The chromodomains of CHD1 are critical for enzymatic activity but less important for chromatin localization.

The molecular motor protein CHD1 has been implicated in the regulation of transcription and in the transcription-independent genome-wide incorporation of H3.3 into paternal chromatin in Drosophila melanogaster. A key feature of CHD1 is the presence of two chromodomains, which can bind to histone H3 methylated at lysine 4 and thus might serve to recruit and/or maintain CHD1 at the chromatin. Here, we describe genetic and biochemical approaches to the study of the Drosophila CHD1 chromodomains. We found that overall localization of CHD1 on polytene chromosomes does not appreciably change in chromodomain-mutant flies. In contrast, the chromodomains are important for transcription-independent activities of CHD1 during early embryonic development as well as for transcriptional regulation of several heat shock genes. However, neither CHD1 nor its chromodomains are needed for RNA polymerase II localization and H3K4 methylation but loss of CHD1 decreases transcription-induced histone eviction at the Hsp70 gene in vivo. Chromodomain mutations negatively affect the chromatin assembly activities of CHD1 in vitro, and they appear to be involved in linking the ATP-dependent motor to the chromatin assembly function of CHD1.

Remote programming of cochlear implants in users of all ages.

BACKGROUND: Remote programming for adult cochlear implant (CI) users is feasible, safe, and effective. Limited evidence, however, exists on if remote CI programming can also be productively done with paediatric CI users. AIMS/OBJECTIVES: To assess the safety and feasibility of remote CI programming in CI users for all ages. MATERIALS AND METHODS: Forty-six (25 children, 21 adults) experienced CI users were fit locally and remotely. The results of these two fitting sessions were compared in terms of safety, Impedance Field Telemetry (IFT), Maximum Comfortable Levels (MCL), Threshold Levels (THR), audiometry, fitting duration, and speech understanding. RESULTS: The subjects' safety was not compromised during any of the fitting procedures. No significant difference was found for IFT, MCL, THR, audiometry, or speech understanding for either remote or local fitting. Remote fittings took slightly longer than local fittings when only the fitting time itself was measured. CONCLUSIONS AND SIGNIFICANCE: Remote follow-up fitting is as safe, feasible, and effective as local fitting for CI users of all ages. A more extensive adoption of remote fitting may allow many CI users greater access to clinics and therefore increased benefit from CI use.

ATP-dependent chromatin remodeling enzymes and their various roles in cell cycle control.

The modification of chromatin structure by various mechanisms has emerged as a key regulatory component of nuclear programs. Cell cycle progression and exit are affected by the integrity of chromatin architecture as well as by regulatory cues that chromatin structure imposes on the expression of cell cycle genes. ATP-dependent chromatin remodeling factors use the energy derived from ATP-hydrolysis to modulate histone-DNA contacts. These molecular machines play important roles in all aspects of chromosome biology and are thus intimately linked to cell cycle control. Regulation of complex activity by various signaling pathways has been a rising theme in recent years. Moreover, some chromatin remodeling factors have been characterized as potent tumor suppressor proteins. Thus, to understand the functions and activities of ATP-utilizing chromatin remodeling factors is an important goal towards their use as potential targets in cancer therapy.

MLL-AF9 Expression in Hematopoietic Stem Cells Drives a Highly Invasive AML Expressing EMT-Related Genes Linked to Poor Outcome.

To address the impact of cellular origin on acute myeloid leukemia (AML), we generated an inducible transgenic mouse model for MLL-AF9-driven leukemia. MLL-AF9 expression in long-term hematopoietic stem cells (LT-HSC) in vitro resulted in dispersed clonogenic growth and expression of genes involved in migration and invasion. In vivo, 20% LT-HSC-derived AML were particularly aggressive with extensive tissue infiltration, chemoresistance, and expressed genes related to epithelial-mesenchymal transition (EMT) in solid cancers. Knockdown of the EMT regulator ZEB1 significantly reduced leukemic blast invasion. By classifying mouse and human leukemias according to Evi1/EVI1 and Erg/ERG expression, reflecting aggressiveness and cell of origin, and performing comparative transcriptomics, we identified several EMT-related genes that were significantly associated with poor overall survival of AML patients.

Two anti-microtubular drugs for two differential responses: a rice cell line resistant to EPC remains susceptible to oryzalin.

Sensitivity to the two anti-microtubular drugs oryzalin and EPC (ethyl-N-phenylcarbamate) is shown to be uncoupled in the rice EPC-resistant ER31d cell line, derived from the corresponding ER31 mutant. The ER31d cell line grows in the presence of EPC but it remains susceptible to oryzalin. In the presence of concentrations of EPC up to 0.4 mM, ER31d cells remain viable maintaining cell anisotropy and detectable cortical microtubule array. The amount of α- and ß-tubulin is also maintained high through a regulatory mechanism that operates at post-transcriptional level. In contrast, all these cellular and molecular parameters are heavily affected by the addition of 1 µM oryzalin. Also, the pattern of post-translationally modified α-tubulins changes in the ER31d cells compared to that of their Nihon-Masari wild type line of reference. The different response elicited by the two herbicides is discussed in relation to a possible differential sensitivity of the cortical MT array, that may in turn relate to their different tubulin-binding specificities and chemical structure.

CHD1 contributes to intestinal resistance against infection by P. aeruginosa in Drosophila melanogaster.

Drosophila SNF2-type ATPase CHD1 catalyzes the assembly and remodeling of nucleosomal arrays in vitro and is involved in H3.3 incorporation in viin vivo during early embryo development. Evidence for a role as transcriptional regulator comes from its colocalization with elongating RNA polymerase II as well as from studies of fly Hsp70 transcription. Here we used microarray analysis to identify target genes of CHD1. We found a fraction of genes that were misregulated in Chd1 mutants to be functionally linked to Drosophila immune and stress response. Infection experiments using different microbial species revealed defects in host defense in Chd1-deficient adults upon oral infection with P. aeruginosa but not upon septic injury, suggesting a so far unrecognized role for CHD1 in intestinal immunity. Further molecular analysis showed that gut-specific transcription of antimicrobial peptide genes was overactivated in the absence of infection in Chd1 mutant flies. Moreover, microbial colonization of the intestine was elevated in Chd1 mutants and oral infection resulted in strong enrichment of bacteria in the body cavity indicating increased microbial passage across intestinal epithelia. However, we did not detect enhanced epithelial damage or alterations of the intestinal stem cell population. Collectively, our data provide evidence that intestinal resistance against infection by P. aeruginosa in Drosophila is linked to maintaining proper balance of gut-microbe interactions and that the chromatin remodeler CHD1 is involved in regulating this aspect.