Zebrafish hindbrain development begins with the folding of the neural plate into the neural tube that gives rise to segments in the hindbrain known as rhombomeres. Each rhombomere gives rise to important structures, such as the otic vesicle and various craniofacial nerves. The first of the rhombomeres to develop is r4—modulated by proper development of hoxb1a. Proper development of r4 triggers a cascade of gene expression of other genes such as fgfs, krox-20, and many other genes required for proper segmentation of the rest of the hindbrain. Another one of these genes responsible for proper rhombomere segregation is pknox1.1. The interaction between pknox1.1 and hoxb1a has not been extensively studied at 19 hpf, thus there could be potential interaction between pknox1.1 and hoxb1a at this time due to similar functionality in the hindbrain. To study this interaction, pknox1.1 expression was knocked down via morpholino technology at the unicellular zygotic stage of zebrafish development and probed with antisense DIG-labeled in situ hoxb1a probe at 19 hpf. The flat-mounted images of the embryos showed identical hoxb1a staining in r4 between wild-type embryos and morpholino-injected embryos. The identical patterns in staining indicate pknox1.1 is not essential for proper hoxb1a expression in r4 which is most likely due to proper activity of other hox cofactors, such as pbx1, lzr/pbx4, and meis1. In order to make the study more cohesive, examining hoxb1a expression at multiple stages of development (16, 18, and 24 hpf) along with knocking down these other hox cofactors and examining their effect on hoxb1a expression could be performed. Phenotypic confirmation via ChIP or immunostaining could have also strengthened the cohesiveness of the study by demonstrating the presence of an interaction between hoxb1a and pknox1.1.
Hess, Kevin (Class of 2015), "The Effects of pknox1.1 Knockdown on hoxb1a Expression in r4 of Danio rerio Hindbrain" (2014). Writing Across the Curriculum. 6.
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