Dose-Dependent Effects of GLD-2 and GLD-1 on Germline Differentiation and Dedifferentiation in the Absence of PUF-8

PUMILIO/FBF (PUF) proteins have a conserved function in stem cell regulation. Caenorhabditis elegans PUF-8 protein inhibits the translation of target mRNAs by interacting with PUF binding element (PBE) in the 30 untranslated region (30 UTR). In this work, an in silico analysis has identified gld-2 [a poly(A) polymerase] as a putative PUF-8 target. Biochemical and reporter analyses showed that PUF-8 specifically binds to a PBE in gld-2 3 0 UTR and represses a GFP reporter gene carrying gld-2 3 0 UTR in the C. elegans mitotic germ cells. GLD-2 enhances meiotic entry at least in part by activating GLD-1 (a KH motif-containing RNA-binding protein). Our genetic analyses also demonstrated that heterozygous gld-2(+/−) gld-1(+/−) genes in the absence of PUF-8 are competent for meiotic entry (early differentiation), but haplo-insufficient for the meiotic division (terminal differentiation) of spermatocytes. Indeed, the arrested spermatocytes return to mitotic cells via dedifferentiation, which results in germline tumors. Since these regulators are broadly conserved, we thus suggest that similar molecular mechanisms may control differentiation, dedifferentiation, and tumorigenesis in other organisms, including humans

Dynamic Channel Adaptation for IP Based Split Spectrum Femto/Macro Cellular Systems

In femto/macro cellular networks, the stability and fairness problems caused by the unplanned and random characteristic of femtocells must be solved. By applying queueing theory in IP based femto/macro cellular networks, we found the stability condition, and described two kinds of cell section policies of users. As a main contribution, we provided the adaptive channel distribution algorithm which minimizes the average packet sojourn time at transmitting systems and keeps the whole systems stable and fair among cells. Through experiments in various environments, we analyzed the influence of channel reuse factor, cell selection policies, and the number of femtocells on system performance

Novel Function of PUF Proteins and Their Partners in Spermatogenesis and Spermatocyte-Derived Germline Tumors in Caenorhabditis elegans

Conserved PUF (Pumilio and FBF) proteins repress the translation by binding to its target mRNA 3’ untranslated region (3’UTR). C. elegans has 11 PUF proteins. Among them, we focused on two FBFs (FBF-1 and FBF-2) and PUF-8. The object of this study is to identify a regulatory network including FBFs and PUF-8 in spermatogenesis and spermatocyte-derived germline tumors in vivo. Specifically, our significant findings are three-fold:\r\n1. FBFs and their repression target CYB-1 (B-type Cyclin) promote sperm viability by inhibiting CED-4 (an Apaf1 homolog)-mediated apoptosis (see Chapter 2)\r\n2. PUF-8 and its repression target, GLD-2 (a Cytoplasmic poly(A) polymerase) inhibit spermatocyte-derived tumorigenesis by activating GLD-1 (a KH motif-containing RNA-binding protein) and inhibiting MPK-1 (an ERK homolog) (see Chapter 3) \r\n3. CYB-1 loss or X-ray irradiation could induce spermatocyte-derived germline tumors in the absence of PUF-8 and activation of MPK-1 (see Chapter 4). \r\nSince the regulators that we propose to study are broadly conserved, we therefore suggest that similar molecular mechanisms may control spermatogenesis and tumorigenesis in other organisms, including humans

Genetic and Chemical Controls of Sperm Fate and Spermatocyte Dedifferentiation via PUF-8 and MPK-1 in <i>Caenorhabditis elegans</i>

Using the nematode C. elegans germline as a model system, we previously reported that PUF-8 (a PUF RNA-binding protein) and LIP-1 (a dual-specificity phosphatase) repress sperm fate at 20 °C and the dedifferentiation of spermatocytes into mitotic cells (termed “spermatocyte dedifferentiation”) at 25 °C. Thus, double mutants lacking both PUF-8 and LIP-1 produce excess sperm at 20 °C, and their spermatocytes return to mitotically dividing cells via dedifferentiation at 25 °C, resulting in germline tumors. To gain insight into the molecular competence for spermatocyte dedifferentiation, we compared the germline phenotypes of three mutant strains that produce excess sperm—fem-3(q20gf), puf-8(q725); fem-3(q20gf), and puf-8(q725); lip-1(zh15). Spermatocyte dedifferentiation was not observed in fem-3(q20gf) mutants, but it was more severe in puf-8(q725); lip-1(zh15) than in puf-8(q725); fem-3(q20gf) mutants. These results suggest that MPK-1 (the C. elegans ERK1/2 MAPK ortholog) activation in the absence of PUF-8 is required to promote spermatocyte dedifferentiation. This idea was confirmed using Resveratrol (RSV), a potential activator of MPK-1 and ERK1/2 in C. elegans and human cells, respectively. Notably, spermatocyte dedifferentiation was significantly enhanced by RSV treatment in the absence of PUF-8, and its effect was blocked by mpk-1 RNAi. We, therefore, conclude that PUF-8 and MPK-1 are essential regulators for spermatocyte dedifferentiation and tumorigenesis. Since these regulators are broadly conserved, we suggest that similar regulatory circuitry may control cellular dedifferentiation and tumorigenesis in other organisms, including humans