Aquaporin-9 (AQP9) is an aquaglyceroporin membrane channel shown biophysically to conduct water, glycerol, and other small solutes. Because the physiological role/s of AQP9 remain undefined and the expression sites of AQP9 remain incomplete and conflicting, we generated AQP9 knockout mice. In the absence of physiological stress, knockout mice did not display any visible behavioral or severe physical abnormalities. Immunohistochemical analyses using multiple antibodies revealed AQP9 specific labeling in hepatocytes, epididymis, vas deferens, and in epidermis of wild type mice, but a complete absence of labeling in AQP9 ؊/؊ mice. In brain, no detectable labeling was observed. Compared with control mice, plasma levels of glycerol and triglycerides were markedly increased in AQP9 ؊/؊ mice, whereas glucose, urea, free fatty acids, alkaline phosphatase, and cholesterol were not significantly different. Oral administration of glycerol to fasted mice resulted in an acute rise in blood glucose levels in both AQP9 ؊/؊ and AQP9 ؉/؊ mice, revealing no defect in utilization of exogenous glycerol as a gluconeogenic substrate and indicating a high gluconeogenic capacity in nonhepatic organs. Obese Lepr db /Lepr db AQP9 ؊/؊ and obese Lepr db /Lepr db AQP9 ؉/؊ mice showed similar body weight, whereas the glycerol levels in obese Lepr db /Lepr db AQP9 ؊/؊ mice were dramatically increased. Consistent with a role of AQP9 in hepatic uptake of glycerol, blood glucose levels were significantly reduced in Lepr db /Lepr db AQP9 ؊/؊ mice compared with Lepr db / Lepr db AQP9 ؉/؊ in response to 3 h of fasting. Thus, AQP9 is important for hepatic glycerol metabolism and may play a role in glycerol and glucose metabolism in diabetes mellitus.aquaglyceroporin ͉ diabetes mellitus ͉ leptin receptor

Background-Disturbances in pH affect artery function, but the mechanistic background remains controversial. We investigated whether Na ϩ ,HCO 3 Ϫ cotransporter NBCn1, by regulating intracellular pH (pH i ), influences artery function and blood pressure regulation. Methods and Results-Knockout of NBCn1 in mice eliminated Na ϩ ,HCO 3 Ϫ cotransport and caused a lower steady-state pH i in mesenteric artery smooth muscle and endothelial cells in situ evaluated by fluorescence microscopy. Using myography, arteries from NBCn1 knockout mice showed reduced acetylcholine-induced NO-mediated relaxations and lower rho-kinase-dependent norepinephrine-stimulated smooth muscle Ca 2ϩ sensitivity. Acetylcholine-stimulated NO levels (electrode measurements) and N-nitro-L-arginine methyl ester-sensitive L-arginine conversion (radioisotope measurements) were reduced in arteries from NBCn1 knockout mice, whereas relaxation to NO-donor S-nitroso-Nacetylpenicillamine, acetylcholine-induced endothelial Ca 2ϩ responses (fluorescence microscopy), and total and Ser-1177 phosphorylated endothelial NO-synthase expression (Western blot analyses) were unaffected. Reduced NO-mediated relaxations in arteries from NBCn1 knockout mice were not rescued by superoxide scavenging. Phosphorylation of myosin phosphatase targeting subunit at Thr-850 was reduced in arteries from NBCn1 knockout mice. Evaluated by an in vitro assay, rho-kinase activity was reduced at low pH. Without CO 2 /HCO 3 Ϫ , no differences in pH i , contraction or relaxation were observed between arteries from NBCn1 knockout and wild-type mice. Based on radiotelemetry and tail-cuff measurements, NBCn1 knockout mice were mildly hypertensive at rest, displayed attenuated blood pressure responses to NO-synthase and rho-kinase inhibition and were resistant to developing hypertension during angiotensin-II infusion. Conclusions-Intracellular acidification of smooth muscle and endothelial cells after knockout of NBCn1 inhibits NO-mediated and rho-kinase-dependent signaling in isolated arteries and perturbs blood pressure regulation. (Circulation. 2011;124:1819-1829.)Key Words: pH Ⅲ hypertension Ⅲ blood pressure Ⅲ nitric oxide Ⅲ rho-kinase B lood pressure dysregulation is a major cause of human disease. Hypertension is a risk factor for development of coronary heart disease, stroke, and peripheral vascular disease 1-3 whereas hypotension is related to syncope and falls. 4,5 Both hyper-and hypotension increase overall mortality. 6 -8 Editorial see p 1806 Clinical Perspective on p 1829Arterial tone regulation is important for blood pressure control and is modulated by local and systemic factors. Sustained changes in intracellular pH (pH i ) of vascular smooth muscle cells (VSMCs) and endothelial cells (ECs) occur physiologically and pathologically, but have been difficult to investigate experimentally, and little is known about their vascular effects. 9 It has, however, been proposed that endothelial enzymes (eg, endothelial nitric oxide synthase [eNOS] 10 and endothelin converting...

Retroviruses have been invading mammalian germlines for millions of years, accumulating in the form of endogenous retroviruses (ERVs) that account for nearly one-tenth of the mouse and human genomes. ERVs are epigenetically silenced during development, yet the cellular factors recognizing ERVs in a sequence-specific manner remain elusive. Here we demonstrate that ZFP809, a member of the Kr€ uppel-associated box zinc finger protein (KRAB-ZFP) family, initiates the silencing of ERVs in a sequence-specific manner via recruitment of heterochromatin-inducing complexes. ZFP809 knockout mice display highly elevated levels of ZFP809-targeted ERVs in somatic tissues. ERV reactivation is accompanied by an epigenetic shift from repressive to active histone modifications but only slight destabilization of DNA methylation. Importantly, using conditional alleles and rescue experiments, we demonstrate that ZFP809 is required to initiate ERV silencing during embryonic development but becomes largely dispensable in somatic tissues. Finally, we show that the DNA-binding specificity of ZFP809 is evolutionarily conserved in the Muroidea superfamily of rodents and predates the endogenization of retroviruses presently targeted by ZFP809 in Mus musculus. In sum, these data provide compelling evidence that ZFP809 evolved to recognize foreign DNA and establish histone modification-based epigenetic silencing of ERVs.

SORLA/SORL1 is a unique neuronal sorting receptor for the amyloid precursor protein that has been causally implicated in both sporadic and autosomal dominant familial forms of Alzheimer's disease (AD). Brain concentrations of SORLA are inversely correlated with amyloid-β (Aβ) in mouse models and AD patients, suggesting that increasing expression of this receptor could be a therapeutic option for decreasing the amount of amyloidogenic products in affected individuals. We characterize a new mouse model in which SORLA is overexpressed, and show a decrease in Aβ concentrations in mouse brain. We trace the underlying molecular mechanism to the ability of this receptor to direct lysosomal targeting of nascent Aβ peptides. Aβ binds to the amino-terminal VPS10P domain of SORLA, and this binding is impaired by a familial AD mutation in SORL1. Thus, loss of SORLA's Aβ sorting function is a potential cause of AD in patients, and SORLA may be a new therapeutic target for AD drug development.

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