Hacking the centromere chromatin code: dissecting the epigenetic regulation of centromere identity

The centromere is a specialized chromatin domain that serves as the assembly site for the mitotic kinetochore structure, thereby playing a fundamental role in facilitating the maintenance of the genetic information. A histone H3 variant termed CENP-A is specifically found at all active centromeres. Beyond this, however, little is known about how and to which extent the chromatin environment of centromeres modulates and contributes towards centromere identity and function. Here, I have employed a novel Human Artificial Chromosome (HAC), the centromere of which can be targeted by fusions to the tet repressor, to characterize the chromatin environment underlying active kinetochores, as well as to specifically probe the role of this environment in the maintenance of kinetochore structure and function. My data demonstrate that centromeric chromatin resembles the downstream regions of actively transcribed genes. This includes the previously unrecognized presence of histone H3 nucleosomes methylated at lysine 36 within the chromatin underlying functional kinetochores. Targeted manipulation of this chromatin through tethering of a heterochromatin-seeding transcriptional repressor results in the inactivation of HAC kinetochore function concomitant with a hierarchical disassembly of the structure. Through an even more selective engineering of the HAC centromere chromatin, I have provided evidence supporting a critical role for nucleosomes dimethylated at lysine 4 on histone H3 in facilitating local transcription of the underlying DNA. Tethering of different chromatin-modifying activities into the HAC kinetochore collectively reveals a critical role for both, histone H3 dimethylated on lysine 4 and low-level, non-coding transcription in the maintenance of the CENP-A chromatin domain. On one hand, repression of centromeric transcription negatively correlates with the maintenance of CENP-A and ultimately results in the loss of kinetochore function. On the other hand, increasing kinetochore-associated RNA polymerase activity to within physiological levels for euchromatin is associated with rapid loss of CENP-A from the HAC centromere. Together, my data point towards the requirement for a delicate balance of transcriptional activity that is required to shape and maintain the chromatin environment of active centromeres

Insect pheromone research in South America

Insect pheromone research has a long and rich history built up primarily by studies conducted in the Northern hemisphere. Not surprisingly, these studies have largely targeted species relevant to these regions of the world, for the most part agricultural and forest pests. Pheromone research in South American countries came a few decades behind, albeit their strong dependence in agriculture and therefore in pest management. In the last 20 years, a combination of economic, environmental and technical factors have come together to generate a small but rising number of chemical ecologists working in pheromone chemistry and biology in South America. In this article we summarize the results of this trend. We review pheromone studies in which South American scientists have participated in collaboration with foreign scientists, mostly chemistry groups, as well as the ever-growing number of studies carried out completely within the region. We have focused mainly in research involving the characterization of pheromones from native species, which involve the most important insect orders, namely Lepidoptera, Coleoptera, Heteroptera and Hymenoptera. We also present a simple meta-analysis including geographical distribution, trends in collaborative or independent work, and a 20-year evolution of published articles in the field. Finally, we emphasize the importance of a coordinated effort to further promote the growth of this field in Latin America, through the endorsement of international collaborations within the region. Such goal would be facilitated by a regional academic organization, which would in turn initiate the occurrence of regular scientific meetings

Random Monoallelic Gene Expression Increases upon Embryonic Stem Cell Differentiation

SummaryRandom autosomal monoallelic gene expression refers to the transcription of a gene from one of two homologous alleles. We assessed the dynamics of monoallelic expression during development through an allele-specific RNA-sequencing screen in clonal populations of hybrid mouse embryonic stem cells (ESCs) and neural progenitor cells (NPCs). We identified 67 and 376 inheritable autosomal random monoallelically expressed genes in ESCs and NPCs, respectively, a 5.6-fold increase upon differentiation. Although DNA methylation and nuclear positioning did not distinguish the active and inactive alleles, specific histone modifications were differentially enriched between the two alleles. Interestingly, expression levels of 8% of the monoallelically expressed genes remained similar between monoallelic and biallelic clones. These results support a model in which random monoallelic expression occurs stochastically during differentiation and, for some genes, is compensated for by the cell to maintain the required transcriptional output of these genes

Deleterious Impact of a Novel CFH Splice Site Variant in Atypical Hemolytic Uremic Syndrome

Atypical hemolytic uremic syndrome (aHUS) is a heterogeneous disorder characterized by microangiopathic hemolytic anemia (MAHA), thrombocytopenia, and acute kidney injury (AKI). In about 50% of cases, pathogenic variants in genes involved in the innate immune response including complement factors complement factor H (CFH), CFI, CFB, C3, and membrane co-factor protein (MCP/CD46) put patients at risk for uncontrolled activation of the alternative complement pathway. As aHUS is characterized by incomplete penetrance and presence of additional triggers for disease manifestation, genetic variant interpretation is challenging and streamlined functional variant evaluation is urgently needed. Here, we report the case of a 27-year-old female without previous medical and family history who presented with confusion, petechial bleeding, and anuric AKI. Kidney biopsy revealed glomerular thrombotic microangiopathy (TMA). Targeted next generation sequencing identified a paternally transmitted novel heterozygous splice site variant in the CFH gene [c.3134-2A>G; p.Asp1045_Thr1053del] which resulted in a partial in-frame deletion of exon 20 transcript as determined by cDNA analysis. On the protein level, the concomitant loss of 9 amino acids in the short consensus repeat (SCR) domains 17 and 18 of CFH includes a highly conserved cysteine residue, which is assumed to be essential for proper structural folding and protein function. Treatment with steroids, plasmapheresis, and the complement inhibitor eculizumab led to complete hematological and clinical remission after several months and stable renal function up to 6 years later. In conclusion, genetic investigation for pathogenic variants and evaluation of their functional impact, in particular in the case of splice site variants, is clinically relevant and enables not only better molecular understanding but helps to guide therapy with complement inhibitors

Epigenetic engineering shows H3K4me2 is required for HJURP targeting and CENP-A assembly on a synthetic human kinetochore

Here, centromeric histone marks on a human artificial chromosome are found to resemble the chromatin landscape in transcribed genes, and selective manipulation shows them to govern the incorporation of the centromere-specifying CENP-A histone variant

Identification of a Sex Pheromone Produced by Sternal Glands in Females of the Caddisfly Molanna angustata Curtis

In the caddisfly Molanna angustata, females produce a sex pheromone in glands with openings on the fifth sternite. Gas chromatographic analyses of pheromone gland extracts with electroantennographic detection revealed four major compounds that stimulated male antennae. These compounds were identified by means of gas chromatography–mass spectrometry and enantioselective gas chromatography as heptan-2-one, (S)-heptan-2-ol, nonan-2-one, and (S)-nonan-2-ol in the approximate ratio of 1:1:4:10, respectively. Field tests showed that the mixture of the two alcohols was attractive to males whereas addition of the corresponding ketones reduced trap catches. The sex pheromone of M. angustata, a species in the family Molannidae within the suborder Integripalpia, is similar to the pheromones or pheromone-like compounds previously reported from six other trichopteran families, including members of the basal suborder Annulipalpia. This suggests that minimal evolutionary change of the pheromone chemistry has taken place within the leptoceroid branch of integripalpian Trichoptera compared to the ancestral character state

MSK-Mediated Phosphorylation of Histone H3 Ser28 Couples MAPK Signalling with Early Gene Induction and Cardiac Hypertrophy

Heart failure is a leading cause of death that develops subsequent to deleterious hypertrophic cardiac remodelling. MAPK pathways play a key role in coordinating the induction of gene expression during hypertrophy. Induction of the immediate early gene (IEG) response including activator protein 1 (AP-1) complex factors is a necessary and early event in this process. How MAPK and IEG expression are coupled during cardiac hypertrophy is not resolved. Here, in vitro, in rodent models and in human samples, we demonstrate that MAPK-stimulated IEG induction depends on the mitogen and stress-activated protein kinase (MSK) and its phosphorylation of histone H3 at serine 28 (pH3S28). pH3S28 in IEG promoters in turn recruits Brg1, a BAF60 ATP-dependent chromatin remodelling complex component, initiating gene expression. Without MSK activity and IEG induction, the hypertrophic response is suppressed. These studies provide new mechanistic insights into the role of MAPK pathways in signalling to the epigenome and regulation of gene expression during cardiac hypertrophy

T‐cell prolymphocytic leukemia is associated with deregulation of oncogenic microRNAs on transcriptional and epigenetic level

Deregulation of micro(mi)-RNAs is a common mechanism in tumorigenesis. We investigated the expression of 2083 miRNAs in T-cell prolymphocytic leukemia (T-PLL). Compared to physiologic CD4+ and CD8+ T-cell subsets, 111 miRNAs were differentially expressed in T-PLL. Of these, 33 belonged to miRNA gene clusters linked to cancer. Genomic variants affecting miRNAs were infrequent with the notable exception of copy number aberrations. Remarkably, we found strong upregulation of the miR-200c/-141 cluster in T-PLL to be associated with DNA hypomethylation and active promoter marks. Our findings suggest that copy number aberrations and epigenetic changes could contribute to miRNA deregulation in T-PLL

Breaking the HAC Barrier: Histone H3K9 acetyl/methyl balance regulates CENP-A assembly

Establishment of Human Artificial Chromosomes (HACs) depends on an interplay of H3 lysine 9 modifications at centromeres, providing insights into the pathways that control incorporation of the kinetochore-specificing histone H3 variant CENP-A