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Gene Delivery for Intervertebral Disc
Published in Raquel M. Gonçalves, Mário Adolfo Barbosa, Gene and Cell Delivery for Intervertebral Disc Degeneration, 2018
Gianluca Vadalà, Luca Ambrosio, Vincenzo Denaro
Thereby, novel transgene regulation systems have been investigated, including heat shock proteins, metallothionine, steroid regulatory promoters, tissue-specific inducible promoters, and ecdysone receptor-based systems (Graham 2002).
Molecular Imaging of Reporter Genes
Published in Michel M. J. Modo, Jeff W. M. Bulte, Molecular and Cellular MR Imaging, 2007
Keren Ziv, Dorit Granot, Vicki Plaks, Batya Cohen, Michal Neeman
A popular approach for inducible gene expression, which was applied for the study of inducible expression of two MR reporter genes, tyrosinase17 and ferritin,18 includes the use of one of the tetracycline (tet)-inducible systems, tTA (Tet-Off) or rtTA (Tet-On). The tetracycline-controlled transactivator (tTA) was generated by fusing the DNA-binding domain of tetracycline resistance operon (TetR) from Escherichia coli with the transcription activation domain of virion protein 16 (VP16) of herpes simplex virus (HSV).19 A second construct contains the target gene under the control of a minimal promoter sequence of the human cytomegalovirus promoter IE (P) combined with tet operator sequences of E. coli (tetO). In the absence of tetracycline, tTA binds to tetO and activates P, which in turn initiates transcription of the downstream target gene. In the presence of tetracycline, tTA dissociates from tetO, terminating transcription. The reverse tetracycline-controlled transcriptional activator system (rtTA), or Tet-On system, includes a mutant Tet repressor fused to VP16 to form rtTA and the responsive element tetO sequences linked to a P-driven target gene. In the absence of tetracycline, the target gene is not transcribed. However, in the presence of Tet, rtTA binds to tetO and P, which in turn activates transcription. Alternative inducible gene expression systems include the ecdysone receptor20 and the estrogen receptor21 systems.
Inter-organ regulation by the brain in Drosophila development and physiology
Published in Journal of Neurogenetics, 2023
Sunggyu Yoon, Mingyu Shin, Jiwon Shim
Drosophila larval molting and metamorphosis are driven by the steroid hormone 20-hydroxyecdysone (20E), which is synthesized and secreted from the prothoracic gland. It enters target cells by simple or facilitated diffusion via an ecdysone importer, EcI (Okamoto et al., 2018). 20E activates the nuclear receptor complex, ultraspiracle (usp), and ecdysone receptor (EcR) to trigger the expression of target genes involved in molting and metamorphosis (Song et al., 2003). Expression of 20E pulses multiple times during larval stages in large and small forms, and the first large pulse occurs in the late wandering third instar past the critical weight (Warren et al., 2006). Timely pulses of 20E are secreted from the brain. Neurons expressing prothoracicotropic hormone (PTTH) innervate the prothoracic gland within the ring gland (Kannangara et al., 2021). PTTH secretion is regulated by changes in the external environment, such as the circadian rhythm, and secreted PTTH binds to the torso receptors of prothoracic gland cells (Selcho et al., 2017). The torso receptor encodes the receptor tyrosine kinase, which in turn activates Ras, Raf, and ERK and induces the transcription of Halloween genes, a set of genes that influence the ecdysone pathway (Kannangara et al., 2021). Thus, the ablation of PTTH neurons or PTTH mutants causes a delay in pupariation and leads to increased overall body size (McBrayer et al., 2007).
Nanoformulations and their mode of action in insects: a review of biological interactions
Published in Drug and Chemical Toxicology, 2021
Kiran Shahzad, Farkhanda Manzoor
Specific molecular biomarkers are used in gene expression research, which allow for reliable biomonitoring. AgNPs are linked to DNA damage following ingestion in the salivary glands, gut, and brain as indicated by the expression levels of gamma-H2AX (a biomarker of breaks in double-stranded DNA) possibly due to ROS production and apoptosis (Mao et al.2018). Nair and Choi (2011) further expanded on the expression of GST genes to ascertain the antioxidant activity in the presence of CdNPs and AgNPs, noting that it varied according to exposure concentration and duration with the maximum mRNA expression in the Epsilon1 GST class, delta3, and Sigma4 in C. riparius. AgNPs were noted to downregulate CrL15, a gene which affects the assembly of ribosomes and upregulate CrGnRH1, the gonadotrophin-releasing hormone gene in C. riparius and the chromosomal puff known as the Balbiani ring protein gene (CrBR2.2) indicating the interference of AgNPs with protein synthesis and immunity (Nair et al.2011). While AgNPs could either upregulate or downregulate mRNA expression of the ecdysone receptor, nonylphenol-NPs upregulated it (Nair and Choi 2012). However, Demir et al. (2013) and Ávalos et al. (2015) reported that Drosophila fed to AgNPs did not show mutagenic activity according to the wing somatic mutation and recombination test and indicated that NPs may act differently in vitro and in vivo.
Antisense techniques provide robust decrease in GnRH receptor expression with minimal cytotoxicity in GT1-7 cells
Published in Systems Biology in Reproductive Medicine, 2018
Maurice Andre Recanati, Hongling Du, Katherine J. Kramer, Maik Hüttemann, Robert A. Welch
The ecdysone-inducible mammalian expression system utilizes a heterodimer of the ecdysone receptor (VgECR) and the retinoid X receptor (RXR) that binds a hybrid ecdysone response element (E/GRE) in the presence of the synthetic analogs of ecdysone, ponasterone A, or muristerone A. Ponasterone A is comparable to muristerone A in its affinity for the ecdysone receptor, induction of molting, and lack of endogenous effects in rodents, and is more readily available. The ecdysone receptor (VgEcR), modified to contain the VP16 transactivation domain, and the retinoid-X receptor (which is the mammalian homologue of USP, the natural partner to the ecdysone receptor) are both expressed from the pVgRXR vector. In the presence of ecdysone analogs, RXR and VgEcR associate together, bind to the hybrid response element, and activate transcription of the insert. This system allows for a tight regulation of expression in the absence of ponasterone A.