Dental Pulp Stem Cells Model Early Life and Imprinted DNA Methylation Patterns.

Early embryonic stages of pluripotency are modeled for epigenomic studies primarily with human embryonic stem cells (ESC) or induced pluripotent stem cells (iPSCs). For analysis of DNA methylation, however, ESCs and iPSCs do not accurately reflect the DNA methylation levels found in preimplantation embryos. Whole genome bisulfite sequencing (WGBS) approaches have revealed the presence of large partially methylated domains (PMDs) covering 30-40% of the genome in oocytes, preimplantation embryos, and placenta. In contrast, ESCs and iPSCs show abnormally high levels of DNA methylation compared to inner cell mass (ICM) or placenta. Here we show that dental pulp stem cells (DPSCs), derived from baby teeth and cultured in serum-containing media, have PMDs and mimic the ICM and placental methylome more closely than iPSCs and ESCs. By principal component analysis, DPSC methylation patterns were more similar to two other neural stem cell types of human derivation (EPI-NCSC and LUHMES) and placenta than were iPSCs, ESCs or other human cell lines (SH-SY5Y, B lymphoblast, IMR90). To test the suitability of DPSCs in modeling epigenetic differences associated with disease, we compared methylation patterns of DPSCs derived from children with chromosome 15q11.2-q13.3 maternal duplication (Dup15q) to controls. Differential methylation region (DMR) analyses revealed the expected Dup15q hypermethylation at the imprinting control region, as well as hypomethylation over SNORD116, and novel DMRs over 147 genes, including several autism candidate genes. Together these data suggest that DPSCs may be useful model for epigenomic and functional studies of human neurodevelopmental disorders. Overall design: Examination of DNA Cytosine methylation in DPSCs, EPI-NCSC, and LUHMES: DPSC_Control: 5 different DPSCs derived from patients with no diagnosed neurological disorders; DPSC_Dup15: 4 different DPSCs derived from patients diagnosed with Dup15q Syndrome; DPSC_Dup15: 1 DPSC derived from a patient diagnosed with Dup15q Syndrome that also had a duplication of part of chromosome 17; EPI-NCSC: 1 EPI-NCSC derived from a single patient; LUHMES: 2 biological replicates of the LUHMES cell line