Human embryonic stem (ES) cells are derived from the inner cell mass of the preimplantation embryo. Human ES cells have the capacity to differentiate into various types of cells in the body. Human ES cells are indefinite source of cells for cell therapy in various degenerative disorders including neuronal disorders. Directed differentiation of human ES cells is a prerequisite for their clinical application. The objective of this study is to develop the culture condition for the derivation of neural precursor cells from human ES cells. Neural precursor cells were derived from human ES cells in a stepwise culture condition. Neural precursor cells in the form of neural rosette structures developed into neurospheres when cultured in suspension. Suspension culture of neurospheres has been maintained over 4 months. Expressions of nestin, soxl, sox2, pax3 and pax6 transcripts were upregulated during differentiation into neural precursor cells by RT-PCR analysis. In contrast, expression of oct4 was dramatically downregulated in neural precursor cells. Immunocytochemical analyses of neural precursor cells demonstrated expression of nestin and SOX1. When induced to differentiate on an adhesive substrate, neuro-spheres were able to differentiate into three lineages of neural systems, including neurons, astrocytes and oligo-dendrocytes. Transcripts of sox1 and pax6 were downregulated during differentiation of neural precursor cells into neurons. In contrast, expression of map2ab was elevated in the differentiated cells, relative to those in neural precursor cells. Neurons derived from neural precursor cells expressed NCAM, Tuj1, MAP2ab, NeuN and NF200 in immunocytochemical analyses. Presence of astrocytes was confirmed by expression of GFAP immuno-cytochemically. Oligodendrocytes were also observed by positive immuno-reactivities against oligodendrocyte marker O1. Results of this study demonstrate that a stepwise culture condition is developed for the derivation of neural precursor cells from human ES cells.

The fragile X mental retardation (FMR) syndrome is the largest source of inherited mental retardation. The syndrome is usually caused by the transcriptional silencing of fragile X mental retardation gene (FMR-1). An 18 years old male wascompla띠ing of multiple toαh missing and abnormal facial profùe, of which signs were matemally dominant in his family. In the C)π。gene디c analysis the pa디ent and his parents did not show any discontinuity in the long arm end of X chromosome, but in the PCR produαs targeω19 the CGG repeat sequence in the 5' untranslated region of FMR gene both the patient'’ s and his mother' s gDNAs produced a normal and an extra bands, sized about 400 and 800 bps, respectively, while the his father' s gDNA produced only one normal band, sized about 400 bps. 까1US ， we suppose that the pa디.ent has heterozygotic alleles of FMR gene inherited matemally, and that the patient s FMR gene was in a premutated state relevant to the dentofacial abnormalities.