dpy-18 encodes an alpha-subunit of prolyl-4-hydroxylase in caenorhabditis elegans

Collagen is an extracellular matrix (ECM) component encoded by a large multigene family in multicellular animals. Procollagen is post-translationally modified by prolyl-4-hydroxylase (EC 1.14.11.2) before secretion and participation in ECM formation. Therefore, collagen processing and regulation can be studied by examining this required interaction of prolyl-4-hydroxylase with procollagen. High-resolution polymorphism mapping was used to place the Caenorhabditis elegans dpy-18 gene on the physical map, and we show that it encodes a prolyl-4-hydroxylase alpha catalytic subunit. The Dpy phenotype of dpy-18(e364) amber mutants is more severe when this mutation is in trans to the noncomplementing deficiency tDf7, while the dpy-18(e499) deletion mutant exhibits the same phenotype as dpy-18(e499)/tDf7. Furthermore, dpy-18 RNA interference (RNAi) in wild-type worms results in Dpy progeny, while dpy-18 (RNAi) in dpy-18(e499) mutants does not alter the Dpy phenotype of their progeny. These observations suggest that the dpy-18 null phenotype is Dpy. A dpy-18::gfp promoter fusion construct is expressed throughout the hypodermis within the cells that abundantly produce the cuticle collagens, as well as in certain head and posterior neurons. While prolyl-4-hydroxylase has been studied extensively by biochemical techniques, this is the first report of a mutationally defined prolyl-4-hydroxylase in any animal.     

Distinct stem cell populations regenerate the follicle and interfollicular epidermis

The regeneration of the skin and its appendages is thought to occur by the regulated activation of a dedicated stem cell population. A population of cells in the bulge region of the hair follicle has been identified as the putative stem cell of both the follicle and the interfollicular epidermis. While this assertion is supported by a variety of surrogate assays, there has been no direct confirmation of the normal contribution of these cells to the regeneration of structures other than the cycling portion of the hair follicle. Here, we report lineage analysis revealing that the follicular epithelium is derived from cells in the epidermal placode that express Sonic hedgehog. This analysis also demonstrates that the stem cells resident in the follicular bulge that regenerate the follicle are neither the stem cells of the epidermis nor the source of the stem cells of the epidermis in the absence of trauma.     

Calcium-activated chloride channels (CaCCs) regulate action potential and synaptic response in hippocampal neurons

Central neurons respond to synaptic inputs from other neurons by generating synaptic potentials. Once the summated synaptic potentials reach threshold for action potential firing, the signal propagates leading to transmitter release at the synapse. The calcium influx accompanying such signaling opens calcium-activated ion channels for feedback regulation. Here, we report a mechanism for modulating hippocampal neuronal signaling that involves calcium-activated chloride channels (CaCCs). We present evidence that CaCCs reside in hippocampal neurons and are in close proximity of calcium channels and NMDA receptors to shorten action potential duration, dampen excitatory synaptic potentials, impede temporal summation, and raise the threshold for action potential generation by synaptic potential. Having recently identified TMEM16A and TMEM16B as CaCCs, we further show that TMEM16B but not TMEM16A is important for hippocampal CaCC, laying the groundwork for deciphering the dynamic CaCC modulation of neuronal signaling in neurons important for learning and memory.     

Ano1 as a regulator of proliferation

Ano1 is a recently discovered Ca(2+)-activated Cl(-) channel expressed on interstitial cells of Cajal (ICC) that has been implicated in slow-wave activity in the gut. However, Ano1 is expressed on all classes of ICC, even those that do not contribute to generation of the slow wave, suggesting that Ano1 may have an alternate function in these cells. Ano1 is also highly expressed in gastrointestinal stromal tumors. Mice lacking Ano1 had fewer proliferating ICC in whole mount preparations and in culture, raising the possibility that Ano1 is involved in proliferation. Cl(-) channel blockers decreased proliferation in cells expressing Ano1, including primary cultures of ICC and in the pancreatic cancer-derived cell line, CFPAC-1. Cl(-) channel blockers had a reduced effect on Ano1(-/-) cultures, confirming that the blockers are acting on Ano1. Ki67 immunoreactivity, 5-ethynyl-2'-deoxyuridine incorporation, and cell-cycle analysis of cells grown in low-Cl(-) media showed fewer proliferating cells than in cultures grown in regular medium. We confirmed that mice lacking Ano1 had less phosphorylated retinoblastoma protein compared with controls. These data led us to conclude that Ano1 regulates proliferation at the G(1)/S transition of the cell cycle and may play a role in tumorigenesis.     

低温对植物叶片中超氧物歧化酶、过氧化氢酶和过氧化氢水平的影响

番茄和鸡蛋果叶片中可提取的SOD活性不受低温的影响。在电泳谱带上SOD主同工酶带被氰化物而不被低温抑制,次同工酶带在低温下不稳定,且活性很低,它的变化不影响总的SOD活性。一些冷敏感植物叶片中CAT活性被低温抑制,而H_2O_3水平在低温下稳定或有增加,这可能使毒性更强的羟基离子(OH·)易于形成。     

Development of the Olfactory Epithelium and Nasal Glands in TMEM16A-/- and TMEM16A+/+ Mice

TMEM16A/ANO1 is a calcium-activated chloride channel expressed in several types of epithelia and involved in various physiological processes, including proliferation and development. During mouse embryonic development, the expression of TMEM16A in the olfactory epithelium is dynamic. TMEM16A is expressed at the apical surface of the entire olfactory epithelium at embryonic day E12.5 while from E16.5 its expression is restricted to a region near the transition zone with the respiratory epithelium. To investigate whether TMEM16A plays a role in the development of the mouse olfactory epithelium, we obtained the first immunohistochemistry study comparing the morphological properties of the olfactory epithelium and nasal glands in TMEM16A^-/- and TMEM16A^+/+ littermate mice. A comparison between the expression of the olfactory marker protein and adenylyl cyclase III shows that genetic ablation of TMEM16A did not seem to affect the maturation of olfactory sensory neurons and their ciliary layer. As TMEM16A is expressed at the apical part of supporting cells and in their microvilli, we used ezrin and cytokeratin 8 as markers of microvilli and cell body of supporting cells, respectively, and found that morphology and development of supporting cells were similar in TMEM16A^-/- and TMEM16A^+/+ littermate mice. The average number of supporting cells, olfactory sensory neurons, horizontal and globose basal cells were not significantly different in the two types of mice. Moreover, we also observed that the morphology of Bowman’s glands, nasal septal glands and lateral nasal glands did not change in the absence of TMEM16A. Our results indicate that the development of mouse olfactory epithelium and nasal glands does not seem to be affected by the genetic ablation of TMEM16A.