Identification and functional characterization of the novel MAR-binding protein, SATB2

The regulation of gene expression is governed in large part by transcription factors that bind to enhancers and promoters. The functions of transcription factors involve both the modulation of chromatin accessibility via the recruitment of histone-modifying enzymes or nucleosome-remodeling complexes, and the stimulation of RNA polymerase via an interaction with the mediator complex. In addition to enhancers and promoters, nuclear matrix attachment regions (MARs) have been implicated in the regulation of gene expression by altering the organization of eukaryotic chromosomes and augmenting the potential of enhancers to act over large distances. Although a lot is known about the function of MARs, the precise mechanism of their action is still obscure and probably diverse. One proposed model stipulates that their function is accomplished through the action of transcription factors, which are components of the nuclear matrix. Here, we identify and characterize a novel cell-type specific MAR-binding protein, SATB2, which binds to the MARs of the endogenous immunoglobulin µ locus in pre-B cells and enhances gene expression. In contrast to the closely related, thymocyte-specific MAR-binding protein SATB1, SATB2 is not proteolytically cleaved by caspase 6, but is instead SUMO-modified at two lysine residues. This modification is specifically augmented by the SUMO E3 ligase PIAS1. Mutation of the sumoylation sites enhances the association of SATB2 with the immunoglobulin MARs, as well as its transactivation potential. Moreover, covalent attachment of SUMO1 and SUMO3 represses SATB2- dependent transcription, without affecting either the DNA binding or the dimerization capacity of SATB2. Interestingly, SUMO conjugation affects the subnuclear localization of SATB2 and is involved in its targeting to distinct nuclear speckles (bodies). Thus, our data indicate that the regulation of SATB2 function through sumoylation can be mediated by both altering its transcriptional activation potential and by sequestering it in specific nuclear locatio

Satb2 Regulates Callosal Projection Neuron Identity in the Developing Cerebral Cortex

SummarySatb2 is a DNA-binding protein that regulates chromatin organization and gene expression. In the developing brain, Satb2 is expressed in cortical neurons that extend axons across the corpus callosum. To assess the role of Satb2 in neurons, we analyzed mice in which the Satb2 locus was disrupted by insertion of a LacZ gene. In mutant mice, β-galactosidase-labeled axons are absent from the corpus callosum and instead descend along the corticospinal tract. Satb2 mutant neurons acquire expression of Ctip2, a transcription factor that is necessary and sufficient for the extension of subcortical projections by cortical neurons. Conversely, ectopic expression of Satb2 in neural stem cells markedly decreases Ctip2 expression. Finally, we find that Satb2 binds directly to regulatory regions of Ctip2 and induces changes in chromatin structure. These data suggest that Satb2 functions as a repressor of Ctip2 and regulatory determinant of corticocortical connections in the developing cerebral cortex

Epigenetic Regulation of S100A9 and S100A12 Expression in Monocyte-Macrophage System in Hyperglycemic Conditions

The number of diabetic patients in Europe and world-wide is growing. Diabetes confers a 2-fold higher risk for vascular disease. Lack of insulin production (Type 1 diabetes, T1D) or lack of insulin responsiveness (Type 2 diabetes, T2D) causes systemic metabolic changes such as hyperglycemia (HG) which contribute to the pathology of diabetes. Monocytes and macrophages are key innate immune cells that control inflammatory reactions associated with diabetic vascular complications. Inflammatory programming of macrophages is regulated and maintained by epigenetic mechanisms, in particular histone modifications. The aim of our study was to identify the epigenetic mechanisms involved in the hyperglycemia-mediated macrophage activation. Using Affymetrix microarray profiling and RT-qPCR we identified that hyperglycemia increased the expression of S100A9 and S100A12 in primary human macrophages. Expression of S100A12 was sustained after glucose levels were normalized. Glucose augmented the response of macrophages to Toll-like receptor (TLR)-ligands Palmatic acid (PA) and Lipopolysaccharide (LPS) i.e., pro-inflammatory stimulation. The abundance of activating histone Histone 3 Lysine 4 methylation marks (H3K4me1, H3K4me3) and general acetylation on histone 3 (AceH3) with the promoters of these genes was analyzed by chromatin immunoprecipitation. Hyperglycemia increased acetylation of histones bound to the promoters of S100A9 and S100A12 in M1 macrophages. In contrast, hyperglycemia caused a reduction in total H3 which correlated with the increased expression of both S100 genes. The inhibition of histone methyltransferases SET domain-containing protein (SET)7/9 and SET and MYND domain-containing protein (SMYD)3 showed that these specifically regulated S100A12 expression. We conclude that hyperglycemia upregulates expression of S100A9, S100A12 via epigenetic regulation and induces an activating histone code on the respective gene promoters in M1 macrophages. Mechanistically, this regulation relies on action of histone methyltransferases SMYD3 and SET7/9. The results define an important role for epigenetic regulation in macrophage mediated inflammation in diabetic conditions

Egg parasitoids of Thaumetopoea pityocampa in the region of Gyumyurdzhinski Snezhnik in Eastern Rhodopes, Bulgaria

The region of Gyumyurdzhinski Snezhnik in the Eastern Rhodopes is the closest in Bulgaria to the Aegean Sea. However, the climate is characterized by specific parameters that are determined by its relief. It is poorly protected from the invasion of cold air masses from the north. From the south, the Gyumyurdzhinski Snezhnik hill restrains the Mediterranean influence. The orography of the area favors the retention of cold air masses and a further drop in temperatures. The experimental material for the study includes 5 generations of Thaumetopoea pityocampa (2016, 2017, 2018, 2019, and 2022), collected in 31 locations of four State Forestry Enterprises: Kirkovo, Ardino, Momchilgrad, and Zlatograd. The sample for analysis included 693 egg batches with 148420 eggs in them. Seven primary egg parasitoids were established in this region: Ooencyrtus pityocampae, Baryscapus servadeii, Pediobius bruchicida, Anastatus bifasciatus, Eupelmus vesicularis, E. vladimiri, Trichogramma sp. and one hyperparasitoid (B. transversalis). Dominant parasitoids were B. servadeii and O. pityocampae, and E. vladimiri and P. bruchicida – occasional parasitoids. The hyperparasitoid B. transversalis participated in the complex with a relatively low share. The survival of the egg parasitoids in the laboratory conditions, in which the samples were kept, was low. The total mortality of the parasitoids in larval and adult stages was 47.8%. After collecting the samples, in laboratory conditions, a total of 442 individuals of the hyperparasitoid B. transversalis emerged, of which 56.3% were females and 43.7% were males. The average number of pine processionary moth eggs in a batch was 214.2. 70.8% of all the eggs in the samples hatched successfully. The egg parasitoids are a very serious natural factor, regulating the density of the pine processionary moth, but their impact varied from 2.1% to 30.3%. The natural characteristics of the area, the air temperature during the stages of eggs and young larvae, are favorable for the development of the pine processionary moth. Unhatched larvae without the influence of entomophages were 7.2%

The Isl1/Ldb1 complex orchestrates heart-specific chromatin organization and transcriptional regulation

Cardiac stem/progenitor cells hold great potential for regenerative therapies however the mechanisms regulating their expansion and differentiation remain insufficiently defined. Here we show that the multi-adaptor protein Ldb1 is a central regulator of cardiac progenitor cell differentiation and second heart field (SHF) development. Mechanistically, we demonstrate that Ldb1 binds to the key regulator of SHF progenitors Isl1 and protects it from proteasomal degradation. Furthermore, the Isl1/Ldb1 complex promotes long-range promoter-enhancer interactions at the loci of the core cardiac transcription factors Mef2c and Hand2. Chromosome conformation capture followed by sequencing identified surprisingly specific, Ldb1-mediated interactions of the Isl1/Ldb1 responsive Mef2c anterior heart field enhancer with genes which play key roles in cardiac progenitor cell function and cardiovascular development. Importantly, the expression of these genes was downregulated upon Ldb1 depletion and Isl1/Ldb1 haplodeficiency. In conclusion, the Isl1/Ldb1 complex orchestrates a network for heart-specific transcriptional regulation and coordination in three-dimensional space during cardiogenesis

Improving load capacity parameters of worm gears

Worm gear drives possess several advantages in comparison to other types of transmissions. Some of the most important advantages are: high gear ratio, compact design and vibration damping. Therefore, the author’s team focused within the framework of research presented on creating opportunities to improve another very important characteristic feature of worm gears: the load capacity. During the process of investigation, optimization procedures have been created aiming to improve the load capacity parameters of worm gear trains. Different functional parameters and certain geometry parameters have been taken into account such as rotational frequency of the worm shaft, gear ratio, module and geometry dimensions of the worm gear set. The research methodology applied includes several stages. The research results obtained are presented and discussed. Conclusions and recommendations are made

Epigenetic inheritance of cell fates during embryonic development

During embryonic development a large number of widely differing and specialized cell types with identical genomes are generated from a single totipotent zygote. Tissue specific transcription factors cooperate with epigenetic modifiers to establish cellular identity in differentiated cells and epigenetic regulatory mechanisms contribute to the maintenance of distinct chromatin states and cell-type specific gene expression patterns, a phenomenon referred to as epigenetic memory. This is accomplished via the stable maintenance of various epigenetic marks through successive rounds of cell division. Preservation of DNA methylation patterns is a well established mechanism of epigenetic memory, but more recently it has become clear that many other epigenetic modifications can also be maintained following DNA replication and cell division. In this review, we present an overview of the current knowledge regarding the role of histone lysine methylation in the establishment and maintenance of stable epigenetic states

Epigenetic inheritance of cell fates during embryonic development

During embryonic development a large number of widely differing and specialized cell types with identical genomes are generated from a single totipotent zygote. Tissue specific transcription factors cooperate with epigenetic modifiers to establish cellular identity in differentiated cells and epigenetic regulatory mechanisms contribute to the maintenance of distinct chromatin states and cell-type specific gene expression patterns, a phenomenon referred to as epigenetic memory. This is accomplished via the stable maintenance of various epigenetic marks through successive rounds of cell division. Preservation of DNA methylation patterns is a well-established mechanism of epigenetic memory, but more recently it has become clear that many other epigenetic modifications can also be maintained following DNA replication and cell division. In this review, we present an overview of the current knowledge regarding the role of histone lysine methylation in the establishment and maintenance of stable epigenetic states