Stem cells in animals often exhibit a slow cell cycle and/or low transcriptional activity referred to as quiescence. Here, we report that the translational activity in the primordial germ cells (PGCs) of the sea urchin embryo (Strongylocentrotus purpuratus) is quiescent. We measured new protein synthesis with O-propargyl-puromycin and Lhomopropargylglycine Click-iT technologies, and determined that these cells synthesize protein at only 6% the level of their adjacent somatic cells. Knockdown of translation of the RNA-binding protein Nanos2 by morpholino antisense oligonucleotides, or knockout of the Nanos2 gene by CRISPR/Cas9 resulted in a significant, but partial, increase (47%) in general translation specifically in the PGCs. We found that the mRNA of the translation factor eEF1A is excluded from the PGCs in a Nanos2-dependent manner, a consequence of a Nanos/Pumilio response element (PRE) in its 3′UTR. In addition to eEF1A, the cytoplasmic pH of the PGCs appears to repress translation and simply increasing the pH also significantly restores translation selectively in the PGCs. We conclude that the PGCs of this sea urchin institute parallel pathways to quiesce translation thoroughly but transiently.
Background Some metazoa have the capacity to regenerate lost body parts. This phenomenon in adults has been classically described in echinoderms, especially in sea stars (Asteroidea). Sea star bipinnaria larvae can also rapidly and effectively regenerate a complete larva after surgical bisection. Understanding the capacity to reverse cell fates in the larva is important from both a developmental and biomedical perspective; yet, the mechanisms underlying regeneration in echinoderms are poorly understood. Results Here, we describe the process of bipinnaria regeneration after bisection in the bat star Patiria miniata. We tested transcriptional, translational, and cell proliferation activity after bisection in anterior and posterior bipinnaria halves as well as expression of SRAP, reported as a sea star regeneration associated protease (Vickery et al., 2001b). Moreover, we found several genes whose transcripts increased in abundance following bisection, including: vasa, dysferlin, vitellogenin 1 and vitellogenin 2. Conclusion These results show a transformation following bisection, especially in the anterior halves, of cell fate reassignment in all three germ layers, with clear and predictable changes. These results define molecular events that accompany the cell fate changes coincident to the regenerative response in echinoderm larvae.
Well, at least it is better than death…Addiction, that is … a behavior or use that starts as pleasurable or comforting, but through continued use becomes compulsive and interferes with ordinary life, responsibilities, and health. The behavioral or chemical addiction (smoking, alcohol, cocaine, shopping, sex, gambling, etcetera) appears to take over the physiology and emotions of the user; an external force changing or even controlling the inner code. Sort of like epigenetics, eh?The pages of this and other journals are replete with descriptions of the molecular and physiological changes that occur in the germ line and its supportive tissues by chemical addictions. A quick search of the literature within Pubmed reveals over 15,000 articles for "reproduction and smoking", 30,000 for "reproduction and alcohol"… as well as 37 articles for "reproduction and shopping", and 88 for "reproduction and gambling". (Yes, we are thorough here at MRD!) Most troubling, though, is the rapid rise in articles under the search for reproduction and opioids -already over 6,000 articles.Opioids are an increasingly large problem in the world; an estimated 69,000 people die from opioid overdose each year worldwide (World Health Organization, 2014), and 15 million people are estimated to suffer from opioid addiction. Opioids are derived from the opium poppy, or are chemically synthesized to mimic these compounds. Commonly used opioids include illicit substances, such as heroin, and medically prescribed pain-relieving variants, such as oxycodone, morphine, hydrocodone (e.g. Vicodin), codeine, and methadone. Opioids are frequently prescribed for pain because they are inexpensive, effective, and long-lasting… and, yes, quite addictive.The path to drug addiction is easy: the United States National Institute on Drug Abuse estimates that one in every four people who uses heroin will become addicted to it. Half of the people who use heroin began by using prescription opioids (www.drugabuse.gov/publications/drugfacts/heroin) and taking opioids leads to neurobiological effects that make it diffi cult to quit. This manifests clinically as increased opioid tolerance, requiring addicts to take higher doses to achieve the same effect.Opioid receptors are seven-transmembrane G-protein coupled receptors (GPCRs) that produce a variety of downstream effects, which can translate to feelings of analgesia. These receptors are found scattered throughout the body, and respond to exogenous opioid compounds as effectively as the endogenous neuropeptides. Within the nervous system, opioids target areas of the brain that control breathing; if opioid use is suddenly stopped, the brain produces strong withdrawal symptoms that for some comes close to the feeling of death.Opioid receptors are also present in the gonads (Holden et. al., 2005); indeed, human gonads utilize a range of endogenous opioid peptides. Pro-opiomelanocortin-derived peptides, the precursors to opioid peptides, are present in human Leydig cells, which produce testosterone in the testis. The prim...
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