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Background: Astrocytes play a central role in maintaining brain energy metabolism, but are also tightly connected to the pathogenesis of Alzheimer's disease (AD). Our previous studies demonstrate that inflammatory astrocytes accumulate large amounts of aggregated amyloid-beta (A beta). However, in which way these A beta deposits influence their energy production remain unclear. Methods: The aim of the present study was to investigate how A beta pathology in astrocytes affects their mitochondria functionality and overall energy metabolism. For this purpose, human induced pluripotent cell (hiPSC)-derived astrocytes were exposed to sonicated A beta(42) fibrils for 7 days and analyzed over time using different experimental approaches. Results: Our results show that to maintain stable energy production, the astrocytes initially increased their mitochondrial fusion, but eventually the A beta-mediated stress led to abnormal mitochondrial swelling and excessive fission. Moreover, we detected increased levels of phosphorylated DRP-1 in the A beta-exposed astrocytes, which co-localized with lipid droplets. Analysis of ATP levels, when blocking certain stages of the energy pathways, indicated a metabolic shift to peroxisomal-based fatty acid beta-oxidation and glycolysis. Conclusions: Taken together, our data conclude that A beta pathology profoundly affects human astrocytes and changes their entire energy metabolism, which could result in disturbed brain homeostasis and aggravated disease progression., De två första författarna delar förstaförfattarskapet.

Spinal cord ependymal cells display neural stem cell properties in vitro and generate scar-forming astrocytes and remyelinating oligodendrocytes after injury. We report that ependymal cells are functionally heterogeneous and identify a small subpopulation (8% of ependymal cells and 0.1% of all cells in a spinal cord segment), which we denote ependymal A (EpA) cells, that accounts for the in vitro stem cell potential in the adult spinal cord. After spinal cord injury, EpA cells undergo self-renewing cell division as they give rise to differentiated progeny. Single-cell transcriptome analysis revealed a loss of ependymal cell gene expression programs as EpA cells gained signaling entropy and dedifferentiated to a stem-cell-like transcriptional state after an injury. We conclude that EpA cells are highly differentiated cells that can revert to a stem cell state and constitute a therapeutic target for spinal cord repair., QC 20220329

Ageing severely affects the chromosome segregation process in human oocytes resulting in aneuploidy, infertility and developmental disorders. A considerable amount of segregation errors in humans are introduced at the second meiotic division. We have here compared the chromosome segregation process in young adult and aged female mice during the second meiotic division. More than half of the oocytes in aged mice displayed chromosome segregation irregularities at anaphase II, resulting in dramatically increased level of aneuploidy in haploid gametes, from 4% in young adult mice to 30% in aged mice. We find that the post-metaphase II process that efficiently corrects aberrant kinetochore-microtubule attachments in oocytes in young adult mice is approximately 10-fold less efficient in aged mice, in particular affecting chromosomes that show small inter-centromere distances at the metaphase II stage in aged mice. Our results reveal that post-metaphase II processes have critical impact on age-dependent aneuploidy in mammalian eggs., QC 20230228

The sodium pump, Na,K-ATPase, is an integral plasma membrane protein, expressed in all eukaryotic cells. Na,K-ATPase transforms chemical energy from ATP into a gradient of Na+ and K+ over the plasma membrane by actively exporting three Na+ ions and importing two K+ ions for each hydrolyzed ATP. It is responsible for maintenance of the transmembrane Na+ gradient and is the major determinant of the membrane potential. It provides the driving force for all Na+-coupled transport processes, thereby controlling essential functions in the cell. Na,K-ATPase is formed by three subunits alpha/beta/FXYD, where alpha is the catalytic ion-transporting subunit, beta is a regulatory subunit and FXYD is accessory. Self-interaction and oligomerization of the Na,K-ATPase alpha/beta heterodimer in cell membranes has been proposed and discussed for a long time but is still an open question. Here we have used a combination of FRET and Fluorescence Correlation Spectroscopy, FRET-FCS, in order to detect oligomers of Na,K-ATPase. Compared to conventional cross-correlation FCCS, FRET-FCS is one to two orders of magnitude more sensitive when detecting oligomers. Moreover, FRET-FCS is inherently insensitive to unbalanced labeling, which is a great advantage during live cell measurements. We hypothesized that Na,K-ATPase can exist in a higher order oligomeric state and demonstrate the use of FRET-FCS to test this hypothesis We have introduced fluorescent labels by using expression of non-canonical amino acid modified beta subunits. The FRET pair Alexa488 and Alexa647 was directly conjugated to the beta subunits using selective click chemistry. Conventional FCS measurements of labeled cells revealed the absolute density of labeled and unlabeled Na,K-ATPase. With FRET-FCS we could observe FRET signals and FCS curves demonstrating the existence of oligomers. Positive controls for the FRET-FCS measurements were constructed by labeling alpha subunits with Alexa488 and beta subunits with Alexa647. F, QC 20220520