Fig. 5. Norrin is a neuro-modulating protein that affects cortical neuron dendritic morphology and spine density.

(A) Norrin-treated mouse cortical neurons show increased length and branching. (B) Treatment with Norrin lead to a significant number of neurite changes including intersections and neurite branchings as revealed by Scholl analytics. (C) Neurite length is increased after Norrin treatment of cultured cortical mouse neurons. (D) Loss of Norrin in vivo leads to a significant defect in cortical neuron spine density. Layer V cortical neurons were identified in adult Norrin-null mouse motor cortex and dendritic spines were examined after Golgi-Cox staining. (E) Norrin-null mice have significantly reduced spine density compared to wild-type. (F) Intracortical nanoparticle injections containing 8.3 kb-Norrin significantly increase dendritic spine density in cortical layer V of the mouse motor cortex. For invitro studies (A,B,C) recombinant Norrin and it’s truncated analogs were applied to 10 different isolations of cortical neurons (n=5 mice) with a minimum of 20 neurons analyzed for each cohort for 48 hours. For spine density analysis, n = five P60-P90 mice were used using Golgi-Cox staining kit; 5–10 cortical neurons, located in the motor cortex cortical layer V, were counted and analyzed per genotype, representative images are shown. Statistics performed by two-sided Student’s T-test of comparing Norrin treated vs control (C,E,F), *p<0.05, **p<0.01, ***p<0.001, ****p<0.0001. Values plotted represent the mean with SEM error bars.