Gbx2 and Otx2 interact with the WD40 domain of Groucho/Tle corepressors.
One of the earliest organizational decisions in the development of the vertebrate brain is the division of the neural plate into Otx2-positive anterior and Gbx2-positive posterior territories. At the junction of these two expression domains, a local signaling center is formed, known as the midbrain-hindbrain boundary (MHB). This tissue coordinates or "organizes" the development of neighboring brain structures, such as the midbrain and cerebellum. Correct positioning of the MHB is thought to depend on mutual repression involving these two homeobox genes. Using a cell culture colocalization assay and coimmunoprecipitation experiments, we show that engrailed homology region 1 (eh1)-like motifs of both transcription factors physically interact with the WD40 domain of Groucho/Tle corepressor proteins. In addition, heat shock-induced expression of wild-type and mutant Otx2 and Gbx2 in medaka embryos demonstrates that Groucho is required for the repression of Otx2 by Gbx2. On the other hand, the repressive functions of Otx2 on Gbx2 do not appear to be dependent on corepressor interaction. Interestingly, the association of Groucho with Otx2 is also required for the repression of Fgf8 in the MHB. Therefore Groucho/Tle family members appear to regulate key aspects in the MHB development of the vertebrate brain.
Heimbucher
Thomas
T
Institute of Animal Breeding and Genetics, University of Veterinary Medicine, Veterinärplatz 1, A-1210 Vienna, Austria.
Murko
Christina
C
Bajoghli
Baubak
B
Aghaallaei
Narges
N
Huber
Anja
A
Stebegg
Ronald
R
Eberhard
Dirk
D
Fink
Maria
M
Simeone
Antonio
A
Czerny
Thomas
T
D000595:Amino Acid Sequence; D000818:Animals; D001921:Brain / Q000378:metabolism; D019556:COS Cells; D002522:Chlorocebus aethiops; D004268:DNA-Binding Proteins / Q000737:chemistry* / Q000378:metabolism; D005786:Gene Expression Regulation; D018398:Homeodomain Proteins / Q000378:metabolism / Q000502:physiology*; D006801:Humans; D051379:Mice; D008969:Molecular Sequence Data; D041681:NIH 3T3 Cells; D009687:Nuclear Proteins / Q000737:chemistry* / Q000378:metabolism; D009990:Oryzias; D051857:Otx Transcription Factors / Q000378:metabolism / Q000502:physiology*; D012097:Repressor Proteins / Q000737:chemistry* / Q000378:metabolism
D004268:DNA-Binding Proteins; C084958:GBX2 protein, human; C513182:Gbx2 protein, mouse; D018398:Homeodomain Proteins; D009687:Nuclear Proteins; C497659:OTX2 protein, human; D051857:Otx Transcription Factors; C497660:Otx2 protein, mouse; D012097:Repressor Proteins; C465817:TLE4 protein, human; C434949:Tle4 protein, mouse