The preneural serotonergic system in <i>Lytechinus pictus</i>: A role in gastrulation

2010 2010

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Abstract (summary)

Serotonergic neurons are the first brainstem neurons to emerge during early embryo development. Serotonin has been implicated in a wide variety of behaviors, physiological mechanisms and disease processes. Though most of what is known about serotonin involves its role in neuronal communication, studies have suggested that serotonin may also have non-neuronal functions during embryogenesis as a signaling molecule in the regulation of cleavage, morphogenesis and cell differentiation. Previous studies in our lab showed that serotonin levels peak immediately prior to gastrulation. In the present study I demonstrate that serotonin triggers primary invagination, the initial phase of gastrulation, in Lytechinus pictus sea urchin embryos. p-Chlorophenylalanine methyl ester (mCPA), an inhibitor of the rate-limiting enzyme for serotonin synthesis, tryptophan hydroxylase (TPH), blocks serotonin synthesis in vitro and embryos treated with mCPA fail to initiate gastrulation. Previous studies in the sea urchin identified TPH expression only in postgastrula embryos, which suggested that there was an additional enzyme present in the genome capable of synthesizing the serotonin necessary to initiate the gastrulation process. I identified a gene, Lp PAH/TPH, in L. pictus with homology to the dual function Drosophila Henna gene. In Drosophila, Henna is the source of non-neuronal serotonin. My expression studies of Lp PAH/TPH show that the mRNA is present in blastula and gastrula embryos prior to the expression of TPH, which strongly supports PAH/TPH-mediated synthesis of serotonin necessary for the initiation of gastrulation and any other non-neuronal functions in the sea urchin. Antagonists of 5-HT2 and 5-HT7 serotonin receptors block primary invagination. Furthermore, primary invagination blocked by mCPA could be rescued with agonists of 5-HT2 and 5-HT7 receptors and with downstream signaling molecules known to be linked to these receptors. In addition, mCPA blocks protein phosphorylation through protein kinase A and C, 5-HT7 and 5-HT2 receptor effectors, respectively. Taken together, these studies strongly suggest that serotonin mediates its effects on the gastrulation process in sea urchin embryos through a signaling mechanism that involves the 5-HT 2 and/or 5-HT7 serotonin receptors.

Indexing (details)

Cellular biology
0287: Morphology
0379: Cellular biology
Identifier / keyword
Biological sciences; Gastrulation; Morphogenesis; Serotonin; Serotonin receptors; Tryptophan hydroxylase
The preneural serotonergic system in <i>Lytechinus pictus</i>: A role in gastrulation
Carroll, Kamali Naomi
Number of pages
Publication year
Degree date
School code
DAI-B 71/09, Dissertation Abstracts International
Place of publication
Ann Arbor
Country of publication
United States
Brown, Ken M.
Committee member
Donaldson, Robert; Hernandez, Patricia; Johnson, Diana; Moody, Sally
The George Washington University
Biological Sciences
University location
United States -- District of Columbia
Source type
Dissertations & Theses
Document type
Dissertation/thesis number
ProQuest document ID
Database copyright ProQuest LLC; ProQuest does not claim copyright in the individual underlying works.
Document URL
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