The aim of this thesis was to identify in the human blood transcriptome, relevant pathways and potential biomarker profiles that associate with chronological age and discriminate between __healthy... Show moreThe aim of this thesis was to identify in the human blood transcriptome, relevant pathways and potential biomarker profiles that associate with chronological age and discriminate between __healthy agers__ from long-lived families and normative ageing controls. Such profiles may harbor determinants of the biological ageing rate. We studied genome-wide gene expression profiles in blood of members of the Leiden Longevity Study (LLS) and replicated our findings by extended sampling within the unique LLS cohort. The findings of the exploratory analysis prompted us to investigate multiple genes in the IL7R and MTOR pathways for association with familial longevity. The results obtained by examining mRNA from blood samples brought us to study mTOR protein levels and signalling in primary skin fibroblasts from the corresponding donors in the LLS. Finally, to discover robust, biologically relevant gene networks as markers of chronological ageing in larger sample sizes, we performed an explorative network-based meta-analysis on large publicly available transcriptomic datasets. We have identified several networks, pathways and candidate genes potentially marking the biological age and the rate of ageing Show less
Cellulose makes up one of the most abundant renewable materials, present in all kinds of plant biomass (Pauly and Keegstra 2010). However, to be able to utilize the cellulose as feedstock, it needs... Show moreCellulose makes up one of the most abundant renewable materials, present in all kinds of plant biomass (Pauly and Keegstra 2010). However, to be able to utilize the cellulose as feedstock, it needs to be separated from lignin which cements the cellulose and hemi-cellulose fibers. Lignolytic peroxidases can be produced by Aspergillus niger, and its production was found to be improved by heme supplementation, suggesting a limiting effect of this co-factor during heterologous expression. The research described in this thesis explores fungal heme biosynthesis and its regulation by means of heme deficient mutant strains and overexpression strains of heme biosynthesis genes or corroborated iron metabolism with the final aim to increase the available intracellular heme for peroxidase production. Using heme deficient strains, we demonstrated that A. niger is capable of heme uptake and utilzation and that siroheme synthesis derives from the first half of the heme biosynthesis pathway as well. The tight regulation on heme biosynthesis on transcription and (post)translational level prohibits large changes in heme content, and indicated a bottleneck on the level of ferrochelatase and possible uroporphyrinogen III decarboxylase and coproporphyrinogen III oxidase and questions whether A. niger would be the most suitable host for heterologous peroxidase production. Show less
