Potential roles for BMP and Pax genes in the development of iris smooth muscle.
The embryonic optic cup generates four types of tissue: neural retina, pigmented epithelium, ciliary epithelium, and iris smooth muscle. Remarkably little attention has focused on the development of the iris smooth muscle since Lewis ([1903] J. Am. Anat. 2:405-416) described its origins from the anterior rim of the optic cup neuroepithelium. As an initial step toward understanding iris smooth muscle development, I first determined the spatial and temporal pattern of the development of the iris smooth muscle in the chick by using the HNK1 antibody, which labels developing iris smooth muscle. HNK1 labeling shows that iris smooth muscle development is correlated in time and space with the development of the ciliary epithelial folds. Second, because neural crest is the only other neural tissue that has been shown to generate smooth muscle (Le Lievre and Le Douarin [1975] J. Embryo. Exp. Morphol. 34:125-154), I sought to determine whether iris smooth muscle development shares similarities with neural crest development. Two members of the BMP superfamily, BMP4 and BMP7, which may regulate neural crest development, are highly expressed by cells at the site of iris smooth muscle generation. Third, because humans and mice that are heterozygous for Pax6 mutations have no irides (Hill et al. [1991] Nature 354:522-525; Hanson et al. [1994] Nat. Genet. 6:168-173), I determined the expression of Pax6. I also examined the expression of Pax3 in the developing anterior optic cup. The developing iris smooth muscle coexpresses Pax6 and Pax3. I suggest that some of the eye defects caused by mutations in Pax6, BMP4, and BMP7 may be due to abnormal iris smooth muscle.
Jensen
Abbie M
AM
Biology Department, 221 Morrill South, University of Massachusetts, Amherst, MA 01003, USA. ajensen@bio.umass.edu
D000199:Actins / Q000378:metabolism; D000818:Animals; D055415:Bone Morphogenetic Protein 4; D055419:Bone Morphogenetic Protein 7; D019485:Bone Morphogenetic Proteins / Q000096:biosynthesis / Q000502:physiology*; D018959:CD57 Antigens / Q000096:biosynthesis; D002642:Chick Embryo; D004268:DNA-Binding Proteins / Q000096:biosynthesis / Q000502:physiology*; D005136:Eye Proteins / Q000502:physiology*; D018507:Gene Expression Regulation, Developmental; D006579:Heterozygote; D018398:Homeodomain Proteins / Q000502:physiology*; D006801:Humans; D007150:Immunohistochemistry; D017403:In Situ Hybridization; D007498:Iris / Q000196:embryology*; D051379:Mice; D008856:Microscopy, Fluorescence; D009130:Muscle, Smooth / Q000196:embryology*; D009432:Neural Crest / Q000196:embryology*; D000072041:PAX3 Transcription Factor; D000071841:PAX6 Transcription Factor; D051761:Paired Box Transcription Factors; D012097:Repressor Proteins / Q000502:physiology*; D013997:Time Factors; D014157:Transcription Factors / Q000096:biosynthesis / Q000502:physiology*; D014158:Transcription, Genetic; D016212:Transforming Growth Factor beta / Q000096:biosynthesis / Q000502:physiology*
D000199:Actins; C525809:BMP4 protein, human; C525819:BMP7 protein, human; C525810:Bmp4 protein, mouse; D055415:Bone Morphogenetic Protein 4; D055419:Bone Morphogenetic Protein 7; D019485:Bone Morphogenetic Proteins; D018959:CD57 Antigens; D004268:DNA-Binding Proteins; D005136:Eye Proteins; D018398:Homeodomain Proteins; D000072041:PAX3 Transcription Factor; D000071841:PAX6 Transcription Factor; C000605730:PAX6 protein, human; D051761:Paired Box Transcription Factors; C000605732:Pax6 protein, mouse; D012097:Repressor Proteins; D014157:Transcription Factors; D016212:Transforming Growth Factor beta; C068686:Pax3 protein, mouse