Faculty Bibliography

Hsa-miR-33a and hsa-miR-33b, intronic microRNAs (miRNAs) located within the sterol regulatory element-binding protein (Srebp)-2 and -1 genes, respectively, have recently been shown to regulate lipid homeostasis in concert with their host genes. Although the functional role of miR-33a/b has been highly investigated, the role of their passenger strands, miR-33a*/b*, remains unclear. Here, we demonstrate that miR-33a*/b* accumulate to steady-state levels in human, mouse and non-human primate tissues and share a similar lipid metabolism target gene network as their sister strands. Analogous to miR-33, miR-33* represses key enzymes involved in cholesterol efflux (ABCA1, NPC1), fatty acid metabolism (CROT, CPT1a) and insulin signaling (IRS2). Moreover, miR-33* also targets key transcriptional regulators of lipid metabolism, including SRC1, SRC3, NFYC, and RIP140. Importantly, inhibition of either miR-33 or miR-33* rescues target gene expression in cells over-expressing pre-miR-33. Consistent with this, over-expression of miR-33* reduces fatty acid oxidation in human hepatic cells. Altogether, these data support a regulatory role for the miRNA* species and suggest that miR-33 regulates lipid metabolism through both arms of the miR-33/miR-33* duplex.

Parathyroid Hormone related Protein (PTHrP) is a critical regulator of mammary gland morphogenesis in the mouse embryo. Loss of PTHrP, or its receptor, PTHR1, results in arrested mammary buds at day 15 of embryonic development (E15). In contrast, overexpression of PTHrP converts the ventral epidermis into hairless nipple skin. PTHrP signaling appears to be critical for mammary mesenchyme specification, which in turn maintains mammary epithelial identity, directs bud outgrowth, disrupts the male mammary rudiment and specifies the formation of the nipple. In the embryonic mammary bud, PTHrP exerts its effects on morphogenesis, in part, through epithelial-stromal crosstalk mediated by Wnt and BMP signaling. Recently, PTHLH has been identified as a strong candidate for a novel breast cancer susceptibility locus, although PTHrP's role in breast cancer has not been clearly defined. The effects of PTHrP on the growth of the embryonic mammary rudiment and its invasion into the dermis may, in turn, have connections to the role of PTHrP in breast cancer.

OBJECTIVE: To study the infection status of Leptospira in rodents on Heixiazi island Heilongjiang province in 2011. METHODS: A total of 356 rodents were captured by night trap on the Heixiazi island from April to October 2011. The kidney tissue samples were collected by asepsis operation and the genomic DNA were extracted from them. Leptospira strains were confirmed by polymerase chain reaction(PCR) amplification of the 482 bp 23 S rDNA gene. Fifteen PCR products selected by the month were purified and sequenced by the methods of Sanger dideoxy, the sequences then compared with other Leptospira strains in Genebank, and phylogenetic analyses were drafted by software Mega 4.0. RESULTS: Among 356 rodents, the dominant species were Clethrionomys rutilus (39.3%, 140/356) and Apodemus agrarius (36.0%, 128/356). The infection rate of Leptospira was 11.0%, with 39 rodent samples detected positive. All the rodent species were infected except for Rattus norvegicus. The infection rate was 9.4% (12/128) in Apodemus agrarius, 12.9%(18/140) in Clethrionomys rutilus, 10.8%(7/65) in Microtus fortis Buchner. No significant difference was found between the infection rate and the species of rodents by chi square test(chi(2) = 1.92, P > 0.05). Among months, the infection rate was 5.6% (4/72) in May, 8.8% (5/57) in June, 12.8% (5/39) in July, 9.8% (5/51) in August, 33.3% (11/33) in September, 22.5% (9/40) in October,but no infection in April. There was significant difference in infection in different months (chi(2) = 32.92, P < 0.05). All the Leptospira in rodents on the Heixiazi island were in the same phylogenetic branch with a high similarity of 97.1%-99.6%, close with the Australia strain U90865 by the similarity above 96.3%. CONCLUSION: Leptospira is probably prevalent in rodents on the Heixiazi island, and the phylogene of the strains were similar. The infection rate in rodents was significantly different in months but not in hosts.

Inhibitor of apoptosis (IAP) proteins play pivotal roles in cellular survival by blocking apoptosis, modulating signal transduction, and affecting cellular proliferation. Through their interactions with inducers and effectors of apoptosis IAP proteins can effectively suppress apoptosis triggered by diverse stimuli including death receptor signaling, irradiation, chemotherapeutic agents, or growth factor withdrawal. Evasion of apoptosis, in part due to the action of IAP proteins, enhances resistance of cancer cells to treatment with chemotherapeutic agents and contributes to tumor progression. Additionally, IAP genes are known to be subject to amplification, mutation, and chromosomal translocation in human malignancies and autoimmune diseases. In this review we will discuss the role of IAP proteins in cancer and the development of antagonists targeting IAP proteins for cancer treatment.

In this issue of Neuron, Griciuc et al. (2013) investigate the Alzheimer's disease risk gene, CD33. AD brains have increased CD33 and CD33-positive microglia. Mice lacking CD33 have less AD pathology suggesting a role of microglia for Abeta clearance and development of future therapies.

Measurement of telomere length currently requires a large population of cells, which masks telomere length heterogeneity in single cells, or requires FISH in metaphase arrested cells, posing technical challenges. A practical method for measuring telomere length in single cells has been lacking. We established a simple and robust approach for single-cell telomere length measurement (SCT-pqPCR). We first optimized a multiplex preamplification specific for telomeres and reference genes from individual cells, such that the amplicon provides a consistent ratio (T/R) of telomeres (T) to the reference genes (R) by quantitative PCR (qPCR). The average T/R ratio of multiple single cells corresponded closely to that of a given cell population measured by regular qPCR, and correlated with those of telomere restriction fragments (TRF) and quantitative FISH measurements. Furthermore, SCT-pqPCR detected the telomere length for quiescent cells that are inaccessible by quantitative FISH. The reliability of SCT-pqPCR also was confirmed using sister cells from two cell embryos. Telomere length heterogeneity was identified by SCT-pqPCR among cells of various human and mouse cell types. We found that the T/R values of human fibroblasts at later passages and from old donors were lower and more heterogeneous than those of early passages and from young donors, that cancer cell lines show heterogeneous telomere lengths, that human oocytes and polar bodies have nearly identical telomere lengths, and that the telomere lengths progressively increase from the zygote, two-cell to four-cell embryo. This method will facilitate understanding of telomere heterogeneity and its role in tumorigenesis, aging, and associated diseases.

The plasma membrane and all membrane-bound organelles except for the Golgi and endoplasmic reticulum (ER) are equipped with pattern-recognition molecules to sense microbes or their products and induce innate immunity for host defense. Here, we report that inositol-requiring-1alpha (IRE1alpha), an ER protein that signals in the unfolded protein response (UPR), is activated to induce inflammation by binding a portion of cholera toxin as it co-opts the ER to cause disease. Other known UPR transducers, including the IRE1alpha-dependent transcription factor XBP1, are dispensable for this signaling. The inflammatory response depends instead on the RNase activity of IRE1alpha to degrade endogenous mRNA, a process termed regulated IRE1alpha-dependent decay (RIDD) of mRNA. The mRNA fragments produced engage retinoic-acid inducible gene 1 (RIG-I), a cytosolic sensor of RNA viruses, to activate NF-kappaB and interferon pathways. We propose IRE1alpha provides for a generalized mechanism of innate immune surveillance originating within the ER lumen.

Atherosclerosis (also known as arteriosclerotic vascular disease) is a chronic inflammatory disease of the arterial wall, characterized by the formation of lipid-laden lesions. The activation of endothelial cells at atherosclerotic lesion-prone sites in the arterial tree results in the up-regulation of cell adhesion molecules and chemokines, which mediate the recruitment of circulating monocytes. Accumulation of monocytes and monocyte-derived phagocytes in the wall of large arteries leads to chronic inflammation and the development and progression of atherosclerosis. The lesion experiences the following steps: foam cell formation, fatty streak accumulation, migration and proliferation of vascular smooth muscle cells, and fibrous cap formation. Finally, the rupture of the unstable fibrous cap causes thrombosis in complications of advanced lesions that lead to unstable coronary syndromes, myocardial infarction and stroke. MicroRNAs have recently emerged as a novel class of gene regulators at the post-transcriptional level. Several functions of vascular cells, such as cell differentiation, contraction, migration, proliferation and inflammation that are involved in angiogenesis, neointimal formation and lipid metabolism underlying various vascular diseases, have been found to be regulated by microRNAs and are described in the present review as well as their potential therapeutic application.

RATIONALE: Endothelial activation and apoptosis release membrane-shed microparticles (EMP) that emerge as important biological effectors. OBJECTIVE: Because laminar shear stress (SS) is a major physiological regulator of endothelial survival, we tested the hypothesis that SS regulates EMP release. METHODS AND RESULTS: EMP levels were quantified by flow cytometry in medium of endothelial cells subjected to low or high SS (2 and 20 dyne/cm(2)). EMP levels augmented with time in low SS conditions compared with high SS conditions. This effect was sensitive to extracellular signal-regulated protein kinases 1 and 2 (ERK1/2) and Rho kinases inhibitors but unaffected by caspase inhibitors. Low SS-stimulated EMP release was associated with increased endothelial Rho kinases and ERK1/2 activities and cytoskeletal reorganization. Overexpression of constitutively active RhoA stimulated EMP release under high SS. We also examined the effect of nitric oxide (NO) in mediating SS effects. L-NG-nitroarginine methyl ester (L-NAME), but not D-NG-nitroarginine methyl ester, increased high SS-induced EMP levels by 3-fold, whereas the NO donor S-nitroso-N-acetyl-D,L-penicillamine (SNAP) decreased it. L-NAME and SNAP did not affect Rho kinases and ERK1/2 activities. Then, we investigated NO effect on membrane remodeling because microparticle release is abolished in ABCA1-deficient cells. ABCA1 expression, which was greater under low SS than under high SS, was augmented by L-NAME under high SS and decreased by SNAP under low SS conditions. CONCLUSIONS: Altogether, these results demonstrate that sustained atheroprone low SS stimulates EMP release through activation of Rho kinases and ERK1/2 pathways, whereas atheroprotective high SS limits EMP release in a NO-dependent regulation of ABCA1 expression and of cytoskeletal reorganization. These findings, therefore, identify endothelial SS as a physiological regulator of microparticle release.