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Background Colorectal cancer (CRC) is one of the most malignant tumors with high incidence, yet its molecular mechanism is not fully understood, hindering the development of targeted therapy. Metabolic abnormalities are a hallmark of cancer. Targeting dysregulated metabolic features has become an important direction for modern anticancer therapy. In this study, we aimed to identify a new metabolic enzyme that promotes proliferation of CRC and to examine the related molecular mechanisms. Methods We performed RNA sequencing and tissue microarray analyses of human CRC samples to identify new genes involved in CRC. Squalene epoxidase (SQLE) was identified to be highly upregulated in CRC patients. The regulatory function of SQLE in CRC progression and the therapeutic effect of SQLE inhibitors were determined by measuring CRC cell viability, colony and organoid formation, intracellular cholesterol concentration and xenograft tumor growth. The molecular mechanism of SQLE function was explored by combining transcriptome and untargeted metabolomics analysis. Western blotting and real‐time PCR were used to assess MAPK signaling activation by SQLE. Results SQLE‐related control of cholesterol biosynthesis was highly upregulated in CRC patients and associated with poor prognosis. SQLE promoted CRC growth in vitro and in vivo. Inhibition of SQLE reduced the levels of calcitriol (active form of vitamin D3) and CYP24A1, followed by an increase in intracellular Ca2+ concentration. Subsequently, MAPK signaling was suppressed, resulting in the inhibition of CRC cell growth. Consistently, terbinafine, an SQLE inhibitor, suppressed CRC cell proliferation and organoid and xenograft tumor growth. Conclusions Our findings demonstrate that SQLE promotes CRC through the accumulation of calcitriol and stimulation of CYP24A1‐mediated MAPK signaling, highlighting SQLE as a potential therapeutic target for CRC treatment., SQLE increases the levels of calcitriol and CYP24A1. Then MAPK signaling is induced to accelerate CRC tumor growth.

The role of cognitive, social and biological factors in the etiology of chronic periodontitis has been reported. The aim of this study was to evaluate the salivary cortisol level and interleukin-1 B level in patients of Chronic periodontitis in smokers and stress and nonsmokers without stress. The design of study randomized, prospective, double-blinded, and prospective study. The total sample size was comprised of 600 subjects between the ages of 20 and 50 years. The sample size was divided into 300 males and 300 females. Out of 600 subjects, 200 subjects comprised of subjects with chronic periodontitis with positive depression level with a history of smoking (Group I), 200 subjects comprised of subjects with chronic periodontitis without depression and without smoking (Group II), and 200 subjects who were taken as the control group comprised of healthy subjects without chronic periodontitis, without depression level, and no smoking history (Group III). Salivary cortisol levels were determined by enzyme-linked immunosorbent assay (ELISA). The result showed that there was a positive correlation between morning and evening salivary cortisol level in all the groups with correlation coefficient. There was significant higher value of salivary cortisol in Group I patients when compared with Group II and Group III. However, when the comparison of salivary cortisol levels was done between the Group II and Control group, the result showed nonsignificant P value. It is suggested that stress is positively correlated with the salivary cortisol levels in smokers and nonsmokers.

Activation of nuclear factor erythroid 2-related factor 2 (NRF2) has been found to ameliorate diabetic testicular damage (DTD) in rodents. However, it was unclear whether NRF2 is required for these approaches in DTD. Epigallocatechin gallate (EGCG) is a potent activator of NRF2 and has shown beneficial effects on multiple diabetic complications. However, the effect of EGCG has not been studied in DTD. The present study aims to explore the role of NRF2 in both self and EGCG protection against DTD. Therefore, streptozotocin-induced diabetic C57BL/6 wild type (WT) and Nrf2 knockout (KO) mice were treated in the presence or absence of EGCG, for 24 weeks. The Nrf2 KO mice exhibited more significant diabetes-induced loss in testicular weight and spermatozoa count, and increase in testicular apoptotic cell death, as compared with the WT mice. EGCG activated NRF2 expression and function, preserved testicular weight and spermatozoa count, and attenuated testicular apoptotic cell death, endoplasmic reticulum stress, inflammation, and oxidative damage in the WT diabetic mice, but not the Nrf2 KO diabetic mice. The present study demonstrated for the first time that NRF2 plays a critical role in both self and EGCG protection against DTD.

The highly conserved polycomb group (PcG) proteins maintain heritable transcription repression of the genes essential for development from fly to mammals. However, sporadic reports imply a potential role of PcGs in positive regulation of gene transcription, although systematic investigation of such function and the underlying mechanism has rarely been reported. Here, we report a Pc-mediated, H3K27me3-dependent positive transcriptional regulation of Senseless (Sens), a key transcription factor required for development. Mechanistic studies show that Pc regulates Sens expression by promoting H4K20me1 at the Sens locus. Further bioinformatic analysis at genome-wide level indicates that the existence of H4K20me1 acts as a selective mark for positive transcriptional regulation by Pc/H3K27me3. Both the intensities and specific patterns of Pc and H3K27me3 are important for the fates of target gene transcription. Moreover, binding of transcription factor Broad (Br), which physically interacts with Pc and positively regulates the transcription of Sens, is observed in Pc(+)H3K27me3(+)H4K20me1(+) genes, but not in Pc(+)H3K27me3(+)H4K20me1(-) genes. Taken together, our study reveals that, coupling with the transcription factor Br, Pc positively regulates transcription of Pc(+)H3K27me3(+)H4K20me1(+) genes in developing Drosophila wing disc.

The Hedgehog (Hh) signaling pathway plays important roles in both embryonic development and adult tissue homeostasis. Such biological functions are mediated by the transcription factor Cubitus interruptus (Ci). Yet the transcriptional regulation of the effector Ci itself is poorly investigated. Through an RNAi-based genetic screen, we identified that female sterile (1) homeotic (Fsh), a transcription co-activator, directly activates Ci transcription. Biochemistry assays demonstrated physical interactions among Fsh, Sex combs extra (Sce), and Polycomb (Pc). Functional assays further showed that both Pc and Sce are required for Ci expression, which is not likely mediated by the derepression of Engrailed (En), a repressor of Ci, in Pc or Sce mutant cells. Finally, we provide evidence showing that Pc/Sce facilitates the binding of Fsh at Ci locus and that the physical interaction between Fsh and Pc is essential for Fsh-mediated Ci transcription. Taken together, we not only uncover that Ci is transcriptionally regulated by Fsh-Pc-Sce complex but also provide evidence for the coordination between Fsh and PcG proteins in transcriptional regulation.

Atrophin suppresses Hedgehog signaling by interacting with the transcriptional effector CiR and recruiting the histone deacetylase Rpd3 to the dpp locus to repress its transcription., The evolutionarily conserved Hedgehog (Hh) signaling pathway is transduced by the Cubitus interruptus (Ci)/Gli family of transcription factors that exist in two distinct repressor (CiR/GliR) and activator (CiA/GliA) forms. Aberrant activation of Hh signaling is associated with various human cancers, but the mechanism through which CiR/GliR properly represses target gene expression is poorly understood. Here, we used Drosophila melanogaster and zebrafish models to define a repressor function of Atrophin (Atro) in Hh signaling. Atro directly bound to Ci through its C terminus. The N terminus of Atro interacted with a histone deacetylase, Rpd3, to recruit it to a Ci-binding site at the decapentaplegic (dpp) locus and reduce dpp transcription through histone acetylation regulation. The repressor function of Atro in Hh signaling was dependent on Ci. Furthermore, Rerea, a homologue of Atro in zebrafish, repressed the expression of Hh-responsive genes. We propose that the Atro–Rpd3 complex plays a conserved role to function as a CiR corepressor.

Stem cell niche is a specialized microenvironment crucial to self-renewal. The testis in Drosophila contains two different types of stem cells, the germline stem cells and the somatic cyst stem cells that are sustained by their respective niche signals, thus is a good system for studying the interaction between the stem cells and their hosting niche. The JAK-STAT and BMP pathways are known to play critical roles in the self-renewal of different kinds of stem cells, but the roles of several other pathways have emerged recently in a complex signaling network in the testis niche. Reports of independent observations from three research groups have uncovered an important role of Hedgehog (Hh) in the Drosophila testis niche. In this review, we summarize these recent findings and discuss the interplay between the Hh signaling mechanisms and those of the JAK-STAT and BMP pathways. We also discuss directions for further investigation.

The Hh pathway controls many morphogenetic processes in metazoans and plays important roles in numerous pathologies and in cancer. Hh signaling is mediated by the activity of the Gli/Ci family of transcription factors. Several studies in Drosophila have shown that ubiquitination by the ubiquitin E3 ligases Slimb and Rdx(Hib) plays a crucial role in controlling Ci stability dependent on the levels of Hh signals. If Hh levels are low, Slimb adds K11- and K48-linked poly-ubiquitin chains on Ci resulting in partial degradation. Ubiquitin E2 enzymes are pivotal in determining the topologies of ubiquitin chains. However, which E2 enzymes participate in the selective ubiquitination-degradation of Ci remains elusive. Here, we find that the E2 enzyme UbcD1 negatively regulates Hh signaling activity in Drosophila wing disks. Genetic and biochemical analyses in wing disks and in cultured cells reveal that UbcD1 directly controls Ci stability. Interestingly, UbcD1 is found to be selectively involved in Slimb-mediated Ci degradation. Finally, we show that the homologs of UbcD1 play a conserved role in modulating Hh signaling in vertebrates.

SUMO (Small ubiquitin-related modifier) modification (SUMOylation) is a highly dynamic post-translational modification (PTM) that plays important roles in tissue development and disease progression. However, its function in adult stem cell maintenance is largely unknown. Here, we report the function of SUMOylation in somatic cyst stem cell (CySC) self-renewal in adult Drosophila testis. The SUMO pathway cell-autonomously regulates CySC maintenance. Reduction of SUMOylation promotes premature differentiation of CySCs and impedes the proliferation of CySCs, which leads to a reduction in the number of CySCs. Consistent with this, CySC clones carrying a mutation of the SUMO-conjugating enzyme are rapidly lost. Furthermore, inhibition of the SUMO pathway phenocopies disruption of the Hedgehog (Hh) pathway, and can block the proliferation of CySCs induced by Hh activation. Importantly, the SUMO pathway directly regulates the SUMOylation of Hh pathway transcription factor Cubitus interruptus (Ci), which is required for promoting CySC proliferation. Thus, we conclude that SUMO directly targets the Hh pathway and regulates CySC maintenance in adult Drosophila testis.

In eukaryotes, aberrant expression of transposable elements (TEs) is detrimental to the host genome. Piwi-interacting RNAs (piRNAs) of ∼23 to 30 nucleotides bound to PIWI clade Argonaute proteins silence transposons in a manner that is strictly dependent on their sequence complementarity. Hence, a key goal in understanding piRNA pathways is to determine mechanisms that modulate piRNA sequences. Here, we identify a protein-protein interaction between the 3′-to-5′ exoribonuclease Nibbler (Nbr) and Piwi that links Nbr activity with piRNA pathways. We show that there is a delicate balance in the interplay between Nbr and Hen1, a methyltransferase involved in 2′-O-methylation at the 3′ terminal nucleotides of piRNAs, thus connecting two genes with opposing activities in the biogenesis of piRNA 3′ ends. With age, piRNAs become shorter and fewer in number, which is coupled with the derepression of select TEs. We demonstrate that activities of Nbr and Hen1 inherently contribute to TE silencing and age-dependent profiles of piRNAs. We propose that antagonistic roles of Nbr and Hen1 define a mechanism to modulate piRNA 3′ ends., Summary: Antagonism between Nbr and Hen1 represents a novel mechanism for the modulation of piRNA sequences, revealing new players involved in the silencing of transposable elements.

Intestinal homeostasis is maintained by intestinal stem cells (ISCs) and their progenies. A complex autonomic nervous system spreads over posterior intestine. However, whether and how neurons regulate posterior intestinal homeostasis is largely unknown. Here we report that neurons regulate Drosophila posterior intestinal homeostasis. Specifically, downregulation of neuronal Hedgehog (Hh) signaling inhibits the differentiation of ISCs toward enterocytes (ECs), whereas upregulated neuronal Hh signaling promotes such process. We demonstrate that, among multiple sources of Hh ligand, those secreted by ECs induces similar phenotypes as does neuronal Hh. In addition, intestinal JAK/STAT signaling responds to activated neuronal Hh signaling, suggesting that JAK/STAT signaling acts downstream of neuronal Hh signaling in intestine. Collectively, our results indicate that neuronal Hh signaling is essential for the determination of ISC fate.

In eukaryotes, aberrant expression of transposable elements (TEs) is detrimental to the host genome. Piwi-interacting RNAs (piRNAs) of ∼23 to 30 nucleotides bound to PIWI clade Argonaute proteins silence transposons in a manner that is strictly dependent on their sequence complementarity. Hence, a key goal in understanding piRNA pathways is to determine mechanisms that modulate piRNA sequences. Here, we identify a protein-protein interaction between the 3'-to-5' exoribonuclease Nibbler (Nbr) and Piwi that links Nbr activity with piRNA pathways. We show that there is a delicate balance in the interplay between Nbr and Hen1, a methyltransferase involved in 2'-O-methylation at the 3' terminal nucleotides of piRNAs, thus connecting two genes with opposing activities in the biogenesis of piRNA 3' ends. With age, piRNAs become shorter and fewer in number, which is coupled with the derepression of select TEs. We demonstrate that activities of Nbr and Hen1 inherently contribute to TE silencing and age-dependent profiles of piRNAs. We propose that antagonistic roles of Nbr and Hen1 define a mechanism to modulate piRNA 3' ends.

Correction to: Cell Research (2016) 26:529–542. doi:10.1038/cr.2016.33; published online on 22 March 2016 The authors apologized for the missing of labeling the first two authors as co-first authors, since they contributed equally to this work. The correct form is as follows. We are also sorry for the delayed notice.

The objective of this study was to evaluate the functional properties of lactic acid bacteria (LAB) isolated from Tibetan kefir grains. Three Lactobacillus isolates identified as Lactobacillus acidophilus LA15, Lactobacillus plantarum B23 and Lactobacillus kefiri D17 that showed resistance to acid and bile salts were selected for further evaluation of their probiotic properties. The 3 selected strains expressed high in vitro adherence to Caco-2 cells. They were sensitive to gentamicin, erythromycin and chloramphenicol and resistant to vancomycin with MIC values of 26 µg/ml. All 3 strains showed potential bile salt hydrolase (BSH) activity, cholesterol assimilation and cholesterol co-precipitation ability. Additionally, the potential effect of these strains on plasma cholesterol levels was evaluated in Sprague-Dawley (SD) rats. Rats in 4 treatment groups were fed the following experimental diets for 4 weeks: a high-cholesterol diet, a high-cholesterol diet plus LA15, a high-cholesterol diet plus B23 or a high-cholesterol diet plus D17. The total cholesterol, triglyceride and low-density lipoprotein cholesterol levels in the serum were significantly (P