Fig. 8

Complete loss of Rac1 in the retina leads to a severe loss of inner retinal neurons and a nearly complete loss of retinal ganglion cell projections to retino-recipient targets in the brain. a Rac1 inactivation by Six3-Cre results in an approximately fivefold reduction in optic nerve diameter, a severe reduction in INL, IPL, and GCL thickness and inner retinal cell number, disorganization of intra-retinal capillaries (IB4), and activation of astrocytes (GFAP). The density of tyrosine hydroxylase (TH)-expressing, GABAergic (GAD), cholinergic (ChAT), calretinin⁺ (CR), and calbindin⁺ (CB) amacrine cell bodies and processes are reduced. GFAP immunostaining is shown as a retina flat mount; all other retina images are transverse sections. ONL outer nuclear layer, INL inner nuclear layer, GCL ganglion cell layer. Bars to the right of the cross-section images: upper bar (ONL), middle bar (INL), lower bar (GCL). N = 3 for each genotype. Scale bars, 100 μm. b Dramatically reduced innervation of brain targets by RGCs in adult Six3-Cre;Rac1 ^CKO/− mice, revealed by anterograde labeling of optic tract axons with intraocular injection of cholera toxin subunit B. LGN lateral geniculate nucleus, MTN medial terminal nucleus, OPN olivary pretectal nucleus, PA pretectal area, SC superior colliculus, SCN suprachiasmatic nucleus. N = 2 for each genotype. Scale bar, 1 mm