SP4 and bipolar disorder: Most relevant to the work described here, we have observed that SP4 phosphorylation at S770 inversely associated with SP4 immunoreactivity in human postmortem cerebellum [18] and this phosphorylation is increased in this region in bipolar disorder patients and in schizophrenia patients with more severe negative symptoms, which both showed reduced SP4 immunoreactivity [11, 12].