Decreased demand for olfactory periglomerular cells impacts on neural precursor cell viability in the rostral migratory stream

Modelling acute myeloid leukemia (AML): What's new? A transition from the classical to the modern

Acute myeloid leukemia (AML) is a heterogeneous malignancy affecting myeloid cells in the bone marrow (BM) but can spread giving rise to impaired hematopoiesis. AML incidence increases with age and is associated with poor prognostic outcomes. There has been a disconnect between the success of novel drug compounds observed in preclinical studies of hematological malignancy and less than exceptional therapeutic responses in clinical trials. This review aims to provide a state-of-the-art overview on the different preclinical models of AML available to expand insights into disease pathology and as preclinical screening tools. Deciphering the complex physiological and pathological processes and developing predictive preclinical models are key to understanding disease progression and fundamental in the development and testing of new effective drug treatments. Standard scaffold-free suspension models fail to recapitulate the complex environment where AML occurs. To this end, we review advances in scaffold/matrix-based 3D models and outline the most recent advances in on-chip technology. We also provide an overview of clinically relevant animal models and review the expanding use of patient-derived samples, which offer the prospect to create more "patient specific" screening tools either in the guise of 3D matrix models, microphysiological "organ-on-chip" tools or xenograft models and discuss representative examples.

α-Synuclein Promotes Maturation of Immature Juxtaglomerular Neurons in the Mouse Olfactory Bulb

α-Synuclein (αSyn), the major constituent of Lewy bodies and Lewy neurites, is generally expressed in presynapses and is involved in synaptic function. However, we previously demonstrated that some neurons, including those in the olfactory bulb, show high αSyn expression levels in the cell body under normal conditions. αSyn is also known to be important for adult neurogenesis. Thus, in present study, we examined the role of αSyn in juxtaglomerular neurons (JGNs) with high αSyn expression in the mouse olfactory bulb. Most αSyn-enriched JGNs expressed sex-determining region Y-box 2 (Sox2), which functions to maintain neural immature identity. Interestingly, in αSyn homozygous (-/-) knockout (KO) mice, Sox2-positive JGNs were significantly increased compared with heterozygous (+/-) KO mice. Following global brain ischemia using wild-type mice, there was also a significant decrease in Sox2-positive JGNs, and in the co-expression ratio of Sox2 in αSyn-enriched JGNs. By contrast, the co-expression ratio of neuronal nuclei (NeuN, mature neuronal marker) was significantly increased in αSyn-enriched JGNs. However, this ischemia-induced decrease of Sox2-positive JGNs was not observed in αSyn homozygous KO mice. Overall, these data suggest that αSyn functions to promote the maturation of immature JGNs in the mouse olfactory bulb.

Neuronal precursor cells with dopaminergic commitment in the rostral migratory stream of the mouse

Neuroblasts born in the subventricular zone of adult mammals migrate via the rostral migratory stream into the granular cell layer or periglomerular layer of the olfactory bulb to differentiate into interneurons. To analyze if new neurons in the granular cell layer or periglomerular layer have different origins, we inserted a physical barrier into the rostral migratory stream, depleted cell proliferation with cytarabine infusions, labeled newborn cells with bromodeoxyuridine, and sacrificed mice after short-term (0, 2, or 14 days) or long-term (55 or 105 days) intervals. After short-term survival, the subventricular zone and rostral migratory stream rapidly repopulated with bromodeoxyuridine⁺ cells after cytarabine-induced depletion. Nestin, glial fibrillary acidic protein and the PAX6 were expressed in bromodeoxyuridine⁺ cells within the rostral migratory stream downstream of the physical barrier. After long-term survival after physical barrier implantation, bromodeoxyuridine⁺ neurons were significantly reduced in the granular cell layer, but bromodeoxyuridine⁺ and dopaminergic neurons in the periglomerular layer remained unaffected by the physical barrier. Thus, newborn neurons for the granular cell layer are mainly recruited from neural stem cells located in the subventricular zone, but new neurons for the periglomerular layer with dopaminergic predisposition can rise as well from neuronal stem or precursor cells in the rostral migratory stream.

The First Mating Experience Induces New Neurons in the Olfactory Bulb in Male Mice

In rodents, neurogenesis in the olfactory bulbs (OBs) is enhanced by exposure to olfactory enriched environments including sexually relevant odors. In the present study we evaluated whether sexual stimulation in male mice increases the number of newly generated cells that reach the OB and whether these cells differentiate into neurons. To this end, we used sexually naive male C57BL mice randomly assigned to one of three groups: (1) control, in which animals were left alone in their home cages; (2) exposure, in which animals were exposed to a receptive female precluding any physical contact; and (3) mating, in which males copulated with females. Males were given three injections of the DNA synthesis marker 5-bromo-2'-deoxyuridine (BrdU) 2 h before, at the end and 2 h after the test. Fifteen days after BrdU administration, brains were removed and processed to identify new cells and evaluate if they had differentiated into neurons in the granular (GR), mitral (MI) and glomerular (GL) cell layers of the main and accessory OB (MOB and AOB, respectively). We found an increase in the percentage of new cells that differentiate into neurons in the GL cell layer of the MOB of males from the mating group compared with those from the exposure and control groups. No differences were found in the number of new cells or percentage of new neurons in the rest of the analyzed regions. In male mice, the first sexual experience increases the percentage of new cells that differentiate into neurons in the GL cell layer of the MOB.

Adult Born Periglomerular Cells of Odorant Receptor Specific Glomeruli

The OR37 subsystem is characterized by a variety of unique features. The odorant receptors (ORs) of this subfamily are selectively tuned to specific ligands which are supposed to play a role in social communication. OR37 expressing sensory neurons project their axons to a single receptor specific glomerulus per bulb which have been shown to be unusually stable in size and to possess a distinct repertoire of periglomerular cells. Since the neuronal network surrounding glomeruli is typically modified by the integration of adult born neurons, in this study it was investigated whether the number of adult born cells might be different for OR37 glomeruli compared to other OR-specific glomeruli. Towards this goal, 23 days after BrdU injection, BrdU labeled cells in the proximity of OR37A glomeruli as well as around OR18-2 and OR256-17 glomeruli were determined. It was found that the number of BrdU labeled cells in the periglomerular region of OR37A glomeruli was significantly lower compared to glomeruli of the other OR types. This finding was in line with a lower number of neuroblasts visualized by the marker protein doublecortin. Double labeling experiments for BrdU and marker proteins revealed that despite a relatively high number of calretinin expressing cells at the OR37A glomeruli, the number of cells co-stained with BrdU was quite low compared to other glomeruli, which may point to an individual turnover rate of this cell type for different glomeruli. Together, the results of the present study support the notion that the neuronal network at the OR37 glomeruli is less dynamic than that of other glomerulus types. This indicates a specific processing of social information in OR37 glomerular networks.

Tracking the Cartoon mouse phenotype: Hemopexin domain-dependent regulation of MT1-MMP pericellular collagenolytic activity

Following ENU mutagenesis, a phenodeviant line was generated, termed the "Cartoon mouse," that exhibits profound defects in growth and development. Cartoon mice harbor a single S466P point mutation in the MT1-MMP hemopexin domain, a 200-amino acid segment that is thought to play a critical role in regulating MT1-MMP collagenolytic activity. Herein, we demonstrate that the MT1-MMP_S466P mutation replicates the phenotypic status of Mt1-mmp-null animals as well as the functional characteristics of MT1-MMP^-/- cells. However, rather than a loss-of-function mutation acquired as a consequence of defects in MT1-MMP proteolytic activity, the S466P substitution generates a misfolded, temperature-sensitive mutant that is abnormally retained in the endoplasmic reticulum (ER). By contrast, the WT hemopexin domain does not play a required role in regulating MT1-MMP trafficking, as a hemopexin domain-deletion mutant is successfully mobilized to the cell surface and displays nearly normal collagenolytic activity. Alternatively, when MT1-MMP_S466P-expressing cells are cultured at a permissive temperature of 25 °C that depresses misfolding, the mutant successfully traffics from the ER to the trans-Golgi network (ER → trans-Golgi network), where it undergoes processing to its mature form, mobilizes to the cell surface, and expresses type I collagenolytic activity. Together, these analyses define the Cartoon mouse as an unexpected gain-of-abnormal function mutation, wherein the temperature-sensitive mutant phenocopies MT1-MMP^-/- mice as a consequence of eliciting a specific ER → trans-Golgi network trafficking defect.

Olfactory memory is enhanced in mice exposed to extremely low-frequency electromagnetic fields via Wnt/β-catenin dependent modulation of subventricular zone neurogenesis

Exposure to extremely low-frequency electromagnetic fields (ELFEF) influences the expression of key target genes controlling adult neurogenesis and modulates hippocampus-dependent memory. Here, we assayed whether ELFEF stimulation affects olfactory memory by modulating neurogenesis in the subventricular zone (SVZ) of the lateral ventricle, and investigated the underlying molecular mechanisms. We found that 30 days after the completion of an ELFEF stimulation protocol (1 mT; 50 Hz; 3.5 h/day for 12 days), mice showed enhanced olfactory memory and increased SVZ neurogenesis. These effects were associated with upregulated expression of mRNAs encoding for key regulators of adult neurogenesis and were mainly dependent on the activation of the Wnt pathway. Indeed, ELFEF stimulation increased Wnt3 mRNA expression and nuclear localization of its downstream target β-catenin. Conversely, inhibition of Wnt3 by Dkk-1 prevented ELFEF-induced upregulation of neurogenic genes and abolished ELFEF’s effects on olfactory memory. Collectively, our findings suggest that ELFEF stimulation increases olfactory memory via enhanced Wnt/β-catenin signaling in the SVZ and point to ELFEF as a promising tool for enhancing SVZ neurogenesis and olfactory function.

Neurovascular EGFL7 regulates adult neurogenesis in the subventricular zone and thereby affects olfactory perception

Adult neural stem cells reside in a specialized niche in the subventricular zone (SVZ). Throughout life they give rise to adult-born neurons in the olfactory bulb (OB), thus contributing to neural plasticity and pattern discrimination. Here, we show that the neurovascular protein EGFL7 is secreted by endothelial cells and neural stem cells (NSCs) of the SVZ to shape the vascular stem-cell niche. Loss of EGFL7 causes an accumulation of activated NSCs, which display enhanced activity and re-entry into the cell cycle. EGFL7 pushes activated NSCs towards quiescence and neuronal progeny towards differentiation. This is achieved by promoting Dll4-induced Notch signalling at the blood vessel-stem cell interface. Fewer inhibitory neurons form in the OB of EGFL7-knockout mice, which increases the absolute signal conducted from the mitral cell layer of the OB but decreases neuronal network synchronicity. Consequently, EGFL7-knockout mice display severe physiological defects in olfactory behaviour and perception.

The vascular stem cell niche regulates the proliferation and differentiation of neural stem cells (NSCs) in the adult subventricular zone. Here the authors identify EGFL7 as a neurovascular regulator of NSCs in vivo; EGFL7-knockout mice show reduced neurogenesis, and exhibit impaired olfactory perception and behaviour.

Poly-protein G-expressing bacteria enhance the sensitivity of immunoassays

The sensitivities of solid-phase immunoassays are limited by the quantity of detection antibodies bound to their antigens on the solid phase. Here, we developed a poly-protein G-expressing bacterium as an antibody-trapping microparticle to enhance the signals of immunoassays by increasing the accumulation of detection antibodies on the given antigen. Eight tandemly repeated fragment crystallisable (Fc) binding domains of protein G were stably expressed on the surface of Escherichia coli BL21 cells (termed BL21/8G). BL21/8G cells showed a higher avidity for trapping antibodies on their surface than monomeric protein G-expressing BL21 (BL21/1G) cells did. In the sandwich enzyme-linked immunosorbent assay (ELISA), simply mixing the detection antibody with BL21/8G provided a detection limit of 6 pg/mL for human interferon-α (IFN-α) and a limit of 30 pg/mL for polyethylene glycol (PEG)-conjugated IFN-α (Pegasys), which are better than that of the traditional ELISA (30 pg/mL for IFN-α and 100 pg/mL for Pegasys). Moreover, the sensitivity of the Western blot for low-abundance Pegasys (0.4 ng/well) was increased by 25 folds upon mixing of an anti-PEG antibody with BL21/8G cells. By simply being mixed with a detection antibody, the poly-protein G-expressing bacteria can provide a new method to sensitively detect low-abundance target molecules in solid-phase immunoassays.