Zebrafish an outstanding molecular model system to study novel physiological function of neuroendocrine related hormones
Date Issued
2011
Date
2011
Author(s)
Abad Cruz, Shelly
Abstract
Chapter I Cortisol controls epidermal ionocyte differentiation and proliferation by targeting Foxi3 transcription factors in zebrafish (Danio rerio)
In teleost fish, skin/gill function, cell morphological changes and cell proliferation were greatly affected by cortisol during environmental acclimation. In the present study we examined the molecular mechanism behind cortisol action including its known receptor, glucocorticoid receptor (gr) in fish epidermal ionocyte progenitor development. Utilizing zebrafish for both in vivo and in vitro assay, together with the involvement of the neuroendocrine system in the skin development which includes the corticotrophin releasing factor (crf), crf receptor 1 (crfr1), crfr2 and melanocotropin 2 receptor (mc2r) or ACTH receptor.
Cortisol treatment of zebrafish newly fertilized eggs suppressed gr transcripts without affecting mr. Transcripts of ionocyte marker genes for Na+-K+-ATPase rich cells (NaRCs): epithelial Ca+ channel (ecac) and H+-ATPase rich cells (HRCs): glial cell missing 2 (gcm2), Na+-H+-exchanger 3b (nhe3b) (B), H+-ATPase A-subunit (atp6v1a) were all upregulated upon cortisol treatment. Immunocytochemistry confirmed that both NaRCs and HRCs density were significantly increased. In addition, ionocyte progenitor specification and differentiation marker genes foxi3a and foxi3b spatial mRNA expression were increased after 24-48 h treatment of cortisol via in situ hybridization. Cell division was not affected but cell apoptosis was decrease at 48 hpf and increased at 72 hpf in the cortisol-treated group.
Knock-down of gr by GR-ATG MO showed immense lowered NaRCs and HRCs numbers among GR morphants which is further confirmed by GR-SV MO. In contrast, loss of MR has no effect in epidermal stem cells and ionocyte density. In vitro, 24 h gill organ culture with cortisol treatment significantly increased NaRCs and HRCs numbers including upregulation of foxi3a/b transcripts. Hence, we propose that cortisol through gr targets foxi3a/b that regulates epidermal ionocyte progenitor specification/differentiation together with delayed apoptosis in which case caused proliferation of matured ionocytes as the apparent outcome.
Chapter II Corticotropin releasing factor (CRF), CRF-receptors and related proteins contribution on skin development of zebrafish (Danio rerio)
The systematic hypothalamus-pituitary-interrenal (HPI) axis was also demonstrated to play a critical role in the skin development. Loss of function assay by morpholino oligos showed crf and crfr1 significantly take part in the stem cell and ionocytes density. CRFR1 is the major receptor that could mediate CRF function. Both present maternally, these may suggest their importance during the early skin development in zebrafish. CRFR2 is also maternally deposited but it can be dispensable during skin development since there is no observed change in epidermal stem cells or ionocytes density and morphology upon crfr2 knock-down. Nevertheless, CRFR2 function cannot be ruled-out in other major physiological functions like in stress.
Altogether, the present results serve as a foundation of the HPI axis as a systematic event or locally present in the zebrafish skin and gills. In which crf initializes this event through crfr1, as a separate and local function or as a complete course of signaling events together with that of cortisol-gr-foxi3a/3b axis major effect in the epidermal ionocyte progenitor differentiation. More future work has to be done to clarify more issues and provide better understanding in the neuroendocrinology of the skin.
Subjects
Cortisol
Type
thesis
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