Cell-free DNA release under psychosocial and physical stress conditions.

The understanding of mechanisms linking psychological stress to disease risk depend on reliable stress biomarkers. Circulating cell-free DNA (cfDNA) has emerged as a potential biomarker of cellular stress, aging, inflammatory processes, and cell death. Recent studies indicated that psychosocial stress and physical exercise might also influence its release. We compared the effects of acute psychosocial and physical exercise stress on cfDNA release by exposing 20 young, healthy men to both an acute psychosocial laboratory stressor and an acute physical exercise stressor. Venous blood and saliva samples were collected before and after stress exposure. Cell-free DNA was extracted from plasma and quantified by qPCR. Furthermore, cfDNA fragment length was analyzed and cfDNA methylation patterns were assayed across time. In addition, release of stress hormones and subjective stress responses were measured. Results showed a twofold increase of cfDNA after TSST and fivefold increase after exhaustive treadmill exercise, with an overabundance of shorter cfDNA fragments after physical exhaustion. Interestingly, cell-free mitochondrial DNA showed similar increase after both stress paradigms. Furthermore, cfDNA methylation signatures-used here as a marker for diverse cellular origin-were significantly different post stress tests. While DNA methylation decreased immediately after psychosocial stress, it increased after physical stress, suggesting different cellular sources of active DNA release. In summary, our results suggest stimulus and cell-specific regulation of cfDNA release. Whereas the functional role of stress-associated cfDNA release remains elusive, it might serve as a valuable biomarker in molecular stress research as a part of the psychophysiological stress response.

Soluble monomers, dimers and HLA-G-expressing extracellular vesicles: the three dimensions of structural complexity to use HLA-G as a clinical biomarker.

The HLA-G molecule belongs to the family of nonclassical human leukocyte antigen (HLA) class I. At variance to classical HLA class I, HLA-G displays (i) a low number of nucleotide variations within the coding region, (ii) a high structural diversity, (iii) a restricted peptide repertoire, (iv) a limited tissue distribution and (v) strong immune-suppressive properties. The physiological HLA-G surface expression is restricted to the maternal-fetal interface and to immune-privileged adult tissues. Soluble forms of HLA-G (sHLA-G) are detectable in various body fluids. Cellular activation and pathological processes are associated with an aberrant or a neo-expression of HLA-G/sHLA-G. Functionally, HLA-G and its secreted forms are considered to be key players in the induction of short- and long-term tolerance. Thus, its unique expression profile and tolerance-inducing functions render HLA-G/sHLA-G an attractive biomarker to monitor the systemic health/disease status and disease activity/progression for clinical approaches in disease management and treatments. Here, we place emphasis on (i) the current status of the tolerance-inducing functions by HLA-G/sHLA-G, (ii) the current complexity to implement this molecule as a meaningful clinical biomarker regarding the three dimensions of structural diversity (monomers, dimers and HLA-G-expressing extracellular vesicles) with its functional implications, and (iii) novel and future approaches to detect and quantify sHLA-G structures and functions.

GFI1 as a novel prognostic and therapeutic factor for AML/MDS.

Genetic and epigenetic aberrations contribute to the initiation and progression of acute myeloid leukemia (AML). GFI1, a zinc-finger transcriptional repressor, exerts its function by recruiting histone deacetylases to target genes. We present data that low expression of GFI1 is associated with an inferior prognosis of AML patients. To elucidate the mechanism behind this, we generated a humanized mouse strain with reduced GFI1 expression (GFI1-KD). Here we show that AML development induced by onco-fusion proteins such as MLL-AF9 or NUP98-HOXD13 is accelerated in mice with low human GFI1 expression. Leukemic cells from animals that express low levels of GFI1 show increased H3K9 acetylation compared to leukemic cells from mice with normal human GFI1 expression, resulting in the upregulation of genes involved in leukemogenesis. We investigated a new epigenetic therapy approach for this subgroup of AML patients. We could show that AML blasts from GFI1-KD mice and from AML patients with low GFI1 levels were more sensitive to treatment with histone acetyltransferase inhibitors than cells with normal GFI1 expression levels. We suggest therefore that GFI1 has a dose-dependent role in AML progression and development. GFI1 levels are involved in epigenetic regulation, which could open new therapeutic approaches for AML patients.

Regenerative therapies in neonatology: clinical perspectives.

Regenerative therapy based on stem cells is applied as standard therapy in pediatric oncology. Furthermore, they are frequently used to treat immunodeficiency disorders of infants. For severe neonatal diseases, e. g. hypoxic-ischemic encephalopathy in term neonates or bronchopulmonary dysplasia in preterm infants, animal models have been established. According to some first preclinical results stem cell administration appears as a promising tool to improve the clinical outcome in high-risk infants. Provided the benefit of regenerative therapies can further be evaluated in appropriate preclinical neonate models, carefully controlled clinical trials to assess the significance of regenerative therapies, such as autologous stem cell administration, are indicated.

The notch signaling pathway is required to specify muscle progenitor cells in Drosophila.

Organization and function of the Notch signaling pathway in Drosophila are best understood with respect to its role in the process of selection of neural progenitor cells. However, there is evidence that, besides neurogenesis, the Notch signaling pathway is involved in several other developmental processes, one of which is the selection of muscle progenitor cells. Thus, the number of these cells is increased in neurogenic mutants, and it has been proposed that muscle progenitor cells are selected from clusters of equivalent cells expressing genes of the achaete-scute gene complex (AS-C). Here, I present evidence for the participation of additional elements of the Notch signaling pathway in myogenesis. Gal4 mediated expression of a Notch variant, E(spl) and Hairless shows that the selection of muscle progenitor cells obeys principles apparently identical to those acting at the selection of neural progenitor cells.

Functional dissection of the Drosophila enhancer of split protein, a suppressor of neurogenesis.

The Enhancer of split [E(spl)] gene complex of Drosophila comprises seven related genes encoding a special type of basic helix-loop-helix proteins, the function of which is to suppress the neural developmental fate. One of these proteins is E(spl) itself. To gain insight into the structural requirements for E(spl) function, we have expressed a large number of deletion variants in transgenic flies. Three protein domains were identified as essential for suppression of bristle development: the carboxyl-terminal tetrapeptide WRPW, the region comprising the putative helix III and helix IV, and the region between helix IV and the WRPW motif. Lack of the basic helix-loop-helix domain, helix III or IV, only partially inhibits the suppressor activity of the protein. Truncated variants that lack all the regions carboxyl-terminal to helix IV elicit the development of additional neural progenitors, and thus act as dominant-negative variants. All these results suggest that E(spl) suppresses neural development by direct interaction with other proteins, such as groucho and the proneural proteins.

Lethal of scute requires overexpression of daughterless to elicit ectopic neuronal development during embryogenesis in Drosophila.

Classical genetics indicates that the achaete-scute gene complex (AS-C) of Drosophila promotes development of neural progenitor cells. To further analyze the function of proneural genes, we have studied the effects of Gal4-mediated expression of lethal of scute, a member of the AS-C, during embryogenesis. Expression of lethal of scute forces progenitor cells of larval internal sensory organs, which are normally committed to this fate independently of the activity of the AS-C, to take on features of external sensory organs. Supernumerary neural cells can be induced ectopically only if daughterless is overexpressed, either alone or together with lethal of scute: cells of the amnioserosa and the hindgut then express neuronal markers. Furthermore, cells of the proctodeal anlage, which normally lack neural competence, acquire the ability to develop as neuroblasts following transplantation into the neuroectoderm. We show here that activated Notch prevents the cells of the neuroectoderm from forming extra neural tissue when they express an excess of proneural proteins. Under the present conditions, lateral inhibition is thus dominant over the activity of proneural genes.

The basic-helix-loop-helix domain of Drosophila lethal of scute protein is sufficient for proneural function and activates neurogenic genes.

The development of most epidermal sensory organs in Drosophila is controlled by achaete and scute, two of the genes of the achaete-scute complex (AS-C). The genes of the AS-C encode members of the basic-helix-loop-helix (bHLH) class of transcriptional regulators, and their activity defines proneural cell clusters in the imaginal discs from which sensory organ mother cells are singled out by a process of lateral inhibition. Ectopic expression of lethal of scute, another member of the AS-C, normally dispensable for sensory organ development in the adult, promotes this process independently of the activity of the other AS-C genes. This demonstrates a high degree of functional redundancy of the products of the AS-C. Furthermore, neurogenic genes are activated in ectopic proneural clusters, allowing development of epidermal progenitor cells. Finally, the bHLH domain is necessary and sufficient to mediate the proneural function, to activate neurogenic genes, and to allow lateral inhibition.