SCRM 555 Abstract 2nd Draft
Susan Chong
SCRM 555
5 March 2015
Abstract: 2nd Draft Revision The small intestinal stem cell niche is a rapidly self-renewing part of the body located at in the crypts of Lieberkuhn. Throughout its lifecycle, a stem cell proliferates and gives rise to multiple types of cells in the transit-amplifying region and eventually in the villus. While the cell undergoes multiple rounds of division, DNA methylation patterns are inherited and maintained by a maintenance methyltransferase enzyme called DNMT1. While the role of DNA methylation has been extensively studied in the development and cellular differentiation in other systems such as the pancreas and embryonic stem cells, it remains unclear in the intestinal stem cell niche. Our initial qPCR and immunohistochemistry results show that in vitro treatment of intestinal “mini-gut” organoids called enteroids with an FDA approved DNA methylation inhibitor called 5-azacytidine (5’azaC) causes an increase in Atoh1, the master regulatory gene for secretory cells. Increasing Atoh1 expression also increases its downstream target genes such as ChgA, Muc, and Def5a, which are markers for differentiated secretory cells. To test whether DNA methylation represses Atoh1 expression, bisulfite conversion was performed. We found that the CpG dinucleotides in an enhancer region of Atoh1 are heavily methylated under normal conditions. Whereas, treating enteroids with 5'azaC decreases DNA methylation. Furthermore, these findings were recapitulated in an in vivo study by isolating single cells and performing bisulfite conversion from intestinal crypts in DNMT1-/- mice. We conclude that DNA methylation is required for the regulation of normal intestinal stem cell differentiation.
SCRM 555
5 March 2015
Abstract: 2nd Draft Revision The small intestinal stem cell niche is a rapidly self-renewing part of the body located at in the crypts of Lieberkuhn. Throughout its lifecycle, a stem cell proliferates and gives rise to multiple types of cells in the transit-amplifying region and eventually in the villus. While the cell undergoes multiple rounds of division, DNA methylation patterns are inherited and maintained by a maintenance methyltransferase enzyme called DNMT1. While the role of DNA methylation has been extensively studied in the development and cellular differentiation in other systems such as the pancreas and embryonic stem cells, it remains unclear in the intestinal stem cell niche. Our initial qPCR and immunohistochemistry results show that in vitro treatment of intestinal “mini-gut” organoids called enteroids with an FDA approved DNA methylation inhibitor called 5-azacytidine (5’azaC) causes an increase in Atoh1, the master regulatory gene for secretory cells. Increasing Atoh1 expression also increases its downstream target genes such as ChgA, Muc, and Def5a, which are markers for differentiated secretory cells. To test whether DNA methylation represses Atoh1 expression, bisulfite conversion was performed. We found that the CpG dinucleotides in an enhancer region of Atoh1 are heavily methylated under normal conditions. Whereas, treating enteroids with 5'azaC decreases DNA methylation. Furthermore, these findings were recapitulated in an in vivo study by isolating single cells and performing bisulfite conversion from intestinal crypts in DNMT1-/- mice. We conclude that DNA methylation is required for the regulation of normal intestinal stem cell differentiation.