Differential responsiveness of distinct retinal domains to Atoh7.
Bottom Line: Atoh7 loss of function results in a massive reduction or even a total loss of RGCs.Photoreceptors were largely absent and the Müller glia cell number was reduced significantly.The majority of cells in this domain were ganglion cells and the abnormal development of this area affected the closure of the optic fissure resulting in coloboma.
Affiliation: Centre for Organismal Studies, Heidelberg University, Heidelberg, Germany; Hartmut Hoffmann-Berling International Graduate School (HBIGS), Heidelberg, Germany.Show MeSH
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Mentions: To investigate the putative differential response of multipotent RPCs to atoh7 expression, we aimed to establish precocious atoh7 expression during early eye development. To this end we produced a construct containing a regulatory region of the retinal homeobox gene two (rx2) (Souren et al., 2009; Martinez-Morales et al., 2009) driving atoh7 expression and generated a transgenic medaka line. The rx2 promoter in medaka is active during early eye development from the optic vesicle stage until the onset of differentiation in all RPCs (Martinez-Morales et al., 2009). We confirmed the precocious atoh7 expression by fluorescent in situ hybridization. In rx2::atoh7 embryos, atoh7 mRNA was detectable already at stage 22 (Supplemental Fig. 1) showing abundant expression in the whole developing optic cup. In controls, however, the first atoh7 expressing cells were detected at stage 25 (Fig. 1A, B) in the central retina. At this stage rx2::atoh7 embryos showed a persistent strong and homogenous expression in the optic cup (Fig. 1C, D). Thus our data show that expression of atoh7 directed by an rx2 promoter resulted in precocious homogeneous expression in the forming optic cup already at stage 22, three developmental stages prior to the expression of the endogenous atoh7, which normally marks the onset of differentiation (Del Bene et al., 2007; Kitambi and Malicki, 2008).
Affiliation: Centre for Organismal Studies, Heidelberg University, Heidelberg, Germany; Hartmut Hoffmann-Berling International Graduate School (HBIGS), Heidelberg, Germany.