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The Ca2+-binding proteins (CBPs) calbindin D28k, calretinin and parvalbumin are phenotypic markers of functionally diverse subclasses of neurons in the adult brain. The developmental dynamics of CBP expression are precisely timed: calbindin and calretinin are present in prospective cortical interneurons from mid-gestation, while parvalbumin only becomes expressed during the early postnatal period in rodents. Secretagogin (scgn) is a CBP cloned from pancreatic β and neuroendocrine cells. We hypothesized that scgn may be expressed by particular neuronal contingents during prenatal development of the mammalian telencephalon. We find that scgn is expressed in neurons transiting in the subpallial differentiation zone by embryonic day (E)11 in mouse. From E12, scgn+ cells commute towards the extended amygdala and colonize the bed nucleus of stria terminalis, the interstitial nucleus of the posterior limb of the anterior commissure, the dorsal substantia innominata (SI) and the central and medial amygdaloid nuclei. Scgn+ neurons can acquire a cholinergic phenotype in the SI or differentiate into GABA cells in the central amygdala. We also uncover phylogenetic differences in scgn expression as this CBP defines not only neurons destined to the extended amygdala but also cholinergic projection cells and cortical pyramidal cells in the fetal nonhuman primate and human brains, respectively. Overall, our findings emphasize the developmentally shared origins of neurons populating the extended amygdala, and suggest that secretagogin can be relevant to the generation of functional modalities in specific neuronal circuitries. [ABSTRACT FROM AUTHOR]

FK506 binding protein 12.6 kDa (FKBP12.6), a protein that regulates ryanodine Ca2+ release channels, may act as an important regulator of insulin secretion. In this study, the role of FKBP12.6 in the control of insulin secretion and blood glucose is clarified using FKBP12.6-/- mice. FKBP12.6-/- mice showed significant fed hyperinsulinemia but exhibited normoglycemia, fasting normoinsulinemia, and normal body weight compared with wild-type (WT) littermate control mice. Deletion of FKBP12.6 resulted in enhanced glucose-stimulated insulin secretion (GSIS) both in vivo and in vitro, a result that is due to enhanced glucose-induced islet Ca2+ elevation. After a high-fat dietary challenge (HF diet) for 3 mo, FKBP12.6-/- mice displayed higher body weight, hyperinsulinemia, and lower fed blood glucose concentrations compared with WT mice. FKBP12.6-/- mice displayed hyperinsulinemia, and resistance to HF diet-induced hyperglycemia, suggesting that FKBP12.6 plays an important role in insulin secretion and blood glucose control, and raising die possibility that it may be a potential therapeutic target for the treatment of type 2 diabetes. [ABSTRACT FROM AUTHOR]

This article reviews genetically encoded Ca2+ indicators (GECIs), with a focus on the use of these novel molecules in the context of understanding complex cell signalling in mammals, in vivo. The review focuses on the advantages and limitations of specific GECI design strategies and the results of experiments in which these molecules have been expressed in transgenic mice, concentrating particularly on recent experiments from our laboratory in which physiological signalling could be monitored in vivo. Finally, newer strategies for effective genetic specification of GECIs are briefly reviewed. [ABSTRACT FROM AUTHOR]

We have investigated the mechanism of mitochondrial— nuclear crosstalk during cellular stress in mouse C2C12 myocytes. For this purpose, we used cells with reduced mitochondrial DNA (mtDNA) contents by ethidium bromide treatment or myocytes treated with known mitochondrial metabolic inhibitors, including carbonyl cyanide m-chlorophenylhydrazone (CCCP), antimycin, valinomycin and azide. Both genetic and metabolic stresses similarly affected mitochondrial membrane potential (ΔΨm) and electron transport-coupled ATP synthesis, which was also accompanied by an elevated steady-state cytosolic Ca2+ level ([Ca2+]i). The mitochondrial stress resulted in: (i) an enhanced expression of the sarcoplasmic reticular ryanodine receptor-1 (RyR-1), hence potentiating the Ca2+ release in response to its modulator, caffeine; (ii) enhanced levels of Ca2+-responsive factors calineurin, calcineurin-dependent NFATc (cytosolic counterpart of activated T-cell-specific nuclear factor) and c-Jun N-terminal kinase (JNK)-dependent ATF2 (activated transcription factor 2); (iii) reduced levels of transcription factor, NF-κB; and (iv) enhanced transcription of cytochrome oxidase Vb (COX Vb) subunit gene. These cellular changes, including the steady-state [Ca2+]i were normalized in genetically reverted cells which contain near-normal mtDNA levels. We propose that the mitochondria-to-nucleus stress signaling occurs through cytosolic [Ca2+]i changes, which are likely to be due to reduced ATP and Ca2+ efflux. Our results indicate that the mitochondrial stress signal affects a variety of cellular processes, in addition to mitochondrial membrane biogenesis. [ABSTRACT FROM AUTHOR]

Genetically encoded Ca2+-sensing proteins provide a great new tool to study complex cellular interactions in vivo. We recently reported an enhanced Ca2+-sensing protein, GCaMP2 and a tetracycline-off system to regulate its expression in the heart (Tallini et al PNAS 2006). GCaMP2 has high brightness, stability at 37°C and a large dynamic range compared to its predecessors. GCaMP2 was conditionally expressed in the heart and used to study Ca2+ signaling during development. As early as 10.5 days post coitus (dpe), Ca2+ signals were recorded from the unseptated heart. Ca2+ waves were initiated in the atria of spontaneously beating hearts with a striking slowing through the atrioventricular canal (AVC) followed by rapid activation of the ventricles providing an effective AV delay prior to the formation of an AV node. At 13.5 dpc, loss of surface conduction through the AVC was observed; instead, Ca2+ wave ended as distinct rings at the junction of the atria and ventricles before activation of the ventricles. In some 10.5 dpc experiments, the Ca2+ wave was initiated within the common ventricle that resulted in retrograde transmission of Ca2+ through the AVC to the atria. Spontaneous retrograde signaling was never observed from 11.5-13.5 dpc. Pacing of the ventricles in hearts less than 13.5 dpc occasionally resulted in retrograde signaling. These studies demonstrate the use of GCaMP2 to study embryonic cardiac development. [ABSTRACT FROM AUTHOR]

Wild type (WT) mice and mice with a null mutation in one α1 or α2 Na+ pump (α1+/- or α2+/-) or Na/Ca exchanger-1 (NCX1+/-) allele were used to determine the roles of arterial Na+ transporters in regulating Ca2+ signaling, arterial contractility and blood pressure (BP). Myogenic tone (MT), sarcoplasmic reticulum (SR) Ca2+ release and arterial contractility in isolated, pressurized mesenteric small arteries and BP were compared in these genotypes. MT was significantly increased in WT arteries treated with 100 nM ouabain (inhibits α2 Na+ pumps only), 1 and in α2+/- arteries, but was normal in α1+/- and NCX1+/- arteries. Augmented IP3-sensitive SR Ca2+ release [phenylephrine (PE, 5 µM) induced vasoconstriction in Ca2+-free solution] was seen in both α2+/- and NCX1+/- mouse arteries. PE dose-response in Ca2+-containing solutions was augmented in arteries with reduced α2 Na+ pump activity. BP was significantly elevated in α2+/-, but not α1+/- or NCX1+/- mice; however, BP was significantly decreased in smooth muscle specific NCX1 knockout mice. Therefore, reduced α2, but not α1, Na+ pump activity augments MT, arterial contractility and elevates long-term BP. Reduced NCX1 activity augments IP3-induced vasoconstriction but not contractility or BP; knockout of NCX1 reduces BP. We conclude that arterial α2 Na+ pumps and NCX1 are two key molecular mechanisms that exert long-term control over MT and BP. [ABSTRACT FROM AUTHOR]