Transformation of primary B lymphocytes by Epstein-Barr virus requires the establishment of a strictly latent infection, the expression of several latent viral proteins, and sustained telomerase activity. Our previous findings indicated that induction of hTERT, the rate-limiting catalytic unit of the telomerase complex, was associated with the expression of the viral latent membrane protein 1 (LMP1). In the present study, we demonstrate that ectopic expression of LMP1 in BJAB and Ramos B cells resulted in an increase of hTERT transcripts, thus suggesting that LMP1 acts at the transcriptional level. This was confirmed by transient expression of a luciferase reporter plasmid containing the hTERT promoter cotransfected with an LMP1-expressing vector or transfected into B cells in which LMP1 expression was inducible. Consistently, silencing of LMP1 by small interfering RNA resulted in a reduction of hTERT transcripts. We also provide evidence indicating that LMP1-induced hTERT activation is independently mediated by NF-B and by mitogen-activated protein kinase and extracellular signal-regulated kinase 1/2 pathways, whereas CD40, Akt, and mTOR signaling has no involvement. Moreover, our results do not support a role for c-Myc in mediating these effects on hTERT, since ectopic expression of LMP1 did not upregulate c-Myc and silencing of this oncogene or E box mutagenesis failed to inhibit LMP1-induced hTERT activation. These findings indicate that LMP1 simultaneously modulates multiple signal transduction pathways in B cells to transactivate the hTERT promoter and enhance telomerase activity, thus confirming the pleiotropic nature of this viral oncoprotein.Epstein-Barr virus (EBV) is a ubiquitous human gammaherpesvirus that establishes a life-long asymptomatic infection in immunocompetent hosts by colonizing memory B lymphocytes. EBV has a potent transforming ability, being able to efficiently induce blast transformation and uncontrolled proliferation of infected B lymphocytes in vitro. Available evidence, particularly the presence of EBV genomes and the constant expression of viral proteins, strongly supports a relevant role for EBV in the pathogenesis of a wide spectrum of human malignancies, most of which are derived from B lymphocytes (12, 44). Latently EBV-infected B cells may express a defined set of latency genes that include those encoding six nuclear antigens (EBNAs) and three latent membrane proteins (latent membrane protein 1 [LMP1], LMP2A, and LMP2B). Among the EBV latency gene products, LMP1 is considered the strongest oncoprotein, being essential for immortalization of B cells. The N terminus and the six transmembrane domains of the protein form aggregates in the cytoplasmic membrane, allowing LMP1 to act like a constitutively activated receptor (5, 15). Indeed, LMP1 shares functional properties with members of the tumor necrosis factor (TNF) receptor superfamily, particularly CD40, and induces the expression of NF-B through activation of the TNF receptor-associated factor signaling pathway (31,40). Cons...

AimsThe sinus venous myocardium, comprising the sinoatrial node (SAN) and sinus horns (SH), is a region subject to congenital malformations and cardiac arrhythmias. It differentiates from symmetric bilateral mesenchymal precursors, but morphological, molecular, and functional left/right differences are progressively established through development. The role of the laterality gene Pitx2 in this process is unknown. We aimed to elucidate the molecular events driving left/right patterning in the sinus venosus (SV) myocardium by using a myocardial Pitx2 knockout mouse.Methods and resultsWe generated a myocardial specific Pitx2 knockout model (cTP mice). cTP embryos present several features of Pitx2 null, including right atrial isomerism with bilateral SANs and symmetric atrial entrance of the systemic veins. By in situ hybridization and optical mapping analysis, we compared throughout development the molecular and functional properties of the SV myocardium in wt and mutant embryos. We observed that Pitx2 prevents the expansion of the left-SAN primordium at the onset of its differentiation into myocardium; Pitx2 promotes expansion of the left SH through development; Pitx2 dose-dependently represses the autorhythmic properties of the left SV myocardium at mid-gestation (E14.5); Pitx2 modulates late foetal gene expression at the left SH-derived superior caval vein.ConclusionPitx2 drives left/right patterning of the SV myocardium through multiple developmental steps. Overall, Pitx2 plays a crucial functional role by negatively modulating a nodal-type programme in the left SV myocardium.

a b s t r a c tConnexin40 (Cx40) is the main connexin expressed in the murine atria and ventricular conduction system. We assess here the developmental role of Cx40 in atrial conduction of the mouse. Cx40 deficiency significantly prolonged activation times in embryonic day 10.5, 12.5 and 14.5 atria during spontaneous activation; the severity decreased with increasing age. In a majority of Cx40 deficient mice the impulse originated from an ectopic focus in the right atrial appendage; in such a case the activation time was even longer due to prolonged activation. Cx40 has thus an important physiological role in the developing atria.

In this article, the authors describe their experience with using cortical deantigenated equine bone sheets in sinus lift grafting procedures performed on 23 patients. The technique employed resembles that described by Tulasne but avoids the need for using harvested calvaria bone and introduces some additional operating variants. The use of heterologous cortical bone sheets effectively managed even large lacerations of the Schneiderian membrane and allowed for immediate stabilization of the heterologous bone granules. Average histomorphometric values for bone cores collected six months after grafting, at the time of implant placement, were: newly formed bone tissue 43.9±4.2%, residual bone substitute 7.4±1.4%, medullary spaces 48.7±4.0%. At seven year follow-up, clinical and radiographic examination indicated that the use of the bone sheets preserved the regenerated bone volume. In conclusion, the use of heterologous cortical bone sheets in association with granular bone graft material enabled long-term stabilization of the graft material and effective management of intra-surgical complications.