H2A.X promotes endosperm-specific DNA methylation in Arabidopsis thaliana.

BACKGROUND: H2A.X is an H2A variant histone in eukaryotes, unique for its ability to respond to DNA damage, initiating the DNA repair pathway. H2A.X replacement within the histone octamer is mediated by the FAcilitates Chromatin Transactions (FACT) complex, a key chromatin remodeler. FACT is required for DEMETER (DME)-mediated DNA demethylation at certain loci in Arabidopsis thaliana female gametophytes during reproduction. Here, we sought to investigate whether H2A.X is involved in DME- and FACT-mediated DNA demethylation during reproduction. RESULTS: H2A.X is encoded by two genes in Arabidopsis genome, HTA3 and HTA5. We generated h2a.x double mutants, which displayed a normal growth profile, whereby flowering time, seed development, and root tip organization, S-phase progression and proliferation were all normal. However, h2a.x mutants were more sensitive to genotoxic stress, consistent with previous reports. H2A.X fused to Green Fluorescent Protein (GFP) under the H2A.X promoter was highly expressed especially in newly developing Arabidopsis tissues, including in male and female gametophytes, where DME is also expressed. We examined DNA methylation in h2a.x developing seeds and seedlings using whole genome bisulfite sequencing, and found that CG DNA methylation is decreased genome-wide in h2a.x mutant endosperm. Hypomethylation was most striking in transposon bodies, and occurred on both parental alleles in the developing endosperm, but not the embryo or seedling. h2a.x-mediated hypomethylated sites overlapped DME targets, but also included other loci, predominately located in heterochromatic transposons and intergenic DNA. CONCLUSIONS: Our genome-wide methylation analyses suggest that H2A.X could function in preventing access of the DME demethylase to non-canonical sites. Overall, our data suggest that H2A.X is required to maintain DNA methylation homeostasis in the unique chromatin environment of the Arabidopsis endosperm.

H2A.X promotes endosperm-specific DNA methylation in Arabidopsis thaliana.

Background: H2A.X is an H2A variant histone in eukaryotes, unique for its ability to respond to DNA damage, initiating the DNA repair pathway. H2A.X replacement within the histone octamer is mediated by the FAcilitates Chromatin Transactions (FACT) complex, a key chromatin remodeler. FACT is required for DEMETER (DME)-mediated DNA demethylation at certain loci in Arabidopsis thaliana female gametophytes during reproduction. Here, we sought to investigate whether H2A.X is involved in DME- and FACT-mediated DNA demethylation during reproduction. Results: H2A.X is encoded by two genes in Arabidopsis genome, HTA3 and HTA5. We generated h2a.x double mutants, which displayed a normal growth profile, whereby flowering time, seed development, and root tip organization, S-phase progression and proliferation were all normal. However, h2a.x mutants were more sensitive to genotoxic stress, consistent with previous reports. H2A.X fused to Green Fluorescent Protein (GFP) under the H2A.X promoter was highly expressed especially in newly developing Arabidopsis tissues, including in male and female gametophytes, where DME is also expressed. We examined DNA methylation in h2a.x developing seeds and seedlings using whole genome bisulfite sequencing, and found that CG DNA methylation is decreased genome-wide in h2a.x mutant seeds. Hypomethylation was most striking in transposon bodies, and occurred on both parental alleles in the developing endosperm, but not the embryo or seedling. h2a.x-mediated hypomethylated sites overlapped DME targets, but also included other loci, predominately located in heterochromatic transposons and intergenic DNA. Conclusions: Our genome-wide methylation analyses suggest that H2A.X could function in preventing access of the DME demethylase to non-canonical sites. Alternatively, H2A.X may be involved in recruiting methyltransferases to those sites. Overall, our data suggest that H2A.X is required to maintain DNA methylation homeostasis in the unique chromatin environment of the Arabidopsis endosperm.

Prognostic Impact of LAG-3 mRNA Expression in Early Breast Cancer.

Background: Monoclonal antibodies against PD-1 or PD-L1 have been established in clinical practice for the treatment of both early and advanced/metastatic triple-negative breast cancer. Beyond the established immune checkpoints (ICPs) (PD-1 and CTLA-4), additional ICPs, such as lymphocyte activation gene-3 (LAG-3), are subject of current research. In the present retrospective gene-expression analysis, we evaluated the prognostic significance of LAG-3 in 461 patients with early breast cancer. In addition, we examined whether there was a correlation between the different ICP and CD8 expressions. Methods: Using microarray-based gene-expression analysis, we examined the prognostic significance of LAG-3 mRNA expression for metastasis-free survival (MFS) in the whole cohort of 461 breast cancer patients and among different molecular subtypes. Correlations were analyzed using Spearman's rho correlation coefficient. Results: In the whole cohort, LAG-3 expression had no significant impact on MFS (p = 0.712, log-rank). In the subgroup analyses, there was a trend that a higher LAG-3 expression was associated with a favorable outcome in the luminal B (p = 0.217), basal-like (p = 0.370) and HER2 (p = 0.089) subtypes, although significance was not reached. In contrast, in a multivariate Cox regression analysis, adjusted for age, tumor size, axillary nodal status, histological grade of differentiation and proliferation marker Ki-67, LAG-3 showed a significant influence on MFS (HR 0.574; 95% CI 0.369−0.894; p = 0.014). High LAG-3 significantly correlated with CD8 (ρ = 0.571; p < 0.001). Conclusions: LAG-3 expression had an independent impact on MFS. In addition to PD-1 and PD-L1, further immune checkpoints, such as LAG-3, could serve as therapeutic targets in breast cancer.

Gestational diabetes mellitus and COVID-19: results from the COVID-19-Related Obstetric and Neonatal Outcome Study (CRONOS).

BACKGROUND: Gestational diabetes mellitus is one of the most frequent pregnancy complications with a global prevalence of 13.4% in 2021. Pregnant women with COVID-19 and gestational diabetes mellitus are 3.3 times more likely to be admitted to an intensive care unit than women without gestational diabetes mellitus. Data on the association of gestational diabetes mellitus with maternal and neonatal pregnancy outcomes in pregnant women with SARS-CoV-2 infection are lacking. OBJECTIVE: This study aimed to investigate whether gestational diabetes mellitus is an independent risk factor for adverse maternal and fetal and neonatal outcomes in pregnant women with COVID-19. STUDY DESIGN: The COVID-19-Related Obstetric and Neonatal Outcome Study is a registry-based multicentric prospective observational study from Germany and Linz, Austria. Pregnant women with clinically confirmed COVID-19 were enrolled between April 3, 2020, and August 24, 2021, at any stage of pregnancy. Obstetricians and neonatologists of 115 hospitals actively provided data to the COVID-19-Related Obstetric and Neonatal Outcome Study. For collecting data, a cloud-based electronic data platform was developed. Women and neonates were observed until hospital discharge. Information on demographic characteristics, comorbidities, medical history, COVID-19-associated symptoms and treatments, pregnancy, and birth outcomes were entered by the local sites. Information on the periconceptional body mass index was collected. A primary combined maternal endpoint was defined as (1) admission to an intensive care unit (including maternal mortality), (2) viral pneumonia, and/or (3) oxygen supplementation. A primary combined fetal and neonatal endpoint was defined as (1) stillbirth at ≥24 0/7 weeks of gestation, (2) neonatal death ≤7 days after delivery, and/or (3) transfer to a neonatal intensive care unit. Multivariable logistic regression analysis was performed to evaluate the modulating effect of gestational diabetes mellitus on the defined endpoints. RESULTS: Of the 1490 women with COVID-19 (mean age, 31.0±5.2 years; 40.7% nulliparous), 140 (9.4%) were diagnosed with gestational diabetes mellitus; of these, 42.9% were treated with insulin. Overall, gestational diabetes mellitus was not associated with an adverse maternal outcome (odds ratio, 1.50; 95% confidence interval, 0.88-2.57). However, in women who were overweight or obese, gestational diabetes mellitus was independently associated with the primary maternal outcome (adjusted odds ratio, 2.69; 95% confidence interval, 1.43-5.07). Women who were overweight or obese with gestational diabetes mellitus requiring insulin treatment were found to have an increased risk of a severe course of COVID-19 (adjusted odds ratio, 3.05; 95% confidence interval, 1.38-6.73). Adverse maternal outcomes were more common when COVID-19 was diagnosed with or shortly after gestational diabetes mellitus diagnosis than COVID-19 diagnosis before gestational diabetes mellitus diagnosis (19.6% vs 5.6%; P<.05). Maternal gestational diabetes mellitus and maternal preconception body mass index of ≥25 kg/m2 increased the risk of adverse fetal and neonatal outcomes (adjusted odds ratio, 1.83; 95% confidence interval, 1.05-3.18). Furthermore, overweight and obesity (irrespective of gestational diabetes mellitus status) were influential factors for the maternal (adjusted odds ratio, 1.87; 95% confidence interval, 1.26-2.75) and neonatal (adjusted odds ratio, 1.81; 95% confidence interval, 1.32-2.48) primary endpoints compared with underweight or normal weight. CONCLUSION: Gestational diabetes mellitus, combined with periconceptional overweight or obesity, was independently associated with a severe maternal course of COVID-19, especially when the mother required insulin and COVID-19 was diagnosed with or after gestational diabetes mellitus diagnosis. These combined factors exhibited a moderate effect on neonatal outcomes. Women with gestational diabetes mellitus and a body mass index of ≥25 kg/m2 were a particularly vulnerable group in the case of COVID-19.

Visualizing Stromule Frequency with Fluorescence Microscopy.

Stromules, or "stroma-filled tubules", are narrow, tubular extensions from the surface of the chloroplast that are universally observed in plant cells but whose functions remain mysterious. Alongside growing attention on the role of chloroplasts in coordinating plant responses to stress, interest in stromules and their relationship to chloroplast signaling dynamics has increased in recent years, aided by advances in fluorescence microscopy and protein fluorophores that allow for rapid, accurate visualization of stromule dynamics. Here, we provide detailed protocols to assay stromule frequency in the epidermal chloroplasts of Nicotiana benthamiana, an excellent model system for investigating chloroplast stromule biology. We also provide methods for visualizing chloroplast stromules in vitro by extracting chloroplasts from leaves. Finally, we outline sampling strategies and statistical approaches to analyze differences in stromule frequencies in response to stimuli, such as environmental stress, chemical treatments, or gene silencing. Researchers can use these protocols as a starting point to develop new methods for innovative experiments to explore how and why chloroplasts make stromules.

Chloroplasts extend stromules independently and in response to internal redox signals.

A fundamental mystery of plant cell biology is the occurrence of "stromules," stroma-filled tubular extensions from plastids (such as chloroplasts) that are universally observed in plants but whose functions are, in effect, completely unknown. One prevalent hypothesis is that stromules exchange signals or metabolites between plastids and other subcellular compartments, and that stromules are induced during stress. Until now, no signaling mechanisms originating within the plastid have been identified that regulate stromule activity, a critical missing link in this hypothesis. Using confocal and superresolution 3D microscopy, we have shown that stromules form in response to light-sensitive redox signals within the chloroplast. Stromule frequency increased during the day or after treatment with chemicals that produce reactive oxygen species specifically in the chloroplast. Silencing expression of the chloroplast NADPH-dependent thioredoxin reductase, a central hub in chloroplast redox signaling pathways, increased chloroplast stromule frequency, whereas silencing expression of nuclear genes related to plastid genome expression and tetrapyrrole biosynthesis had no impact on stromules. Leucoplasts, which are not photosynthetic, also made more stromules in the daytime. Leucoplasts did not respond to the same redox signaling pathway but instead increased stromule formation when exposed to sucrose, a major product of photosynthesis, although sucrose has no impact on chloroplast stromule frequency. Thus, different types of plastids make stromules in response to distinct signals. Finally, isolated chloroplasts could make stromules independently after extraction from the cytoplasm, suggesting that chloroplast-associated factors are sufficient to generate stromules. These discoveries demonstrate that chloroplasts are remarkably autonomous organelles that alter their stromule frequency in reaction to internal signal transduction pathways.

The cytosol must flow: intercellular transport through plasmodesmata.

Plant cells are connected across cell walls by nanoscopic channels called plasmodesmata (PD), which allow plant cells to share resources and exchange signaling molecules. Several protein components of PD membranes have been identified, and recent advances in superresolution live-cell microscopy are illuminating PD ultrastructure. Restricting transport through PD is crucial for morphogenesis, since hormones and hundreds of transcription factors regularly move through PD, and this transport must stop to allow cells to begin differentiating. Chloroplasts and mitochondria regulate PD function through signal transduction networks that coordinate plant physiology and development. Recent discoveries on the relationships of land plants and their algal relatives suggest that PD have evolved independently in several lineages, emphasizing the importance of cytosolic bridges in multicellular biology.

Evolution. Comment on "A promiscuous intermediate underlies the evolution of LEAFY DNA binding specificity".

Sayou et al. (Reports, 7 February 2014, p. 645) proposed a new model for evolution of transcription factors without gene duplication, using LEAFY as an archetype. Their proposal contradicts the evolutionary history of plants and ignores evidence that LEAFY evolves through gene duplications. Within their data set, we identified a moss with multiple LEAFY orthologs, which contests their model and supports that LEAFY evolves through duplications.

Investigating plasmodesmata genetics with virus-induced gene silencing and an agrobacterium-mediated GFP movement assay.

Plasmodesmata (PD) are channels that connect the cytoplasm of adjacent plant cells, permitting intercellular transport and communication. PD function and formation are essential to plant growth and development, but we still know very little about the genetic pathways regulating PD transport. Here, we present a method for assaying changes in the rate of PD transport following genetic manipulation. Gene expression in leaves is modified by virus-induced gene silencing. Seven to ten days after infection with Tobacco rattle virus carrying a silencing trigger, the gene(s) of interest is silenced in newly arising leaves. In these new leaves, individual cells are then transformed with Agrobacterium to express GFP, and the rate of GFP diffusion via PD is measured. By measuring GFP diffusion both within the epidermis and between the epidermis and mesophyll, the assay can be used to study the effects of silencing a gene(s) on PD transport in general, or transport through secondary PD specifically. Plant biologists working in several fields will find this assay useful, since PD transport impacts plant physiology, development, and defense.

Natural variation at sympathy for the ligule controls penetrance of the semidominant Liguleless narrow-R mutation in Zea mays.

Leaf architecture determines plant structural integrity, light harvesting, and economic considerations such as plant density. Ligules, junctions at the leaf sheath and blade in grasses, protect stalks from environmental stresses and, in conjunction with auricles, controls leaf angle. Previous studies in mutants have recessive liguleless mutants (lg1 and lg2) and dominant mutations in knotted1-like homeobox genes (Lg3-O, Lg4, and Kn1) involved in ligule development. Recently, a new semidominant liguleless mutant, Liguleless narrow (Lgn-R), has been characterized in maize that affects ligule and auricle development and results in a narrow leaf phenotype. We show that quantitative genetic variation affects penetrance of Lgn-R. To examine the genetic architecture underlying Lgn-R expressivity, crosses between Lgn-R/+ mutants in a B73 background and intermated B73 x Mo17 recombinant inbred lines were evaluated in multiple years and locations. A single main-effect quantitative trait locus (QTL) on chromosome 1 (sympathy for the ligule; sol) was discovered with a Mo17-contributed allele that suppressed Lgn-R mutant phenotypes. This QTL has a genetic-interaction with a locus on chromosome 7 (lucifer; lcf) for which the B73-contributed allele increases the ability of the sol(Mo17) allele to suppress Lgn-R. Neither of the genetic intervals likely to contain sol or lcf overlap with any current liguleless genes nor with previously identified genome-wide association QTL connected to leaf architecture. Analysis of phenotypes across environments further identified a genotype by enviroment interaction determining the strength of the sol x lcf interaction.

Plasmodesmata dynamics are coordinated by intracellular signaling pathways.

Membrane-lined channels called plasmodesmata (PD) connect the cytoplasts of adjacent plant cells across the cell wall, permitting intercellular movement of small molecules, proteins, and RNA. Recent genetic screens for mutants with altered PD transport identified genes suggesting that chloroplasts play crucial roles in coordinating PD transport. Complementing this discovery, studies manipulating expression of PD-localized proteins imply that changes in PD transport strongly impact chloroplast biology. Ongoing efforts to find genes that control root and stomatal development reveal the critical role of PD in enforcing tissue patterning, and newly discovered PD-localized proteins show that PD influence development, intracellular signaling, and defense against pathogens. Together, these studies demonstrate that PD function and formation are tightly integrated with plant physiology.

Evaluation of transcranial sonographic findings and MIBG cardiac scintigraphy in the diagnosis of idiopathic Parkinson's disease.

The diagnosis of idiopathic Parkinson's disease (IPD) is based on clinical criteria. In the last two decades several neuroimaging methods using transcranial sonography (TCS) or radiolabelled tracers such as the myocardial MIBG scintigraphy were applied to support diagnosis of IPD. They have been used independently of each other and their interrelation is not yet clear. In the present study we analyzed the relation between findings of TCS, MIBG scintigraphy, and clinical presentation in 42 patients with IPD who were clinically diagnosed and underwent clinical follow-up over ≥3 years in order to confirm IPD diagnosis throughout the clinical course. The extent of substantia nigra hyperechogenicity (SN+) contralateral to the clinically more affected body side (SN(contra)) was compared to myocardial (123)I-MIBG uptake. SN(contra) did not correlate with the myocardial MIBG uptake (r = -0.10; p = 0.52). Both myocardial MIBG uptake and TCS did not correlate significantly with Hoehn and Yahr stage (r = -0.03; p = 0.87 and r = -0.10; p = 0.54, respectively). Sensitivity of TCS in the diagnosis of IPD was 79%, of MIBG scintigraphy 81%. The combination of both measurements reached a sensitivity of 95%. TCS and MIBG scintigraphy may disclose complementary aspects of IPD. The combined use of both neuroimaging methods might improve the diagnostic sensitivity regarding IPD.

Long-term course of substantia nigra hyperechogenicity in Parkinson's disease.

A hyperechogenicity of the (SN+) in transcranial sonography corroborates the diagnosis of idiopathic Parkinson's disease (iPD). Although it is thought to represent a biomarker of the disease that is independent of disease severity and progression, differing results have been reported describing a positive correlation of the size and advancing clinical stage. In 50 parkinsonian patients, transcranial ultrasound and clinical examination was performed twice with a mean time interval of 6.4 years. SN+ did not change in size significantly between the first and second examination, whereas clinical parkinsonian symptoms--as determined by the motor part of the UPDRS--significantly worsened (P < 0.001). We found a highly significant intraindividual correlation in SN+ sizes between both examinations (P < 0.001). The size of SN+ did not correlate with the UPDRS part III at the time of first or second ultrasound examination. Progression of motor symptoms between the first and second investigation did not correlate with the size of SN+ at baseline. Furthermore, even in the subgroup of patients with an interval of ≥ 8 years between examinations, there was no significant change in SN+ size. SN+ represents a largely stable biomarker in iPD and does not reflect disease progression. The size of SN+ does not predict the further course of the disease.