A label-free ratiometric homogeneous electrochemical aptasensor based on dual catalytic hairpin self-assembly for rapid and sensitive detection of ochratoxin A in food.

The food contamination with Ochratoxin A (OTA) has highlighted the need to create precise, sensitive, and convenient techniques. Herein, we proposed a label-free and immobilization-free ratiometric homogeneous electrochemical aptasensor based on dual catalytic hairpin self-assembly (CHA) for OTA detection. Methylene blue (MB) and ferrocene (Fc) in solution were utilized as label-free signaling molecules, generating a response signal (IMB) and a reference signal (IFc), respectively. The ratio of IMB/IFc was utilized as a measure to quantify OTA. Dual CHA was exploited to increase the ratiometric signal and enhance the amplification efficiency. This aptasensor achieved trace-level detection for OTA over a linear range of lower concentrations (1.0 × 10-3 ng/mL-1.0 × 103 ng/mL) with LOD of 92 fg/mL. The aptasensor was successfully applied to detect OTA in cereal and wine, with comparable results of HPLC-MS/MS. This strategy provided a viable platform for rapid, sensitive, and accurate detection of OTA in food.

An accurate and ultrasensitive ratiometric electrochemical aptasensor for determination of Ochratoxin A based on catalytic hairpin assembly.

Ochratoxin A (OTA) pollution in agricultural products has raised the pressing to develop sensitive, accurate and convenient detection methods. Herein, an accurate and ultrasensitive ratiometric electrochemical aptasensor was proposed based on catalytic hairpin assembly (CHA) for OTA detection. In this strategy, the target recognition and CHA reaction were both accomplished in the same system, which avoided tedious multi-steps operation and extra reagents, providing the advantage of convenience with only a one-step reaction and without enzyme. The labeled Fc and MB were used as the signal-switching molecules, avoiding various interferences and greatly improving the reproducibility (RSD: 3.197%). This aptasensor achieved trace-level detection for OTA with LOD of 81 fg/mL in the linear range of lower concentration (100 fg/mL-50 ng/mL). Moreover, this strategy was successfully applied to OTA detection in cereals with comparable results of HPLC-MS. This aptasensor provided a viable platform for accurate, ultrasensitive, and one-step detection of OTA in food.

SHP2 participates in decidualization by activating ERK to maintain normal nuclear localization of progesterone receptor.

In brief: The establishment and maintenance of embryo implantation and pregnancy require decidualization of endometrial stromal cells. This paper reveals that SHP2 ensures the correct subcellular localization of progesterone receptor, thereby safeguarding the process of decidualization. Abstract: Decidualization is the process of conversion of endometrial stromal cells into decidual stromal cells, which is caused by progesterone production that begins during the luteal phase of the menstrual cycle and then increases throughout pregnancy dedicated to support embryonic development. Decidualization deficiency is closely associated with various pregnancy complications, such as recurrent miscarriage (RM). Here, we reported that Src-homology-2-containing phospho-tyrosine phosphatase (SHP2), a key regulator in the signal transduction process downstream of various receptors, plays an indispensable role in decidualization. SHP2 expression was upregulated during decidualization. SHP2 inhibitor RMC-4550 and shRNA-mediated SHP2 reduction resulted in a decreased level of phosphorylation of ERK and aberrant cytoplasmic localization of progesterone receptor (PR), coinciding with reduced expression of IGFBP1 and various other target genes of decidualization. Solely inhibiting ERK activity recapitulated these observations. Administration of RMC-4550 led to decidualization deficiency and embryo absorption in mice. Moreover, reduced expression of SHP2 was detected in the decidua of RM patients. Our results revealed that SHP2 is key to PR's nuclear localization, thereby indispensable for decidualization and that reduced expression of SHP2 might be engaged in the pathogenesis of RM.

A cross-sectional study of the association between heavy metals and pan-cancers associated with sex hormones in NHANES 1999-2018.

Given the complexity of tumorigenesis, numerous studies have also shown that excessive exposure to heavy metals increases the risk of cancers and disrupts the secretion of sex hormones. However, the specific effects of heavy metals on cancers remain to be proven. To confirm the association between heavy metals and pan-cancer sex hormone levels among adults, 94,337 individuals from the National Health and Nutrition Examination Survey were assessed. We examined the associations between pan-cancers associated with sex hormones (ovarian, testicular, breast, and prostate cancers) and heavy metals in blood/urine. The methods (the WQS (weighted quantile sums) and SVYGLM (survey generalized linear model) regressions) were used to evaluate the association between sex hormone-related cancers and each metal category by incorporating covariates. To evaluate the overall effect of heavy metals and detect the dose-response relationship between the prevalence of pan-cancers associated with sex hormones and heavy metals, RCS (restricted cubic splines) were applied. Environmental exposure to heavy metals may be associated with pan-cancers associated with sex hormones in adults in the USA. Prostate cancer was inversely associated with blood cadmium while positively associated with blood lead, urinary tin, and thallium. Breast cancer was inversely associated with blood lead. Ovarian cancer was positively associated with blood cadmium. We also found a non-linear dose-response relationship between pan-cancers associated with sex hormones and heavy metals, which was non-parametric, using RCS models. The OR for breast cancer decreased along with the increase in lead concentration under approximately 20 µg/dl, while the OR for prostate cancer increased between urine thallium levels of approximately 0.17-1.1 ng/ml. Pan-cancers associated with sex hormones are associated with exposure to heavy metals. Considering the design of the NHANES study, further studies need to be conducted on other nationally representative surveys.

Evaluation of volume-based flow cytometry as a potential primary method for quantification of bacterial reference material.

Bacterial reference materials (RMs) play a crucial role in many analytical processes of microbiological detection. Currently, bacteria are typically counted using the traditional plate-based approach, which results in a higher uncertainty of bacterial RMs unfortunately. Therefore, novel methods are urgently required for the value assignment of RMs in the field of microbiology to derive measurement traceability and accuracy. A potential primary method for microbiological quantification based on flow cytometry (FCM) is described in this study using Escherichia coli O157 (E. coli O157) as an example. The proposed method was applied to determine the number of viable E. coli O157 cells in the RMs with a result of (5.48 ± 0.27) × 108 cells mL-1, which was in good agreement with the result obtained using the plate-based method (En = 0.47). Additionally, this method could be entirely described and understood by equations, and provides formal traceability to the SI for counts of viable bacterial cells, while the associated relative expanded uncertainty (4.93%, k = 2) was significantly lower in comparison to the plate-based method. Therefore, the FCM-based method might be a potential primary method for characterizing bacterial RMs. To our knowledge, this is the first description of FCM as a potential primary method for accurate and traceable quantification of viable bacterial cells with a comprehensive uncertainty statement in microbiological metrology.

An electrochemical biosensor for the highly sensitive detection of Staphylococcus aureus based on SRCA-CRISPR/Cas12a.

As one of the major foodborne pathogens, Staphylococcus aureus (S. aureus) can cause infectious diseases. In the current study, a novel electrochemical biosensor based on saltatory rolling circle amplification (SRCA) combined with CRISPR/Cas12a system was developed for the accurate detection of S. aureus. The thio-modified reporter probes (SH-ssDNA-MB) was immobilized on the surface of gold nanoparticle-modified electrode through the Au-S bond. In the presence of S. aureus, the target DNA double strands obtained by SRCA can be specifically recognized with Cas12a/crRNA complex. The trans-cleavage activity of Cas12a induces SH-ssDNA-MB to be cleaved from the electrode surface, resulting in a decrease in the current signal. Subsequently, the ratio of the current can be calculated as the detection result. Under optimal conditions, the detection limits were 2.51 fg/µL for genomic DNA and 3 CFU/mL for S. aureus in pure cultures, respectively. Moreover, the method demonstrated satisfactory specificity, acceptable stability and reproducibility. In comparison with ISO methods, the sensitivity, specificity and accuracy of the developed method were 100%, 97.8% and 98%, respectively. In conclusion, the developed novel electrochemical biosensor provides a potential powerful platform for the accurate detection of S. aureus.

A Novel Fluorescent Aptasensor Based on Real-Time Fluorescence and Strand Displacement Amplification for the Detection of Ochratoxin A.

It is urgently necessary to develop convenient, reliable, ultrasensitive and specific methods of ochratoxin A determination in food safety owing to its high toxicity. In the present study, an ultrasensitive and labeled-free fluorescent aptamer sensor combining real-time fluorescence with strand displacement amplification (SDA) was fabricated for the determination of OTA. In the presence of OTA, the OTA-aptamer combines with OTA, thus opening hairpins. Then, SDA primers specifically bind to the hairpin stem, which is used for subsequent amplification as a template. SDA amplification is initiated under the action of Bst DNA polymerase and nicking endonuclease. The amplified products (ssDNA) are dyed with SYBR Green II and detected with real-time fluorescence. The method has good linearity in the range of 0.01-50 ng mL-1, with the lowest limit of detection of 0.01 ng mL-1. Additionally, the fluorescent aptamer sensor shows outstanding specificity and reproducibility. Furthermore, the sensor shows excellent analytical performance in the artificial labeled detection of wheat and oat samples, with a recovery rate of 96.1~100%. The results suggest that the developed sensor has a promising potential application for the ultrasensitive detection of contaminants in food.

Closed-tube saltatory rolling circle amplification with hydroxynaphthol blue for visual on-site detection of peanut as an allergenic food.

Peanut allergy as one of the major causes of food-induced anaphylaxis is usually life-threatening for specific individuals. Nowadays, the effective remedy is avoidance of consuming allergen-containing food, urging monitoring the presence of peanut in foods. Herein, we proposed a closed-tube saltatory rolling circle amplification (SRCA) assay with hydroxynaphthol blue (HNB) for visual on-site detection of peanut allergen, displaying highly specificity for Ara h 1-encoding gene. The results can be discriminated by naked eye without opening the tube, averting costly sophisticated apparatus and reducing the risk of cross-contamination. The assay was 1000-, 100- and 10-fold more sensitive than PCR, LAMP and SRCA, respectively. The relative limit of detection is 0.01% in a binary mixture. The relative sensitivity, specificity and accuracy of this method were 100%, 97.50% and 98.67%, respectively. Thus, the visual closed-tube HNB-SRCA assay with superiorities of easy-to-perform, cost-effective and user-friendly has excellent potential for on-site application of food allergy.

Heat management of a compact x-ray source for microbeam radiotherapy and FLASH treatments.

BACKGROUND: Microbeam and x-ray FLASH radiation therapy are innovative concepts that promise reduced normal tissue toxicity in radiation oncology without compromising tumor control. However, currently only large third-generation synchrotrons deliver acceptable x-ray beam qualities and there is a need for compact, hospital-based radiation sources to facilitate clinical translation of these novel treatment strategies. PURPOSE: We are currently setting up the first prototype of a line-focus x-ray tube (LFxT), a promising technology that may deliver ultra-high dose rates (UHDRs) of more than 100 Gy/s from a table-top source. The operation of the source in the heat capacity limit allows very high dose rates with micrometer-sized focal spot widths. Here, we investigate concepts of effective heat management for the LFxT, a prerequisite for the performance of the source. METHODS: For different focal spot widths, we investigated the temperature increase numerically with Monte Carlo simulations and finite element analysis (FEA). We benchmarked the temperature and thermal stresses at the focal spot against a commercial x-ray tube with similar power characteristics. We assessed thermal loads at the vacuum chamber housing caused by scattering electrons in Monte Carlo simulations and FEA. Further, we discuss active cooling strategies and present a design of the rotating target. RESULTS: Conventional focal spot widths led to a temperature increase dominated by heat conduction, while very narrow focal spots led to a temperature increase dominated by the heat capacity of the target material. Due to operation in the heat capacity limit, the temperature increase at the focal spot was lower than for the investigated commercial x-ray tube. Hence, the thermal stress at the focal spot of the LFxT was considered uncritical. The target shaft and the vacuum chamber housing require active cooling to withstand the high heat loads. CONCLUSIONS: The heat capacity limit allows very high power densities at the focal spot of the LFxT and thus facilitates very high dose rates. Numerical simulations demonstrated that the heat load imparted by scattering electrons requires active cooling.

Establishing a survival prediction model for esophageal squamous cell carcinoma based on CT and histopathological images.

Currently, the incidence of esophageal squamous cell carcinoma (ESCC) in China is high and its prognosis is poor. To evaluate the prognosis of patients with ESCC, we performed computerized quantitative analyses on diagnostic computed tomography (CT) and digital histopathological slices. A retrospective study was conducted to assess the prognosis of ESCC in 153 patients who underwent esophagectomy, and the cohort was selected based on strict clinical criteria. Each patient had an enhanced CT image, and there were two imaging protocols for CT images of all patients. Each patient in the cohort also had a histopathological tissue slide after hematoxylin-eosin staining. Under an electron microscope, the tissue slide was scanned as an image of large size. We then performed quantitative analyses to identify factors related to the prognosis of ESCC on digital histological images and diagnostic CT images. For CT images, we used the radiomics method. For histological images, we designed a set of quantitative features based on machine learning algorithms, such as K-means and principal component analysis. These features describe the patterns of different cell types in histopathological images. Subsequently, we used the survival analysis model established using only CT image features as the baseline. We also compared multiple machine learning models and adopted a five-fold cross-validation method to establish a robust survival model. In establishing survival models, we first used CT image features to establish survival models, and the C-index from the Weibull Cox model on the test set reached 0.624. Then we used histopathlogical features to establish survival models, and the C-index from the Weibull Cox model on the test set reached 0.664, which was obviously better than CT's. Lastly, we combined CT image features and histopathological image features to establish survival models. The performance was better than that in the models built using only CT image features or histopathological image features, and the C-index from the regularized Cox model on the test set reached 0.694. We also proved the effectiveness of the quantified histopathological image features in terms of prognosis using the log-rank test. Histopathological image features are more relevant to prognosis than features extracted from CT images using radiomics. The results of this study provide clinicians with a reference to improve the survival rate of patients with ESCC after surgery. These results have implications for advancing the process of explaining the poor prognosis of esophageal cancer.

Development of the Saltatory Rolling Circle Amplification Assay for Rapid and Visual Detection of Alicyclobacillus acidoterrestris in Apple Juice.

A novel nucleic acid isothermal amplification method based on saltatory rolling circle amplification (SRCA) for rapid and visual detection of Alicyclobacillus acidoterrestris in apple juice was established. Fourteen A. acidoterrestris strains and 44 non-A. acidoterrestris strains were used to confirm the specificity. The sensitivity of SRCA was 4.5 × 101 CFU/mL by observing the white precipitate with the naked eye, while it was 4.5 × 100 CFU/mL by fluorescence visualization. The detection limit of SRCA in artificially inoculated apple juice was 7.1 × 101 and 7.1 × 100 CFU/mL via visualization of the white precipitate and fluorescence, respectively. Compared with the traditional PCR method, SRCA exhibited at least a 100-fold higher sensitivity and 100-fold lower detection limit. Seventy samples were investigated for A. acidoterrestris contamination, and the results showed 100% sensitivity, 97.01% specificity, and 97.14% accuracy compared with those by the conventional microbiological cultivation method. Overall, this method is a potentially useful tool for visual and rapid detection of A. acidoterrestris.

Review of Electrochemical DNA Biosensors for Detecting Food Borne Pathogens.

The vital importance of rapid and accurate detection of food borne pathogens has driven the development of biosensor to prevent food borne illness outbreaks. Electrochemical DNA biosensors offer such merits as rapid response, high sensitivity, low cost, and ease of use. This review covers the following three aspects: food borne pathogens and conventional detection methods, the design and fabrication of electrochemical DNA biosensors and several techniques for improving sensitivity of biosensors. We highlight the main bioreceptors and immobilizing methods on sensing interface, electrochemical techniques, electrochemical indicators, nanotechnology, and nucleic acid-based amplification. Finally, in view of the existing shortcomings of electrochemical DNA biosensors in the field of food borne pathogen detection, we also predict and prospect future research focuses from the following five aspects: specific bioreceptors (improving specificity), nanomaterials (enhancing sensitivity), microfluidic chip technology (realizing automate operation), paper-based biosensors (reducing detection cost), and smartphones or other mobile devices (simplifying signal reading devices).

Saltatory rolling circle amplification for sensitive visual detection of Staphylococcus aureus in milk.

Monitoring Staphylococcus aureus with high sensitivity is very important for ensuring milk quality and food safety. In this study, we used a rapid nucleic acid isothermal amplification method, saltatory rolling circle amplification (SRCA), for the detection of Staph. aureus in milk. The results of the SRCA method can be assessed visually by the presence of white precipitate or by fluorescence measurement. Thirteen Staph. aureus strains and 31 non-Staph. aureus strains were used to evaluate the specificity of SRCA. The method exhibited excellent detection of Staph. aureus genomic DNA at a concentration of 7.8 × 101 fg/µL when assessed by visible precipitate, and at 7.8 × 100 fg/µL when detected by fluorescence after addition of the fluorochrome SYBR Green I. In artificially inoculated milk, the detection limits of SRCA were 5.6 × 102 cfu/mL by precipitate and 5.6 × 101 cfu/mL by fluorescence, respectively. Compared with conventional PCR approaches, the SRCA assay achieved at least 100-fold higher sensitivity. Moreover, the sensitivity, specificity, and accuracy of the SRCA-based system were calculated to be 100.00, 97.73, and 97.78%, respectively. These results indicate that SRCA has potential application as a sensitive and visual technique for the detection of Staph. aureus in milk.

Discovery and optimization of phthalazinone derivatives as a new class of potent dengue virus inhibitors.

Using a dengue replicon cell line-based screening, we identified 3-(dimethylamino)propyl(3-((4-(4-fluorophenyl)-1-oxophthalazin-2(1H)-yl)methyl)phenyl)carbamate (10a) as a potent DENV-2 inhibitor, with an IC50 value of 0.64 µM. A series of novel phthalazinone derivatives based on hit 10a were synthesized and evaluated for their in vitro anti-DENV activity and cytotoxicity. The subsequent SAR study and optimization led to the discovery of the most promising compound 14l, which displayed potent anti-DENV-2 activity, with low IC50 value against DENV-2 RNA replication of 0.13 µM and high selectivity (SI = 89.2) with acceptable pharmacokinetics profiles.

Distinct polymer physics principles govern chromatin dynamics in mouse and Drosophila topological domains.

BACKGROUND: In higher eukaryotes, the genome is partitioned into large "Topologically Associating Domains" (TADs) in which the chromatin displays favoured long-range contacts. While a crumpled/fractal globule organization has received experimental supports at higher-order levels, the organization principles that govern chromatin dynamics within these TADs remain unclear. Using simple polymer models, we previously showed that, in mouse liver cells, gene-rich domains tend to adopt a statistical helix shape when no significant locus-specific interaction takes place. RESULTS: Here, we use data from diverse 3C-derived methods to explore chromatin dynamics within mouse and Drosophila TADs. In mouse Embryonic Stem Cells (mESC), that possess large TADs (median size of 840 kb), we show that the statistical helix model, but not globule models, is relevant not only in gene-rich TADs, but also in gene-poor and gene-desert TADs. Interestingly, this statistical helix organization is considerably relaxed in mESC compared to liver cells, indicating that the impact of the constraints responsible for this organization is weaker in pluripotent cells. Finally, depletion of histone H1 in mESC alters local chromatin flexibility but not the statistical helix organization. In Drosophila, which possesses TADs of smaller sizes (median size of 70 kb), we show that, while chromatin compaction and flexibility are finely tuned according to the epigenetic landscape, chromatin dynamics within TADs is generally compatible with an unconstrained polymer configuration. CONCLUSIONS: Models issued from polymer physics can accurately describe the organization principles governing chromatin dynamics in both mouse and Drosophila TADs. However, constraints applied on this dynamics within mammalian TADs have a peculiar impact resulting in a statistical helix organization.

Solitons of four-wave mixing in competing cubic-quintic nonlinearity.

We experimentally investigate the soliton formation and dynamics in the nonlinear propagation of the generated signal and probe beams in four-wave mixing (FWM) process with atomic coherence in a three-level atomic system, under the competition between focusing and defocusing nonlinearities, as well as between gain and dissipation, due to the third- and fifth-order nonlinear susceptibilities with opposite signs. With multi-parameter controllability and nonlinear competition in the system, fundamental, dipole, and azimuthally-modulated vortex FWM solitons can transform mutually from one to the other. Such investigations have potential applications in optical pattern formation and control, and all-optical communication.

Histone h1.3 suppresses h19 noncoding RNA expression and cell growth of ovarian cancer cells.

Ovarian cancer is a deadly gynecologic malignancy for which novel biomarkers and therapeutic targets are imperative for improving survival. Previous studies have suggested the expression pattern of linker histone variants as potential biomarkers for ovarian cancer. To investigate the role of histone H1 in ovarian cancer cells, we characterize individual H1 variants and overexpress one of the major somatic H1 variants, H1.3, in the OVCAR-3 epithelial ovarian cancer cell line. We find that overexpression of H1.3 decreases the growth rate and colony formation of OVCAR-3 cells. We identify histone H1.3 as a specific repressor for the noncoding oncogene H19. Overexpression of H1.3 suppresses H19 expression, and knockdown of H1.3 increases its expression in multiple ovarian epithelial cancer cell lines. Furthermore, we demonstrate that histone H1.3 overexpression leads to increased occupancy of H1.3 at the H19 regulator region encompassing the imprinting control region (ICR), concomitant with increased DNA methylation and reduced occupancy of the insulator protein CTCF at the ICR. Finally, we demonstrate that H1.3 overexpression and H19 knockdown synergistically decrease the growth rate of ovarian cancer cells. Our findings suggest that H1.3 dramatically inhibits H19 expression, which contributes to the suppression of epithelial ovarian carcinogenesis.

Electromagnetically induced transparency and fluorescence in blockaded Rydberg atomic system.

We investigate the interaction between dark states and Rydberg excitation blockade by using electromagnetically induced transparency (EIT), fluorescence, and four-wave mixing (FWM) signals both theoretically and experimentally. By scanning the frequency detunings of the probe and dressing fields, respectively, we first observe these signals (three coexisting EIT windows, two fluorescence signals, and two FWM signals) under Rydberg excitation blockade. Next, frequency detuning dependences of these signals are obtained, in which the modulated results are well explained by introducing the dressing effects (leading to the dark states) with the corrected factor of the Rydberg excitation blockade. In addition, the variations by changing the principal quantum number n of Rydberg state shown some interesting phenomena resulting from Rydberg blockade are observed. The unique nature of such blockaded signals can have potential application in the demonstration of quantum computing.

High-resolution mapping of h1 linker histone variants in embryonic stem cells.

H1 linker histones facilitate higher-order chromatin folding and are essential for mammalian development. To achieve high-resolution mapping of H1 variants H1d and H1c in embryonic stem cells (ESCs), we have established a knock-in system and shown that the N-terminally tagged H1 proteins are functionally interchangeable to their endogenous counterparts in vivo. H1d and H1c are depleted from GC- and gene-rich regions and active promoters, inversely correlated with H3K4me3, but positively correlated with H3K9me3 and associated with characteristic sequence features. Surprisingly, both H1d and H1c are significantly enriched at major satellites, which display increased nucleosome spacing compared with bulk chromatin. While also depleted at active promoters and enriched at major satellites, overexpressed H1(0) displays differential binding patterns in specific repetitive sequences compared with H1d and H1c. Depletion of H1c, H1d, and H1e causes pericentric chromocenter clustering and de-repression of major satellites. These results integrate the localization of an understudied type of chromatin proteins, namely the H1 variants, into the epigenome map of mouse ESCs, and we identify significant changes at pericentric heterochromatin upon depletion of this epigenetic mark.

Reduction of Hox gene expression by histone H1 depletion.

The evolutionarily conserved homeotic (Hox) genes are organized in clusters and expressed collinearly to specify body patterning during embryonic development. Chromatin reorganization and decompaction are intimately connected with Hox gene activation. Linker histone H1 plays a key role in facilitating folding of higher order chromatin structure. Previous studies have shown that deletion of three somatic H1 subtypes together leads to embryonic lethality and that H1c/H1d/H1e triple knockout (TKO) embryonic stem cells (ESCs) display bulk chromatin decompaction. To investigate the potential role of H1 and higher order chromatin folding in the regulation of Hox gene expression, we systematically analyzed the expression of all 39 Hox genes in triple H1 null mouse embryos and ESCs by quantitative RT-PCR. Surprisingly, we find that H1 depletion causes significant reduction in the expression of a broad range of Hox genes in embryos and ESCs. To examine if any of the three H1 subtypes (H1c, H1d and H1e) is responsible for decreased expression of Hox gene in triple-H1 null ESCs, we derived and characterized H1c(-/-), H1d(-/-), and H1e(-/-) single-H1 null ESCs. We show that deletion of individual H1 subtypes results in down-regulation of specific Hox genes in ESCs. Finally we demonstrate that, in triple-H1- and single-H1-null ESCs, the levels of H3K4 trimethylation (H3K4me3) and H3K27 trimethylation (H3K27me3) were affected at specific Hox genes with decreased expression. Our data demonstrate that marked reduction in total H1 levels causes significant reduction in both expression and the level of active histone mark H3K4me3 at many Hox genes and that individual H1 subtypes may also contribute to the regulation of specific Hox gene expression. We suggest possible mechanisms for such an unexpected role of histone H1 in Hox gene regulation.