Spatial, temporal and interindividual epigenetic variation of functionally important DNA methylation patterns

DNA methylation is an epigenetic modification that plays an important role in gene regulation. It can be influenced by stochastic events, environmental factors and developmental programs. However, little is known about the natural variation of gene-specific methylation patterns. In this study, we performed quantitative methylation analyses of six differentially methylated imprinted genes (H19, MEG3, LIT1, NESP55, PEG3 and SNRPN), one hypermethylated pluripotency gene (OCT4) and one hypomethylated tumor suppressor gene (APC) in chorionic villus, fetal and adult cortex, and adult blood samples. Both average methylation level and range of methylation variation depended on the gene locus, tissue type and/or developmental stage. We found considerable variability of functionally important methylation patterns among unrelated healthy individuals and a trend toward more similar methylation levels in monozygotic twins than in dizygotic twins. Imprinted genes showed relatively little methylation changes associated with aging in individuals who are >25 years. The relative differences in methylation among neighboring CpGs in the generally hypomethylated APC promoter may not only reflect stochastic fluctuations but also depend on the tissue type. Our results are consistent with the view that most methylation variation may arise after fertilization, leading to epigenetic mosaicism

Pectus excavatum: History, hypotheses and treatment options

Abstract Pectus excavatum and pectus carinatum represent the most frequent chest wall deformations. However, the pathogenesis is still poorly understood and research results remain inconsistent. To focus on the recent state of knowledge, we summarize and critically discuss the pathological concepts based on the history of these entities, beginning with the first description in the sixteenth century. Based on the early clinical descriptions, we review and discuss the different pathogenetic hypotheses. To open new perspectives for the potential pathomechanisms, the embryonic and foetal development of the ribs and the sternum is highlighted following the understanding that the origin of these deformities is given by the disruption in the maturation of the parasternal region. In the second, different therapeutical techniques are highlighted and based on the pathogenetic hypotheses and the embryological knowledge potential new biomaterial-based perspectives with interesting insights for tissue engineering-based treatment options are presented

Extreme Methylation Values of Imprinted Genes in Human Abortions and Stillbirths

Imprinted genes play an important role in fetal and placental development. Using quantitative bisulfite pyrosequencing assays, we determined the DNA methylation levels at two paternally methylated (H19 and MEG3) and four maternally methylated (LIT1, NESP55, PEG3, and SNRPN) imprinted regions in fetal muscle samples from abortions and stillbirths. Two of 55 (4%) spontaneous abortions and 10 of 57 (18%) stillbirths displayed hypermethylation in multiple genes. Interestingly, none of 34 induced abortions had extreme methylation values in multiple genes. All but two abortions/stillbirths with multiple methylation abnormalities were male, indicating that the male embryo may be more susceptible to excess methylation. Hypermethylation of multiple imprinted genes is consistent with stochastic failures of the mechanism, which normally protects the hypomethylated allele from de novo methylation after fertilization. Two of six informative abortions/stillbirths with H19 hypermethylation revealed significant biallelic expression of the autocrine growth factor IGF2. In two other cases hypermethylation of MEG3 was associated with transcriptional down-regulation. We propose that primary epimutations resulting in inappropriate methylation and expression patterns of imprinted genes may contribute to both normal human variation and disease, in particular spontaneous pregnancy loss