Age‐dependent expression of retinoic acid‐related orphan receptor‐alpha (Rora) in the developing mouse cortex and hippocampus

Abstract

We investigate if retinoic acid‐related orphan receptor‐α (Rora) is sexually dimorphic in developing mouse cortex and hippocampus. Recent study shows autistic patients express lower Rora mRNA in their cortex and cerebellum than controls do. Rora may cause sexual bias in autism susceptibility because it regulates expression of aromatase that converts testosterone to estrogen. Reduction of Rora may decrease aromatase levels to increase testosterone levels in autistic subjects (Sarachana et al., 2011). We predict male mice express lower Rora in the cortex and hippocampus as compared to females on the day of birth (PN0), 7 days after birth (PN7), 14 days (PN14), and 21 days after birth (PN21). We extracted RNA from cortexes and hippocampi of male and female C57BL/6J mice at PN0, PN7, PN14, and PN21 (n=8 per group). We measured mRNA levels of Rora and β‐actin (Actb) by RT‐qPCR, normalized Ct values of Rora and Actb, and analyzed two‐way ANOVA (sexes vs. ages) with Bonferroni's test for post‐hoc comparisons. Rora levels in the cortex and hippocampus were significantly higher in PN14 and PN21 mice than in PN0 and PN7 mice (p<0.05), but there was no significant difference between the sexes (p=0.183). Thus, Rora levels in the mouse cortex and hippocampus in early development is age‐dependent, but not sexually dimorphic. This research is supported by CSUPERB Faculty‐Student Collaborative Research Seed Grant and CSULB startup fund.