FABP4 expression and function during normal retinal development.

(A) qPCR quantification of FABP4 mRNA in total retinas from P1 to P33 WT mice. Results are expressed as RE (relative expression) normalized to housekeeping genes (mean ± SEM, n = 3–4). FABP4 is significantly induced during the postnatal stage of retinal development. (B) FABP4 distribution was determined on retina flat-mounts and paraffin sections. At P7, FABP4 expression (red) was not observed in the inner retinal vessels stained by the pan-EC marker EMCN (green). FABP4 was strongly detected in the vitreal macrophages (arrowheads) and hyaloid endothelial cells (arrows). Paraffin sections of adult retina demonstrate faint, but uniform expression of FABP4 in all retinal layers. (C) WT and FABP4−/− P7 flat-mount retinas were immunostained with Collagen IV to identify the vascular network. (D) Vascular coverage and density was similar in WT and FABP4−/− animals indicating that FABP4 expression is not required for normal retinal vascularization. (E) Hematoxylin and eosin stained sagittal retinal sections of adult WT and FABP4−/− mice showed no morphological anomalies or degeneration in FABP4−/− animals. gcl: ganglion cell layer; ipl: inner plexiform layer; inl: inner nuclear layer; onl: outer nuclear layer; os: outer segment.