Small RNAs derived from lncRNA RNase MRP have gene-silencing activity relevant to human cartilage-hair hypoplasia

Post-transcriptional processing of some long non-coding RNAs (lncRNAs) reveals that they are a source of miRNAs. We show that the 268-nt non-coding RNA component of mitochondrial RNA processing endoribonuclease, (RNase MRP), is the source of at least two short (∼20 nt) RNAs designated RMRP-S1 and RMRP-S2, which function as miRNAs. Point mutations in RNase MRP cause human cartilage-hair hypoplasia (CHH), and several disease-causing mutations map to RMRP-S1 and -S2. SHAPE chemical probing identified two alternative secondary structures altered by disease mutations. RMRP-S1 and -S2 are significantly reduced in two fibroblast cell lines and a B-cell line derived from CHH patients. Tests of gene regulatory activity of RMRP-S1 and -S2 identified over 900 genes that were significantly regulated, of which over 75% were down-regulated, and 90% contained target sites with seed complements of RMRP-S1 and -S2 predominantly in their 3' UTRs. Pathway analysis identified regulated genes that function in skeletal development, hair development and hematopoietic cell differentiation including PTCH2 and SOX4 among others, linked to major CHH phenotypes. Also, genes associated with alternative RNA splicing, cell proliferation and differentiation were highly targeted. Therefore, alterations RMRP-S1 and -S2, caused by point mutations in RMRP, are strongly implicated in the molecular mechanism of CHH.

An anillin-Ect2 complex stabilizes central spindle microtubules at the cortex during cytokinesis

Cytokinesis occurs due to the RhoA-dependent ingression of an actomyosin ring. During anaphase, the Rho GEF (guanine nucleotide exchange factor) Ect2 is recruited to the central spindle via its interaction with MgcRacGAP/Cyk-4, and activates RhoA in the central plane of the cell. Ect2 also localizes to the cortex, where it has access to RhoA. The N-terminus of Ect2 binds to Cyk-4, and the C-terminus contains conserved DH (Dbl homologous) and PH (Pleckstrin Homology) domains with GEF activity. The PH domain is required for Ect2's cortical localization, but its molecular function is not known. In cultured human cells, we found that the PH domain interacts with anillin, a contractile ring protein that scaffolds actin and myosin and interacts with RhoA. The anillin-Ect2 interaction may require Ect2's association with lipids, since a novel mutation in the PH domain, which disrupts phospholipid association, weakens their interaction. An anillin-RacGAP50C (homologue of Cyk-4) complex was previously described in Drosophila, which may crosslink the central spindle to the cortex to stabilize the position of the contractile ring. Our data supports an analogous function for the anillin-Ect2 complex in human cells and one hypothesis is that this complex has functionally replaced the Drosophila anillin-RacGAP50C complex. Complexes between central spindle proteins and cortical proteins could regulate the position of the contractile ring by stabilizing microtubule-cortical interactions at the division plane to ensure the generation of active RhoA in a discrete zone.

Abstract 507: Autonomic intratumoral neo-nerves drive prostate cancer development and metastasis

Cancer cells seize and shape the healthy tissue microenvironment to promote their growth, invasion and metastasis. While multiple tumor-stroma interactions have been examined, the role of nerves in cancer progression remains unclear. Here, we show that autonomic intratumoral nerve development at the primary cancer site is a pivotal event that regulates prostate cancer initiation and its dissemination. We established an orthotopic luciferase-expressing (PC3luc) xenogeneic tumor model to track serially tumor initiation and dissemination. In addition, we used transgenic mice expressing c-Myc under the probasin promoter (AAR2/Pbsn-MYC) to evaluate the role of intratumor nerves in cancer progression from prostatic intraepithelial neoplasia (PIN) to invasive adenocarcinomas. Immunofluorescence analyses revealed that PC3luc tumors were invaded by numerous nerve fibers from the sympathetic (SNS) and parasympathetic nervous system (PNS). To investigate the role of SNS nerves in cancer progression, prostate glands were sympathectomized either chemically or surgically. Unexpectedly, adrenergic nerve ablation jeopardized PC3luc tumor cell survival at the primary site and delayed the emergence of PIN. In addition, we found that tumor formation was severely impaired in nu/nu mice lacking both β2-and β3-adrenergic receptors whereas it was slightly delayed in littermates deficient in a single adrenergic receptor. These results suggest that adrenergic signals delivered by intratumor nerve fibers are critical role for prostate cancer initiation. In the course of immunofluorescence analyses, we have noted a strong correlation between cholinergic fiber densities at the primary site and prostate cancer dissemination, suggesting a potential role for the PNS in tumor cell migration. To test this possibility, we mimicked endogenous cholinergic signal by treatment of mice with the non-selective cholinergic agonist carbachol, either alone or in combination with muscarinic receptor antagonists. Carbachol administration markedly increased invasion of lymph nodes and triggered tumor cell dissemination to distant organs (p < 0.05). This process was mediated specifically by M1R (encoded by Chrm1) since invasion and metastasis were inhibited after pharmacological blockade or genetic disruption of M1R in the stroma using nu/nu Chrm1-/- mice (p=0.05) or AAR2/Pbsn-MYC Chrm1-/- mice (p = 8 × 10-14). Consistent with a potential role of neo-nerve development in prostate cancer, quantitative immunofluorescence analyses revealed that human prostate invasive adenocarcinoma from primary biopsies exhibited robust infiltration of SNS and PNS nerve fibers by comparison with benign human prostatic hyperplasia. This study uncovers a dual role for the autonomic nervous system in cancer where SNS neo-nerves critically regulate the early-stage cancer development and, by contrast, PNS fibers promote cancer dissemination.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 507. doi:10.1158/1538-7445.AM2011-507

Bone marrow mesenchymal stem cells calibrate the innate immune tone by inducing monocyte emigration in response to circulating TLR-ligands (162.1)

Inflammatory (Ly6Chi CCR2+) monocytes provide defense against infections but also contribute to autoimmune diseases and atherosclerosis. Monocytes originate from the bone marrow and their entry into the bloodstream requires stimulation of CCR2 chemokine receptors by MCP1. How monocyte emigration from bone marrow is triggered by infections in anatomically remote sites remains unclear. We demonstrate that low concentrations of TLR ligands in the bloodstream drive CCR2-dependent emigration of monocytes from bone marrow. Bone marrow mesenchymal stem cells (MSCs) rapidly express MCP1 in response to circulating TLR ligands or systemic bacterial infection and induce inflammatory monocyte trafficking into the bloodstream. Targeted deletion of MCP1 from MSCs impaired monocyte emigration from bone marrow upon LPS stimulation and increased susceptibility to Listeria monocytogenes infection. Our findings suggest that bone marrow MSCs respond to circulating microbial molecules and regulate bloodstream monocyte frequencies by secreting MCP1 in proximity to bone marrow vascular sinuses.