Suppression of the basic transcription element-binding protein in brain neuronal cultures inhibits thyroid hormone-induced neurite branching.
The molecular mechanisms underlying the effect of thyroid hormone (T(3)) on neurite outgrowth are unknown. We recently identified the small GC-box binding protein BTEB (basic transcription element-binding protein) as a T(3)-regulated gene in the developing rat brain. BTEB mRNAs are rapidly (by 1 h) up-regulated by T(3) in primary rat embryonic neuronal cultures. Antisense oligodeoxynucleotides (ODNs), added to the cultures, reduced by 60% the level of BTEB mRNA. Addition of BTEB antisense ODNs to the cultures, before the onset of neurite polarity, had no effect on neurite elaboration but significantly decreased, in a dose-dependent manner, the effect of T(3) on neurite branching. We then examined the effects of antisense ODNs on a thyroid hormone target neuronal population, i.e. the acetylcholinesterase-positive neurons after the onset of neurite polarity. Exposure to BTEB antisense ODNs completely abolished the effects of T(3) on neurite branching and on the elaboration of neuritic filopodia-like structures in acetylcholinesterase cells. By contrast, antisense ODNs did not alter the effect of T(3) on neurite length. Our results show that titration of BTEB levels by T(3) regulates the degree of neurite branching and that the T(3)-induced neurite elongation and the T(3)-induced neurite branching are regulated by distinct mechanisms.
Cayrou
Christelle
C
Unit of Human Genetics, Centre Hospitalier de l'Université Laval Research Center, Sainte-Foy, Québec, GIV 4G2, Canada.
Denver
Robert J
RJ
Puymirat
Jack
J
D000110:Acetylcholinesterase / Q000378:metabolism; D000818:Animals; D015152:Blotting, Northern; D015153:Blotting, Western; D001923:Brain Chemistry / Q000187:drug effects*; D002478:Cells, Cultured; D002846:Chromatography, Affinity; D004268:DNA-Binding Proteins / Q000037:antagonists & inhibitors* / Q000302:isolation & purification; D004586:Electrophoresis; D005260:Female; D005786:Gene Expression Regulation / Q000187:drug effects; D051741:Kruppel-Like Transcription Factors; D016501:Neurites / Q000187:drug effects*; D009474:Neurons / Q000187:drug effects* / Q000378:metabolism* / Q000648:ultrastructure; D016376:Oligonucleotides, Antisense; D012333:RNA, Messenger / Q000032:analysis / Q000096:biosynthesis; D051381:Rats; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013778:Tetrazolium Salts; D013844:Thiazoles; D014157:Transcription Factors / Q000037:antagonists & inhibitors* / Q000302:isolation & purification; D014284:Triiodothyronine / Q000494:pharmacology*; D014404:Tubulin / Q000378:metabolism; D015854:Up-Regulation / Q000187:drug effects
D004268:DNA-Binding Proteins; D051741:Kruppel-Like Transcription Factors; D016376:Oligonucleotides, Antisense; D012333:RNA, Messenger; D013778:Tetrazolium Salts; D013844:Thiazoles; D014157:Transcription Factors; D014404:Tubulin; D014284:Triiodothyronine; C077017:Klf9 protein, rat; D000110:Acetylcholinesterase; C022616:thiazolyl blue