Research has shown that when individuals are in situations that do not occasion one form of motoric responding, they will engage in another so that the overall level of motoric responding is homeostatic. The purpose of this study was to test whether students would substitute task-related behaviors for stereotypic or other challenging behaviors when the opportunity for active responding did or did not match the level of motoric responding in a free-operant baseline. Four students with mental retardation participated. Results showed that they did substitute behaviors, with stereotypic and other challenging behaviors occurring 1.5-14 times as much in the Non-matched condition for the four students. Further analysis showed considerably more of these behaviors in passive than in active tasks (by a factor up to 21 times as much). Results were discussed in terms of homeostasis, functional assessment, and opportunities to improve educational behaviors.

Le Système Nerveux Central (SNC) est un acteur majeur de la régulation de l’homéostasie énergétique, intégrant différents signaux nerveux, hormonaux ou nutritionnels. Le métabolisme lipidique joue un rôle essentiel notamment dans la détection des signaux lipidiques, et les enzymes y participant sont donc fortement impliquées dans la régulation de ces signaux et leur expression est cruciale au bon équilibre énergétique. La Lipoprotéine Lipase (LPL), enzyme clé de l'hydrolyse des triglycérides, nous est apparue comme une cible de choix dans la mesure où elle est exprimée dans différentes structures cérébrales comme l'hippocampe ou l'hypothalamus. L'hypothalamus a été identifié depuis de nombreuses années comme un centre de régulation de la prise alimentaire et donc de l'équilibre entre entrées et dépenses d'énergie. Ainsi, il est apparu comme légitime que de s'intéresser plus précisément au rôle de la LPL hypothalamique et son implication dans la régulation de l'homéostasie énergétique.L'objet de cette thèse a donc été d'étudier, dans un premier temps, les effets d'une délétion de LPL dans le VMH, réalisée grâce à une injection d'un AAV2/9 exprimant la Cre recombinase chez des souris LPL lox/lox âgées de 8 semaines. La diminution de l'activité LPL dans le VMH conduit au développement d'une obésité au bout de 3 semaines post-injection, ainsi qu'au développement d'une intolérance au glucose, d'une résistance à l'insuline ainsi qu'une diminution de l'activité locomotrice.Ce phénotype est dû à une diminution transitoire de la quantité de céramides synthétisées par l’enzyme CerS1 au sein de l'hypothalamus durant les semaines qui suivent l'injection et qui perturbent la signalisation homéostatique. Il apparait également que le système endocannabinoïde pourrait être impliqué dans la mise en place de ce phénotype. Les caractéristiques de ce phénotype rappelant celles d'un état de torpeur, nous avons cherché dans la deuxième partie de ce travail de thèse, à reproduire celui-ci pour pouvoir étudier plus précisément les liens et les conséquences entre torpeur et lipases cérébrales. Nous avons donc exposés les animaux à 4°C pendant 4 heures et étudié les répercussions de ce stress thermique sur les gènes des lipases centrales ainsi que ceux du rythme circadien : nous avons pu mettre en évidence une modification du rythme circadien. Nous avons également exposé des animaux délétés en LPL hypothalamique et pu établir que cette délétion centrale en LPL modifie la thermogenèse du tissu adipeux brun ainsi et favorise le développement du tissu adipeux beige. Ce travail de thèse a donc permis de mettre en lumière pour la première fois l'implication de la LPL hypothalamique dans la régulation de l'homéostasie énergétique ainsi que son rôle dans la réponse adaptative à une exposition aiguë au froid. / The Central Nervous System (CNS) is a major actor in the energy balance regulation, integrating different nervous, hormonal or nutritional signals. The lipid metabolism plays an essential role especially in the detection of lipid signals. So, the enzymes taking part in it are involved in the regulation of these signals and their expression is crucial to the energy balance. The Lipoprotein Lipase (LPL), the key enzyme in triglycerides hydrolysis appeared to us as a target of choice as it is expressed in different brain structures like the hypothalamus or the hippocampus.The hypothalamus has long been known as a regulation center of food intake and so of the balance between entrance and expenditure of energy. It seemed interesting to focus more precisely on the role of hypothalamic LPL and its implication in the regulation of energy homeostasis.This dissertation’s main objective was to identify the effects of LPL deletion in the VMH, achieved by injection of an AAV2/9 expressing the Cre-recombinase in LPL lox/lox mice aged of 8 weeks. The decrease of LPL activity in the VMH leads to obesity development around 3 weeks post-injection and to the development of glucose intolerance, resistance to insulin and a decrease in locomotor activity.This phenotype is probably due to a transient decrease of ceramides synthesized by the CerS1 enzyme in the hypothalamus during the weeks post-injection and which disrupts the homeostatic signalling. The endocannabinoid system also seems to be involved in the onset of this phenotype.As the characteristics of this phenotype were reminiscent of a torpor state, we tried in a second part of work to reproduce it to study more precisely the links between torpor and brain lipases. We exposed animals to 4°C for 4 hours and studied the repercussions of this thermic stress on the central lipases genes and on circadian rhythm genes: we were able to highlight a modulation of the circadian rhythm. We also exposed to the cold VMH-LPL-depleted mice and established that this depletion in VMH-LPL modifies the thermogenesis of brown adipose tissue and so promotes the development of beige adipocytes.This work highlights for the first time the implication of hypothalamic LPL in the regulation of energy homeostasis and its role in adaptive response to cold exposure.

京都大学 / 0048 / 新制・課程博士 / 博士(理学) / 甲第18838号 / 理博第4096号 / 新制||理||1589(附属図書館) / 31789 / 京都大学大学院理学研究科生物科学専攻 / (主査)教授 阿形 清和, 教授 杤尾 豪人, 教授 森 和俊 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DFAM

京都大学 / 0048 / 新制・課程博士 / 博士(医学) / 甲第20233号 / 医博第4192号 / 新制||医||1019(附属図書館) / 京都大学大学院医学研究科医学専攻 / (主査)教授 斎藤 通紀, 教授 松田 文彦, 教授 近藤 玄 / 学位規則第4条第1項該当 / Doctor of Medical Science / Kyoto University / DFAM

Ionic and osmotic homeostasis, and the intricately linked mechanisms of acid-base balance are critical for the survival of fish. To date, the role of the gastrointestinal (GI) tract in these processes has received only limited study, and our knowledge has been gained almost exclusively through studies conducted in fasting animals. The impacts of feeding and digestion, ubiquitous processes in the natural environment, are likely to be significant but have been overlooked. The current thesis addressed these shortfalls in our current understanding. Research focused on the rainbow trout (Oncorhynchus mykiss), a euryhaline species capable of withstanding the opposing challenges of life in seawater (diffusive influx of ions and loss of water) and freshwater (diffusive loss of ions and gain of water), and concentrated on its physiological response to ingestion of a meal of commercial, dry trout food, containing concentrated salts and little water. The net absorption and secretion of ions and water was tracked in each section of the GI tract of the rainbow trout over a detailed time course using an experimental diet that contained a simple inert marker, in the presence of external freshwater or seawater. Additionally, changes in overall blood chemistry were investigated to examine changes in osmotic, ionic and acid-base regulation during digestion. Feeding in freshwater resulted in the loss of endogenous water to the GI tract during digestion. Additionally, the meal provided much needed ions to balance those lost by diffusion; indeed all of the ingested ions were assimilated along the GI tract except for sodium which was absorbed in the stomach, but secreted in the intestine such that overall sodium balance was close to zero. Feeding also created a metabolic base load (an increase in the concentration of base, or HC03- due HCl secretion into the stomach lumen) that alkalinized the blood (i.e. caused a rise in pH), a phenomenon known as an alkaline tide. The base load was subsequently removed from the blood through increasedexcretion of base to the water via the gills. In seawater, the commercial diet again provided an avenue for water loss. This was potentially deleterious to an organism already suffering from diffusive water loss to the environment. Ion absorption from the diet was negligible, except for potassium and calcium, which were readily assimilated. As in freshwater, digestion resulted in an alkaline tide, however the mechanism of acid-base homeostasis differed with the excess base likely being excreted into the intestine. In contrast to freshwater fish, the gills took up additional base from the external environment, prolonging the acid-base disturbance in seawater fish. Overall, feeding was a dynamic process with far reaching systemic physiological effects. The research described highlighted intimate interactions between the processes of feeding and digestion and ion, water and acid-base homeostasis, and elucidated mechanisms that enable fish to inhabit a wide range of environments. / Thesis / Doctor of Philosophy (PhD)

R-loop is a specific nucleic acid structure, and that forms during RNA transcription. It comprises an RNA:DNA hybrid and displaced ssDNA. R-loops are prevalent and dynamic in the mammalian genome occupying up to 5%. R-loops are known to act as modulators of genome dynamics. They regulate a variety of gene transcription mechanisms and influence genomic stability. Dysregulation of R-loop is linked to a variety of human diseases. For this reason, protein factors involved in DNA and RNA metabolism are known to mediate R-loop resolution. Dysfunction of these factors resulted in aberrant R-loop accumulation, often resulting in transcription disruption and genomic instability as reported in tumorigenesis and a number of genetic disorders, including trinucleotide repeat-associated diseases and neurological disorders. Here I describe the roles of Senataxin (SETX) and Replication protein A (RPA) complex in nucleolar R-loop resolution. I demonstrate their function in nucleolar homeostasis and in particular in RNA polymerase I mediated rRNA transcription and the maintenance of nucleolar structure.This dissertation is composed of three sessions. Section 1: I review nucleolar transcription that generate a complex network of RNAs, and their contribution to nucleolar R-loops formation, with multiple roles in maintaining nucleolar homeostasis. Section 2: I describe novel roles of Replication Protein A in nucleolar homeostasis. Senataxin (SETX) mutations are linked to two different neurological disease: Amyotrophic Lateral Sclerosis (ALS4) and Ataxia Oculomotor Apraxia (AOA2) both defective in R-loop resolution. We show that loss of SETX promotes RPA translocation into nucleolus in an R-loop dependent manner where it associates with rDNA. The same nucleolar RPA phenotype is evident in SETX- deficient AOA2 patient cells. We further explored this phenotype under conditions of CPT- induced genotoxic stress, which is coupled with accumulation of nucleolar R loops. Additionally, we show that loss of RPA decreased 47S pre-rRNA levels, but increased “promoter and pre-rRNA antisense” RNA (PAPAS) and promoter RNA (pRNA). Meanwhile, we also showed loss of RPA disrupted nucleolar structure. Section 3: I describe the identification and characterization of nucleolar lncRNA (PAPAS) which encodes a short polypeptide RIEP that plays a role in combating genomic instability and mitochondrial stress. We show that this novel peptide encoded by PAPAS is localized to the nucleolus and mitochondria but is translocated to the peri-nucleolus and peri-nucleus region upon heat shock induced cellular stresses. We also showed that RIEP facilitates SETX protein stability and plays a role in restricting genomic instability possibly through its association with H3K9me3 which maintains a heterochromatin state. Finally, we show that RIEP interacts with CHCHD2 and C1QBP(P32) and may consequently function in mitochondrial stress responses.

Adipose tissue is a key metabolic organ responsible for maintaining energy homeostasis throughout the body. Healthy adipocytes respond to physiological changes and perform a variety of important functions to regulate glucose and lipid metabolism. Dysregulation of adipose tissue function, on the other hand, is strongly associated with the development of metabolic diseases. Peroxisome Proliferator Activated Receptor gamma (PPARγ) is a key transcription factor that regulates various activities in adipocytes as well as other cell types. A growing body of evidence indicates a more complex role for PPARγ beyond its classical ligand-dependent activity, including the exploration of posttranslational modifications and associated target proteins in non-canonical adipogenic reservoirs and adipocyte-associated cells. The first part of the thesis describes our study identifying Adipsin as a downstream target of PPARγ deacetylation and further uncovers its function within the bone marrow niche. Unlike peripheral adipose tissues, marrow adipose tissue has been shown to be uniquely responsive to nutrient fluctuations, hormonal changes, and metabolic disturbances such as obesity and diabetes mellitus. Expansion of marrow adipose tissue has also been strongly associated with bone loss in mice and humans. However, the regulation of bone marrow plasticity remains poorly understood, as does the mechanism that links changes in marrow adiposity with bone remodeling. We show that Adipsin was robustly induced in the bone marrow during bone loss in mouse and humans, in a manner dependent on PPARγ acetylation. Ablation of Adipsin inhibited marrow adipose expansion and improved skeletal health in bone loss conditions of calorie restriction, thiazolidinedione treatment for insulin resistance, and aging. These effects were mediated by Adipsin’s downstream effector, Complement Component 3, to prime common progenitor cells toward adipogenesis rather than osteoblastogenesis through the inhibition of Wnt/β-catenin signaling. Together, our findings reveal an unknown function of Adipsin, mediated by PPARγ acetylation, to promote adiposity and affect skeletal remodeling in the bone marrow niche. The second part of the thesis addresses another novel role for PPARγ, through acetylation in macrophages, to promote adipose tissue inflammation. Chronic, low-grade inflammation characteristic of obesity and metabolic dysfunction is partially driven by macrophage infiltration of adipose tissue and associated inflammatory signaling. PPARγ plays a critical role in regulating anti-inflammatory, M2 polarization of macrophages. However, the involvement of post-translational modifications, such as acetylation, in macrophages is unknown. Here we generated a macrophage specific, PPARγ constitutive acetylation-mimetic mouse line (K293Qflox/flox;LysMcre, mK293Q) to dissect its role. Upon stimulating macrophage infiltration into adipose tissue by high-fat diet feeding, we assessed the overall metabolic profile and tissue-specific phenotype of the mutant mice. We found that the mK293Q mutant promotes pro-inflammatory macrophage infiltration and subsequent fibrosis specifically in epididymal but not subcutaneous white adipose tissue, driving an impaired metabolic response including decreased energy expenditure, insulin sensitivity, glucose tolerance, and adipose tissue function. These detriments are driven by suppressed anti-inflammatory activation of macrophages. Furthermore, mK293Q mice are resistant to improvements in adipose remodeling by Rosiglitazone treatment. Our study reveals acetylation as a new layer of PPARγ regulation in macrophage activation. These findings highlight the importance of post-translational modifications in determining the function of PPARγ when regulating metabolism and promote the discovery of anti-inflammatory associated therapeutics.

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Regulation of intracellular pH is responsible for many cellular processes, such as metabolism, cell cycle progression, and apoptosis. Many chemotherapeutic agents work by inducing target cells to undergo apoptosis, a cell death process still poorly understood. Previous studies demonstrated that a rise in intracellular pH activated apoptotic proteins leading to cytochrome C release. This "apoptotic alkalinization" occurred upon activation of the plasma membrane protein, sodium hydrogen exchanger-1 (NHE1), whose activity is regulated by the stress kinase p38 MAPK. In previous studies, upon cytokine withdrawal from cytokine-dependent lymphocytes induced the activity of the p38 MAP kinase which then phosphorylated the C-terminus of NHE1. To identify the p38 MAPK phosphorylation sites on NHE1, in vitro p38 MAP kinase assays coupled to deletion analysis of NHE1 and mass spectrometry, identified four possible p38 MAPK phosphorylation sites. To establish that NHE1 causes apoptotic alkalinization and determine whether the identified phosphorylation sites on NHE1 are functionally significant, we used PCR site directed mutagenesis to mutate T717, S722, S725, and S728 on the C-terminus of NHE1. Stable NHE1 deficient cell lines, expressing wild type (WT) NHE or the four mutated sites (F4MUTNHE), were assessed for apoptotic alkalinization using the pH-sensitive fluorescent protein, destabilized YFP. Our results show that NHE1 is required for apoptotic alkalinization, since expression of WT NHE restored alkalinization in an NHE deficient cell line, and that this process requires the phosphorylation of the p38 MAPK target sites, since mutation of all four sites prevented the apoptotic alkalinization response.