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Coming dissertations at MedFak

  • Development of allergic and respiratory symptoms in adolescence and early adulthood : Risk factors and gender differences Author: Pia Kalm-Stephens Link: http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-421570 Publication date: 2020-11-26 09:45

    Background: Asthma and allergic diseases have increased in prevalence for several decades and affect a substantial number of individuals in everyday life, as well as their families and public healthcare resources. Subjects with asthma report impaired self-rated health. Fractional exhaled nitric oxide (FeNO) is a marker of type 2 inflammation in the airways and higher levels may precede the development of allergic and respiratory disease.

    Aims: To investigate the development of allergic and respiratory symptoms in adolescence and early adulthood, and related baseline risk factors. Further, to study self-rated health in young adults with reported asthma.

    Methods: A total of 959 schoolchildren completed a standardized respiratory questionnaire and underwent lung function and FeNO measurements at baseline (12–15 years; early adolescence). Four (late adolescence) and sixteen (early adulthood) years later, 921 (96%) and 502 (52%) of these individuals completed a similar questionnaire. A total of 491 subjects participated in all three examinations. Nineteen clinically assessed non-asthmatic subjects with elevated FeNO and 28 control subjects with low FeNO and without symptoms of asthma or allergy in early adolescence were identified. Their FeNO, IgE sensitization, airway responsiveness, and inflammatory markers in blood and sputum were measured.

    Results: The main finding was that higher FeNO in early adolescence was associated with an increased risk of developing allergic symptoms to cat and dog, but not pollen allergens, during adolescence. Gender-stratified data showed that obesity at baseline in girls and an atopic constitution in boys were associated with increased risk of developing wheeze during adolescence. The prevalence of asthma and wheeze had increased in early adulthood, but the increase was significant only in females. Reduced lung function at baseline in females and higher FeNO in males were associated with an increased risk of incident asthma sixteen years later. The increase in allergic symptoms during this period was significant but without sex differences. Asthmatic females rated their health worse than non-asthmatic females, a difference not observed in males. Non-asthmatic adolescents with higher FeNO at baseline were to a higher extent sensitized, had more reactive airways, higher blood eosinophil counts, and lower systemic activation of neutrophils, compared with controls.

    Conclusions: It is important to detect risk factors for the development of allergic and respiratory diseases at an early stage to optimize health and wellbeing. Gender differences in respiratory development, associated risk factors, and treatment of respiratory symptoms must be taken into account.

  • Animal genomics – gene discovery and gene characterization Author: Rakan Naboulsi Link: http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-423787 Publication date: 2020-11-25 10:54

    This thesis involves two projects. The aim in the first project was to identify genomic regions associated with spontaneous autoimmune thyroiditis (SAT), which is a hereditary autoimmune disease that affects the obese strain (OS) of chicken, an animal model for human Hashimoto’s thyroiditis (HT). In the second project, we study ZBED6, a highly conserved protein unique to placental mammals. Here we explore the functional significance of ZBED6 in general, and its effect on the regulation of Igf2 and miR483 in specific.

     

    To identify genomic regions predisposing to SAT, a nine-generation intercross between OS and their wild ancestor, the red junglefowl (RJF), was previously generated. In paper I, we developed a cell-based assay to phenotype the F9 chickens by measuring the TSH levels in their serum. We found that 1) SAT is similar to HT in the sense that the serum-TSH levels increase in affected individuals, and 2) that TSH levels in SAT-affected chickens starts to increase after 20 weeks of age. In paper II, a whole genome sequencing experiment was performed to compare a healthy and a severely SAT-affected groups of chicken. This analysis revealed 12 genomic loci to be significantly different between the two groups.

     

    In the second project, we utilized a mouse myoblast cell line, C2C12, to characterize the function of ZBED6. In paper III, we affect ZBED6 function, by either mutating its binding site in Igf2 (Igf2dGGCT), or by completely knocking it out (Zbed6-/-). Functional analysis of the mutant cells revealed that ZBED6 overexpression induces cell cycle arrest and apoptosis, that ZBED6 directly affects mitochondrial activity, and that ZBED6 in myoblast cells mainly exerts its effect through regulating Igf2. In paper IV, we use ZBED6 knock-out and knock-in mice to investigate the effect of ZBED6 on the regulation of miRNA expression. We found that ZBED6 is not a general regulator for miRNA, with the exception of miR483, which exists in an intron of Igf2. Thereafter, we generated miR483-/- cells, using the Igf2dGGCT cell line. In this analysis we found that the main function of miR483 in myoblast cells is to regulate the expression of Igf2, and that ZBED6 partially regulates Igf2 through regulating miR483.

  • Deciphering molecular mechanisms in the evolution of new functions Author: Hind Abdalaal Link: http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-423421 Publication date: 2020-11-23 12:17

    The evolution of new genes and functions is considered to be a major contributor to biological diversity in organisms. Through de novo origination, “duplication and divergence”, and horizontal gene transfer, organisms can acquire new genetic material that can evolve to perform novel functions. In this thesis, we investigate how functional trade-offs, “gene duplication and amplification”, and neutral divergence contribute to the emergence of a new function from a preexisting gene.

     In Paper i, we investigated the ability of Salmonella enterica to compensate for the loss of peptide release factor 1 (RFI) and the potential of peptide release factor 2 (RF2) to gain a new function to replace RFI. The amplification of RF2 and accumulated mutations within RF2 were the main evolutionary routes by which the fitness cost was restored. However, further characterization of the evolved RF2 showed a toxic effect to the cell due to the termination on tryptophan codon (UGG). This evolutionary trade-off - which we named “collateral toxicity” - might present a serious barrier for evolving an efficient RF2 to replace RF1.

    In Paper ii, we determined whether we could evolve a generalist enzyme with two functions (HisA + TrpF) from the specialist enzyme HisA, which can only synthesize histidine. In a previous study, we showed that HisA evolved a TrpF activity through strong trade-off trajectories. Here, we developed a selection scheme in which we constantly selected for keeping the original function (HisA), while intermittently selecting for the new function (TrpF). Our results showed that all evolved lineages shared the same “stepping stone” mutations in the hisA gene, which enabled them to grow well in the absence of both histidine and tryptophan. Additional accumulated mutations in the hisA gene gave the strains an increased ability to grow without both amino acids, indicating that the HisA enzyme evolved to be an efficient generalist.  

    In Paper iii, we explored how differences between diverged orthologs influence evolvability. We generated artificial orthologs using a random mutagenesis approach. First, we screened for orthologs with a lower HisA activity and then selected for orthologs with a higher HisA activity; these steps were repeated in alternating rounds. We then tested the ability of each ortholog to evolve  TrpF activity. As expected, the orthologs showed varying abilities to evolve the new function. In particular, orthologs with higher HisA activity levels showed both a higher potential to evolve the new function and a higher TrpF activity when they acquired the new function. 

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