ErbB2 interacting protein (Erbin) is a widely expressed protein and participates in inhibition of several intracellular signaling pathways. Its mRNA has been found to be present in relatively high levels in the heart. However, its physiological role in the heart has not been explored. In the present work, we elucidated the role of Erbin in cardiac hypertrophy. Cardiac hypertrophy was induced in mice either by isoproterenol administration or by aortic constriction. The level of Erbin was significantly decreased in both models. Erbin −/− mice rapidly develop decompensated cardiac hypertrophy, and following severe pressure overload all Erbin −/− mice died from heart failure. Down-regulation of Erbin expression was also observed in biopsies derived from human failing hearts. It is known that Erbin inhibits Ras-mediated activation of the extracellular signal-regulated kinase (ERK) by binding to Soc-2 suppressor of clear homolog (Shoc2). Our data clearly show that ERK phosphorylation is enhanced in the heart tissues of Erbin −/− mice. Furthermore, we clearly demonstrate here that Erbin associates with Shoc2 in both whole hearts and in cardiomyocytes, and that in the absence of Erbin, Raf is phosphorylated and binds Shoc2, resulting in ERK phosphorylation. In conclusion, Erbin is an inhibitor of pathological cardiac hypertrophy, and this inhibition is mediated, at least in part, by modulating ERK signaling.C ardiovascular disease remains the number one cause of mortality in the Western world, with heart failure representing the fastest-growing subclass over the past decade (1, 2). In myocardial hypertrophy caused by exercise, pregnancy, or developmental signals, cardiac structure and function are normal. However, in response to insults such as sustained excessive workloads, pathological cardiac hypertrophy is characterized by changes in contractility, loss of myocytes with fibrosis, systolic or diastolic dysfunction, and fetal gene reactivation. Pathological cardiac hypertrophy predisposes individuals to heart failure, arrhythmia, and sudden death (1, 2). The tyrosine kinase receptor avian erythroblastic leukemia viral oncogene homolog 2 (ErbB2), also known in humans as Her2, is an important regulator in cardiac hypertrophy development and heart failure (3). ErbB2-deficient conditional mutants develop dilated cardiomyopathy (3). ErbB2 signaling in cardiomyocytes is therefore essential for the prevention of dilated cardiomyopathy. However, the mechanism by which ErbB2 exerts its cardiac effects in general, and on cardiac hypertrophy in particular, is poorly defined.ErbB2 interacting protein (Erbin), a member of the leucine-rich repeat and PDZ domain proteins (4), was originally reported as a binding partner of Her2/neu (ErbB2) (4). Erbin is a widely expressed protein, and high levels of Erbin are present in the heart (5). Recently, Erbin has been demonstrated to form a complex with Her2 and β2-adrenergic receptor in cardiomyocytes. Also, Erbin has been shown to protect cardiomyocytes from apoptosis induced by chronic ca...

Beta-thalassemia major (TM) is caused by any of approximately 150 mutations within the beta-globin gene. To establish the degree of chimerism after bone marrow transplantation (BMT), we have performed molecular analysis of beta-globin mutations in 14 patients with TM over a period of 10 years. All patients underwent T cell-depleted allogeneic BMT from HLA-identical related donors, using either in vitro T-cell depletion with CAMPATH 1M and complement or in vivo depletion using CAMPATH 1G in the bone marrow collection bag. To date, at different time periods after BMT, seven patients have some degree of chimerism; six of these patients, all blood transfusion-independent, have donor cells in the range of 70% to 95%, with stable mixed chimerism (MC). The seventh patient has less than 10% donor cells with, surprisingly, only minimal transfusion requirements. The detection of beta-globin gene point mutation, as used here, is a highly specific and sensitive marker for engraftment and MC in patients with thalassemia. In light of its specificity, the method is applicable in all cases of TM, as it is independent of sex and other non-globin-related DNA markers. The high incidence of MC found in our patients may be a consequence of the pre-BMT T-cell depletion. Because MC was associated with transfusion independence, complete eradication of residual host cells for effective treatment of TM and possibly other genetic diseases may prove not to be essential.

The study supports the notion of a restricted golden time for remodeling reversal but not for vascular endothelial growth factor-induced neovascularization, which is feasible even during advanced disease stages.

RationaleRescuing adverse myocardial remodeling is an unmet clinical goal and, correspondingly, pharmacological means for its intended reversal are urgently needed.ObjectivesTo harness a newly-developed experimental model recapitulating progressive heart failure development for the discovery of new drugs capable of reversing adverse remodeling.Methods and ResultsA VEGF-based conditional transgenic system was employed in which an induced perfusion deficit and a resultant compromised cardiac function lead to progressive remodeling and eventually heart failure. Ability of candidate drugs administered at sequential remodeling stages to reverse hypertrophy, enlarged LV size and improve cardiac function was monitored. Arguing for clinical relevance of the experimental system, clinically-used drugs operating on the Renin-Angiotensin-Aldosterone-System (RAAS), namely, the ACE inhibitor Enalapril and the direct renin inhibitor Aliskerin fully reversed remodeling. Remodeling reversal by these drugs was not accompanied by neovascularization and reached a point-of-no-return. Similarly, the PPARγ agonist Pioglitazone was proven capable of reversing all aspects of cardiac remodeling without affecting the vasculature. Extending the arsenal of remodeling-reversing drugs to pathways other than RAAS, a specific inhibitor of 11β-hydroxy-steroid dehydrogenase type 1 (11β HSD1), a key enzyme required for generating active glucocorticoids, fully rescued myocardial hypertrophy. This was associated with mitigating the hypertrophy-associated gene signature, including reversing the myosin heavy chain isoform switch but in a pattern distinguishable from that associated with neovascularization-induced reversal.ConclusionsA system was developed suitable for identifying novel remodeling-reversing drugs operating in different pathways and for gaining insights into their mechanisms of action, exemplified here by uncoupling their vascular affects.

Allogeneic bone marrow transplantation (BMT) for beta-thalassaemia major carries the risks of disease recurrence due to residual thalassaemic stem cells or true immune-mediated rejection. We report a thalassaemic patient who displayed stable mixed chimaerism with only 5% donor-derived cells for about 5 years after BMT. Displacement of host cells was accomplished by ambulatory non-myeloablative conditioning and allogeneic G-CSF mobilized peripheral blood stem cell transplantation from the same donor, resulting in full reconstitution. Patients featuring stable mixed chimaerism after BMT may benefit from allogeneic cell therapy with immunocompetent lymphocytes and stem cells, whilst avoiding supralethal conditioning.