dc.description.abstract | Background: The intestinal epithelium is a vital organ that absorbs nutrients and water from
luminal contents and provide protection against pathogens and chemicals through the
stimulation of the immune system and secretion of antimicrobials and mucus. The development
and cellular maturation of the intestinal epithelium is orchestrated by signaling factors,
epigenetic regulators and transcription factors, but it is still incompletely defined. Lysinespecific demethylase 1 (LSD1) is a chromatin-modifying enzyme expressed in the intestine and
acts on methyl groups connected to lysines 4 or 9 on histone H3-tails. LSD1 has been implicated
in processes including embryogenesis and tissue-specific differentiation, but its function in
intestinal epithelial development remains unknown.
Objectives: The Oudhoff lab group has explored the expression and function of LSD1 in the
intestinal epithelium of adult mice. Unpublished data has shown that mice with an intestinal
epithelial deletion of Lsd1 (Lsd1∆IEC) have abnormal quantities of stem cells and differentiated
cell types when compared to wildtype (Lsd1f/f) mice. In this study, the expression pattern of the
LSD1 protein in wildtype mice and the effects of its deletion on differentiated cell types in the
intestinal epithelium during development were studied. The study aimed to elucidate how and
when LSD1 affects intestinal epithelial cell differentiation during development.
Methods: To study the role of LSD1 in intestinal epithelial development, we used wildtypeand knockout mice from five developmental timepoints: E16.5, P0.5, P7, P14 and P21.
Morphological features were visualized by hematoxylin- and eosin-staining. Staining patterns
and cellular composition of the intestinal epithelium was studied by immunohistochemistry and
immunofluorescence.
Results: Through two different staining methods, we retrieved two possible expression patterns
of LSD1 during intestinal epithelial development. Immunofluorescent staining showed
expression of LSD1 in the whole epithelium at every developmental timepoint, whereas
immunohistochemical detection suggested a restriction of LSD1 towards crypts and intervillous
zones in late development. When comparing Lsd1f/f with Lsd1∆IEC mice, no alterations to the
proliferative compartment or to the intestinal morphology was observed. Goblet cells were
significantly reduced in the Lsd1∆IEC mice from the second postnatal week in the duodenum and
jejunum, whereas tuft cells were significantly increased in all small intestinal segments from
P21. Enteroendocrine cells were unaffected by the tissue-specific knockout of Lsd1.
Furthermore, immunohistochemical staining of H3K4me2 did not reveal any difference in
staining intensity.
Conclusion: In this study, we have presented two potential expression patterns of LSD1 in the
developing intestinal epithelium. The role of LSD1 in the intestinal epithelial development has
been elucidated, where it regulates goblet- and tuft cell differentiation in late intestinal epithelial
development and is intrinsic to Paneth cell development. Global staining of the active
transcription mark H3K4me2 did not reveal any differences between the Lsd1∆IEC- and Lsd1f/f
mice, suggesting that the observed phenotype is controlled by the regulation of H3K4-
dimethylation at distinct sites or through other regulatory mechanisms. Further investigation is
required to validate these findings and uncover the exact role of LSD1 in intestinal epithelial
differentiation. | |