Direct crossregulation between retinoic acid receptor {beta} and Hox genes during hindbrain segmentation.
During anteroposterior (AP) patterning of the developing hindbrain, the expression borders of many transcription factors are aligned at interfaces between neural segments called rhombomeres (r). Mechanisms regulating segmental expression have been identified for Hox genes, but for other classes of AP patterning genes there is only limited information. We have analysed the murine retinoic acid receptor beta gene (Rarb) and show that it is induced prior to segmentation, by retinoic-acid (RA) signalling from the mesoderm. Induction establishes a diffuse expression border that regresses until, at later stages, it is stably maintained at the r6/r7 boundary by inputs from Hoxb4 and Hoxd4. Separate RA- and Hox-responsive enhancers mediate the two phases of Rarb expression: a regulatory mechanism remarkably similar to that of Hoxb4. By showing that Rarb is a direct transcriptional target of Hoxb4, this study identifies a new molecular link, completing a feedback circuit between Rarb, Hoxb4 and Hoxd4. We propose that the function of this circuit is to align the initially incongruent expression of multiple RA-induced genes at a single segment boundary.
Serpente
Patricia
P
Medical Research Council, National Institute for Medical Research, The Ridgeway, Mill Hill, London, NW7 1AA, UK.
Tümpel
Stefan
S
Ghyselinck
Norbert B
NB
Niederreither
Karen
K
Wiedemann
Leanne M
LM
Dollé
Pascal
P
Chambon
Pierre
P
Krumlauf
Robb
R
Gould
Alex P
AP
D000445:Aldehyde Oxidoreductases / Q000235:genetics / Q000378:metabolism; D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D002645:Chickens; D004622:Embryo, Mammalian / Q000166:cytology / Q000196:embryology / Q000378:metabolism; D004625:Embryo, Nonmammalian; D004742:Enhancer Elements, Genetic / Q000235:genetics; D018507:Gene Expression Regulation, Developmental; D018398:Homeodomain Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D051379:Mice; D018345:Mice, Knockout; D008969:Molecular Sequence Data; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D018168:Receptors, Retinoic Acid / Q000235:genetics / Q000378:metabolism*; D012249:Rhombencephalon / Q000166:cytology / Q000196:embryology* / Q000378:metabolism*; D016415:Sequence Alignment; D013997:Time Factors; D014157:Transcription Factors / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D014212:Tretinoin / Q000378:metabolism
C090460:HOXB4 protein, human; D018398:Homeodomain Proteins; C513262:Hoxb4 protein, mouse; C489520:Hoxd4 protein, mouse; D012333:RNA, Messenger; D018168:Receptors, Retinoic Acid; D014157:Transcription Factors; C082925:retinoic acid receptor beta; D014212:Tretinoin; D000445:Aldehyde Oxidoreductases; C470579:RALDH2 protein, mouse