Identification of Tbr-1/CASK complex target genes in neurons.
Tbr-1, a neuron-specific T-box transcription factor, plays a critical role in brain development. Here, we performed a computational search using the non-palindromic T-box binding sequence, namely the non-palindromic T-element, to determine the putative downstream target genes of Tbr-1. More than 20 identified genes containing the non-palindromic T-element in the 5' regulatory region were found expressed in brain. Luciferase reporter assays using cultured hippocampal neurons showed that overexpression of Tbr-1 and CASK-enhanced promoter activities of some of these putative target genes, including NMDAR subunit 2b (NR2b), glycine transporter, interleukin 7 receptor (IL-7R) and OX-2. Among these genes, NR2b promoter responded strongest to overexpression of Tbr-1 and CASK. Deletion of the non-palindromic T-elements from NR2b promoter impaired the induction by Tbr-1 and CASK. We also examined expression of these target genes in Tbr-1 knockout mice, it was found that NR2b expression was consistently downregulated. Similarly, both RNA and protein expression levels of NMDAR subunit 1 (NR1), which also contains the non-palindromic T-elements in its 5' regulatory region, were reduced in Tbr-1 knockout mice. We suggest that Tbr-1/CASK protein complex regulates expression of these downstream target genes and thus modulates neuronal activity and function.
Wang
Ting-Fang
TF
Institute of Biological Chemistry, Academia Sinica, Taipei, Taiwan.
Ding
Chia-Nung
CN
Wang
Guey-Shin
GS
Luo
Shih-Chi
SC
Lin
Yi-Ling
YL
Ruan
Youlin
Y
Hevner
Robert
R
Rubenstein
John L R
JL
Hsueh
Yi-Ping
YP
D026921:Amino Acid Transport Systems, Neutral / Q000235:genetics; D000818:Animals; D015703:Antigens, CD; D000954:Antigens, Surface / Q000235:genetics; D001483:Base Sequence; D019556:COS Cells; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000502:physiology*; D002478:Cells, Cultured; D002522:Chlorocebus aethiops; D004268:DNA-Binding Proteins / Q000502:physiology*; D004622:Embryo, Mammalian; D005786:Gene Expression Regulation; D050487:Glycine Plasma Membrane Transport Proteins; D051528:Guanylate Kinases; D006624:Hippocampus / Q000166:cytology; D006801:Humans; D051379:Mice; D018345:Mice, Knockout; D008969:Molecular Sequence Data; D009474:Neurons / Q000378:metabolism*; D011401:Promoter Regions, Genetic / Q000502:physiology; D051381:Rats; D020395:Receptors, Interleukin-7 / Q000235:genetics; D016194:Receptors, N-Methyl-D-Aspartate / Q000235:genetics; D020825:T-Box Domain Proteins
D026921:Amino Acid Transport Systems, Neutral; D015703:Antigens, CD; D000954:Antigens, Surface; D004268:DNA-Binding Proteins; D050487:Glycine Plasma Membrane Transport Proteins; C121001:NR2B NMDA receptor; D020395:Receptors, Interleukin-7; D016194:Receptors, N-Methyl-D-Aspartate; D020825:T-Box Domain Proteins; C492271:Tbr1 protein, mouse; C106868:CASK kinases; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D051528:Guanylate Kinases; C042739:antigens, CD200