SP4 and schizophrenia: Other schizophrenia-related manipulations assessed in the 5C-CPT include hypoexpression of Sp4 [64] (a transcription factor linked to schizophrenia and BD; [65,66]) and developmental vitamin D deficiency [67] (a proposed mechanism for demographic correlations with schizophrenia and other psychiatric diagnoses, e.g. BD; [68]).