<P>Abnormal DNA Methylation in Pluripotent Stem Cells from a Patient with Prader-Willi Syndrome Results in Neuronal Differentiation Defects</P>

Abstract

DNA methylation is a common method of gene expression regulation, and this form of regulation occurs in the neurodevelopmental disorder Prader Willi syndrome (PWS). Gene expression regulation via methylation is important for humans, although the role of methylation in neuronal differentiation is unknown. We characterized the cellular differentiation potential of iPS cells derived from a patient with PWS with abnormal methylation (M-iPWS cells). A CGH array revealed that, unlike iPWS cells, the abnormally methylated M-iPWS cells had no deletion in the15q11.2-q13 chromosome region. In addition, methylation-specific PCR showed that M-iPWS cells had strong methylation of the SNRPN CpG island. To assess the effect of abnormal methylation on cell differentiation, the M-iPWS cells and iPWS cells were induced to differentiate into embryoid bodies, which contain endoderm, mesoderm, and ectoderm. The results suggest that iPS cells from patients with PWS are defective at differentiation into ectoderm. When directionally differentiated into neuronal cells, the expression of neural stem cells (NSCs) markers in M-iPWS cells was relatively low compared to those from control cells. Nestin and Musashi-1 immunoreactivity was also low in NSCs from M-iPWS cells. MAP2 and βIII-tubulin immunoreactivity was also sparse, and marker expression was low in neuronal cells differentiated from M-iPWS cells. We conclude that abnormal methylation in the PWS region is involved in neuronal differentiation.