Local and global crosstalk among heterochromatin marks drives DNA methylome patterning in Arabidopsis.

Transposable elements (TEs) are robustly silenced by multiple epigenetic marks, but dynamics of crosstalk among these marks remains enigmatic. In Arabidopsis, TEs are silenced by cytosine methylation in both CpG and non-CpG contexts (mCG and mCH) and histone H3 lysine 9 methylation (H3K9me). While mCH and H3K9me are mutually dependent for their maintenance, mCG and mCH/H3K9me are independently maintained. Here, we show that establishment, rather than maintenance, of mCH depends on mCG, accounting for the synergistic colocalization of these silent marks in TEs. When mCG is lost, establishment of mCH is abolished in TEs. mCG also guides mCH in active genes, though the resulting mCH/H3K9me is removed thereafter. Unexpectedly, targeting efficiency of mCH depends on relative, rather than absolute, levels of mCG within the genome, suggesting underlying global negative controls. We propose that local positive feedback in heterochromatin dynamics, together with global negative feedback, drive robust and balanced DNA methylome patterning.

A feasibility study of a peer discussion group intervention for patients with pancreatobiliary cancer and their caregivers.

OBJECTIVES: The purpose of this feasibility study was to examine the impacts of a peer discussion group intervention called "the pancreatobiliary cancer salon" on psychological distress among patients with pancreatobiliary cancer and their caregivers. METHODS: We recruited patients with pancreatic or biliary tract cancer and their caregivers. We conducted a within-group pre-post comparison study. Participants were grouped by the type of cancer and treatment. Each group consisted of four to five patients or caregivers. Hospital staff members facilitated group discussions where participants freely talked for 1 h. We evaluated participants' psychological condition using the Profile of Mood States (POMS) and their impressions of the pancreatobiliary cancer salon. RESULTS: We analyzed data from 42 patients and 27 caregivers who joined the salon for the first time. Thirty-five patients (83.3%) had pancreatic cancer. Thirty-one patients (71.4%) had unresectable pancreatobiliary cancer and 14 patients (33.3%) were being treated with second-line or third-line chemotherapy at the time of the survey. Twenty-two patients (52.4%) participated in the salon within 6 months after diagnosis. Most participating caregivers were the patient's spouse/partner (51.9%) or child (34.6%). Both patients and caregivers experienced high levels of satisfaction with the pancreatobiliary cancer salon. Both patients and caregivers had significantly lower psychological distress as assessed by POMS after the salon. SIGNIFICANCE OF RESULTS: A peer discussion group intervention might be well-received and has potential to benefit for patients with pancreatobiliary cancer and their caregivers.

RNA interference-independent reprogramming of DNA methylation in Arabidopsis.

DNA methylation is important for silencing transposable elements (TEs) in diverse eukaryotes, including plants. In plant genomes, TEs are silenced by methylation of histone H3 lysine 9 (H3K9) and cytosines in both CG and non-CG contexts. The role of RNA interference (RNAi) in establishing TE-specific silent marks has been extensively studied, but the importance of RNAi-independent pathways remains largely unexplored. Here, we directly investigated transgenerational de novo DNA methylation of TEs after the loss of silent marks. Our analyses uncovered potent and precise RNAi-independent pathways for recovering non-CG methylation and H3K9 methylation in most TE genes (that is, coding regions within TEs). Characterization of a subset of TE genes without the recovery revealed the effects of H3K9 demethylation, replacement of histone H2A variants and their interaction with CG methylation, together with feedback from transcription. These chromatin components are conserved among eukaryotes and may contribute to chromatin reprogramming in a conserved manner.

A novel dominant-negative mutation in Gdf5 generated by ENU mutagenesis impairs joint formation and causes osteoarthritis in mice.

Growth and differentiation factor 5 (GDF5) has been implicated in chondrogenesis and joint formation, and an association of GDF5 and osteoarthritis (OA) has been reported recently. However, the in vivo function of GDF5 remains mostly unclarified. Although various human GDF5 mutations and their phenotypic consequences have been described, only loss-of-function mutations that cause brachypodism (shortening and joint ankylosis of the digits) have been reported in mice. Here, we report a new Gdf5 allele derived from a large-scale N-ethyl-N-nitrosourea mutagenesis screen. This allele carries an amino acid substitution (W408R) in a highly conserved region of the active signaling domain of the GDF5 protein. The mutation is semi-dominant, showing brachypodism and ankylosis in heterozygotes and much more severe brachypodism, ankylosis of the knee joint and malformation with early-onset OA of the elbow joint in homozygotes. The mutant GDF5 protein is secreted and dimerizes normally, but inhibits the function of the wild-type GDF5 protein in a dominant-negative fashion. This study further highlights a critical role of GDF5 in joint formation and the development of OA, and this mouse should serve as a good model for OA.