Role of Chd7 in Developing Zebrafish Figure 7. Chd7 plays an essential role in retinal development. Retinal organization of control-MO embryos (A) and chd7 morphants (B) was revealed by toludiene blue staining. Compared with the highly organized cells and laminated retinal structure in control-MO fish, chd7-MO retinal cells are disorganized (A–B: Left panels). Retinal lamination defect, including rosette formation,is clearly visible in the chd7 morphants (examples of rosettes are indicated by dotted lines and arrow heads). GL, ganglion cell layer; INL, inner nuclear layer; L, lens; ONL, outer nuclear layer; R, retina; RPE, retinal pigment epithelium. Scale bar: 50 mm. Zn-8 immunoreactivity was performed to label (brown) retinal gangion cells in control-MO (C) and chd7-MO embryos (D). Scale bar: 30 mm. The expression of retinal ganglion cell-specific marker zn-8 is greatly reduced in chd7 morphants. The photoreceptor layer of control-MO (E) and chd7-MO-injected (F) embryos were stained with 3A10. Chd7 morphants lacked the photoreceptor layer. Scale bar: 5 mm. doi:10.1371/journal.pone.0031650.g007 efnb2a expression observed here could be the result of an accumulation of upstream defects occurring early in the somitogen- esis signaling pathway (i.e., indirect effects). Alternatively, it is also possible that Chd7 modulates efnb2a expression in a manner that is independent of the process of somite formation (i.e., direct effects). CHARGE syndrome patients often have microphthalmia [33,34,35] and here we found that loss of function of Chd7 in zebrafish resulted in a small eye phenotype. The retinas in zebrafish develop rapidly and begin differentiation by 36 hpf [36,37]. The differentiating retinal neurons undergo terminal PLoS ONE | www.plosone.org 8 February 2012 | Volume 7 | Issue 2 | e31650