NRN1 and Alzheimer disease: The relative ratio of neuritin to GAPDH mRNA in the AD patients was 15.10±6.28% compared to the control subjects in the cortical regions and 69.16±5.95% compared to the control subjects in the hippocampus (p<0.001 and p<0.05, respectively, by a Student's t-test, Fig. 1A).