Live-cell analysis of DNA methylation during sexual reproduction in Arabidopsis reveals context and sex-specific dynamics controlled by noncanonical RdDM

Cytosine methylation is a key epigenetic mark in many organisms, important for both transcriptional control and genome integrity. While relatively stable during somatic growth, DNA methylation is reprogrammed genome-wide during mammalian reproduction. Reprogramming is essential for zygotic totipotency and to prevent transgenerational inheritance of epimutations. However, the extent of DNA methylation reprogramming in plants remains unclear. Here, we developed sensors reporting with single-cell resolution CG and non-CG methylation in Arabidopsis. Live imaging during reproduction revealed distinct and sex-specific dynamics for both contexts. We found that CHH methylation in the egg cell depends on DOMAINS REARRANGED METHYLASE 2 (DRM2) and RNA polymerase V (Pol V), two main actors of RNA-directed DNA methylation, but does not depend on Pol IV. Our sensors provide insight into global DNA methylation dynamics at the single-cell level with high temporal resolution and offer a powerful tool to track CG and non-CG methylation both during development and in response to environmental cues in all organisms with methylated DNA, as we illustrate in mouse embryonic stem cells.

Histone variants in plant transcriptional regulation

Chromatin based organization of eukaryotic genome plays a profound role in regulating gene transcription. Nucleosomes form the basic subunits of chromatin by packaging DNA with histone proteins, impeding the access of DNA to transcription factors and RNA polymerases. Exchange of histone variants in nucleosomes alters the properties of nucleosomes and thus modulates DNA exposure during transcriptional regulation. Growing evidence indicates the important function of histone variants in programming transcription during developmental transitions and stress response. Here we review how histone variants and their deposition machineries regulate the nucleosome stability and dynamics, and discuss the link between histone variants and transcriptional regulation in plants. This article is part of a Special Issue entitled: Plant Gene Regulatory Mechanisms and Networks, edited by Dr. Erich Grotewold and Dr. Nathan Springer.

Impacts of land-use and land-cover changes on rockfall propagation: Insights from the Grenoble conurbation

Several studies have debated the incidence of global warming on the probability of rock instability, whereas the impacts of land use and land cover (LULC) changes on rockfall propagation and associated hazards have received comparably little interest. In this study we evaluate the impacts of LULC changes on rockfall hazards on the slopes above the village of Crolles (Chartreuse massif, Grenoble conurbation, French Alps) through a three-level approach: (i) diachronic landscape analysis for four different periods of the past (i.e. 1850, 1956, 1975, and 2013), (ii) computation of 3D rockfall simulations taking explicitly account of reconstructed LULC changes, and (iii) resulting changes in rockfall hazards over time. We reveal that the disappearance of viticultural landscapes (relating to the decline of cropping areas during the interwar period) and intense afforestation of the steepest upper portion of the slope resulted in a significant increase of rockfall return period associated to a gradual decrease of mean kinetic energy at the level of the urban front of Crolles. According to the Eurobloc methodology, the degree of hazard decreased significantly despite the continuous and rapid urban sprawl on the slopes. These results underline that forests can indeed have significant protection function but also call for a more systematic inclusion of LULC changes in hazard assessments in the future.

Abstract P1-14-09: Long term survival of locally advanced breast cancers (LABC) treated with neoadjuvant treatment, results of a multicenter randomised phase II study (Remagus 02 trial)

Backgound : The primary analysis of the REMAGUS-02 multicenter randomized phase II trial demonstrated that celecoxib did not improve pCR rates in pts with HER2-negative localized invasive breast cancer (BC), whereas trastuzumab increased pCR rates in HER2-positive ones [Pierga BCRT 2010]. We report here the long-term follow-up results of this trial for disease free survival (DFS) and overall survival (OS).

Patients and methods: From May 2004 to October 2007, 340 stage II-III BC patients were randomly assigned to receive 4 cycles (c) of epirubicin–cyclophosphamide q 3 w followed by 4 c of docetaxel q 3 w +/- trastuzumab in HER2 positive pts (120 pts) or +/- celecoxib in HER2 negative pts (n=220). From September 2005, all pts with HER2 positive BC received adjuvant T for a total of 18 c (n=106). Patients with hormone receptors (HR) positive tumor received adjuvant endocrine treatment according to menopausal status

Results: With a median follow up of nearly 8 years (94.4 months, 20-127m), 112 relapses and 75 deaths have been observed (median DFS and OS not reached). Eight years DFS and OS were respectively 63 % [57%-71%] and 75 % [70%-81%] in HER2 negative group; and 75% [67%-83%] and 82 % [74%-90%] in HER2 positive group. DFS was significantly higher in HER+ pts than in HER2-(HR: 0.64 [0.42-0.99], p=0.042), whereas OS did not differ significantly (HR: 0.67, [0.41-1.11], p=0.123).

In the overall population, progesterone receptor (PgR) positivity was associated with a better DFS (p=0.012) and OS (p<0.001) as compared to ER+/PgR- (DFS: HR=2.07 [1.27-3.39]; OS: HR=2.53 [1.3-4.92]) and ER-/PR-; DFS: HR=1.56 [0.98-2.46]; OS: HR: 3.34 [1.87 – 5.97]. In the ER-/PR- group, DFS reached a "plateau" after three years follow-up, while the annual risk of relapse remained constant in the ER+/PR- subgroup.

In the HER2- subgroup, no effect of neoadjuvant celocoxib was observed on survival, neither in intention to treat (ITT) nor in per protocol analyses. In the multivariate analysis clinical stage (T3/T4 versus T2, HR: 1.92 [1.209 - 3.05], p=0.006), PgR status (positive versus negative HR : 0.52, [0.32-0.84], p=0.007) and pCR (yes vs no, HR : 0.213 [0.066-0.687], p=0.01) were significant predictors of DFS.

In the HER2+ subgroup, neoadjuvant versus adjuvant trastuzumab was not significantly associated with DFS, neither in the ITT, nor in the per protocol analysis.

Conclusion: Celecoxib was not associated with pCR or survival benefit when added to conventional neoadjuvant CT in Her2-negative BC pts. Lack of PgR expression is a major prognostic factor for survival. Neoadjuvant versus adjuvant trastuzumab increased pCR rates but did not change significantly DFS and OS of HER2 positive BC pts.

Citation Format: Giacchetti S, Hamy-Petit A-S, Delaloge S, Brain E, Berger F, Mathieu M-C, de Cremoux P, Bertheau P, Guinebretière J-M, Saghatchian M, Tembo O, Marty M, Pierga J-Y. Long term survival of locally advanced breast cancers (LABC) treated with neoadjuvant treatment, results of a multicenter randomised phase II study (Remagus 02 trial). [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P1-14-09.

Evaluation of contraceptive methods in women with congenital heart disease in Germany, Hungary and Japan

AIMS

For women with congenital heart defects (CHD), pregnancy may pose a health risk. Sexually active women with CHD without the desire for own children or for whom pregnancy would imply considerable health risks require adequate counselling regarding appropriate contraception. This study gathers data on the contraceptive behaviour of women with CHD from three different cultural regions.

METHODS AND RESULTS

634 women with CHD from Germany, Hungary and Japan were surveyed regarding contraception and contraceptive methods (CM) used. The patients were divided into groups according to different criteria such as pregnancy associated cardiovascular risk or "safety" of the contraceptive methods used. 59% of the study participants had already gained experience with CM. The average age at the first time of use was 18.4 years; the German patients were significantly younger at the first time of using a CM than those from Hungary and Japan. Overall the condom was the method used the most (38%), followed by oral contraceptives (30%) and coitus interruptus (11%). The range of CM used in Japan was much smaller than that in Germany or Hungary. Unsafe contraceptives were currently, or had previously been used, by 29% of the surveyed patients (Germany: 25%, Hungary: 37%, Japan: 32%).

CONCLUSION

Most women with CHD use CM. There are differences between the participating countries. Adequate contraceptive counselling of women with CHD requires considering the individual characteristics of each patient, including potential contraindications. For choosing an appropriate CM, both the methods' "safety", as well as the maternal cardiovascular risk, are important.

Chromatin remodelling during male gametophyte development

The plant life cycle alternates between a diploid sporophytic phase and haploid gametophytic phase, with the latter giving rise to the gametes. Male gametophyte development encompasses two mitotic divisions that results in a simple three-celled structure knows as the pollen grain, in which two sperm cells are encased within a larger vegetative cell. Both cell types exhibit a very different type of chromatin organization - highly condensed in sperm cell nuclei and highly diffuse in the vegetative cell. Distinct classes of histone variants have dynamic and differential expression in the two cell lineages of the male gametophyte. Here we review how the dynamics of histone variants are linked to reprogramming of chromatin activities in the male gametophyte, compaction of the sperm cell genome and zygotic transitions post-fertilization.