Recurrent DICER1 hotspot mutations in endometrial tumours and their impact on microRNA biogenesis

DICER1 plays a critical role in microRNA (miRNA) biogenesis. Recurrent somatic 'hotspot' mutations at the four metal‐binding sites within the RNase IIIb domain of DICER1 were identified in ovarian sex cord‐stromal tumours and have since been described in other paediatric tumours. In this study, we screened the RNase IIIb domain of DICER1 in 290 endometrial tumours and identified six cases with hotspot mutations, including two cases affected by an atypical G1809R mutation directly adjacent to a metal‐binding site. Using Illumina and Sanger targeted resequencing, we observed and validated biallelic DICER1 mutations in several cases with hotspot mutations. Through in vitro DICER1 cleavage assays, small RNA deep sequencing and real‐time PCR, we demonstrated that mutations adding a positively charged side chain to residue 1809 have similar detrimental effects on 5p miRNA production to mutations at the metal‐binding sites. As expected, 5p miRNAs were globally reduced in tumours and cell lines with hotspot mutations. Pathway analysis of gene expression profiles indicated that genes de‐repressed due to loss of 5p miRNAs are strongly associated with pathways regulating the cell cycle. Using a Dicer1‐null mouse cell line model, we found that expression of DICER1 hotspot mutants promoted cell proliferation, whereas wild‐type (WT) DICER1 inhibited cell proliferation. Furthermore, targets of let‐7 family miRNAs are enriched among the up‐regulated genes, suggesting that loss of let‐7 may be impacting downstream pathways. Our results reveal that DICER1 hotspot mutations are implicated in common malignancies and may constitute a unique oncogenic pathway. Copyright © 2015 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.     

Potential capsule switching from serogroup Y to B: The characterization of three such Neisseria meningitidis isolates causing invasive meningococcal disease in Canada

Three group B Neisseria meningitidis isolates, recovered from meningococcal disease cases in Canada and typed as B:2c:P1.5, were characterized. Multilocus sequence typing showed that all three isolates were related because of an identical sequence type (ST) 573. Isolates typed as 2c:P1.5 are common in serogroup Y meningococci but rare in isolates from serogroups B or C. Although no serogroup Y isolates have been typed as ST-573, eight isolates showed five to six housekeeping gene alleles that were identical to that of ST-573. This suggested that the B:2c:P1.5 isolates may have originated from serogroup Y organisms, possibly by capsule switching.Key Words: Capsule switching, Neisseria meningitidis, Serogroup YNeisseria meningitidis is a significant pathogen that causes invasive meningococcal disease (IMD). The average case fatality rate of 9% to 12% remains high despite the availability of effective antibiotics and vaccines (1). Laboratory study and surveillance of N meningitidis involves the characterization of a number of surface markers of the bacterium, including its capsule and outer membrane proteins (OMPs). Most epidemiological studies of meningococcal disease rely on differentiating meningococcal isolates based on their serogroup, serotype and serosubtype. Serogrouping is determined by the demonstration of serologically distinct epitopes present on chemically and structurally different capsules. Serotyping and serosubtyping rely on the detection of distinct epitopes present on three of five different classes of OMPs of N meningitidis. Serotyping epitopes are found on the class 2 or class 3 OMP (also called PorB) of N meningitidis; these OMPs are expressed in a mutually exclusively manner (ie, a strain will only express either a class 2 or class 3 OMP but not both). Serosubtyping epitopes are present on the class 1 OMP (also called PorA). Based on this nomenclature scheme, a strain can therefore be characterized by its antigenic formula; for example, B:15:P1.7,16 refers to serogroup B, serotype 15 and serosubtype P1.7,16.One of the most important virulence factors of meningococci is the capsular polysaccharide antigen, which is also the basis for serogrouping and is the target antigen for the currently licensed vaccines against A, C, Y and W135 organisms. Of the 13 known serogroups, five (serogroups A, B, C, Y and W135) are responsible for most of the meningococcal disease worldwide (2). In North America, most endemic and epidemic strains belong to serogroups B, C, Y and W135 (3,4). Capsules of serogroups B, C, Y and W135 meningococci contain sialic acid, either as a homopolymer of sialic acids assembled by alpha-2,8 linkages (serogroup B) or alpha-2,9 linkages (serogroup C), or as a heteropolymer of sialic acids with glucose (serogroup Y) or galactose (serogroup W135). Besides demonstrating structural similarities, these four serogroups of meningococci also have very similar capsule polysaccharide synthesis (cps) gene loci (5). Because of this similarity, capsule switching has been demonstrated in vivo and in vitro by specific gene replacement within the cps loci between different serogroups. To date, a number of IMD cases have been described in the literature to be caused by organisms in which capsule switching between serogroup B and C meningococci occurred (6-8).In the present paper, the authors describe three unusual serogroup B meningococci isolated from separate IMD cases in Nanaimo, British Columbia, that presented with the OMP antigens 2c:P1.5, characteristic of serogroup Y strains found in Canada (4). This antigenic profile prompted the authors to examine the relationship of these three serogroup B strains with antigenically similar serogroup Y organisms isolated in Canada. The authors describe the characterization of these antigenically similar isolates and postulate that the B:2c:P1.5 isolates arose by capsule switching from serogroup Y organisms.     

米帕明对局灶性脑缺血再灌注大鼠脑组织一氧化氮浓度和一氧化氮合酶活性的影响

目的:观察米帕明对局灶性脑缺血再灌注大鼠脑组织中含一氧化氮浓度和一氧化氮合酶活性的影响。方法:实验于2005-03/12在解放军总医院老年心血管病研究所生化药理实验室进行。①选用健康Wistar大鼠96只,随机分成假手术组、模型组、尼莫地平组和米帕明组4组,每组24只。②米帕明组腹腔注射米帕明10mg/kg,尼莫地平组腹腔注射尼莫地平2mg/kg,假手术组和模型组腹腔注射等容积生理盐水;60min后用线栓法建立大鼠局灶性脑缺血-再灌注损伤模型,假手术组尼龙线的头端不插入颈内动脉。③于缺血2h再灌注2,12和24h每组随机取6只大鼠断头,测定脑组织中一氧化氮浓度和一氧化氮合酶活性。每组剩余6只再灌注2h处死取脑,光镜下观察脑组织病理变化。结果:96只大鼠进入结果分析。①一氧化氮浓度:模型组、尼莫地平组和米帕明组再灌注2,12和24h均高于假手术组(P<0.05);尼莫地平组再灌注2,12和24h均低于模型组[(45.99±8.13),(40.63±3.13),(36.72±4.38)μmol/L;(65.54±6.01),(57.08±4.79),(48.13±5.12)μmol/L;P均<0.05];米帕明组再灌注2h和24h也低于同期模型组[(55.98±6.89),(39.42±4.28)μmol/L;P均<0.05]。②一氧化氮合酶活性:模型组、尼莫地平组和米帕明组再灌注2,12和24h均高于假手术组(P<0.05);尼莫地平组和米帕明组各个时间点均低于模型组(P<0.05)。③脑组织病理变化:尼莫地平组和米帕明组神经元损伤较模型组轻。结论:米帕明可降低局灶性脑缺血再灌注大鼠脑组织中一氧化氮浓度和一氧化氮合酶活性,从而对大鼠脑缺血再灌注有保护作用,其效果与尼莫地平相似。     

Effects of repetitive superficial chemical peels on facial sebum secretion in acne patients

BACKGROUND: Glycolic acid and Jessner's solution are popular superficial chemical peel agents for the treatment of facial acne, and increased sebum secretion is one of the major aetiological factors of acne. OBJECTIVE: To compare the effects of 30% glycolic acid peels and Jessner's solution peels on sebum secretion in facial acne patients. METHODS: Thirty-eight patients with mild to moderate facial acne were included. Twenty-seven patients were treated with 30% glycolic acid peels and 11 patients with Jessner's solution peels. Each peel was performed twice with an interval of 2 weeks. Before and 2 weeks after each peel, sebum levels of forehead, nose, chin and cheeks were measured by using a Sebumeter (SM810 Courage & Khazaka, Cologne, Germany). RESULTS: The sebum levels were not significantly changed by two peels treatments of 30% glycolic acid peels or Jessner's solution peels on the facial skins of patients with facial acne. CONCLUSIONS: The two types of peels, 30% glycolic acid peels and Jessner's solution peels, did not affect sebum secretion of the facial skins of patients with facial acne after the two peels treatments. The accumulative effects of more than two peels treatments using these modalities need further evaluation.