Epigenetic modification of long interspersed elements-1 in cumulus cells of mature and immature oocytes from patients with polycystic ovary syndrome / 대한생식의학회지

OBJECTIVE: The long interspersed elements (LINE-1, L1s) are a group of genetic elements found in large numbers in the human genome that can translate into phenotype by controlling genes. Growing evidence supports the role of epigenetic in polycystic ovary syndrome (PCOS). The purpose of this study is to evaluate the DNA methylation levels in LINE-1 in a tissue-specific manner using cumulus cells from patients with PCOS compared with normal controls. METHODS: The study included 19 patients with PCOS and 22 control patients who were undergoing controlled ovarian hyperstimulation. After oocyte retrieval, cumulus cells were extracted. LINE-1 DNA methylation levels were analysed by bisulfite treatment, polymerase chain reaction, and restriction enzyme digestion. The Connection Up- and Down-Regulation Expression Analysis of Microarrays software package was used to compare the gene regulatory functions of intragenic LINE-1. RESULTS: The results showed higher LINE-1 DNA methylation levels in the cumulus cells of mature oocytes in PCOS patients, 79.14 (±2.66) vs. 75.40 (±4.92); p=0.004, but no difference in the methylation of cumulus cells in immature oocytes between PCOS and control patients, 70.33 (±4.79) vs. 67.79 (±5.17); p=0.155. However, LINE-1 DNA methylation levels were found to be higher in the cumulus cells of mature oocytes than in those of immature oocytes in both PCOS and control patients. CONCLUSION: These findings suggest that the epigenetic modification of LINE-1 DNA may play a role in regulating multiple gene expression that affects the pathophysiology and development of mature oocytes in PCOS.

Risk factors for methamphetamine-induced paranoia and latency of symptom onset in a Thai drug treatment cohort

Background: Methamphetamine (MA) produces a range of psychotic experiences, ranging from a sub-syndromal symptom to a full-scale psychosis. While the characteristics of and risk factors for MA-psychosis have been studied extensively, MA-induced paranoia (MIP) has received only limited attention.Methods: Demographic, diagnostic, and drug use variables were assessed in 96 experienced MA-users from a Thai drug treatment center using the Semi-Structured Assessment for Drug Dependence and Alcoholism (SSADDA) and the Methamphetamine Experienced Questionnaire (MEQ). Individuals with and without MIP were compared. Latency of the initial symptom onset was also examined.Results: Ninety-six subjects participated in the study including 44 (46%) endorsed MIP. Individuals with MIP were dependent on MA more severely than those without the trait (p=0.02). Subjects with MIP were also more likely to use solvents (p=0.03), be dependent on alcohol (p=0.048), and attempt suicide (p=0.04) than those without. Individuals with short latency to a first MIP episode (i.e., within two years of their first use of MA) did not differ from those with prolonged latency (≥ 3 years) with respect to MA use at symptom onset. However, they reported lower lifetime use (p=0.007), heaviest period use (p=0.008) and past-year MA use (p=0.04) than those with later onset.Conclusion: Severe dependence on MA, solvent use, alcohol dependence, and suicide attempts were associated with MIP. Though the vulnerability to MIP was associated with greater dependence severity as a group, those who experience MIP earlier in the course of their dependence reported less MA use than those in whom symptoms arose later. This suggests a subgroup of individuals that are intrinsically more vulnerable to the MA effects (e.g., habit forming and psychotic effects) and in whom MIP’s subjectively aversive effects may lead to reduced MIP use over the course of their MA dependence.

The association between Piwil2 expression and LINE-1 methylation in cancer cells

Background: Down-regulation of Piwil2 (P-element induced wimpy testis like 2) expression induced hypomethylation, the loss of methylation levels, of long interspersed nuclear element-1 (LINE-1 or L1) sequences in the testes of mutant mice. Moreover, the expression of Piwil2 can be found in various cancers. The levels of LINE-1 hypomethylation in cancers are not only generally varied, but also possess a locus-specific pattern. Objective: This study focused on the association between Piwil2 and LINE-1 methylation. Methods: Eleven WSU-HN cancer cell lines were examined for the expression of Piwil2 using semi-quantitative reverse transcription polymerase chain reaction (RT-PCR). Genome-wide and specific loci LINE-1 methylation levels were measured using Combined Bisulfite Restriction Analysis (COBRA) and COBRA for unique LINE-1 (CU-L1), respectively. Results: The levels of Piwil2 expression and LINE-1 methylation were varied. Significant association between Piwil2 RNA and LINE-1 methylation of two loci, L1-EPHA3IVS5 and L1-SPOCK3, was observed (Pearson’s r = 0.7332; p ≤ 0.01 and r = 0.6124; p \< 0.05, respectively). There was no association with both genome wide LINE- 1 methylation and the other 15 loci. Conclusion: Piwil2 expression may be associated with LINE-1 methylation of selective loci in cancer cells.

Methylation status of endogenous DNA double strand breaks: possible connection between genomic hypomethylation and instability

Background: DNA methylation and repair of double-strand breaks (DSBs) are crucial for maintaining genomic integrity. In cancer, global hypomethylation leads to genomic instability. Nonetheless, the underlying mechanism(s) has not been identified. Although DSBs can be produced by numerous agents, they also occur spontaneously as endogenous DSBs (EDSBs). Interestingly, methylation levels of EDSBs are higher than at the genomic level. Objectives and methods: I propose a hypothesis as to how EDSBs are hypermethylated and suggest how this hypothesis may connect with the underlying mechanism by which global hypomethylation leads to genomic instability. Results: EDSBs are hypermethylated. EDSB processing is distinct and depends on DNA methylation status. Methylation of EDSBs exists in the genome prior to DNA breaks. There are significant levels of EDSBs in both replicating and non-replicating cells. However, hypermethylation of EDSBs is replication-independent. Ethylated DNA is often associated with heterochromatin and radiation-induced DSB repair may be different depending on chromatin status. There are reports of a unique radiation-induced heterochromatin DNA-repair pathway in nonreplicating cells. A DSB-related histone modification, γ-H2AX, serine-139 phosphorylated form of histone H2AX, is formed less preferentially in heterochromatin after ionizing radiation. Moreover, radiation-induced heterochromatin DSB repair was also shown to be repaired slowly and is Ataxia Telangiectasia Mutated (ATM)- dependent. Therefore, if EDSB repair is similar to radiation-induced DSB repair, methylated EDSB repair may also be dependent on a more precise ATM-dependent non-homologous end-joining repair. Conclusion: The higher methylation level of EDSBs may be due to methylation-dependent EDSB repair. This repair may be slower and thereby possess better precision. Consequently, the increase in the spontaneous mutation rate in the hypomethylated cancer genome may be due to the fact that unmethylated EDSB repair is more error prone.