GRIN2B and Anxiety: Interestingly, researchers found that mice lacking methyl donors displayed decreased expression levels of both Dnmt3a and Dnmt3b in the hippocampus, a finding that correlated with impairment in hippocampal fear memory acquisition and reduced anxiety-like behaviors, as well as a decrease in the expression of Grin2b, a glutamate receptor involved in excitatory pathways (Ishii et al., 2014; Nuss, 2015).