Neuronal differentiation defects in induced pluripotent stem cells derived from a Prader-Willi syndrome patient

Prader-Willi syndrome (PWS) is a neurodevelopmental disorder caused by a lack of expression of paternally inherited genes located in the15q11.2-q13 chromosome region. An obstacle in the study of human neurological diseases is the inaccessibility of brain material. Generation of induced pluripotent stem cells (iPSC cells) from patients can partially overcome this problem. We characterized the cellular differentiation potential of iPS cells derived from a PWS patient with a paternal 15q11-q13 deletion. A gene tip transcriptome array revealed very low expression of genes in the 15q11.2-q13 chromosome region, including SNRPN, SNORD64, SNORD108, SNORD109, and SNORD116, in iPS cells of this patient compared to that in control iPS cells. Methylation-specific PCR analysis of the SNRPN gene locus indicated that the PWS region of the paternal chromosome was deleted or methylated in iPS cells from the patient. Both the control and patient-derived iPS cells were positive for Oct3/4, a key marker of pluripotent cells. After 11 days of differentiation into neural stem cells (NSCs), Oct3/4 expression in both types of iPS cells was decreased. The NSC markers Pax6, Sox1, and Nestin were induced in NSCs derived from control iPS cells, whereas induction of these NSC markers was not apparent in NSCs derived from iPS cells from the patient. After 7 days of differentiation into neurons, neuronal cells derived from control iPS cells were positive for βIII-tubulin and MAP2. However, neuronal cells derived from patient iPS cells only included a few immunopositive neurons. The mRNA expression levels of the neuronal marker βIII-tubulin were increased in neuronal cells derived from control iPS cells, while the expression levels of βIII-tubulin in neuronal cells derived from patient iPS cells were similar to those of NSCs. These results indicate that iPS cells derived from a PWS patient exhibited neuronal differentiation defects.