RESUMO
SVA (SINE (short interspersed nuclear element)-VNTR (variable number of tandem repeats)-Alu) retrotransposons remain active in humans and contribute to individual genetic variation. Polymorphic SVA alleles harbor gene regulatory potential and can cause genetic disease. However, how SVA insertions are controlled and functionally impact human disease is unknown. Here we dissect the epigenetic regulation and influence of SVAs in cellular models of X-linked dystonia parkinsonism (XDP), a neurodegenerative disorder caused by an SVA insertion at the TAF1 locus. We demonstrate that the KRAB zinc finger protein ZNF91 establishes H3K9me3 and DNA methylation over SVAs, including polymorphic alleles, in human neural progenitor cells. The resulting mini-heterochromatin domains attenuate the cis-regulatory impact of SVAs. This is critical for XDP pathology; removal of local heterochromatin severely aggravates the XDP molecular phenotype, resulting in increased TAF1 intron retention and reduced expression. Our results provide unique mechanistic insights into how human polymorphic transposon insertions are recognized and how their regulatory impact is constrained by an innate epigenetic defense system.
RESUMO
OBJECTIVE: The aim of the study was to investigate the potential interaction between TCF7L2 rs7903146 genotype, which is implicated for type-2 diabetes mellitus genetic susceptibility, HbA1c levels, and the periodontal status of dental patients. MATERIALS AND METHODS: HbA1c levels, clinical periodontal parameters (probing depth, clinical attachment level, bleeding on probing, and plaque index), and several parameters (such as body mass index [BMI], smoking habits, education level, and age) were recorded in 150 patients who fulfilled the criteria for screening for prediabetes/diabetes of the Centers for Disease Control and Prevention. DNA was extracted and the TCF7L2 single nucleotide polymorphism (SNP) rs7903146 was genotyped in all participants. RESULTS: Thirty-one patients out of 150 tested were found with unknown hyperglycemia (20.7%). Regarding sex, education, parent with diabetes, normal BMI, smoking, age ≥45 years and prior testing for diabetes, no differences were observed between patients displaying HbA1c < 5.7 and ≥ 5.7% (Pearson's Chi-square test, p > 0.05). Regarding periodontal parameters and differences between subgroups (HbA1c levels ≥ 5.7 and HbA1c levels < 5.7), statistically significant differences were observed for probing depth (3.20 ± 0.94 vs. 2.81 ± 0.78 mm), clinical attachment level (3.54 ± 1.20 vs. 3.18 ± 1.06 mm) and bleeding on probing (0.62 ± 0.25 vs. 0.50 ± 0.24%) with hyperglycemic patients exhibiting worse periodontal conditions (Mann-Whitney test p < 0.05). The allelic and genotype frequencies for the transcription factor 7-like 2 (TCF7L2) gene, SNPs 7903146 did not exhibit a significant difference between the HbA1c > 5.7 and HbA1c < 5.7 groups and the periodontitis and nonperiodontitis subgroups respectively (Fisher's exact test >0.05). Statistical Analysis Patient characteristics and their association with prediabetes were tested by Pearson's Chi-square test (asymptotic, two sided). Differences of periodontal parameters between subgroups were tested with the Mann-Whitney U-test. The associations of allele and genotype frequencies in the patient and control groups were analyzed using the Fisher's exact test of independence.The significance level was set at the 0.05 for all tests. CONCLUSION: A statistically significant association between TCF7L2 rs7903146 genotype and periodontal condition or HbA1c levels was not observed in contrast to statistically significant differences of clinical parameters of periodontitis in patients with hyperglycemia.
