimulating proliferation and cell survival. The EGFR family are often activated, overexpressed or mutated in cancer cells and therapeutic drugs (including antibodies) can slow the progress of some cancers. This article provides a brief, annotated summary of the presentations and discussion which occurred at the Epidermal Growth Factor Receptor – Future Directions Conference held in Jerusalem in November 2013.