ABSTRACT
The proliferation marker Ki67 has been attributed critical functions in maintaining mitotic chromosome morphology and heterochromatin organization during the cell cycle, indicating a potential role in developmental processes requiring rigid cell-cycle control. Here, we discovered that despite normal fecundity and organogenesis, germline deficiency in Ki67 resulted in substantial defects specifically in peripheral B and T lymphocytes. This was not due to impaired cell proliferation but rather to early lymphopoiesis at specific stages where antigen-receptor gene rearrangements occurred. We identified that Ki67 was required for normal global chromatin accessibility involving regulatory regions of genes critical for checkpoint stages in B cell lymphopoiesis. In line with this, mRNA expression of Rag1 was diminished and gene rearrangement was less efficient in the absence of Ki67. Transgenes encoding productively rearranged immunoglobulin heavy and light chains complemented Ki67 deficiency, completely rescuing early B cell development. Collectively, these results identify a unique contribution from Ki67 to somatic antigen-receptor gene rearrangement during lymphopoiesis.
Subject(s)
B-Lymphocytes , Chromatin , Ki-67 Antigen , Ki-67 Antigen/metabolism , Animals , Chromatin/metabolism , Chromatin/genetics , B-Lymphocytes/metabolism , B-Lymphocytes/immunology , Lymphopoiesis/genetics , Receptors, Antigen, B-Cell/metabolism , Receptors, Antigen, B-Cell/genetics , Mice , Gene Rearrangement , Homeodomain Proteins/genetics , Homeodomain Proteins/metabolism , T-Lymphocytes/metabolism , T-Lymphocytes/immunology , Mice, Inbred C57BL , Cell Proliferation/geneticsABSTRACT
Several lines of study suggest that peripheral metabolism of amyloid beta (Aß) is associated with risk for Alzheimer disease (AD). In blood, greater than 90% of Aß is complexed as an apolipoprotein, raising the possibility of a lipoprotein-mediated axis for AD risk. In this study, we report that genetic modification of C57BL/6J mice engineered to synthesise human Aß only in liver (hepatocyte-specific human amyloid (HSHA) strain) has marked neurodegeneration concomitant with capillary dysfunction, parenchymal extravasation of lipoprotein-Aß, and neurovascular inflammation. Moreover, the HSHA mice showed impaired performance in the passive avoidance test, suggesting impairment in hippocampal-dependent learning. Transmission electron microscopy shows marked neurovascular disruption in HSHA mice. This study provides causal evidence of a lipoprotein-Aß /capillary axis for onset and progression of a neurodegenerative process.
