P3688Familial recurrent autoimmune myocarditis associated with a truncating nonsense mutation of the desmoplakin gene

Background

Arrhythmogenic cardiomyopathy (AC) is an important cause of ventricular arrhythmias in children and young adults. AC is associated with mutation of desmosomal proteins, however, cardiac disease penetrance is incomplete and the clinical course varies widely without recognizable exogenous or epi/genetic co-factors. Importantly, DSP mutation carriers may also display entirely non-cardiac e.g. dermatological phenotypes.

Methods and results

In two brothers with recurrent fulminant myocarditis, mutation screening of 218 cardiomyopathy-related genes identified a truncating mutation Arg1458* of desmoplakin (DSP). DSP immunhistology unexpectedly revealed complete loss (“knockout”) of DSP protein in endomyocardial biopsies (EMBs), but none of the histological anomalies of AC. Criteria for histological diagnosis of myocarditis were not either fulfilled, and cardiac MRI revealed no features associated with AC. Screening for infections was negative, there was no substance abuse, medication or vaccination. Possible disease triggers were competitive sport events. Myosin and troponin I autoantibodies were detected at titers up to 1:320.

We used allele-specific RT-PCR to distinguish if the patients' allele classified as “normal” was actually defective due to promotor mutation or epigenetic silencing. RT-PCRs were done on EMBs and peripheral blood mononuclear cells (PBMCs). In a cohort of dilated cardiomyopathy (DCM) patients we were able to detect DSP transcripts in both, PBMC and left-ventricular heart tissue. RNA sequencing of human PBMC subpopulations suggested that DSP transcription may be restricted to certain immune cell subtypes. RT-PCRs revealed that both Arg1458* carriers have a functional second DSP allele, indicating that their “DSP knockout” occurs at the protein level and may be due to protein instability and degradation within desmosomes.

We screened additional existing cohorts for such variants and identified stopgain variant Gln307Ter in a 37-yrs-old woman with ARVC. This patient's sister died from heart failure at the age of 39. In a 59-yrs-old female LVNC patient, stopgain variant Y1391X was identified. Here, family history was unclear, her brother probably died from coronary artery disease. In a 71-yrs-old female DCM patient with no family history, stopgain variant Tyr1512Ter was identified.

Conclusions

The described patients with DSP truncations strongly suggest the existence of additional genetic or exogenous modifiers driving pathogenesis either way. DSP defects may cause recurrent myocarditis, and mutation screening is advisable to enable early detection of high-risk patients with similar phenotypes. Our finding of complete myocardial DSP protein loss emphasizes that DNA sequencing may miss critical molecular disturbances. It is indispensable to also analyze transcriptome and protein level in the tissue actually affected in a patient in order to recognize his/her individual pathogenesis.

EvoChromo: towards a synthesis of chromatin biology and evolution

Over the past few years, interest in chromatin and its evolution has grown. To further advance these interests, we organized a workshop with the support of The Company of Biologists to debate the current state of knowledge regarding the origin and evolution of chromatin. This workshop led to prospective views on the development of a new field of research that we term 'EvoChromo'. In this short Spotlight article, we define the breadth and expected impact of this new area of scientific inquiry on our understanding of both chromatin and evolution.

Building new insights in plant gametogenesis from an evolutionary perspective

Extant bryophytes are thought to preserve characteristics of ancestral land plants, with a life cycle dominated by the haploid gametophyte. The gametophyte produces gametes in specialized organs that differentiate after an extensive phase of vegetative development. During land plant evolution, these organs became extremely reduced. As a result, in flowers of angiosperms the haploid phase of the life cycle is reduced to few-celled gametophytes, namely the embryo sac (female) and pollen (male). Although many factors contributing to gametogenesis have been identified in flowering plants, the extreme reduction of the gametophytes has prevented a clear molecular dissection of key processes of gametogenesis. Recent studies in the model bryophyte Marchantia polymorpha have identified conserved transcription factors regulating the equivalent steps in the sexual reproduction of land plants. These include FEMALE GAMETOPHYTE MYB for female gametophyte development, BONOBO for gamete progenitor cell specification, DUO POLLEN1 for sperm differentiation and members of the RWP-RK domain family for female gamete formation. These studies demonstrate that M. polymorpha is a powerful model to untangle the core processes of gametogenesis in land plants. We anticipate that a deeper understanding of gametogenesis in bryophytes will circumscribe the origin of plant germ cells and define the differentiation programmes of sperm and eggs.

A multivariate Th17 metagene for prognostic stratification in T cell non-inflamed triple negative breast cancer

A diversity of T helper (Th) subsets (Th1, Th2, Th17) has been identified in the human tumor microenvironment. In breast cancer, the role of Th subsets remains controversial, and a systematic study integrating Th subset diversity, T cell inflammation, breast cancer molecular subtypes, and patient prognosis, is lacking. In primary untreated breast cancer samples, we analyzed 19 Th cytokines at the protein level. Eight were T cell-specific, and subsequently measured in 106 prospectively-collected untreated samples. The dominant Th cytokines across all breast cancer samples were IFN-γ and IL-2. Th2 cytokines (IL-4, IL-5, IL-13) were expressed at low levels and not associated with any breast cancer subtype. Th17 cytokines (IL-17A and IL-17F) were up-regulated in triple negative breast cancer (TNBC), specifically in T cell non-inflamed tumors. In order to get insight into prognosis, we exploited the METABRIC transcriptomic dataset. We derived Th1, Th2, and Th17 metagenes based on manually curated Th signatures, and found that a high Th17 metagene was of good prognosis in T cell non-inflamed TNBC. Multivariate Cox modeling selected the Nottingham Prognostic Index (NPI), Th2 and Th17 metagenes as additive predictors of breast cancer-specific survival, which defined novel and highly distinct prognostic groups within TNBC. Our results reveal that Th17 is a novel prognostic composite biomarker in T cell non-inflamed TNBC.

Integrating immune cell and tumor molecular diversity is an efficient strategy for prognostic stratification of cancer patients.

A simple and robust protocol for immunostaining Arabidopsis pollen nuclei

Pollen represents the male sexual lineage in flowering plants. At maturity, pollen grains are composed of a companion vegetative cell with embedded sperm. During pollen development, these two cell types acquire vastly differing cell fates. Underlying this differential fate acquisition is dramatic reconfiguration of pollen chromatin that is highly evident at a cytological level. The precise link between histone mark deposition and fate acquisition remains largely unexplored, which in part has been hindered by the difficulty in working with pollen in model plant species like Arabidopsis. Here, we describe a simple and robust protocol to isolate Arabidopsis pollen nuclei and immunostain for histone marks. Plant growth aside, the protocol can be performed over 2 days with few Arabidopsis plants, thus allowing multiple genotypes to be analysed in parallel. We also describe a method to de-mask epitopes through antigen retrieval, which vastly improves the signal for antibodies that target heterochromatic histone marks.

Abstract GS3-07: Clinical utility of circulating tumor cell count as a tool to chose between first line hormone therapy and chemotherapy for ER+ HER2- metastatic breast cancer: Results of the phase III STIC CTC trial

Background: In ER+ HER2- metastatic breast cancer (MBC) patients, the clinical choice between 1st line hormone therapy (HT, the recommended option) or chemotherapy (CT) is based on the absence of “visceral crisis” or adverse prognostic factors, with no proven/objective criteria. In that context, STIC CTC (NCT01710605) was set up as a strategy trial to test whether circulating tumor cells (CTC) count could help customize the choice between 1st line HT or CT.

Methods: For this multicenter phase 3 non-inferiority trial, the main inclusion criteria were: ER+ HER2- MBC with no prior therapy, PS≤2, no contra-indication to HT or CT and informed consent. The a priori treatment choice (HT or CT) and CTC count (CellSearch®) were obtained in all patients prior to randomization. Patients were randomized 1:1 between clinically-driven choice (CTC count not disclosed, HT or CT administered as decided a priori), or a CTC-driven choice (HT if <5 CTC/7.5ml, CT if ≥5 CTC/7.5ml). The primary objective was treatment efficacy (PFS hazard ratio), non-inferiority being established if the upper bound of the PFS HR 2-sided 90%CI is ≤1.25; secondary objectives included subgroup analyses (CTC status, patient characteristics) and OS.

Results: 761 MBC patients were randomized between 02/2012 and 08/2016. Baseline characteristics: 7.8% of patients had a PS=2, 24.1% had a de novo metastatic disease; 63.3% received prior adjuvant HT and 49.9% prior adjuvant CT; 31.3% had ≥3 metastatic sites. A priori treatments (HT or CT) and CTC count (< or ≥5 CTC/7.5ml) were well balanced between the two arms. After randomization, in the clinically-driven arm, N=267 (72.4%) patients received HT and N=102 (27.6%) CT (as decided a priori). In the CTC-driven arm: (1) the a priori choice of HT was confirmed by a low CTC count in N=181 (67.5%) of patients, while N=87 (32.5%) were switched to CT due to a high CTC count; (2) the a priori choice of CT was confirmed by high CTC count in only N=48 (48%) patients, while N=52 (52%) were switched to HT. The primary endpoint was met, PFS being not inferior in the CTC-driven arm (HR=0.98, 90%CI=[0.84–1.13]). Analyses focusing on discordant subgroups showed that for patients with a priori choice of HT but with high CTC count (leading to a switch to CT in the CTC-arm), PFS was significantly longer in the CTC-driven arm than in the standard arm (HR=0.67, 95%CI=[0.49–0.92]; p=0.01), with a non-significant trend toward longer OS (HR=0.68, 95%CI=[0.44–1.07]; p=0.09). Inversely, for patients with a priori choice of CT but with low CTC count (i.e. de-escalation to HT in the CTC arm), PFS was not statistically different between the two arms.

Conclusion: This trial demonstrates the clinical utility of CTC count as an objective decision tool when considering 1st line therapy in ER+ HER2- MBC. In most patients, CTC count did confirm the a priori clinical choice; however, trial results show that in discrepant cases, CTC count may be trusted for either escalating (i.e. considering CT in patients if high CTC count) or de-escalating (i.e. considering HT in patients if low CTC count) 1st line therapy.

Funding: French National Cancer Institute; Menarini Silicon Biosystems.

Citation Format: Bidard F-C, Jacot W, Dureau S, Brain E, Bachelot T, Bourgeois H, Goncalves A, Ladoire S, Naman H, Dalenc F, Gligorov J, Espie M, Levy C, Ferrero J-M, Loirat D, Cottu P, Dieras V, Simondi C, Berger F, Alix-Panabieres C, Pierga J-Y. Clinical utility of circulating tumor cell count as a tool to chose between first line hormone therapy and chemotherapy for ER+ HER2- metastatic breast cancer: Results of the phase III STIC CTC trial [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr GS3-07.

Abstract PD2-03: Circulating tumor DNA (ctDNA) and circulating tumor cells (CTC) predictive value in HER2 negative metastatic breast cancer patients treated with first line weekly paclitaxel and bevacizumab: Results of a prospective cohort from the French Breast Cancer InterGroup Unicancer (UCBG): COMET study

Background: Increased levels of CTC and a persistent elevated level after just one cycle of chemotherapy are very strong and independent markers of worse progression-free survival (PFS) and overall survival (OS) in patients (pts) with metastatic breast cancer (MBC) (Bidard et al, Lancet Oncol 2014). ctDNA can be used to detect mutation associated with resistance to treatment. It has also been shown that dynamic changes in ctDNA levels closely reflect changes in tumor burden. We prospectively monitored CTC and ctDNA early variations during first line chemotherapy for MBC.

Patients & methods: The French cohort COMET is a prospective study including first line HER2 negative patients (pts) receiving weekly paclitaxel and bevacizumab according to EMA approved combination. The aim of this cohort is to evaluate clinical, biological and radiological parameters associated with pts outcome (CTC, serum markers, ctDNA, pharmacogenomic polymorphisms, metabolomic parameters, visceral fat, serum estradiol level and quality of life). We present here the first planned analysis on pts evaluated for CTC (CellSearch) and ctDNA using targeted sequencing (Roche SeqCap technology) of a panel of 46 genes and 8 promoters, using unique molecular identifiers to increase ctDNA detection sensitivity. Blood samples were obtained at baseline (BL) and before the second cycle of chemotherapy (C2).

Results: From 09/2012 to 5/2014, 218 pts were included in this substudy. Median age was 55 years and 22% of pts had triple negative BC. At BL, 70% of pts had ≥1 detectable CTC per 7.5 ml of blood (median 4 CTC, range 1- 30,000) and 37% at C2. With a threshold of ≥5 CTC, 47% of pts were positive at BL and 22% at C2. For ctDNA, out of the first 141 pts analyzed, 105 had at least one somatic mutation detected in plasma (74%). The average number of mutations per pt was 2.7 and most commonly mutated genes were TP53 and PIK3CA. ESR1 was found mutated in 9% of all cases and restricted to the ER+ subgroup. Median Allelic Frequency was 10% (range 0.6-83%). Only 33% of pts had detectable ctDNA at C2. At BL, CTC and ctDNA levels were correlated (r=0.46, p<0.0001). Despite no complete overlap, 11% of pts had no CTC nor ctDNA detected. Median follow-up was 53 months and median OS was 32 months. Increased level of CTC and ctDNA were significantly associated with decreased PFS and OS. At C2, ≥5 CTC or still detectable ctDNA were strong markers of reduced OS: HR 4.6 (CI95 3.1-7) and HR 3.2 (CI95 1.8 – 5.5), respectively (both p< 0.0001). At multivariate analysis for PFS, detectable ctDNA at C2 and triple negative status were the only significant prognostic factors. None of serum marker level at BL or their early variations had prognostic value.

Conclusion: This is the largest prospective cohort assessing the respective prognostic values of early CTC and ctDNA changes in homogenously treated first line MBC patients. Analysis of mutations profile variations and comparison with primary tumor and metastasis biopsies are ongoing and may reveal early mechanisms of resistance.

Citation Format: Pierga J-Y, Silveira A, Lorgis V, Tanguy M-L, Tredan O, Dubot C, Jacot W, Goncalves A, Debled M, Levy C, Ferrero J-M, Jouannaud C, Luporsi E, Mouret-Reynier M-A, Dalenc F, Lemonnier J, Berger F, Proudon C, Bidard F-C. Circulating tumor DNA (ctDNA) and circulating tumor cells (CTC) predictive value in HER2 negative metastatic breast cancer patients treated with first line weekly paclitaxel and bevacizumab: Results of a prospective cohort from the French Breast Cancer InterGroup Unicancer (UCBG): COMET study [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr PD2-03.

New cues for body axis formation in plant embryos

Plant embryogenesis initiates with the fusion of sperm and egg cell, and completes the generation of the basic outline of the future plant. Here, we summarize the recent findings about the signaling cascade triggering the zygotic transcription, and the intracellular events and regulatory factors involved in the formation of the two major body axes. We highlight the lack of systematic de novo transcriptional activation in the zygote, and emphasize the importance of cytoskeletal reorganization to polarize the zygote and control the first asymmetric division that establishes the apical-basal axis. Finally, the limited knowledge of mechanisms that control the cell divisions separating the inner and outer cell layers is summarized and we propose approaches to enhance our understanding of basic principles of plant embryogenesis.

Transcription factor DUO1 generated by neo-functionalization is associated with evolution of sperm differentiation in plants

Evolutionary mechanisms underlying innovation of cell types have remained largely unclear. In multicellular eukaryotes, the evolutionary molecular origin of sperm differentiation is unknown in most lineages. Here, we report that in algal ancestors of land plants, changes in the DNA-binding domain of the ancestor of the MYB transcription factor DUO1 enabled the recognition of a new cis-regulatory element. This event led to the differentiation of motile sperm. After neo-functionalization, DUO1 acquired sperm lineage-specific expression in the common ancestor of land plants. Subsequently the downstream network of DUO1 was rewired leading to sperm with distinct morphologies. Conjugating green algae, a sister group of land plants, accumulated mutations in the DNA-binding domain of DUO1 and lost sperm differentiation. Our findings suggest that the emergence of DUO1 was the defining event in the evolution of sperm differentiation and the varied modes of sexual reproduction in the land plant lineage.

Histone H2A variants confer specific properties to nucleosomes and impact on chromatin accessibility

In eukaryotes, variants of core histone H2A are selectively incorporated in distinct functional domains of chromatin and are distinguished by conserved sequences of their C-terminal tail, the L1 loop and the docking domain, suggesting that each variant confers specific properties to the nucleosome. Chromatin of flowering plants contains four types of H2A variants, which biochemical properties have not been characterized. We report that in contrast with animals, in Arabidopsis thaliana H2A variants define only four major types of homotypic nucleosomes containing exclusively H2A, H2A.Z, H2A.X or H2A.W. In vitro assays show that the L1 loop and the docking domain confer distinct stability of the nucleosome. In vivo and in vitro assays suggest that the L1 loop and the docking domain cooperate with the C-terminal tail to regulate chromatin accessibility. Based on these findings we conclude that the type of H2A variant in the nucleosome impacts on its interaction with DNA and propose that H2A variants regulate the dynamics of chromatin accessibility. In plants, the predominance of homotypic nucleosomes with specific physical properties and their specific localization to distinct domains suggest that H2A variants play a dominant role in chromatin dynamics and function.

LHP1 Interacts with ATRX through Plant-Specific Domains at Specific Loci Targeted by PRC2

Heterochromatin Protein 1 (HP1) is a major regulator of chromatin structure and function. In animals, the network of proteins interacting with HP1 is mainly associated with constitutive heterochromatin marked by H3K9me3. HP1 physically interacts with the putative ortholog of the SNF2 chromatin remodeler ATRX, which controls deposition of histone variant H3.3 in mammals. In this study, we show that the Arabidopsis thaliana ortholog of ATRX participates in H3.3 deposition and possesses specific conserved domains in plants. We found that plant Like HP1 (LHP1) protein interacts with ATRX through domains that evolved specifically in land plant ancestors. Loss of ATRX function in Arabidopsis affects the expression of a limited subset of genes controlled by PRC2 (POLYCOMB REPRESSIVE COMPLEX 2), including the flowering time regulator FLC. The function of ATRX in regulation of flowering time requires novel LHP1-interacting domain and ATPase activity of the ATRX SNF2 helicase domain. Taken together, these results suggest that distinct evolutionary pathways led to the interaction between ATRX and HP1 in mammals and its counterpart LHP1 in plants, resulting in distinct modes of transcriptional regulation.