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In the present study, the ease of rearing, short generation time and molecular research tools available for the zebrafish model (Danio rerio, Hamilton) were exploited to investigate transcriptional regulation in relation to feeding, photoperiod and experimental selection. Chapter 2 describes transcriptional regulation in fast skeletal muscle following fasting and a single satiating meal of bloodworms. Changes in transcript abundance were investigated in relation to the food content in the gut. Using qPCR, the transcription patterns of 16 genes comprising the insulin-like growth factor (IGF) system were characterized, and differential regulation between some of the paralogues was recorded. For example, feeding was associated with upregulation of igf1a and igf2b at 3 and 6h after the single-meal was offered, respectively, whereas igf1b was not detected in skeletal muscle. On the other hand, fasting triggered the upregulation of the igf1 receptors and igfbp1a/b, the only binding proteins whose transcription was responsive to a single-satiating meal. In addition to the investigation of the IGF-axis, an agnostic approach was used to discover other genes involved in transcriptional response to nutritional status, by employing a whole-genome microarray containing 44K probes. This resulted in the discovery of 147 genes in skeletal muscle that were differentially expressed between fasting and satiation. Ubiquitin-ligases involved in proteasome-mediated protein degradation, and antiproliferative and pro-apoptotic genes were among the genes upregulated during fasting, whereas satiation resulted in an upregulation of genes involved in protein synthesis and folding, and a gene highly correlated with growth in mice and fish, the enzyme ornithine decarboxylase 1. Zebrafish exhibit circadian rhythms of breeding, locomotor activity and feeding that are controlled by molecular clock mechanisms in central and peripheral organs. In chapter 3 the transcription of 17 known clock genes was investigated in skeletal muscle in relation to the photoperiod and food content in the gut. The hypothesis that myogenic regulatory factors and components of the IGF-pathway were clock-controlled was also tested. Positive (clock1 and bmal1 paralogues) and negative oscillators (cry1a and per genes) showed a strong circadian pattern in skeletal muscle in anti-phase with each other. MyoD was not clock-controlled in zebrafish in contrast to findings in mice, whereas myf6 showed a circadian pattern of expression in phase with clock and bmal. Similarly, the expression of two IGF binding proteins (igfbp3 and 5b) was circadian and in phase with the positive oscillators clock and bmal. It was also found that some paralogues responded differently to photoperiod. For example, clock1a was 3-fold more responsive than clock1b. Cry1b did not show a circadian pattern of expression. These patterns of expression provide evidence that the molecular clock mechanisms in skeletal muscle are synchronized with the molecular clock in central pacemaker organs such as eyes and the pineal gland. Using the short generation time of zebrafish the effects of selective breeding for body size at age were investigated and are described in chapter 4. Three rounds of artificial selection for small (S-lineage) and large body size (L-lineage) resulted in zebrafish populations whose average standard length were, respectively, 2% lower and 10% higher than an unselected control lineage (U-lineage). Fish from the L-lineage showed an increased egg production and bigger egg size with more yolk, possibly contributing to the larger body size observed in the early larval stage (6dpf) of fish from this lineage. Fish from S- and L-lineage exposed to fasting and refeeding showed very similar feed intake, providing evidence that experimental selection did not cause significant changes in appetite control. Investigation of the expression of the IGF-axis and nutritionally-response in skeletal muscle after fasting and refeeding revealed that the pattern of expression was not different between the selected lineages, but that a differential responsiveness was observed in a limited number of genes, providing evidence that experimental selection might have changed the way fish allocate the energy acquired through feeding. For example, a constitutive higher expression of igf1a was recorded in skeletal muscle of fish from the L-lineage whereas igfbp1a/b transcripts were higher in muscle of fish from the S-lineage. These findings demonstrate the rapid changes in growth and transcriptional response in skeletal muscle of zebrafish after only three rounds of selection. Furthermore, it provides evidences that differences in growth during embryonic and larval stages might be related to higher levels of energy deposited during oogenesis, whereas differences in adult fish were better explained by changes in energy allocation instead of energy acquisition. In chapter 5 the main findings made during this study and their impact on the literature are discussed.

The skin has a system that can detect light in a fashion similar to the retina. Although its presence was initially reported almost 20 years ago, only in 2011 functional studies started to be reported. The biological clock of the skin has also been reported in the beginning of the century, but its function and relevance still remain unexplored. Thus, this Ph.D. project was designed to explore the functionality of both systems in melanocytes, and whether the disruption of these systems is associated with the development of melanoma cancer. Using in vitro, in vivo, and bioinformatics approaches, we have shown that: 1) the biological clock of malignant melanocytes is more responsive to visible light, UVA radiation, estradiol, and temperature compared to normal cells; 2) UVA radiation is detected by melanopsin (OPN4) and rhodopsin (OPN2), which triggers a cGMP related cascade that leads to immediate pigment darkening (IPD) in normal and malignant melanocytes; 3) in addition to detecting UVA radiation, OPN4 also senses thermal energy, which activates the biological clock of both normal and malignant melanocytes; 4) regarding the biological clock, we have provided several layers of evidence that proves that in melanoma a chronodisruption scenario is established compared to healthy skin and/or normal pigment cells; 5) in vivo tumor samples display a low amplitude circadian rhythm of clock gene expression and an ultradian oscillatory profile in melanin content; 6) a non-metastatic melanoma leads to a systemic chronodisruption, which we suggest that could favor the metastatic process; 7) in human melanoma, we demonstrated the role of BMAL1 as a prognostic marker and a putative marker of immune therapy success. Taken altogether, these results significantly contributed to the literature as it brought to light new and interesting targets and processes, which will be explored in future projects / A pele possui um sistema que pode detectar luz de forma análoga à retina. Embora a presença deste sistema tenha sido inicialmente descrita quase há 20 anos, apenas no ano de 2011 estudos funcionais começaram a ser relatados. Sabe-se que o relógio biológico da pele também foi identificado no início do século, mas sua função e relevância ainda continuam pouco exploradas. Diante deste cenário, este projeto de doutorado foi desenhado para investigar a funcionalidade de ambos os sistemas em melanócitos e se perturbação dos mesmos estaria associada com o desenvolvimento de melanoma. Através do uso de abordagens in vitro, in vivo e de bioinformática, nós demonstramos que: 1) o relógio biológico de melanócitos malignos é mais responsivo à luz visível, radiação UVA, estradiol e temperatura comparado ao de células normais; 2) a radiação UVA é detectada por melanopsina (OPN4) e rodopsina (OPN2), que ativam uma via de sinalização dependente de GMPc, levando ao processo de pigmentação imediata (IPD) em melanócitos normais e malignos; 3) além de detecção de radiação UVA, a OPN4 também detecta energia térmica que, por sua vez, ativa o relógio biológico de melanócitos normais e malignos; 4) relativo ao relógio biológico, provamos por diferentes abordagens que, no melanoma, um cenário de cronoruputura está estabelecido em comparação a pele saudável e/ou melanócitos; 5) tumores in vivo apresentam um ritmo circadiano de baixa amplitude na expressão dos genes de relógio e um ritmo ultradiano oscilatório no conteúdo de melanina; 6) um melanoma não metastático leva a um quadro sistêmico de cronoruptura, o qual sugerimos favorecer o processo de metástase; 7) em melanoma humano, demonstramos o papel do gene BMAL11 como marcador de prognóstico e um possível indicador de sucesso de imunoterapias. Portanto, este projeto contribuiu de forma significante para a literatura científica uma vez que trouxe à luz novos e interessantes alvos terapêuticos e processos, os quais serão explorados em projetos futuros

Arterial blood pressure (BP) undergoes a 24-hour oscillation that peaks in the active day and reaches a nadir at night during sleep in humans. Reduced nocturnal BP fall (also known as non-dipper) is the most common disruption of BP circadian rhythm and is associated with increased risk of untoward cardiovascular events and target organ injury. Up to 75% of diabetic patients are non-dippers. However, the mechanisms underlying diabetes associated non-dipping BP are largely unknown. To address this important question, we generated a novel diabetic db/db-mPer2Luc mouse model (db/db-mPer2Luc) that allows quantitatively measuring of mPER2 protein oscillation by real-time mPer2Luc bioluminescence monitoring in vitro and in vivo. Using this model, we demonstrated that the db/db-mPer2Luc mice have a diminished BP daily rhythm. The phase of the mPER2 daily oscillation is advanced to different extents in explanted peripheral tissues from the db/db-mPer2Luc mice relative to that in the control mice. However, no phase shift is found in the central oscillator, the suprachiasmatic nucleus (SCN). The results indicate that the desynchrony of mPER2 daily oscillation in the peripheral tissues contributes to the loss of BP daily oscillation in diabetes. Extensive research over the past decades has been focused on how the components of food (what we eat) and the amount of food (how much we eat) affect metabolic diseases. Only recently has it become appreciated that the timing of food intake (when we eat), independent of total caloric and macronutrient quality, is also critical for metabolic health. To investigate the potential effect of the timing of food intake on the BP circadian rhythm, we simultaneously monitored the BP and food intake profiles in the diabetic db/db and control mice using radiotelemetry and BioDAQ systems. We found the loss of BP daily rhythm is associated with disrupted food intake rhythm in the db/db mice. In addition, the normal BP daily rhythm is altered in the healthy mice with abnormal feeding pattern, in which the food is available only during the inactive-phase. To explore whether imposing a normal food intake pattern is able to prevent and restore the disruption of BP circadian rhythm, we conducted active-time restricted feeding (ATRF) in the db/db mice. Strikingly, ATRF completely prevents and restorers the disrupted BP daily rhythm in the db/db mice. While multiple mechanisms likely contribute to the protection of ATRF on the BP daily rhythm, we found that ATRF improves the rhythms of energy metabolism, sleep-wake cycle, BP-regulatory hormones and autonomic nervous system (ANS) in the db/db mice. To further investigate the molecular mechanism by which ATRF regulates BP circadian rhythm, we determined the effect of ATRF on the mRNA expressions of core clock genes and clock target genes in the db/db mice. Of particular interest is that we found among all the genes we examined, the mRNA oscillation of Bmal1, a key core clock gene, is disrupted by diabetes and selectively restored by the ATRF in multiple peripheral tissues in the db/db mice. More importantly, we demonstrated that Bmal1 is partially required for ATRF to protect the BP circadian rhythm. In summary, our findings indicate that the desynchrony of peripheral clocks contributes to the abnormal BP circadian pattern in diabetes. Moreover, our studies suggest ATRF as a novel and effective chronotherapy against the disruption of BP circadian rhythm in diabetes.