Daniel S. Greenspan

Mitochondrial dysfunction has been linked to both idiopathic and familial forms of Parkinson’s disease (PD). We have previously identified RCC1-like (RCC1L) as a protein of the inner mitochondrial membrane important to mitochondrial fusion. Herein, to test whether deficits in RCC1L mitochondrial function might be involved in PD pathology, we have selectively ablated the Rcc1l gene in the dopaminergic (DA) neurons of mice. A PD-like phenotype resulted that includes progressive movement abnormalities, paralleled by progressive degeneration of the nigrostriatal tract. Experimental and control groups were examined at 2, 3-4, and 5-6 months of age. Animals were tested in the open field task to quantify anxiety, exploratory drive, locomotion, and immobility; and in the cylinder test to quantify rearing behavior. Beginning at 3-4 months, both female and male Rcc1l knockout mice show rigid muscles and resting tremor, kyphosis and a growth deficit compared with heterozygous or wild type littermate controls. Rcc1l knockout mice begin showing locomotor impairments at 3-4 months, which progress until 5-6 months of age, at which age the Rcc1l knockout mice die. The progressive motor impairments were associated with progressive and significantly reduced tyrosine hydroxylase immunoreactivity in the substantia nigra pars compacta (SNc), and dramatic loss of nigral DA projections in the striatum. Dystrophic spherical mitochondria are apparent in the soma of SNc neurons in Rcc1l knockout mice as early as 1.5-2.5 months of age and become progressively more pronounced until 5-6 months. Together, the results reveal the RCC1L protein to be essential to in vivo mitochondrial function in DA neurons. Further characterization of this mouse model will determine whether it represents a new model for in vivo study of PD, and the putative role of the human RCC1L gene as a risk factor that might increase PD occurrence and severity in humans.

Background. Individuals harbor preexisting HLA−DR/DQ−restricted responses to collagen type V (ColV) mediated by Th17 cells under Treg control, both specific to peptides that bind to inherited HLA class II antigens. Yet after transplant, the donor−DR type somehow influences graft outcome. We hypothesized that, long after a lung or heart allograft, the particular HLA−DR type of the mismatched transplant donor transforms the specificity of the “anti−self” response. This could explain why, over long term, certain donor DRs could be more immunogenic than others. Methods. We analyzed 7 HLA−DR15^neg patients who had received a lung allograft from a DR15⁺ donor. To determine the mechanism of acquired specificity in self−reactivity, we analyzed the kinetics of DR1 (host) and DR15 (donor) peptide restriction in a heart transplant model using DR−transgenic mice. Results. Beyond 1.5 years post-lung transplant, all patients tested had acquired DR15−restricted immune responses to ColV peptides. These responses were either unrestrained Th17 type (n = 4) or Th17 controlled by Treg arising early (7 y) after transplant (n = 4). Treg suppression via conventional (transforming growth factor−β [TGF−β]) and extracellular vesicle−associated (IL−35) cytokines correlated with superior outcomes. Naïve DR1 and DR15 transgenic mice had preexisting DR−restricted responses, exclusively to ColV fragments containing DR1− or DR15−binding peptides. When HLA−DR1 transgenic recipients of a HLA−DR15 heart developed ColV reactivity post-transplant, mice that acutely rejected (20–25 d) responded only to the DR1−restricted ColV peptide epitope. In animals whose grafts survived long term, we could detect acquisition of DR from the transplant donor onto the surface of recipient dendritic cells, and immune responses against a donor DR15–restricted ColV peptide. Conclusions. These results might explain how certain donor HLA−DR types redirect host immune responses to novel peptides of critical self−antigens. Unless regulated, such responses may predispose the allograft to chronic rejection.

This article corrects: Synergistic effect of PCPE1 and sFRP2 on the processing of procollagens via BMP1, Volume 593, Issue 1, 119–127. Article first published 09 November 2018. https://doi.org/10.1002/1873-3468.13291Dr Daniel S. Greenspan was inadvertently omitted from the list of authors in the original publication. The correct list of authors is as shown above.Dr Daniel S. Greenspan affiliation and contact details are as follows:Department of Cell and Regenerative Biology, University of Wisconsin, Room 4503, WIMRII, 1111 Highland Ave, Madison, WI 53705, dsgreens@wisc.edu

Procollagen C-proteinase enhancer 1 (PCPE-1) has been characterized as a protein capable of enhancing the activity of bone morphogenetic protein 1/tolloid-like proteinases in the biosynthetic processing of C-propeptides from procollagens I–III. This processing step is thought necessary to the formation of collagen I–III monomers capable of forming fibrils. Thus, PCPE-1 is predicted to play an important role in scarring, as scar tissue is predominantly composed of fibrillar collagen. Corneal scarring is of great clinical importance, as it leads to loss of visual acuity and, in severe cases, blindness. Here, we investigate a possible role for PCPE-1 in corneal scarring. Although differences in corneal opacity associated with scarring following injury of Pcolce ^−/− and wild-type (WT) mice using full-thickness excision or alkali burn models of corneal injury were not grossly apparent, differences in procollagen I processing levels between Pcolce ^−/− and WT primary corneal keratocytes were consistent with a role for PCPE-1 in corneal collagen deposition. An unexpected finding was that neoangiogenesis, which follows alkali burn cornea injury, was strikingly increased in Pcolce ^−/− cornea, compared to WT. A series of aortic ring assays confirmed the anti-angiogenic effects of PCPE-1. Another unexpected finding was of abnormalities of epithelial basement membrane and of re-epithelialization following Pcolce ^−/− corneal injury. Thus, PCPE-1 appears to be of importance as an anti-angiogenic factor and in re-epithelialization following injury in cornea and perhaps in other tissues as well.

Pericellular α3(V) collagen can affect the functioning of cells, such as adipocytes and pancreatic β cells. Here we show that α3(V) chains are an abundant product of normal mammary gland basal cells, and that α3(V) ablation in a mouse mammary tumour model inhibits mammary tumour progression by reducing the proliferative potential of tumour cells. These effects are shown to be primarily cell autonomous, from loss of α3(V) chains normally produced by tumour cells, in which they affect growth by enhancing the ability of cell surface proteoglycan glypican-1 to act as a co-receptor for FGF2. Thus, a mechanism is presented for microenvironmental influence on tumour growth. α3(V) chains are produced in both basal-like and luminal human breast tumours, and its expression levels are tightly coupled with those of glypican-1 across breast cancer types. Evidence indicates α3(V) chains as potential targets for inhibiting tumour growth and as markers of oncogenic transformation.

Mutations in bone morphogenetic protein 1 (BMP1) in humans or deletion of BMP1 and related protease tolloid like 1 (TLL1) in mice lead to osteogenesis imperfecta (OI). Here, we show progressive periodontal defects in mice in which both BMP1 and TLL1 have been conditionally ablated, including malformed periodontal ligament (PDL) (recently shown to play key roles in normal alveolar bone formation), significant loss in alveolar bone mass (P < 0.01), and a sharp reduction in cellular cementum. Molecular mechanism studies revealed a dramatic increase in the uncleaved precursor of type I collagen (procollagen I) and a reduction in dentin matrix protein 1 (DMP1), which is partially responsible for defects in extracellular matrix (ECM) formation and mineralization. We also showed a marked increase in the expression of matrix metallopeptidase 13 (MMP13) and tartrate-resistant acid phosphatase (TRAP), leading to an acceleration in periodontal breakdown. Finally, we demonstrated that systemic application of antibiotics significantly improved the alveolar bone and PDL damage of the knockdown phenotype, which are thus shown to be partially secondary to pathogen-induced inflammation. Together, identification of the novel roles of BMP1 and TLL1 in maintaining homeostasis of periodontal formation, partly via biosynthetic processing of procollagen I and DMP1, provides novel insights into key contributions of the extracellular matrix environment to periodontal homeostasis and contributes toward understanding of the pathology of periodontitis.