Of particular interest is the significant reduction of Sin3A in the phosphoproteomic pattern after 3 days of transduction. Sin3A is a component of Sin3A/HDAC co-repressor complexes, which functions in transcription repression [49] [50] [51] , but its role in astrocyte differentiation has not been characterized. By a Western blot analysis of samples through the course of differentiation (control, 7, 14, and 21 days), we further confirmed that the protein expression of Sin3A decreased significantly and continuously after differentiation (Fig. 3D) . Reduction of the expression of Sin3A may lead to disintegration of Sin3A/HDAC complexes thus causing de-suppression of the transcriptional program that favors astrocyte-like differentiation, such as activation of GFAP.