Gene, genetics and genetic medicines in gastroenterology: Current status and its future

Table 1 Different types of epigenetic changes and their impact on gene[6-9]

Mechanism	How it works	Effect on genes with example
DNA methylation[6]	Addition of methyl groups (-CH3) to DNA (usually at CpG islands)	MLH1 silenced: Leads to microsatellite instability increased mutation rate
Histone modification[7]	Acetylation, methylation, phosphorylation of histone proteins	CDH1 (E-cadherin) silenced by H3 acetylation in promoter regions of cytokine genes (e.g., TNF-α) leads to increased transcription
Chromatin remodeling[8]	Changing the physical structure of chromatin	Loss of ARID1A failure of chromatin remodeling improper gene silencing or activation. Progression of HCC, CRC
Non-coding RNAs (e.g., miRNA, lncRNA)[9]	Bind to mRNA or DNA to regulate expression	CRC (miR-21, miR-135b, lncRNA HOTAIR); gastric cancer (miR-148a, miR-21, lncRNA MALAT1, circPVT1); inflammatory bowel disease (miR-155, miR-21, lncRNA IFNG-AS1); HCC (miR-122, miR-221/222, lncRNA HULC); celiac disease (miR-449a)

miRNA: MicroRNA; lncRNA: Long non-coding RNA; CH₃: Methyl group; mRNA: Messenger RNA; TNF-α: Tumor necrosis factor alpha; CRC: Colorectal cancer; HCC: Hepatocellular carcinoma; circPVT1: Circular RNA plasmacytoma variant translocation 1.