Identification of Tbr‐1/CASK complex target genes in neurons

• Published in: Journal of neurochemistry 2004-12, Vol.91 (6), p.1483-1492
• Main Authors: Wang, Ting‐Fang, Ding, Chia‐Nung, Wang, Guey‐Shin, Luo, Shih‐Chi, Lin, Yi‐Ling, Ruan, Youlin, Hevner, Robert, Rubenstein, John L. R., Hsueh, Yi‐Ping
• Format: Article
• Language: English
• Subjects: Amino Acid Transport Systems, Neutral - genetics; Animals; Antigens, CD; Antigens, Surface - genetics; Base Sequence; Biological and medical sciences; Calcium-Calmodulin-Dependent Protein Kinases - physiology; Cells, Cultured; Cercopithecus aethiops; COS Cells; development; Development. Senescence. Regeneration. Transplantation; DNA-Binding Proteins - physiology; Embryo, Mammalian; forebrain; Fundamental and applied biological sciences. Psychology; Gene Expression Regulation; Glycine Plasma Membrane Transport Proteins; Guanylate Kinases; Hippocampus - cytology; Humans; membrane associated guanylate kinase; Mice; Mice, Knockout; Molecular Sequence Data; neurite; Neurons - metabolism; N‐methyl‐D‐aspartate; Promoter Regions, Genetic - physiology; Rats; Receptors, Interleukin-7 - genetics; Receptors, N-Methyl-D-Aspartate - genetics; transcription; Vertebrates: nervous system and sense organs
• ISSN: 0022-3042; 1471-4159
• DOI: 10.1111/j.1471-4159.2004.02845.x

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.