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Michelle W M Li Population Council, 1230 York Avenue, New York 10021, USA
Department of Zoology, The University of Hong Kong, Hong Kong, China

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Weiliang Xia Population Council, 1230 York Avenue, New York 10021, USA
Department of Zoology, The University of Hong Kong, Hong Kong, China

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Dolores D Mruk Population Council, 1230 York Avenue, New York 10021, USA
Department of Zoology, The University of Hong Kong, Hong Kong, China

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Claire Q F Wang Population Council, 1230 York Avenue, New York 10021, USA
Department of Zoology, The University of Hong Kong, Hong Kong, China

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Helen H N Yan Population Council, 1230 York Avenue, New York 10021, USA
Department of Zoology, The University of Hong Kong, Hong Kong, China

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Michelle K Y Siu Population Council, 1230 York Avenue, New York 10021, USA
Department of Zoology, The University of Hong Kong, Hong Kong, China

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Wing-yee Lui Population Council, 1230 York Avenue, New York 10021, USA
Department of Zoology, The University of Hong Kong, Hong Kong, China

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Will M Lee Population Council, 1230 York Avenue, New York 10021, USA
Department of Zoology, The University of Hong Kong, Hong Kong, China

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C Yan Cheng Population Council, 1230 York Avenue, New York 10021, USA
Department of Zoology, The University of Hong Kong, Hong Kong, China

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The timely restructuring of the blood–testis barrier (BTB) that facilitates the migration of preleptotene and leptotene spermatocytes from the basal to the adluminal compartment in the seminiferous epithelium of adult rat testes, which occurs at late stage VII through early stage VIII of the epithelial cycle, is a crucial cellular event of spermatogenesis. However, the regulation of BTB dynamics at the biochemical level remains elusive. In this study, tumor necrosis factor α (TNFα), a secretory product of Sertoli and germ cells in rat testes, was shown to affect junction dynamics in vivo. Following an acute administration of recombinant TNFα directly to adult rat testes in vivo at 0.5 and 2 μg/testis (with a body weight ~300 g), this treatment significantly and transiently disrupted the BTB. It also transiently inhibited the steady-state protein levels of occludin, zonula occludens-1, and N-cadherin, but not junction adhesion molecule-A, α-, and β-catenin in testes at the BTB site as illustrated by immunoblottings, immunohistochemistry, electron microscopy, and fluorescent microscopy. This transient disruption of the BTB integrity induced by TNFα treatment was further demonstrated by a functional test to assess the passage of a fluorescent dye (e.g. fluorescein-5-isothiocyanate) from the systemic circulation to the adluminal compartment. Additionally, both the phosphorylated-Ser/Thr protein kinase activated by MAP kinase kinase (p-p38) and phosphorylated-externally regulated kinase (p-ERK) mitogen -activated protein kinase-signaling pathways were transiently activated. Collectively, these data coupled with the recently published in vitro studies have illustrated that the BTB is likely utilizing a novel mechanism in which localized production of TNFα by Sertoli and germ cells into the microenvironment at the basal compartment facilitates the timely restructuring (‘opening’?) of the BTB during spermatogenesis to facilitate germ cell migration.

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M G Gnanalingham Centre for Reproduction and Early Life, Institute of Clinical Research, University of Nottingham, Nottingham NG7 2UH, UK
Department of Animal Sciences, University of Missouri, Columbia, Missouri, USA
Institute of Biochemistry, Food Science and Nutrition, Faculty of Agricultural, Food and Environmental Quality Sciences, The Hebrew University of Jerusalem, Rehovot, Israel
Faculté de Médecine Necker-Enfants-Malades, CNRS-UPR 9078, Paris, France

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A Mostyn Centre for Reproduction and Early Life, Institute of Clinical Research, University of Nottingham, Nottingham NG7 2UH, UK
Department of Animal Sciences, University of Missouri, Columbia, Missouri, USA
Institute of Biochemistry, Food Science and Nutrition, Faculty of Agricultural, Food and Environmental Quality Sciences, The Hebrew University of Jerusalem, Rehovot, Israel
Faculté de Médecine Necker-Enfants-Malades, CNRS-UPR 9078, Paris, France

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J Wang Centre for Reproduction and Early Life, Institute of Clinical Research, University of Nottingham, Nottingham NG7 2UH, UK
Department of Animal Sciences, University of Missouri, Columbia, Missouri, USA
Institute of Biochemistry, Food Science and Nutrition, Faculty of Agricultural, Food and Environmental Quality Sciences, The Hebrew University of Jerusalem, Rehovot, Israel
Faculté de Médecine Necker-Enfants-Malades, CNRS-UPR 9078, Paris, France

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R Webb Centre for Reproduction and Early Life, Institute of Clinical Research, University of Nottingham, Nottingham NG7 2UH, UK
Department of Animal Sciences, University of Missouri, Columbia, Missouri, USA
Institute of Biochemistry, Food Science and Nutrition, Faculty of Agricultural, Food and Environmental Quality Sciences, The Hebrew University of Jerusalem, Rehovot, Israel
Faculté de Médecine Necker-Enfants-Malades, CNRS-UPR 9078, Paris, France

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D H Keisler Centre for Reproduction and Early Life, Institute of Clinical Research, University of Nottingham, Nottingham NG7 2UH, UK
Department of Animal Sciences, University of Missouri, Columbia, Missouri, USA
Institute of Biochemistry, Food Science and Nutrition, Faculty of Agricultural, Food and Environmental Quality Sciences, The Hebrew University of Jerusalem, Rehovot, Israel
Faculté de Médecine Necker-Enfants-Malades, CNRS-UPR 9078, Paris, France

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N Raver Centre for Reproduction and Early Life, Institute of Clinical Research, University of Nottingham, Nottingham NG7 2UH, UK
Department of Animal Sciences, University of Missouri, Columbia, Missouri, USA
Institute of Biochemistry, Food Science and Nutrition, Faculty of Agricultural, Food and Environmental Quality Sciences, The Hebrew University of Jerusalem, Rehovot, Israel
Faculté de Médecine Necker-Enfants-Malades, CNRS-UPR 9078, Paris, France

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M C Alves-Guerra Centre for Reproduction and Early Life, Institute of Clinical Research, University of Nottingham, Nottingham NG7 2UH, UK
Department of Animal Sciences, University of Missouri, Columbia, Missouri, USA
Institute of Biochemistry, Food Science and Nutrition, Faculty of Agricultural, Food and Environmental Quality Sciences, The Hebrew University of Jerusalem, Rehovot, Israel
Faculté de Médecine Necker-Enfants-Malades, CNRS-UPR 9078, Paris, France

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C Pecqueur Centre for Reproduction and Early Life, Institute of Clinical Research, University of Nottingham, Nottingham NG7 2UH, UK
Department of Animal Sciences, University of Missouri, Columbia, Missouri, USA
Institute of Biochemistry, Food Science and Nutrition, Faculty of Agricultural, Food and Environmental Quality Sciences, The Hebrew University of Jerusalem, Rehovot, Israel
Faculté de Médecine Necker-Enfants-Malades, CNRS-UPR 9078, Paris, France

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B Miroux Centre for Reproduction and Early Life, Institute of Clinical Research, University of Nottingham, Nottingham NG7 2UH, UK
Department of Animal Sciences, University of Missouri, Columbia, Missouri, USA
Institute of Biochemistry, Food Science and Nutrition, Faculty of Agricultural, Food and Environmental Quality Sciences, The Hebrew University of Jerusalem, Rehovot, Israel
Faculté de Médecine Necker-Enfants-Malades, CNRS-UPR 9078, Paris, France

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T Stephenson Centre for Reproduction and Early Life, Institute of Clinical Research, University of Nottingham, Nottingham NG7 2UH, UK
Department of Animal Sciences, University of Missouri, Columbia, Missouri, USA
Institute of Biochemistry, Food Science and Nutrition, Faculty of Agricultural, Food and Environmental Quality Sciences, The Hebrew University of Jerusalem, Rehovot, Israel
Faculté de Médecine Necker-Enfants-Malades, CNRS-UPR 9078, Paris, France

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M E Symonds Centre for Reproduction and Early Life, Institute of Clinical Research, University of Nottingham, Nottingham NG7 2UH, UK
Department of Animal Sciences, University of Missouri, Columbia, Missouri, USA
Institute of Biochemistry, Food Science and Nutrition, Faculty of Agricultural, Food and Environmental Quality Sciences, The Hebrew University of Jerusalem, Rehovot, Israel
Faculté de Médecine Necker-Enfants-Malades, CNRS-UPR 9078, Paris, France

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Many tissues undergo a rapid transition after birth, accompanied by dramatic changes in mitochondrial protein function. In particular, uncoupling protein (UCP) abundance increases at birth in the lung and adipose tissue, to then gradually decline, an adaptation that is important in enabling normal tissue function. Leptin potentially mediates some of these changes and is known to promote the loss of UCP1 from brown fat but its effects on UCP2 and related mitochondrial proteins (i.e. voltage-dependent anion channel (VDAC) and cytochrome c) in other tissues are unknown. We therefore determined the effects of once-daily jugular venous administration of ovine recombinant leptin on mitochondrial protein abundance as determined by immunoblotting in tissues that do (i.e. the brain and pancreas) and do not (i.e. liver and skeletal muscle) express UCP2. Eight pairs of 1-day-old lambs received either 100 μg leptin or vehicle daily for 6 days, before tissue sampling on day 7. Administration of leptin diminished UCP2 abundance in the pancreas, but not the brain. Leptin administration had no affect on the abundance of VDAC or cytochrome c in any tissue examined. In leptin-administered animals, but not controls, UCP2 abundance in the pancreas was positively correlated with VDAC and cytochrome c content, and UCP2 abundance in the brain with colonic temperature. In conclusion, leptin administration to neonatal lambs causes a tissue-specific loss of UCP2 from the pancreas. These effects may be important in the regulation of neonatal tissue development and potentially for optimising metabolic control mechanisms in later life.

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Pearl P Y Lie Center for Biomedical Research, Population Council, 1230 York Avenue, New York, New York 10021, USA
Department of Zoology, University of Hong Kong, Hong Kong, China

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Weiliang Xia Center for Biomedical Research, Population Council, 1230 York Avenue, New York, New York 10021, USA
Department of Zoology, University of Hong Kong, Hong Kong, China

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Claire Q F Wang Center for Biomedical Research, Population Council, 1230 York Avenue, New York, New York 10021, USA
Department of Zoology, University of Hong Kong, Hong Kong, China

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Dolores D Mruk Center for Biomedical Research, Population Council, 1230 York Avenue, New York, New York 10021, USA
Department of Zoology, University of Hong Kong, Hong Kong, China

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Helen H N Yan Center for Biomedical Research, Population Council, 1230 York Avenue, New York, New York 10021, USA
Department of Zoology, University of Hong Kong, Hong Kong, China

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Ching-hang Wong Center for Biomedical Research, Population Council, 1230 York Avenue, New York, New York 10021, USA
Department of Zoology, University of Hong Kong, Hong Kong, China

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Will M Lee Center for Biomedical Research, Population Council, 1230 York Avenue, New York, New York 10021, USA
Department of Zoology, University of Hong Kong, Hong Kong, China

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C Yan Cheng Center for Biomedical Research, Population Council, 1230 York Avenue, New York, New York 10021, USA
Department of Zoology, University of Hong Kong, Hong Kong, China

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In adult rat testes, blood–testis barrier (BTB) restructuring facilitates the migration of preleptotene spermatocytes from the basal to the adluminal compartment that occurs at stage VIII of the epithelial cycle. Structural proteins at the BTB must utilize an efficient mechanism (e.g. endocytosis) to facilitate its transient ‘opening’. Dynamin II, a large GTPase known to be involved in endocytosis, was shown to be a product of Sertoli and germ cells in the testis. It was also localized to the BTB, as well as the apical ectoplasmic specialization (apical ES), during virtually all stages of the epithelial cycle. By co-immunoprecipitation, dynamin II was shown to associate with occludin, N-cadherin, zonula occludens-1 (ZO-1), β-catenin, junctional adhesion molecule-A, and p130Cas, but not nectin-3. An in vivo model in rats previously characterized for studying adherens junction (AJ) dynamics in the testes by adjudin (formerly called AF-2364, 1-(2,4-dichlorobenzyl)-1H-indazole-3-car-hohydrizide) treatment was used in our studies. At the time of germ cell loss from the seminiferous epithelium as a result of adjudin-induced AJ restructuring without disrupting the BTB integrity, a significant decline in the steady-state dynamin II protein level was detected. This change was associated with a concomitant increase in the levels of two protein complexes at the BTB, namely occludin/ZO-1 and N-cadherin/β-catenin. Interestingly, these changes were also accompanied by a significant increase in the structural interaction of dynamin II with β-catenin and ZO-1. β-Catenin and ZO-1 are adaptors that structurally link the cadherin- and occludin-based protein complexes together at the BTB in an ‘engaged’state to reinforce the barrier function in normal testes. However, β-catenin and ZO-1 were ‘disengaged’ from each other but bound to dynamin II during adjudin-induced AJ restructuring in the testis. The data reported herein suggest that dynamin II may assist the ‘disengagement’ of β-catenin from ZO-1 during BTB restructuring. Thus, this may permit the occludin/ZO-1 complexes to maintain the BTB integrity when the cadherin/catenin complexes are dissociated to facilitate germ cell movement.

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