Thyroid hormone responsiveness in N-Tera-2 cells.
N-TERA-2 cl/D1 (NT2) cells, a human embryonal cell line with characteristics of central nervous system precursor cells, were utilised to study thyroid hormone action during early neuronal growth and differentiation. Undifferentiated NT2 cells expressed mRNAs encoding thyroid hormone receptors (TRs) alpha1, alpha2 and beta1, iodothyronine deiodinases types 2 (D2) and 3 (D3) (which act as the pre-receptor regulators), and the thyroid hormone-responsive genes myelin basic protein (MBP) and neuroendocrine specific protein A (NSP-A). When terminally differentiated into post-mitotic neurons (hNT), TRalpha1 and TRbeta1 mRNA expression was decreased by 74% (P=0.05) and 95% (P<0.0001) respectively, while NSP-A mRNA increased 7-fold (P<0.05). However, mRNAs encoding TRalpha2, D2, D3 and MBP did not alter significantly upon neuronal differentiation and neither did activities of D2 and D3. With increasing 3,5,3'-triiodothyronine (T(3)) concentrations, TRbeta1 mRNA expression in cultured NT2 cells increased 2-fold at 10 nM T(3) and 1.3-fold at 100 nM T(3) (P<0.05) compared with that in T(3)-free media but no change was seen with T(3) treatment of hNT cells. D3 mRNA expression in NT2 cells also increased 3-fold at 10 nM T(3) (P=0.01) and 2.4-fold at 100 nM T(3) (P<0.05) compared with control, but there was no change in D3 enzyme activity. In contrast there was a 20% reduction in D3 mRNA expression in hNT cells at 10 nM T(3) (P<0.05) compared with control, with accompanying reductions in D3 activity with increasing T(3) concentrations (P<0.05). There was no significant change in the expression of the TRalpha isoforms, D2, MBP and NSP-A with increasing T(3) concentrations in either NT2 or hNT cells. Undifferentiated NT2 and differentiated hNT cells show differing patterns of T(3)-responsiveness, suggesting that there are different regulatory factors operating within these cell types.
Chan
S
S
Division of Reproductive and Child Health, University of Birmingham, Birmingham Women's Hospital, Edgbaston, Birmingham B15 2TG, UK.
McCabe
C J
CJ
Visser
T J
TJ
Franklyn
J A
JA
Kilby
M D
MD
D002454:Cell Differentiation; D002460:Cell Line; D002490:Central Nervous System / Q000196:embryology* / Q000201:enzymology; D004305:Dose-Response Relationship, Drug; D015870:Gene Expression; D006706:Homeostasis; D006801:Humans; D007453:Iodide Peroxidase / Q000378:metabolism; D007527:Isoenzymes / Q000378:metabolism; D004676:Myelin Basic Protein / Q000378:metabolism; D009419:Nerve Tissue Proteins / Q000378:metabolism; D009474:Neurons / Q000201:enzymology; D039904:Pluripotent Stem Cells / Q000187:drug effects / Q000201:enzymology*; D012333:RNA, Messenger / Q000032:analysis; D020133:Reverse Transcriptase Polymerase Chain Reaction; D018709:Statistics, Nonparametric; D013963:Thyroid Hormones / Q000494:pharmacology*; D014284:Triiodothyronine / Q000378:metabolism
D007527:Isoenzymes; D004676:Myelin Basic Protein; D009419:Nerve Tissue Proteins; D012333:RNA, Messenger; C081781:RTN1 protein, human; D013963:Thyroid Hormones; D014284:Triiodothyronine; D007453:Iodide Peroxidase