Niche Tet maintains germline stem cells independently of dioxygenase activity.

Ten-eleven translocation (TET) proteins are dioxygenases that convert 5-methylcytosine (5mC) into 5-hydroxylmethylcytosine (5hmC) in DNA and RNA. However, their involvement in adult stem cell regulation remains unclear. Here, we identify a novel enzymatic activity-independent function of Tet in the Drosophila germline stem cell (GSC) niche. Tet activates the expression of Dpp, the fly homologue of BMP, in the ovary stem cell niche, thereby controlling GSC self-renewal. Depletion of Tet disrupts Dpp production, leading to premature GSC loss. Strikingly, both wild-type and enzyme-dead mutant Tet proteins rescue defective BMP signaling and GSC loss when expressed in the niche. Mechanistically, Tet interacts directly with Bap55 and Stat92E, facilitating recruitment of the Polybromo Brahma associated protein (PBAP) complex to the dpp enhancer and activating Dpp expression. Furthermore, human TET3 can effectively substitute for Drosophila Tet in the niche to support BMP signaling and GSC self-renewal. Our findings highlight a conserved novel catalytic activity-independent role of Tet as a scaffold protein in supporting niche signaling for adult stem cell self-renewal.

Gap junction-transported cAMP from the niche controls stem cell progeny differentiation.

The niche has been shown to control stem cell self-renewal in different tissue types and organisms. Recently, a separate niche has been proposed to control stem cell progeny differentiation, called the differentiation niche. However, it remains poorly understood whether and how the differentiation niche directly signals to stem cell progeny to control their differentiation. In the Drosophila ovary, inner germarial sheath (IGS) cells contribute to two separate niche compartments for controlling both germline stem cell (GSC) self-renewal and progeny differentiation. In this study, we show that IGS cells express Inx2 protein, which forms gap junctions (GJs) with germline-specific Zpg protein to control stepwise GSC lineage development, including GSC self-renewal, germline cyst formation, meiotic double-strand DNA break formation, and oocyte specification. Germline-specific Zpg and IGS-specific Inx2 knockdowns cause similar defects in stepwise GSC development. Additionally, secondary messenger cAMP is transported from IGS cells to GSCs and their progeny via GJs to activate PKA signaling for controlling stepwise GSC development. Therefore, this study demonstrates that the niche directly controls GSC progeny differentiation via the GJ-cAMP-PKA signaling axis, which provides important insights into niche control of stem cell differentiation and highlights the importance of GJ-transported cAMP in tissue regeneration. This may represent a general strategy for the niche to control adult stem cell development in various tissue types and organisms since GJs and cAMP are widely distributed.

Drosophila YBX1 homolog YPS promotes ovarian germ line stem cell development by preferentially recognizing 5-methylcytosine RNAs.

5-Methylcytosine (m5C) is a RNA modification that exists in tRNAs and rRNAs and was recently found in mRNAs. Although it has been suggested to regulate diverse biological functions, whether m5C RNA modification influences adult stem cell development remains undetermined. In this study, we show that Ypsilon schachtel (YPS), a homolog of human Y box binding protein 1 (YBX1), promotes germ line stem cell (GSC) maintenance, proliferation, and differentiation in the Drosophila ovary by preferentially binding to m5C-containing RNAs. YPS is genetically demonstrated to function intrinsically for GSC maintenance, proliferation, and progeny differentiation in the Drosophila ovary, and human YBX1 can functionally replace YPS to support normal GSC development. Highly conserved cold-shock domains (CSDs) of YPS and YBX1 preferentially bind to m5C RNA in vitro. Moreover, YPS also preferentially binds to m5C-containing RNAs, including mRNAs, in germ cells. The crystal structure of the YBX1 CSD-RNA complex reveals that both hydrophobic stacking and hydrogen bonds are critical for m5C binding. Overexpression of RNA-binding-defective YPS and YBX1 proteins disrupts GSC development. Taken together, our findings show that m5C RNA modification plays an important role in adult stem cell development.

Changes in shape and size of the stiff branched ß-glucan in dimethlysulfoxide/water solutions.

The conformation transition of the short branched ß-glucan AF1 isolated from Auricularia auricula-judae in DMSO/water solutions was investigated with viscometry and static/dynamic light scattering (SLS/DLS). AF1 in the mixed solution exhibited a sharp decrease in viscosity and molecular size in a narrow DMSO volume fraction (vDMSO) range of 0.80-1.0. It indicated that the stiff AF1 transformed into flexible chains probably, resulting from the destruction of intra- and inter-molecular hydrogen bonds of the polysaccharides. AF1 solutions with dialyzed treatment gave a more narrow transition range of 0.90-1.0. The conformation transition of AF1 was further conformed by transition electron microscopy (TEM) and atomic force microscopy (AFM). The multiple hydrogen bonds of polysaccharides affect the chain conformation, which in turn affect the application in food and pharmaceutical fields.

Anti-hepatoma activity of the stiff branched ß-d-glucan and effects of molecular weight.

The water soluble ß-(1 → 3)-d-glucan with short branches (AF1) isolated from Auricularia auricula-judae was successfully fractionated by ultrasonication into three fractions with different weight-average molecular weights (Mws). The results of static and dynamic laser light scattering, viscometry and atomic force microscopy confirmed that the AF1 samples adopted a stiff chain conformation in water, and the coexistence of individuals and aggregates occurred gradually with increasing concentration. The AF1 sample with the highest Mw easily self-entangled, and exhibited a strong shear rate-dependence of viscosity in water. The glucans displayed anti-hepatoma activity and significantly inhibited H22 tumour growth without cytotoxicity towards normal tissues. They displayed both molecular weight- and dosage-dependencies of anti-tumour activity, and the sample with an Mw of 7.7 × 105 at the dosage of 5 mg kg-1 exhibited the highest inhibition ratio of ∼77% against H22 tumour, even significantly higher than the positive control of cytoxan. The immunohistochemical and western blot analyses revealed that the AF1 glucans triggered cell apoptosis, indicated by the activation of caspase 3/9 and down-regulated tumour angiogenesis factors of VEGF and CD31. The underlying antitumor mechanism was suggested to induce tumour cell apoptosis and to inhibit angiogenesis in tumour tissues via enhancement of the immune-response. Taken together, the AF1 ß-glucan was a potent natural drug candidate with high anti-cancer activities and less cytotoxicity, and the AF1 sample with a moderate molecular weight existed in aqueous solution as a more extended chain conformation, which plays an important role in activating immune responses.

Synthesis of 6-O-poly(ϵ-caprolactone)-L-ascorbic acid and its controlled release from supramolecular polymer micelles.

Lipophilic 6-O-poly (ϵ-caprolactone)-L-ascorbic acid (AA-6-PCL) is synthesized through ROP of ϵ-caprolactone (CL). The number of repeating CL units in the polymer chain varies from 6 to 19. AA-6-PCL loaded supramolecular polymer micelles (SMPMs) are constructed with ß-cyclodextrin (ß-CD) and PCL as blocks. Transmission electron microscopy images show a nanospheric morphology of the micelles with a size range of 43.3 ± 5.0 nm. The drug loading contents are 22.53-39.23% for AA-6-PCL. AA-6-PCL exhibits high radical scavenging capacity (93.96-96.73%) and efficient scavenging potency, and a cytotoxicity study proves the excellent cytocompatibility of AA-6-PCL loaded ß-CD/PCL SMPMs, which altogether herald their potential application in the study of the induced pluripotent stem cells.