Reduced expression of SP1 and SP4 transcription factors in peripheral blood mononuclear cells in first-episode psychosis

Alterations of transcription factor specificity protein 4 (SP4) and 1 (SP1) have been linked to different neuropsychiatric diseases. Reduced SP4 and SP1 protein levels in the prefrontal cortex have been associated with bipolar disorder and schizophrenia, respectively, suggesting that both factors could be involved in the pathogenesis of disorders with psychotic features. The aim of this study was to investigate whether the reduction of SP1, SP4 and SP3 protein and mRNA expression in peripheral blood mononuclear cells in the early stages of psychosis may act as a potential biomarker of these disorders. A cross-sectional study of first-episode psychosis patients (n = 14) compared to gender- and age-matched healthy controls (n = 14) was designed. Patients were recruited through the adult mental health services of Parc Sanitari Sant Joan de Déu. Protein and gene expression levels of SP1, SP4 and SP3 were assessed in peripheral blood mononuclear cells of patients with first-episode psychosis and healthy control subjects. We report that protein levels of SP1 and SP4, but not SP3, are significantly reduced in patients compared to controls. In contrast, we did not observe any differences in expression levels for SP1, SP4 or SP3 genes between patient and control groups. In patients, SP4 protein levels were significantly associated with SP1 protein levels. No association was found, however, between protein and gene expression levels for each factor. Our study shows reduced SP1 and SP4 protein levels in first-episode psychosis in lymphocytes, suggesting that these transcription factors are potential peripheral biomarkers of psychotic spectrum disorders in the early stages.