Function of RARgamma and RARalpha2 at the initiation of retinoid signaling is essential for avian embryo survival and for distinct events in cardiac morphogenesis.
Avian embryogenesis requires retinoid receptor activation by the vitamin A active form, retinoic acid (RA), during neurulation. We conducted loss-of-function analysis in quail embryos by nutritional deprivation of RA and by blocking generation of retinoid receptors. Here we identify a distinct role for RARalpha2 in cardiac inflow tract morphogenesis and for RARgamma in cardiac left/right orientation and looping morphogenesis. Blocking normal embryos with antisense oligonucleotides to RARalpha2 or RXRalpha diminishes GATA-4 transcripts, while blocking RARgamma or RXRalpha diminishes nodal and Pitx2 transcripts; the expression of these genes in the heart forming region resembles that of the vitamin A-deficient embryo. Blocking the function of RARgamma, RARalpha2, and RXRalpha recapitulates the complete vitamin A-deficient phenotype. RARgamma is the most potent mediator of the retinoid signal at this time of development. Our studies provide strong evidence that critical RA-requiring developmental events in the early avian embryo are regulated by means of distinct retinoid receptor signaling pathways.
Romeih
Mahmoud
M
Department of Food Science and Human Nutrition, Michigan State University, East Lansing, Michigan 48824, USA.
Cui
Jian
J
Michaille
Jean-Jacques
JJ
Jiang
Weihong
W
Zile
Maija H
MH
D000818:Animals; D002470:Cell Survival; D003370:Coturnix; D004268:DNA-Binding Proteins / Q000096:biosynthesis; D004625:Embryo, Nonmammalian / Q000378:metabolism*; D050991:GATA4 Transcription Factor; D018507:Gene Expression Regulation, Developmental; D018398:Homeodomain Proteins / Q000378:metabolism; D017403:In Situ Hybridization; D009206:Myocardium / Q000473:pathology*; D016376:Oligonucleotides, Antisense / Q000494:pharmacology; D010641:Phenotype; D012333:RNA, Messenger / Q000378:metabolism; D018168:Receptors, Retinoic Acid / Q000378:metabolism / Q000502:physiology*; D000072482:Retinoic Acid Receptor alpha; D047488:Retinoid X Receptors; D012176:Retinoids / Q000378:metabolism*; D015398:Signal Transduction; D013997:Time Factors; D014157:Transcription Factors / Q000096:biosynthesis / Q000378:metabolism; D000097577:Homeobox Protein PITX2; D000097768:Retinoic Acid Receptor gamma
D004268:DNA-Binding Proteins; D050991:GATA4 Transcription Factor; D018398:Homeodomain Proteins; D016376:Oligonucleotides, Antisense; D012333:RNA, Messenger; D018168:Receptors, Retinoic Acid; D000072482:Retinoic Acid Receptor alpha; D047488:Retinoid X Receptors; D012176:Retinoids; D014157:Transcription Factors; D000097577:Homeobox Protein PITX2; D000097768:Retinoic Acid Receptor gamma; C000607071:RARA protein, human