Altered nuclear architecture in blood cells from Huntington's disease patients.

BACKGROUND: Cell nuclear architecture has been explored in cancer and laminopathies but not in neurodegenerative disorders. Huntington's disease (HD) is a neurodegenerative disorder that leads to neuronal death. Chromosome-wide changes in gene expression have been reported in HD, not only in the brain but also in peripheral blood cells, but whether this translates into nuclear and chromosome architecture alterations has not yet been studied. METHODS: We investigate nuclear structure and chromosome organization in HD blood cells using fluorescence in situ hybridization in ultrathin cryosections (cryoFISH), coupled with machine learning image analysis to evaluate size, distribution, and morphology of nuclei and chromosomes. Four chromosomes were analyzed based on up- or downregulation of gene expression in HD. RESULTS: We show that blood cells from HD patients display increased nuclear size and filamentary shape, increased size of gene-rich chromosome 19, decreased filamentary shape of gene-rich chromosome 22, and a more radially centralized position for chromosome 19, whereas chromosomes 4 and 5 do not show detectable differences. CONCLUSIONS: We identify gross changes in nuclear architecture and chromosome organization associated with HD in blood. This adds a new layer of information onto disrupting mechanisms in HD and increases the potential of using blood to survey HD.

Hypoxic Environment Promotes Barrier Formation in Human Intestinal Epithelial Cells through Regulation of MicroRNA 320a Expression.

Intestinal epithelial cells (IECs) are exposed to the low-oxygen environment present in the lumen of the gut. These hypoxic conditions on one hand are fundamental for the survival of the commensal microbiota and, on the other hand, favor the formation of a selective semipermeable barrier, allowing IECs to transport essential nutrients/water while keeping the sterile internal compartments separated from the lumen containing commensals. The hypoxia-inducible factor (HIF) complex, which allows cells to respond and adapt to fluctuations in oxygen levels, has been described as a key regulator in maintaining IEC barrier function by regulating their tight junction integrity. In this study, we sought to better evaluate the mechanisms by which low oxygen conditions impact the barrier function of human IECs. By profiling miRNA expression in IECs under hypoxia, we identified microRNA 320a (miRNA-320a) as a novel barrier formation regulator. Using pharmacological inhibitors and short hairpin RNA-mediated silencing, we could demonstrate that expression of this microRNA (miRNA) was HIF dependent. Importantly, using overexpression and knockdown approaches of miRNA-320a, we could confirm its direct role in the regulation of barrier function in human IECs. These results reveal an important link between miRNA expression and barrier integrity, providing a novel insight into mechanisms of hypoxia-driven epithelial homeostasis.

CDK1 and PLK1 coordinate the disassembly and reassembly of the nuclear envelope in vertebrate mitosis.

Micronuclei (MN) arise from chromosomes or fragments that fail to be incorporated into the primary nucleus after cell division. These structures are a major source of genetic instability caused by DNA repair and replication defects coupled to aberrant Nuclear Envelope (NE). These problems ultimately lead to a spectrum of chromosome rearrangements called chromothripsis, a phenomenon that is a hallmark of several cancers. Despite its importance, the molecular mechanism at the origin of this instability is still not understood. Here we show that lagging chromatin, although it can efficiently assemble Lamin A/C, always fails to recruit Nuclear Pore Complexes (NPCs) proteins and that Polo-Like Kinase (PLK1) negatively regulates NPC assembly. We also provide evidence for the requirement of PLK1 activity for the disassembly of NPCs, but not Lamina A/C, at mitotic entry. Altogether this study reveals the existence of independent regulatory pathways for Lamin A/C and NPC reorganization during mitosis where Lamin A/C targeting to the chromatin is controlled by CDK1 activity (a clock-based model) while the NPC loading is also spatially monitored by PLK1.