Identification of a thyroid hormone response element in the mouse Kruppel-like factor 9 gene to explain its postnatal expression in the brain.
Brain development is critically dependent on thyroid hormone (T(3)). Krüppel-like factor 9 (Klf9) is a T(3)-inducible gene in developing rat brain, and several lines of evidence support that KLF9 plays a key role in neuronal morphogenesis. Here we extend our findings to the mouse and demonstrate the presence of a functional T(3) response element (T(3)RE) in the 5' flanking region of the mouse Klf9 gene. Klf9 mRNA is strongly induced in the mouse hippocampus and cerebellum in a developmental stage- and T(3)-dependent manner. Computer analysis identified a near optimal direct repeat 4 (DR-4) T(3)RE 3.8 kb upstream of the Klf9 transcription start site, and EMSAs showed that T(3) receptor (TR)-retinoid X receptor heterodimers bound to the T(3)RE with high affinity. The T(3)RE acts as a strong positive response element in transfection assays using a minimal heterologous promoter. In the mouse neuroblastoma cell line N2a[TRbeta1], T(3) caused a dose-dependent up-regulation of Klf9 mRNA. Chromatin immunoprecipitation assays conducted with N2a[TRbeta1] cells showed that TRs associated with the Klf9 T(3)RE, and this association was promoted by T(3). Treatment of N2a[TRbeta1] cells with T(3) led to hyperacetylation of histones 3 and 4 at the T(3)RE site. Furthermore, TRs associated with the DR-4 T(3)RE in postnatal d 4 mouse brain, and histone 4 acetylation was greater at this site compared with other regions of the Klf9 gene. Our study identifies a functional DR-4 T(3)RE located in the mouse Klf9 gene to explain its regulation by T(3) during mammalian brain development.
Department of Molecular, Cellular, and Developmental Biology, The University of Michigan, Ann Arbor, Michigan 48109-1048, USA. rdenver@umich.edu
Robert J
RJ
Denver
Keith E
KE
Williamson
D000107:Acetylation / Q000187:drug effects; D000818:Animals; D000831:Animals, Newborn; D001921:Brain / Q000187:drug effects / Q000378:metabolism*; D045744:Cell Line, Tumor; D002531:Cerebellum / Q000187:drug effects / Q000378:metabolism; D047369:Chromatin Immunoprecipitation; D024202:Electrophoretic Mobility Shift Assay; D005786:Gene Expression Regulation / Q000187:drug effects; D006624:Hippocampus / Q000187:drug effects / Q000378:metabolism; D006657:Histones / Q000378:metabolism; D066298:In Vitro Techniques; D051741:Kruppel-Like Transcription Factors / Q000235:genetics* / Q000378:metabolism*; D051379:Mice; D008810:Mice, Inbred C57BL; D020218:Response Elements / Q000235:genetics*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013963:Thyroid Hormones / Q000494:pharmacology*; D024363:Transcription Initiation Site; D014162:Transfection; D014284:Triiodothyronine / Q000494:pharmacology
D006657:Histones; C489675:Klf9 protein, mouse; D051741:Kruppel-Like Transcription Factors; D013963:Thyroid Hormones; D014284:Triiodothyronine