Figure 2

Deletion of both VLDLR and LRP8 results in dramatic defects in retinogeniculate projections. Retinogeniculate projections in (A) P19 control, (B) P19 vldlr^−/−;lrp8^−/− double mutant and (C) P16 vldlr^−/−;lrp8^−/− double mutant mice were labeled by intraocular injection of fluorescently conjugated CTB. In vldlr^−/−;lrp8^−/− double mutants (B,C), note the absence of projection between the IGL and vLGN, the ectopic clusters of retinal arbors adjacent to the optic tract (arrowheads), and the ectopic region of binocular retinal input in the dorsomedial pole of the dLGN (asterisks). Double asterisks (**) indicate regions where retinal arbors from the ipsilateral retina have not been fully refined into segregated, eye-specific domains. (D) High magnification views of the boxed region in (C). Blue and yellow arrowheads in (D) highlight differences in retinal terminal size in dLGN (yellow) and the ectopic region at the dorsomedial pole of dLGN (blue). Left eyes were injected with Alexa Fluor 594 CTB and right eyes were injected with Alexa Fluor 488 CTB. LGN from right hemispheres are shown. ‘Contra’ denotes projections originating from the contralateral retina and ‘ipsi’ denotes projections originating from the ipsilateral retina. dLGN are labeled ‘d’, vLGN are labeled ‘v’ and arrows indicate IGL. The color of the label in panels (A to D) and (A’ to D’) indicates the color of the image shown in (A” to D”). Scale bar = 200 μm for (A to C) and 75 μm for (D). CTB, cholera toxin B subunit; dLGN, dorsal LGN; IGL, intergeniculate leaflet; LGN, lateral geniculate nucleus; LRP8, low-density lipoprotein receptor-related protein 8; VLDLR, very-low-density lipoprotein receptor; vLGN, ventral LGN.