Thesis advisor: Sara Moorman / Improved survival for medical conditions that were previously fatal in infancy has led to more individuals living longer with chronic illnesses. These individuals, some of whom have largely unapparent, unpredictable, and yet severe symptoms from birth, may experience a unique set of physical, social, and emotional impacts associated with their condition as compared to youth with less severe, treatable pediatric conditions or individuals with adult-onset conditions. This dissertation explores these challenges using the case of youth with Barth Syndrome (BTHS), a rare, severe, genetic condition in males associated with life-limiting and life-threatening symptoms. Research questions explored: (1) how symptom severity, visibility, and controllability informed individuals’ social management and legitimization of BTHS; (2) how awareness regarding their limited, uncertain prognosis impacted life planning for youth with BTHS; and (3) which coping strategies individuals with BTHS used to manage the physical, social, and emotional impacts associated with their incurable, life-limiting condition. Thirty-three sixty-minute interviews were conducted in two groups: individuals with BTHS ≤15 years of age (n=18) and/or their caregivers, and individuals with BTHS ≥16 years of age (n=15). Interview transcripts were analyzed using Atlas.ti. Results demonstrated that (1) the severity, visibility, and lack of control over BTHS symptoms was associated with individuals needing to seek social support for their condition, rather than attempting to pass as healthy as other males with chronic conditions have been found to do; (2) individuals opted to forgo socially “on-time” goals (i.e., long-term, knowledge-based goals) based on their perceptions of their limited, uncertain time horizons and struggled to identify alternative goals; and (3) individuals used secondary coping strategies (i.e., regulating their emotional responses to their external stressor rather than controlling the stressor itself) to cope with the impacts associated with having an incurable, severe, and chronic health condition. These results can be used to inform practices for providing increased social and institutional support to chronically ill youth, including promoting positive coping strategies and facilitating meaningful, attainable, goal selection. These interventions may alleviate some of the challenges faced by the growing number of youth living with chronic illnesses seeking to safely and meaningfully engage in the realms of work, family, education, and social life. / Thesis (PhD) — Boston College, 2019. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Sociology.

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Isolated noncompaction of the left ventricular myocardium (INVM) is characterized by the presence of numerous prominent trabeculations and deep intertrabecular recesses within the left ventricle, sometimes also affecting the right ventricle and interventricular septum. Familial occurrence of this disorder was described previously. We present a family in which 6 affected individuals demonstrated X-linked recessive inheritance of this trait. Affected relatives presented postnatally with left ventricular failure and arrhythmias, associated with the pathognomonic echocardiographic findings of INVM. The usual findings of Barth syndrome (neutropenia, growth retardation, elevated urinary organic acids, low carnitine levels, and mitochondrial abnormalities) were either absent or found inconsistently. Fetal echocardiograms obtained between 24-30 weeks of gestation in 3 of the affected males showed a dilated left ventricle in one heart, but were not otherwise diagnostic of INVM in any of the cases. Four of the affected individuals died during infancy, one is in cardiac failure at age 8 months, and one is alive following cardiac transplant at age 9 months. The hearts from infants who died or underwent transplantation appeared, on gross examination, to be enlarged, with coarse, deep ventricular trabeculations and prominent endocardial fibroelastosis. Histologically, there were loosely organized fascicles of myocytes in subepicardial and midmyocardial zones of both ventricles, and the myocytes showed thin, often angulated fibers with prominent central clearing and reduced numbers of filaments. Markedly elongated mitochondria were present in some ventricular myocytes from one specimen, but this finding was not reproducible. Genetic linkage analysis has localized INVM to the Xq28 region, where other myopathies with cardiac involvement have been located.

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Les cardiolipines (CL) sont des phospholipides possédant de nombreux rôles dans la structure et le fonctionnement des mitochondries. Elles sont, par exemple, impliquées dans la stabilisation des complexes des oxydations phosphorylantes, la fusion/fission des membranes mitochondriales, l’import de protéines mitochondriales, la biogénèse des centres fer-soufre (Fe-S), l’apoptose, la protection des mitochondries contre le stress oxydatif…L’ensemble de ces fonctions nécessitent que les chaînes d’acides gras de la CL soient majoritairement insaturées. Le maintien de cette composition en chaînes insaturées requiert une activité acyltransférase portée par la protéine tafazzine, qui est codée par le gène nucléaire TAZ. Des mutations dans ce gène sont la cause du syndrome de Barth (BTHS), qui se caractérise notamment par des myopathies cardiaques et squelettiques, une neutropénie (responsable de nombreuses infections) et des défauts de la chaîne respiratoire. Malgré des progrès considérables dans la compréhension des mécanismes conduisant à la pathogénicité, il n’existe toujours aucune thérapie pour traiter cette maladie. Nous avons donc utilisé la levure Saccharomyces cerevisiae, chez qui la voie de remodelage des CL par la tafazzine est bien conservée, pour modéliser le BTHS et, ainsi non seulement étudier les mécanismes moléculaires sous-jacents de cette maladie, mais aussi identifier différentes voies thérapeutiques potentielles (suppresseurs génétiques et molécules pharmacologiques). Nous avons tout d’abord construit une levure délétée pour le gène orthologue TAZ (TAZ1 chez la levure), la souche Δtaz1. En accord avec des études précédentes, la souche Δtaz1 présente une diminution quantitative de la CL accompagnée d’un changement qualitatif des chaînes d’acides gras1,2 (plus d’acides gras saturés et moins d’insaturés). Nous montrons aussi que cette levure mutante a un défaut de croissance en milieu respiratoire à température élevée (36°C) ainsi que des défauts dans plusieurs composants impliqués dans les oxydations phosphorylantes2. De façon intéressante, alors que le défaut primaire (diminution des CL et changement qualitatif des chaines d’acide gras) est toujours présent, nous montrons que les oxydations phosphorylantes sont restaurées dans la souche Δtaz1 surexprimant Odc1p2, un transporteur mitochondrial d’intermédiaires du cycle de Krebs, ou par plusieurs composés chimiques. Plusieurs de ces drogues sauvant le mutant, dont la cycloheximide, sont des inhibiteurs partiels de la synthèse protéique cytosolique. Cet effet a été confirmé génétiquement par des mutations affectant les ribosomes cytosoliques. L’ensemble des résultats suggère qu’un défaut au niveau des CL provoquerait un stress protéostatique probablement impliqué dans le processus pathologique. / The phospholipid cardiolipin (CL) has many roles in mitochondrial structure and function, ranging from assembly/stability and functioning of the oxidative phosphorylation (OXPHOS) system, fusion and fission of mitochondrial membranes, mitochondrial protein import, iron-sulfur (Fe-S) biogenesis, apoptosis, and protection of mitochondria against oxidative damage. The maintenance of a proper unsaturated acyl chain composition of CL involves the acyltransferase tafazzin in which mutations cause Barth syndrome (BTHS), resulting in cardiac and skeletal myopathy, cyclic neutropenia and respiratory chain defects. Despite considerable progress in the understanding of the underlying pathogenic mechanisms, there are still no effective therapies to treat this disease. We are using the yeast Saccharomyces cerevisiae, in which the tafazzin-based cardiolipin remodeling pathway is conserved, as a model system for the exploration of potential therapeutic pathways against BTHS, by way of genetic suppressors and chemical screening. We first constructed a yeast strain lacking the orthologous taffazin gene (Δtaz1). Consistent with previous studies, our Δtaz1 yeast failed to grow on non-fermentable carbon sources at elevated temperatures (36°C) and exhibited defects in several components of the mitochondrial respiratory system. Interestingly, we found that oxidative phosphorylation was fully restored in Δtaz1 yeast by overexpressing Odc1p [1]-a mitochondrial carrier that transports Krebs cycle intermediates- and by a number of chemical compounds. Some of the rescuing drugs, especially cycloheximide, act by partially inhibiting cytosolic protein synthesis leading to a full recovery of oxidative phosphorylations. Our findings identify potential cellular components and pathways for the pharmacological treatment of BTHS patients.

Introduction: Diagnosing inborn metabolic diseases, as a large subgroup of rare diseases, due to their rarity and wide variety of clinical manifestations, can be demanding and often prolonged. Objective: The aim of this work is, with the regard to clinical, biochemical and genetical aspects of selected rare diseases, to contribute to their rapid detection, widen the features of the natural course of the disease and contribute to their preventability. Material: This work includes cohort studies of patiens with cardiac manifestations in mitochondrial diseases, namely a group of 48 patients with TMEM70 protein deficiency, a group of 4 patients with Barth syndrome and individual cases of rare mitochondrial cardiomyopathies, thimidine kinase 2 deficiency and alanyl tRNA synthetase 2 deficiency. By determining the frequency, severity and type of heart disease, the phenotype was expanded, and the design of a therapeutic algorithm then made a positive impact on the prognosis of these patients. The work is also focused on the role of cardiac disease in the differential diagnosis of other genetically determined rare diseases, Marfan's syndrome and especially Pompe disease, where the emphasis is on early diagnosis, mainly due to the existence of an effective therapy. Focus on a broader differential diagnosis...