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DTSTART:20191103T020000
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UID:calendar.3867.field_date_time.0@www.umces.edu
DTSTAMP:20260403T195852Z
CREATED:20190605T132857Z
DESCRIPTION:June 26\, 2019 11:30am to 12:30pm    \n    \n      \n\n\n    \n
 \n              \nInstitute of Marine & Environmental Technology\n      \n
 \n\n\n\n  \n\n    \n\n              \n\n\n      \n  \n\n    \n\n          
     \n\n\nTitle: The roles of Gonadotropin-releasing hormone 2 (Gnrh2) in 
 feeding and reproduction in zebrafish: a potential mediator between the tw
 o processes.\n\n\n\nSpeaker: Miranda Marvel (Ph.D. Candidate\, MEES Progra
 m)\n\n\n\nAbstract: The neuropeptide in the brain of vertebrates most well
 -known for controlling reproduction is called the Gonadotropin-releasing h
 ormone (GNRH). There are three isoforms of GNRH\, named for their location
  and function in the brain. GNRH1 is found in the hypothalamus and project
 s to the median eminence (in mammals) or pituitary (in teleosts)\, and thu
 s termed hypophysiotropic\, and is the main stimulator of the gonadotropin
 s\, luteinizing hormone (LH) and follicle-stimulating hormone (FSH)\, whic
 h circulate to the gonads and stimulate steroidogenesis and gametogenesis.
  The teleost-specific Gnrh3 is found in the olfactory bulb terminal nerve 
 (OB-TN)\, and is thought to have neuromodulatory roles. GNRH2 is found in 
 the midbrain tegmentum and despite being the most evolutionarily conserved
  and ubiquitous\, is the least studied form among the three. The lack of s
 tudies on Gnrh2 is most likely due to the absence of a functional GNRH2 pr
 otein in the common murine research models. Zebrafish\, another common ver
 tebrate model for genetic manipulation and biological studies\, possesses 
 Gnrh2\, unlike murine models\, and is therefore an ideal organism to study
  this neuropeptide. Through a combination of gene knockout/knockdown\, neu
 roanatomical imaging\, molecular tools\, and functional assays\, the roles
  of Gnrh2 in zebrafish were comprehensively explored. Characterization of 
 the Gnrh2 knockout (gnrh2-/-) zebrafish lines demonstrated decreased lhb e
 xpression and compromised oocyte quality\, increased feeding and growth\, 
 and\, most strikingly\, major inhibitions in spawning and oocyte maturatio
 n after long-term fasting. Interestingly\, Gnrh2 was unable to compensate 
 for Gnrh3 loss\, as the double knockout (gnrh2-/-\;gnrh3-/-) fish were fer
 tile and displayed normal reproduction. Functional and neuroanatomical ass
 ays confirmed that Gnrh2 exhibits plasticity under fasting conditions\, an
 d projects more neurons to Lh and Fsh gonadotropes\, whereas Gnrh3 is inhi
 bited by the same conditions.  Through transcriptomics and targeted qPCR\,
  several novel differentially expressed reproductive factors were discover
 ed in the Gnrh2 and Gnrh3 single and double knockout lines\, potentially p
 laying a part in the regulation of reproductive processes in zebrafish. In
  addition\, thorough examination of Gnrh2 neuronal projections under norma
 l feeding conditions identified projections innervating melatonin cells in
  the pineal gland\, neurons of the feeding factor\, Agouti-related peptide
  1 (Agrp1) in the mediobasal hypothalamus\, and neurons of the reproductio
 n regulator\, Gonadotropin-inhibitory hormone (Gnih)\, in the hypothalamus
 . Gnrh2 was found to be either inhibitory or stimulatory to gnih expressio
 n\, but able to potently downregulate agrp1expression. It is likely that G
 nrh2 exerts its reproductive/feeding effects through these three factors. 
 For the first time in vertebrates\, using tg(Gnrh2:eGFP) transgenic fish t
 o map neuronal projections throughout the brain\, a previously unstudied p
 opulation of Gnrh2 was identified in the olfactory region. Social studies 
 combined with neuroanatomical studies implicate these neurons in transduci
 ng pheromonal cues\, and thus affecting reproductive behavior. As a result
  of these studies\, it was found that overall\, under normal conditions\, 
 Gnrh2 most likely has roles in stimulating lhb expression\, maintaining op
 timal oocyte quality\, transducing pheromonal cues from the olfactory bulb
 \, and regulating energy expenditure by reducing feeding behavior through 
 the downregulation of agrp1\, and potentially indirectly through stimulati
 ng melatonin secretion. Under fasting conditions\, Gnrh2 most likely exhib
 its plasticity to become the main hypophysiotropic stimulator of gonadotro
 pin secretion. Gnrh2 therefore appears to be an important upstream factor 
 mediating feeding and reproductive processes in vertebrates.\n\n\n\nHost: 
 Dr. Yonathan Zohar
DTSTART;TZID=America/New_York:20190626T113000
DTEND;TZID=America/New_York:20190626T123000
LAST-MODIFIED:20190605T132857Z
SUMMARY:IMET Seminar: Miranda Marvel (Ph.D. Candidate\, MEES Program)
URL;TYPE=URI:https://www.umces.edu/events/imet-seminar-miranda-marvel-phd-c
 andidate-mees-program
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