The influence of alcohol on telomere length and shelterin complex gene expression in human embryonic stem cells
Moazzam, Muhammad Talha
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BACKGROUND: Telomeres are specialized heterochromatic structures found at the ends of chromosomes that serve to protect the integrity of the genome. Theoretically, telomeres, and thereby chromosomes, should be constantly shortening however that is not the case. Telomere length homeostasis is maintained via the activity of the enzyme Telomerase as well as a complex of 6 proteins, called the shelterin complex. Decreased telomere length is associated with a variety of neuropsychological diseases such as Alzheimer’s disease, and chronic depression. OBJECTIVE: The primary objective was to understand the effect of alcohol exposure on telomere dynamics, specifically on telomere length as well as the expression of the shelterin complex genes. This was accomplished using human embryonic stem cells (hESCs) as models. This study was exploratory with the goal of increasing our knowledge of genes involved in telomere maintenance. METHODS: hESCs were cultured in cell culture media containing 25 mM, 50 mM, or 100 mM of ethanol. After a 3-, 7-, or 14-day ethanol exposure plus a 24-hour withdrawal, hESCs were collected and genomic DNAs and total RNAs was extracted. Ethanol-induced telomere length changes were examined by quantitative polymerase chain reactions (qPCR).Ethanol-induced shelterin complex gene expression changes were examined by reverse-transcription and quantitative polymerase chain reactions (RT-qPCRs). RESULTS: Extended alcohol exposure exerted a deleterious effect on telomeres, causing them to diminish in length. The effects of alcohol on the expression of shelterin complex genes were varied, ranging from consistent upregulation or downregulation to a combination of both. The concentration of alcohol was inversely correlated with the expression of shelterin complex genes, and the correlation was influenced by the duration of ethanol exposure. CONCLUSION: Chronic exposure to alcohol resulted in the shortening of telomeres. The effect ethanol was both time- and concentration-dependent, with telomere length having a negative relationship with the concentration of ethanol as well as the duration of exposure. Additionally, the shelterin subunit genes had their expression levels altered by ethanol in a manner which was consistent with what has been observed in prior studies as well as what aligns with their respective functions.