![]() Additionally, it appears that otx2 does not affect the rudimentary lens formation which is seen in loss-of-function rx3 mutants, i.e., eyeless mutants. Moreover, it was observed that rx3, while involved in RPE pigmentation, does not contribute to choroid fissure closure. Otx Gene Expression In midgestation mouse embryos the two Otx genes are expressed in specific restricted regions of the developing brain (Simeone et al. Furthermore, it was also observed that additional knockdown of otx1b using morpholinos worsened the coloboma phenotype. The OTX2 gene is part of a family of homeobox genes, which act during early embryonic development to control the formation of many body structures. It was observed that while the otx2 loss-of-function mutant, otx2hu3237 displayed small colobomas and the otx1a mutant, otx1a6del, did not exhibit any morphological eye defects, zebrafish possessing both mutations presented with a range of colobomas, some of which were more severe than otx2 single mutants and the size of the coloboma corresponded with the gene dosage of otx1a. The Otx family of genes plays essential roles in head development (49). Phylogenetic analyses show that, together with their osteichthyan. In this study, the roles of the zebrafish Otx genes, otx2 and otx1a, as well as the Rx family gene, rx3, in choroid fissure closure, the disruption of which leads to the onset of colobomas, were studied. Recently, to gain insight into the possibility that a basic genetic program of cephalic development may be conserved between vertebrates and invertebrates, human Otx genes have been introduced and overexpressed in Drosophila otd mutants and the murine Otx1 has been replaced with the Drosophila otd gene (Acampora et al. In mouse, Drosophila and intermediate species otd/Otx genes have shown a remarkable similarity in expression pattern suggesting that they could be part of a conserved control system operating in the brain and different from that coded by the HOX complexes controlling the hindbrain and spinal cord. of all craniate Otx genes identified thus far, including the highly divergent Crx gene. Colobomas are a type of eye defect characterized by the presence of a hole in certain eye structures. ![]()
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