Effects of sodium valproate on the chromatin of Triatoma infestans (Klug, 1834) (Hemiptera,Reduviidae) under in vitro culture conditions

Sodium valproate (VPA) is a classic anticonvulsive, a histone deacetylase inhibitor, and a chromatin remodeling inducer. When injected into specimens of Triatoma infestans, a vector of Chagas disease, VPA affects the chromatin supraorganization of chromocenter heterochromatin in only a few cells of the Malpighian tubules. To test whether this result was explained by the inaccessibility of all of the organ’s cells to the drug, we investigated the nuclear phenotypes and global acetylation of lysine 9 in histone H3 (H3K9ac) in Malpighian tubules cultivated in vitro for 1–24 h in the presence of 0.05 mM–1 mM VPA. The present results revealed that the chromatin decondensation event in the chromocenter body, which was detected only under low VPA concentrations up to a 4-h treatment, was not frequent during organ culture, similar to the results for injected insects. Cultivation of T. infestans Malpighian tubules in vitro for 24 h revealed inadequate for cell preservation even in the absence of the drug. Immunofluorescence signals for H3K9ac following VPA treatment showed a slightly increased intensity in the euchromatin, but were never detected in the chromocenter bodies, except with great intensity at their periphery, where the 18S rDNA is located. In conclusion, when VPA affects the chromocenter heterochromatin in this animal cell model, it occurs through a pathway that excludes a classic global H3K9ac mark. Investigation of nonhistone proteins associated with histone methylation marks is still required to further explain the differential response of T. infestans chromatin to VPA.     

组蛋白化学修饰改变对c-Myb结合的影响及其在职业性苯中毒患者造血损伤中的作用

 目的:研究职业性苯中毒造血损伤患者中与拓扑异构酶Ⅱα启动子调控因子c-Myb结合的组蛋白化学修饰改变, 证实组蛋白乙酰化修饰水平改变在职业性苯中毒造血损伤中发挥一定的作用。方法:25例职业性苯中毒再生障碍性贫血患者为病例组,25例正常人为对照组,提取骨髓单个核细胞,用染色质免疫沉淀(ChIP)探讨与c-Myb结合的组蛋白乙酰化和甲基化水平的改变,RT-PCR法检测c-Myb的mRNA表达水平,组蛋白去乙酰化酶(HDAC)试剂盒检测HDAC活性的变化。结果:与正常对照组相比,职业性苯中毒再生障碍性贫血患者c-Myb与乙酰化组蛋白H4、H3结合的水平下降(P<0.01), 而与甲基化组蛋白H3K4和H3K9结合的水平无明显改变,差异无统计学显著性。与正常对照组相比,职业性苯中毒再生障碍性贫血患者c-Myb的mRNA表达水平降低,HDAC活性明显升高,差异均有统计学显著性(P<0.05)。结论:拓扑异构酶Ⅱα启动子调控因子c-Myb可能通过组蛋白乙酰化修饰的改变在职业性苯中毒造血损伤中发挥作用。     

Contribution of AT-, GC-, and methylated cytidine-rich DNA to chromatin composition in Malpighian tubule cell nuclei of Panstrongylus megistus (Hemiptera, Reduviidae)

The Malpighian tubule cell nuclei of male Panstrongylus megistus, a vector of Chagas disease, contain one chromocenter, which is composed solely of the Y chromosome. Considering that different chromosomes contribute to the composition of chromocenters in different triatomini species, the aim of this study was to determine the contribution of AT-, GC-, and methylated cytidine-rich DNA in the chromocenter as well as in euchromatin of Malpighian tubule cell nuclei of P. megistus in comparison with published data for Triatoma infestans. Staining with 4′,6-diamidino-2-phenylindole/actinomycin D and chromomycin A₃/distamycin, immunodetection of 5-methylcytidine and AgNOR test were used. The results revealed AT-rich/GC-poor DNA in the male chromocenter, but equally distributed AT and GC DNA sequences in male and female euchromatin, like in T. infestans. Accumulation of argyrophilic proteins encircling the chromocenter did not always correlate with that of GC-rich DNA. Methylated DNA identified by immunodetection was found sparsely distributed in the euchromatin of both sexes and at some points around the chromocenter edge, but it could not be considered responsible for chromatin condensation in the chromocenter, like in T. infestans. However, unlike in T. infestans, no correlation between the chromocenter AT-rich DNA and nucleolus organizing region (NOR) DNA was found in P. megistus.     

The role of epigenetics in aging and age-related diseases

The role of epigenetics in aging and age-related diseases is a key issue in molecular physiology and medicine because certain epigenetic factors are thought to mediate, at least in part, the relationship between the genome and the environment. An active role for epigenetics in aging must meet two prior conditions: there must be specific epigenetic changes during aging and they must be functionally associated with the aged phenotype. Assuming that specific epigenetic modifications can have a direct functional outcome in aging, it is also essential to establish whether they depend on genetic, environmental or stochastic factors, and if they can be transmitted from one generation to the next. Here we discuss current knowledge about these matters and future directions in the field.     

Epigenetic Role of Histone 3 Lysine Methyltransferase and Demethylase in Regulating Apoptosis Predicting the Recurrence of Atypical Meningioma

Alteration of apoptosis is related with progression and recurrence of atypical meningiomas (AMs). However, no comprehensive study has been conducted regarding histone modification regulating apoptosis in AMs. This study aimed to determine the prognostic values of certain apoptosis-associated factors, and examine the role of histone modification on apoptosis in AMs. The medical records of 67 patients with AMs, as diagnosed during recent 13 yr, were reviewed retrospectively. Immunohistochemical staining was performed on archived paraffin-embedded tissues for pro-apoptotic factors (CASP3, IGFBP, TRAIL-R1, BAX, and XAF1), anti-apoptotic factors (survivin, ERK, RAF1, MDM2, and BCL2), and the histone modifying enzymes (MLL2, RIZ, EZH1, NSD2, KDM5c, JMJD2a, UTX, and JMJD5). Twenty-six (38.8%) patients recurred during the follow-up period (mean duration 47.7 months). In terms of time-to-recurrence (TTR), overexpression of CASP3, TRAIL-R1, and BAX had a longer TTR than low expression, and overexpression of survivin, MDM2, and BCL2 had a shorter TTR than low expression (P<0.05). Additionally, overexpression of MLL2, UTX, and JMJ5 had shorter TTRs than low expression, and overexpression of KDM5c had a longer TTR than low expression. However, in the multi-variate analysis of predicting factors for recurrence, low expression of CASP3 (P<0.001), and BAX (P<0.001), and overexpression of survivin (P=0.007), and MDM2 (P=0.037) were associated with recurrence independently, but any enzymes modifying histone were not associated with recurrence. Conclusively, this study suggests certain apoptosis-associated factors should be associated with recurrence of AMs, which may be regulated epigenetically by histone modifying enzymes.

Graphical Abstract

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An XX/XY Sex Chromosome System in a Fish Species, Hoplias malabaricus, with a Polymorphic NOR-Bearing X Chromosome

Cytogenetic studies were carried out in the fish, Hoplias malabaricus, from the Parque Florestal do Rio Doce (Brazil). This population is characterized by 2n = 42 chromosomes for both males and females and an XX/XY sex chromosome system, confirmed through several banding methods. Females show 24 metacentric, 16 submetacentric and 2 subtelocentric chromosomes. Males show 24 metacentric, 17 submetacentric and 1 subtelocentric chromosomes. While the X chromosome is easily recognized (the only subtelocentric element), the Y chromosome is somewhat difficult to identify but appears to correspond to the smallest submetacentric in the male karyotype. In-situ hybridization with an 18S rDNA probe showed 10 well-labeled chromosomes, including the X chromosome. The 5S rDNA is interstitially located in a single metacentric pair independent of the 18S rDNA sites. The NOR on the X chromosome is always active and occurs adjacent to a heterochromatic distal segment on the long arm. Variations in size of the NORs and/or heterochromatic segment correspond to a polymorphic size condition observed in the X chromosome. The present results confirm the XX/XY sex chromosome system in the population analyzed as well as a new cytotype in the Hoplias malabaricus group.     

Dynamics of thermopreference in the Chagas disease vector Panstrongylus megistus (Hemiptera: Reduviidae)

The thermopreference of resting P. megistus (Burmeister, 1834) adults was studied in a temperature gradient. We also determined the thermopreference for oviposition and ecdysis. Thermopreference of resting individuals depended on the feeding state of the insects. Results demonstrated an initial resting preference of approximately 290 degrees C, which gradually changed to 26-27 degrees C with increasing starvation. A daily variation in thermopreference was also observed with this species. The insects showed a daily maximum preference at the beginning of the dark phase, and a minimum preference during the first half of the light phase. Ecdysis took place all along the gradient, but exhibited a maximum frequency at 30 degrees C. Most eggs were found between 25 and 29 degrees C. Results are discussed in relation to the ecology of P. megistus as compared with other related species, and the existence of mechanisms of behavioral thermoregulation in the group.     

Histone deacetylase 1 (HDAC1) participates in the down-regulation of corticotropin releasing hormone gene (crh) expression

The paraventricular nucleus of the hypothalamus (PVH) plays a central role in regulating the hypothalamic-pituitary-adrenal (HPA) axis. Medial parvocellular neurons of the PVH (mpPVH) integrate sensory and humoral inputs to maintain homeostasis. Humoral inputs include glucocorticoids secreted by the adrenals, which down-regulate HPA activation. A primary glucocorticoid target is the population of mpPVH neurons that synthesize and secrete corticotropin-releasing factors, the most potent of which is corticotropin-releasing hormone (CRH). Although CRH gene (crh) expression is known to be down-regulated by glucocorticoids, the mechanisms by which this process occurs are still poorly understood. To begin this study we postulated that glucocorticoid repression of crh involves HDAC recruitment to the region of the crh proximal promoter. To evaluate this hypothesis, we treated hypothalamic cells that express CRH with the HDAC inhibitor trichostatin A (TSA). As predicted, treatment with TSA led to increased CRH mRNA levels and crh promoter activity. Although co-treatment with Dex (10⁻⁷ M) reduced the TSA effect on mRNA levels, it failed to reduce promoter activity; however co-transfection of HDAC1 but not 3 restored Dex inhibition. A distinction between HDAC1 and 3 was also apparent with respect to crh promoter occupancy. Dex led to increased HDAC1 but not HDAC3 occupancy. In vivo studies revealed that CRH-immunoreactive (-ir) neurons contained HDAC1- and HDAC3-ir. Collectively, these data point to a role for HDAC1 in the physiologic regulation of crh.     

Ultrastructural localization of basic proteins and carbohydrates in male accessory glands of two Triatoma species (Hemiptera, Reduviidae, Triatominae)

The male accessory glands in Triatoma are tubular and produce substances with some functions related to production of the spermatophore. In the current study, the cytochemistry of male accessory glands was evaluated in starved Triatoma brasiliensis and adult Triatoma melanica. The storage of carbohydrates and proteins in T. melanica male accessory glands occurs earlier than in T. brasiliensis. In addition, the occurrence of eletron-lucent granules without carbohydrates and proteins suggests that other substances are released by these glands, which may be used for lubrication of the male genitalia. Male T. brasiliensis has more intense secretory activity in the fifth day of adult life, which may indicate a higher reproductive capacity. The analysis of lipid production in male accessory glands can contribute to the knowledge of spermatophore formation in these species.     

Flight muscle dimorphism and heterogeneity in flight initiation of field-collected Triatoma infestans (Hemiptera: Reduviidae)

Recent experiments demonstrated that most field-collected Triatoma infestans (Klug) (Hemiptera: Reduviidae) adults from northern Argentina either never initiated flight or did so repeatedly in both sexes. This pattern could not be explained by sex, adult age, weight, weight-to-length ratio (W/L), or chance. We examined whether bugs that never initiated flight possessed developed flight muscles, and whether flight muscle mass relative to total body mass (FMR) was related to the probability of flight initiation. Approximately half of the adults that never initiated flight had no flight muscles. The absence of flight muscles was 2.4 times more frequent in males than females. Females had significantly larger flight muscle mass than males. For both sexes, the frequency of bugs with no flight muscles was spatially heterogeneous among individual collection sites. A logistic regression model of flight initiation that included both FMR and W/L provided abetter fit than models including either one of these predictors. FMR is a novel predictor of flight initiation in Triatominae, with a stronger effect than W/L. The higher frequency of females initiating flight in our experiments may be explained by females having flight muscles more frequently than males, and having FMR and W/L values more suitable for flying. These findings demonstrate that individuals and natural populations of T. infestans can differ dramatically with regard to flight initiation.