Lack of collagen alpha 6(IV) chain in mice does not cause severe-to-profound hearing loss or cochlear malformation, a distinct phenotype from nonsyndromic hearing loss with COL4A6 missense mutation

Congenital hearing loss affects 1 in every 1000 births, with genetic mutations contributing to more than 50% of all cases. X-linked nonsyndromic hereditary hearing loss is associated with six loci (DFNX1-6) and five genes. Recently, the missense mutation (c.1771G>A, p.Gly591Ser) in COL4A6, encoding the basement membrane (BM) collagen alpha 6(IV) chain, was shown to be associated with X-linked congenital nonsyndromic hearing loss with cochlear malformation. However, the mechanism by which the COL4A6 mutation impacts hereditary hearing loss has not yet been elucidated. Herein, we investigated Col4a6 knockout (KO) effects on hearing function and cochlear formation in mice. Immunohistochemistry showed that the collagen alpha 6(IV) chain was distributed throughout the mouse cochlea within subepithelial BMs underlying the interdental cells, inner sulcus cells, basilar membrane, outer sulcus cells, root cells, Reissner's membrane, and perivascular BMs in the spiral limbus, spiral ligament, and stria vascularis. However, the click-evoked auditory brainstem response analysis did not show significant changes in the hearing threshold of Col4a6 KO mice compared with wild-type (WT) mice with the same genetic background. In addition, the cochlear structures of Col4a6 KO mice did not exhibit morphological alterations, according to the results of high-resolution micro-computed tomography and histology. Hence, loss of Col4a6 gene expression in mice showed normal click ABR thresholds and normal cochlear formation, which differs from humans with the COL4A6 missense mutation c.1771G>A, p.Gly591Ser. Therefore, the deleterious effects in the auditory system caused by the missense mutation in COL4A6 are likely due to the dominant-negative effects of the alpha 6(IV) chain and/or alpha 5 alpha 6 alpha 5(IV) heterotrimer with an aberrant structure that would not occur in cases with loss of gene expression

Modeling of the inherence of feedback regulation and stem cell behavior in granulopoiesis

金沢大学医学部附属病院小児科Long-standing controversies in hematopoiesis are the mechanisms of self-maintenance and differentiation commitment of the hematopoietic stem cells (HSC), and regulation of the peripheral control of hematopoiesis. In the present study, we have applied a threedimensional cellular automaton (CA) model to granulopoiesis in order to identify the internally generative theoretical relationship between microscopic mechanisms and macroscopic behavior of hematopoietic processes. The number of mitotic event of the cells in a proliferating phase, the transit time of each of 15 differential stages from HSC to mature cells (designated as Tl to Tl 5, and Tdup for HSC duplication time), and the neighborhood rules for HSC self-renewal were incorporated in this model system as analytical parameters. Homeostatic granulopoiesis was achieved when the following inequalities for the transit times were fulfilled: Tl > Z Tn (n = 2 to 15) and Tdup > 1/2 Tl. Importantly, stabilization of the cell production was induced in a negative feedback manner following external perturbation of the peripheral granulocyte numbers. The Tdup of individual HSC was dramatically fluctuated to produce the offspring responding to this perturbation. A single cell kinetic analysis demonstrated that symmetrical or asymmetrical cell division of the HSC was recruited in a transitional manner resulting in generation of the regulatory effect on the lineage-commitment processes. The inherence of feedback regulation would be a characteristic feature of the emergent dynamical property in the hematopoietic system. The CA modeling will provide the framework to analyze the behavior of HSC and to understand abnormal kinetics of the cells such as minimal residual disease in the treatment of leukemias

Collagen XVIII deposition in the basement membrane zone beneath the newly forming epidermis during wound healing in mice

Abstract The basement membrane (BM) is composed of various extracellular molecules and regulates tissue regeneration and maintenance. Here, we demonstrate that collagen XVIII was spatiotemporally expressed in the BM during skin wound healing in a mouse excisional wound-splinting model. Re-epithelialization was detected at days 3 and 6 post-wounding. The ultrastructure of epidermal BM was discontinuous at day 3, whereas on day 6 a continuous BM was observed in the region proximal to the wound edge. Immunohistochemistry demonstrated that collagen XVIII was deposited in the BM zone beneath newly forming epidermis in day 3 and 6 wounds. Laminin-332, known to be the earliest BM component appearing in wounds, was colocalized with collagen XVIII in the epidermal BM zone at days 3 and 6. The deposition of α1(IV) collagen and nidogen-1 in the epidermal BM zone occurred later than that of collagen XVIII. We also observed the short isoform of collagen XVIII in the epidermal BM zone at day 3 post-wounding. Collectively, our results suggested that collagen XVIII plays a role in the formation of the dermal-epidermal junction during re-epithelialization, and that it is the short isoform that is involved in the early phase of re-epithelialization