Hypomethylation and ADA gene expression in mouse CAK cells

Epigenetic Control of Vascular Smooth Muscle Cell Function in Atherosclerosis: A Role for DNA Methylation

Atherosclerosis is a complex vascular inflammatory disease in which multiple cell types are involved, including vascular smooth muscle cells (VSMCs). In response to vascular injury and inflammatory stimuli, VSMCs undergo a "phenotypic switching" characterized by extracellular matrix secretion, loss of contractility, and abnormal proliferation and migration, which play a key role in the progression of atherosclerosis. DNA methylation modification is an important epigenetic mechanism that plays an important role in atherosclerosis. Studies investigating abnormal DNA methylation in patients with atherosclerosis have determined a specific DNA methylation profile, and proposed multiple pathways and genes involved in the etiopathogenesis of atherosclerosis. Recent studies have also revealed that DNA methylation modification controls VSMC function by regulating gene expression involved in atherosclerosis. In this review, we summarize the recent advances regarding the epigenetic control of VSMC function by DNA methylation in atherosclerosis and provide insights into the development of VSMC-centered therapeutic strategies.

The effects of 5-azacytidine and 5-azadeoxycytidine on chromosome structure and function: implications for methylation-associated cellular processes

5-Azacytidine (5-aza-C) analogs demonstrate a remarkable ability to induce heritable changes in gene and phenotypic expression. These cellular processes are associated with the demethylation of specific DNA sequences. On the other hand, 5-aza-C analogs have dramatic effects on chromosomes, leading to decondensation of chromatin structure, chromosomal instability and an advance in replication timing. Condensation inhibition of genetically inactive chromatin occurs when the DNA is still hemimethylated or fully methylated. In cell cultures prolonged for several replication cycles, chromosomal rearrangements and instability affect the 5-aza-C-sensitive regions. Moreover, the normally late-replicating inactive chromatin undergoes a transient temporal shift to an earlier DNA replication, characteristic of activatable chromatin. zThe induced alterations of chromosome structure and behavior may trigger the 5-aza-C-dependent process of cellular reprogramming. Apart from their differentiating and gene-modifying effects, 5-aza-C analogs can tumorigenically transform cells and modulate their metastatic potential. High doses of 5-aza-C analogs have cytotoxic and antineoplastic activities.

Methylation of mouse adenine phosphoribosyltransferase gene is altered upon cellular differentiation and loss of phenotypic expression

Morphologically differentiated cell lines were previously isolated from a mouse teratocarcinoma stem cell line exhibiting an unstable heterozygous deficiency for adenine phosphoribosyltransferase (APRT) expression. In this study, the methylation sensitive and insensitive isoschizomer restriction endonucleases HpaII and MspI, respectively, were used to demonstrate that the aprt gene in the heterozygous deficient stem cell line was hypomethylated. Loss of APRT activity in this stem cell line was not associated with DNA methylation change. However, differentiation of this stem cell line was associated with hypermethylation of three consecutive HpaII/MspI sites that were located in the second intron and the third exon of the aprt gene. A total of 15 independent APRT homozygous deficient cell lines were isolated from three differentiated heterozygous deficient cell lines, and in all 15 cell lines this differentiation-related methylation pattern was altered. Two classes of alterations were noted: (1) hypomethylation of a site located in the second intron or (2) the apparent spreading of methylation to downstream methylation sites. The CpG-rich promoter region remained hypomethylated in the APRT homozygous deficient differentiated cell lines and a methylation change affecting a specific CpG site upstream of the promoter region was noted in only two of the 15 homozygous deficient cell lines. It is proposed that methylation of the mouse aprt gene may be involved in controlling phenotypic expression in the differentiated cell lines, but not in the stem cell line they were derived from.