Endometrial expression of antimicrobial peptides as markers of subclinical endometritis in mares

BACKGROUND

Endometritis is a major cause of subfertility in mares. Multiparous old mares are more susceptible to developing endometritis given that ageing is associated with an altered immune response and with inadequate physiological uterine clearance after breeding, which can lead to degenerative changes in the endometrium. Molecules such as antimicrobial peptides (AMPs) have been proposed as endometritis markers in the equine species.

STUDY DESIGN

Cross-sectional.

OBJECTIVES

To investigate the endometrial expression of defensin-beta 4B (DEFB4B), lysozyme (LYZ) and secretory leukocyte peptidase inhibitor (SLPI) genes in mares either affected or not by subclinical endometritis, due to the role of these AMPs in the immune response to bacteria and inflammatory reactions.

METHODS

Endometrial biopsy for histopathological and gene expression examinations was performed on 26 mares. The inclusion criteria for the normal mare group (NM, N = 7) were 2-4 years of age, maiden status, no clinical signs of endometritis and a uterine biopsy score of I, while for mares affected by subclinical endometritis (EM, N = 19) the inclusion criteria were 10-22 years of age, barren status for 1-3 years, no clinical signs of endometritis and a uterine biopsy score between IIA and III.

RESULTS

A significantly higher expression of LYZ (NM: 0.76 [1.84-0.37] vs. EM: 2.78 [5.53-1.44], p = 0.0255) and DEFB4B (NM: 0.06 [0.11-0.01] vs. EM: 0.15 [0.99-0.08], p = 0.0457) genes was found in endometritis mares versus normal mares. Statistically significant moderate positive correlations were found between the level of expression of LYZ gene and both the age (r = 0.4071, p = 0.039) and the biopsy grade (r = 0.4831, p = 0.0124) of the mares.

MAIN LIMITATIONS

The study investigated a limited number of genes and mares, and the presence/location of the proteins coded by these genes was not confirmed within the endometrium by IHC.

CONCLUSIONS

If the results of this study are confirmed, LYZ and DEFB4B genes can be used as markers to identify mares that are affected by subclinical endometritis.

Converging Role for REEP1/SPG31 in Oxidative Stress

Mutations in the receptor expression-enhancing protein 1 gene (REEP1) are associated with hereditary spastic paraplegia type 31 (SPG31), a neurological disorder characterized by length-dependent degeneration of upper motor neuron axons. Mitochondrial dysfunctions have been observed in patients harboring pathogenic variants in REEP1, suggesting a key role of bioenergetics in disease-related manifestations. Nevertheless, the regulation of mitochondrial function in SPG31 remains unclear. To elucidate the pathophysiology underlying REEP1 deficiency, we analyzed in vitro the impact of two different mutations on mitochondrial metabolism. Together with mitochondrial morphology abnormalities, loss-of-REEP1 expression highlighted a reduced ATP production with increased susceptibility to oxidative stress. Furthermore, to translate these findings from in vitro to preclinical models, we knocked down REEP1 in zebrafish. Zebrafish larvae showed a significant defect in motor axon outgrowth leading to motor impairment, mitochondrial dysfunction, and reactive oxygen species accumulation. Protective antioxidant agents such as resveratrol rescued free radical overproduction and ameliorated the SPG31 phenotype both in vitro and in vivo. Together, our findings offer new opportunities to counteract neurodegeneration in SPG31.

Zebrafish Avatar to Develop Precision Breast Cancer Therapies

BACKGROUND

Zebrafish (Danio rerio) is a vertebrate that has become a popular alternative model for the cellular and molecular study of human tumors and for drug testing and validating approaches. Notably, zebrafish embryos, thanks to their accessibility, allow rapid collection of in vivo results prodromal to validation in the murine models in respect to the 3R principles. The generation of tumor xenograft in zebrafish embryos and larvae, or zebrafish avatar, represents a unique opportunity to study tumor growth, angiogenesis, cell invasion and metastatic dissemination, interaction between tumor and host in vivo avoiding immunogenic rejection, representing a promising platform for the translational research and personalized therapies.

OBJECTIVE

In this mini-review we report recent advances in breast cancer research and drug testing that took advantage of the zebrafish xenograft model using both breast cancer cell lines and patient's biopsy.

CONCLUSION

Patient derived xenograft, together with the gene editing, the omics biotechnology, the in vivo time lapse imaging and the high-throughput screening that are already set up and largely used in zebrafish, could represent a step forward towards precision and personalized medicine in the breast cancer research field.

Three-dimensional model of glioblastoma by co-culturing tumor stem cells with human brain organoids

Emerging three-dimensional (3D) cultures of glioblastoma are becoming powerful models to study glioblastoma stem cell behavior and the impact of cell-cell and cell-microenvironment interactions on tumor growth and invasion. Here we describe a method for culturing human glioblastoma stem cells (GSCs) in 3D by co-culturing them with pluripotent stem cell-derived brain organoids. This requires multiple coordinated steps, including the generation of cerebral organoids, and the growth and fluorescence tagging of GSCs. We highlight how to recognize optimal organoid generation and how to efficiently mark GSCs, before describing optimized co-culture conditions. We show that GSCs can efficiently integrate into brain organoids and maintain a significant degree of cell fate heterogeneity, paving the way for the analysis of GSC fate behavior and lineage progression. These results establish the 3D culture system as a viable and versatile GBM model for investigating tumor cell biology and GSC heterogeneity.This article has an associated First Person interview with the first author of the paper.

Alexander Disease Modeling in Zebrafish: An In Vivo System Suitable to Perform Drug Screening

Alexander disease (AxD) is a rare astrogliopathy caused by heterozygous mutations, either inherited or arising de novo, on the glial fibrillary acid protein (GFAP) gene (17q21). Mutations in the GFAP gene make the protein prone to forming aggregates which, together with heat-shock protein 27 (HSP27), αB-crystallin, ubiquitin, and proteasome, contribute to form Rosenthal fibers causing a toxic effect on the cell. Unfortunately, no pharmacological treatment is available yet, except for symptom reduction therapies, and patients undergo a progressive worsening of the disease. The aim of this study was the production of a zebrafish model for AxD, to have a system suitable for drug screening more complex than cell cultures. To this aim, embryos expressing the human GFAP gene carrying the most severe p.R239C under the control of the zebrafish gfap gene promoter underwent functional validation to assess several features already observed in in vitro and other in vivo models of AxD, such as the localization of mutant GFAP inclusions, the ultrastructural analysis of cells expressing mutant GFAP, the effects of treatments with ceftriaxone, and the heat shock response. Our results confirm that zebrafish is a suitable model both to study the molecular pathogenesis of GFAP mutations and to perform pharmacological screenings, likely useful for the search of therapies for AxD.

The Stemness Gene Mex3A Is a Key Regulator of Neuroblast Proliferation During Neurogenesis

Mex3A is an RNA binding protein that can also act as an E3 ubiquitin ligase to control gene expression at the post-transcriptional level. In intestinal adult stem cells, MEX3A is required for cell self-renewal and when overexpressed, MEX3A can contribute to support the proliferation of different cancer cell types. In a completely different context, we found mex3A among the genes expressed in neurogenic niches of the embryonic and adult fish brain and, notably, its expression was downregulated during brain aging. The role of mex3A during embryonic and adult neurogenesis in tetrapods is still unknown. Here, we showed that mex3A is expressed in the proliferative region of the developing brain in both Xenopus and mouse embryos. Using gain and loss of gene function approaches, we showed that, in Xenopus embryos, mex3A is required for neuroblast proliferation and its depletion reduced the neuroblast pool, leading to microcephaly. The tissue-specific overexpression of mex3A in the developing neural plate enhanced the expression of sox2 and msi-1 keeping neuroblasts into a proliferative state. It is now clear that the stemness property of mex3A, already demonstrated in adult intestinal stem cells and cancer cells, is a key feature of mex3a also in developing brain, opening new lines of investigation to better understand its role during brain aging and brain cancer development.

LIN28B increases neural crest cell migration and leads to transformation of trunk sympathoadrenal precursors

The RNA-binding protein LIN28B regulates developmental timing and determines stem cell identity by suppressing the let-7 family of microRNAs. Postembryonic reactivation of LIN28B impairs cell commitment to differentiation, prompting their transformation. In this study, we assessed the extent to which ectopic lin28b expression modulates the physiological behavior of neural crest cells (NCC) and governs their transformation in the trunk region of developing embryos. We provide evidence that the overexpression of lin28b inhibits sympathoadrenal cell differentiation and accelerates NCC migration in two vertebrate models, Xenopus leavis and Danio rerio. Our results highlight the relevance of ITGA5 and ITGA6 in the LIN28B-dependent regulation of the invasive motility of tumor cells. The results also establish that LIN28B overexpression supports neuroblastoma onset and the metastatic potential of malignant cells through let-7a-dependent and let-7a-independent mechanisms.

PDGF-B: The missing piece in the mosaic of PDGF family role in craniofacial development

BACKGROUND

The platelet-derived growth factor (PDGF) family consists of four ligands (PDGF-A, PDGF-B, PDGF-C, PDGF-D) and two tyrosine kinase receptors (PDGFR-α and PDGFR-β). In vertebrates, PDGF signaling influences cell proliferation, migration, and matrix deposition, and its up-regulation is implicated in cancer progression. Despite this evidence, the role of each family member during embryogenesis is still incomplete and partially controversial. In particular, study of the role of pdgf signaling during craniofacial development has been focused on pdgf-a, while the role of pdgf-b is almost unknown due to the lethal phenotypes of pdgf-b-null mice.

RESULTS

By using a pdgf-b splice-blocking morpholino approach, we highlighted impairment of neural crest cell (NCC) migration in Xenopus laevis morphants, leading to alteration of NCC derivatives formation, such as cranial nerves and cartilages. We also uncovered a possible link between pdgf-b and the expression of cadherin superfamily members cdh6 and cdh11, which mediate cell-cell adhesion promoting NCC migration.

CONCLUSIONS

Our results suggested that pdgf-b signaling is involved in cranial NCC migration and it is required for proper formation of craniofacial NCC derivatives. Taken together, these data unveiled a new role for pdgf-b during vertebrate development, contributing to complete the picture of pdgf signaling role in craniofacial development.

The age-regulated zinc finger factor ZNF367 is a new modulator of neuroblast proliferation during embryonic neurogenesis

Global population aging is one of the major social and economic challenges of contemporary society. During aging the progressive decline in physiological functions has serious consequences for all organs including brain. The age-related incidence of neurodegenerative diseases coincides with the sharp decline of the amount and functionality of adult neural stem cells. Recently, we identified a short list of brain age-regulated genes by means of next-generation sequencing. Among them znf367 codes for a transcription factor that represents a central node in gene co-regulation networks during aging, but whose function in the central nervous system (CNS), is completely unknown. As proof of concept, we analysed the role of znf367 during Xenopus laevis neurogenesis. By means of a gene loss of function approach limited to the CNS, we suggested that znf367 might act as a key controller of the neuroblast cell cycle, particularly in the progression of mitosis and spindle checkpoint. A candidate gene approach based on a weighted-gene co-expression network analysis, revealed fancd2 and ska3 as possible targets of znf367. The age-related decline of znf367 correlated well with its role during embryonic neurogenesis, opening new lines of investigation also in adult neurogenesis to improved maintenance and even repair of neuronal function.

Neurotrophin-conjugated nanoparticles prevent retina damage induced by oxidative stress

Glaucoma and other optic neuropathies are characterized by a loss of retinal ganglion cells (RGCs), a cell layer located in the posterior eye segment. Several preclinical studies demonstrate that neurotrophins (NTs) prevent RGC loss. However, NTs are rarely investigated in the clinic due to various issues, such as difficulties in reaching the retina, the very short half-life of NTs, and the need for multiple injections. We demonstrate that NTs can be conjugated to magnetic nanoparticles (MNPs), which act as smart drug carriers. This combines the advantages of the self-localization of the drug in the retina and drug protection from fast degradation. We tested the nerve growth factor and brain-derived neurotrophic factor by comparing the neuroprotection of free versus conjugated proteins in a model of RGC loss induced by oxidative stress. Histological data demonstrated that the conjugated proteins totally prevented RGC loss, in sharp contrast to the equivalent dose of free proteins, which had no effect. The overall data suggest that the nanoscale MNP-protein hybrid is an excellent tool in implementing ocular drug delivery strategies for neuroprotection and therapy.

Platelet derived growth factor B gene expression in the Xenopus laevis developing central nervous system

Platelet-derived growth factor B (PDGF-B) belongs to the mitogen and growth factor family and like the other members it has many roles in cell differentiation, proliferation and migration during development, adult life and in pathological conditions. Among them it has been observed that aberrant PDGF signalling is frequently linked to glioma development and progression, and Pdgf-b over-expression in mouse neural progenitors leads to the formation of gliomas. Despite this evidence, the mechanisms underlying PDGF-B driven tumorigenesis and its role during brain development are not fully understood. In order to contribute to clarifying possible new roles of pdgf-b signalling, we present here the embryonic gene expression pattern of pdgf-b, so far unknown in early vertebrate development. By using Xenopus laevis as a model system we performed qRT-PCR and whole mount in situ hybridization. Pdgf-b mRNA is expressed in discrete regions of the developing central nervous system, in the cranial nerve placodes and in the notochord. We also compared the gene expression of pdgf-b with that of its receptor pdgfr-α suggesting so far unsuspected roles for this signalling pathway during the development of specific embryonic structures.

The zebrafish as a model for studying neuroblastoma

Neuroblastoma is a tumor arising in the peripheral sympathetic nervous system and is the most common cancer in childhood. Since most of the cellular and molecular mechanisms underlying neuroblastoma onset and progression remain unknown, the generation of new in vivo models might be appropriate to better dissect the peripheral sympathetic nervous system development in both physiological and disease states. This review is focused on the use of zebrafish as a suitable and innovative model to study neuroblastoma development. Here, we briefly summarize the current knowledge about zebrafish peripheral sympathetic nervous system formation, focusing on key genes and cellular pathways that play a crucial role in the differentiation of sympathetic neurons during embryonic development. In addition, we include examples of how genetic changes known to be associated with aggressive neuroblastoma can mimic this malignancy in zebrafish. Thus, we note the value of the zebrafish model in the field of neuroblastoma research, showing how it can improve our current knowledge about genes and biological pathways that contribute to malignant transformation and progression during embryonic life.

RNA-seq of the aging brain in the short-lived fish N. furzeri - conserved pathways and novel genes associated with neurogenesis

The brains of teleost fish show extensive adult neurogenesis and neuronal regeneration. The patterns of gene regulation during fish brain aging are unknown. The short-lived teleost fish Nothobranchius furzeri shows markers of brain aging including reduced learning performances, gliosis, and reduced adult neurogenesis. We used RNA-seq to quantify genome-wide transcript regulation and sampled five different time points to characterize whole-genome transcript regulation during brain aging of N. furzeri. Comparison with human datasets revealed conserved up-regulation of ribosome, lysosome, and complement activation and conserved down-regulation of synapse, mitochondrion, proteasome, and spliceosome. Down-regulated genes differ in their temporal profiles: neurogenesis and extracellular matrix genes showed rapid decay, synaptic and axonal genes a progressive decay. A substantial proportion of differentially expressed genes (∼40%) showed inversion of their temporal profiles in the last time point: spliceosome and proteasome showed initial down-regulation and stress-response genes initial up-regulation. Extensive regulation was detected for chromatin remodelers of the DNMT and CBX families as well as members of the polycomb complex and was mirrored by an up-regulation of the H3K27me3 epigenetic mark. Network analysis showed extensive coregulation of cell cycle/DNA synthesis genes with the uncharacterized zinc-finger protein ZNF367 as central hub. In situ hybridization showed that ZNF367 is expressed in neuronal stem cell niches of both embryonic zebrafish and adult N. furzeri. Other genes down-regulated with age, not previously associated with adult neurogenesis and with similar patterns of expression are AGR2, DNMT3A, KRCP, MEX3A, SCML4, and CBX1. CBX7, on the other hand, was up-regulated with age.

Unraveling new roles for serotonin receptor 2B in development: key findings from Xenopus

The serotonin receptor 5-HT2B has been shown to be critically important during embryogenesis as the knockout of this gene in mice causes heart defects and embryonic lethality that impairs further analyses on other embryonic cell and tissue types. In the present review, we highlight how the use of Xenopus laevis, an alternative vertebrate model suitable for gene loss and gain of function analyses, has contributed to our understanding of the role of 5-HT2B signaling during development. In vivo studies showed that 5-HT2B signaling is not only required for heart development, but that it also has a crucial role in ocular and craniofacial morphogenesis, being involved in shaping the first branchial arch and the jaw joint, in retinogenesis and possibly in periocular mesenchyme development. These findings may be relevant for our understanding of congenital defects including human birth malformations. In addition, 5-HT2B appears to be required for the therapeutic actions of selective serotonin reuptake inhibitors commonly prescribed as antidepressant drugs to pregnant and lactating women. We discuss how the understanding of the molecular basis of serotonin signaling in a suitable animal embryogenesis model may open new lines of investigations and therapies in humans.

Hyaluronan is required for cranial neural crest cells migration and craniofacial development

BACKGROUND

Hyaluronan is a crucial glycosaminoglycan of the vertebrate embryonic extracellular matrix able to influence cell behaviour, both by assembling the pericellular matrices and by activating signal transducing receptors such as CD44.

RESULTS

We showed that the hyaluronan synthases, Has1 and Has2, and CD44 display a dynamic expression pattern during cranial neural crest cells (NCC) development. By knocking down Has1 and Has2 gene functions, we revealed that hyaluronan synthesized by Has1 and Has2 is necessary for the proper development of the visceral skeleton.

CONCLUSIONS

The data suggest that hyaluronan helps to maintain the active migratory behaviour of cranial NCC, and that its presence around pre-chondrogenic NCC is crucial for their survival. CD44 knock down also suggests that the role of hyaluronan in cranial NCC migration could be mediated, at least in part, by the activation of CD44. These findings contribute to the unveiling of the functional relation between NCC and their extracellular environment during craniofacial development.

Hox and Pbx factors control retinoic acid synthesis during hindbrain segmentation

In vertebrate embryos, retinoic acid (RA) synthesized in the mesoderm by Raldh2 emanates to the hindbrain neuroepithelium, where it induces anteroposterior (AP)-restricted Hox expression patterns and rhombomere segmentation. However, how appropriate spatiotemporal RA activity is generated in the hindbrain is poorly understood. By analyzing Pbx1/Pbx2 and Hoxa1/Pbx1 null mice, we found that Raldh2 is itself under the transcriptional control of these factors and that the resulting RA-deficient phenotypes can be partially rescued by exogenous RA. Hoxa1-Pbx1/2-Meis2 directly binds a specific regulatory element that is required to maintain normal Raldh2 expression levels in vivo. Mesoderm-specific Xhoxa1 and Xpbx1b knockdowns in Xenopus embryos also result in Xraldh2 downregulation and hindbrain defects similar to mouse mutants, demonstrating conservation of this Hox-Pbx-dependent regulatory pathway. These findings reveal a feed-forward mechanism linking Hox-Pbx-dependent RA synthesis during early axial patterning with the establishment of spatially restricted Hox-Pbx activity in the developing hindbrain.

Serotonin 2B receptor signaling is required for craniofacial morphogenesis and jaw joint formation in Xenopus

Serotonin (5-HT) is a neuromodulator that plays many different roles in adult and embryonic life. Among the 5-HT receptors, 5-HT2B is one of the key mediators of 5-HT functions during development. We used Xenopus laevis as a model system to further investigate the role of 5-HT2B in embryogenesis, focusing on craniofacial development. By means of gene gain- and loss-of-function approaches and tissue transplantation assays, we demonstrated that 5-HT2B modulates, in a cell-autonomous manner, postmigratory skeletogenic cranial neural crest cell (NCC) behavior without altering early steps of cranial NCC development and migration. 5-HT2B overexpression induced the formation of an ectopic visceral skeletal element and altered the dorsoventral patterning of the branchial arches. Loss-of-function experiments revealed that 5-HT2B signaling is necessary for jaw joint formation and for shaping the mandibular arch skeletal elements. In particular, 5-HT2B signaling is required to define and sustain the Xbap expression necessary for jaw joint formation. To shed light on the molecular identity of the transduction pathway acting downstream of 5-HT2B, we analyzed the function of phospholipase C beta 3 (PLC) in Xenopus development and showed that PLC is the effector of 5-HT2B during craniofacial development. Our results unveiled an unsuspected role of 5-HT2B in craniofacial development and contribute to our understanding of the interactive network of patterning signals that is involved in the development and evolution of the vertebrate mandibular arch.

Identification and gene expression of versican during early development of Xenopus

The chondroitin sulfate proteoglycan (PG) PG-M/versican is known to be a primary component of the vertebrate embryonic extracellular matrix and, in the mouse, functional abrogation of the versican gene leads to severe cardiovascular malformations and embryonic lethality. In order to provide a means for approaching the study of the role of versican during embryogenesis, we have cloned the Xenopus versican cDNA and we have performed in situ hybridization on embryos at different stages of development. We showed maternal Xversican transcription, as well as a previously undocumented early expression of the PG during gastrulation and neurulation. At later stages of development, spatial transcription of Xversican correlates with the patterns of migrating neural crest cells (NCC) and it is expressed in embryonic regions representing the final sites of arrest of NCC. Xversican mRNA was also detected in a subpopulation of trunk NCC migrating into the fin, in tissues flanking the trunk NCC ventral migratory pathway and in post-migratory cranial skeletogenic NCC. Further embryonic sites expressing Xversican were the pronephros, pronephric ducts, heart anlage and branchial pouches. These findings constitute the basis for future studies aimed at clarifying unresolved aspects of versican function during embryogenesis.

Hoxa2 knockdown in Xenopus results in hyoid to mandibular homeosis

The skeletal structures of the face and throat are derived from cranial neural crest cells (NCCs) that migrate from the embryonic neural tube into a series of branchial arches (BAs). The first arch (BA1) gives rise to the upper and lower jaw cartilages, whereas hyoid structures are generated from the second arch (BA2). The Hox paralogue group 2 (PG2) genes, Hoxa2 and Hoxb2, show distinct roles for hyoid patterning in tetrapods and fishes. In the mouse, Hoxa2 acts as a selector of hyoid identity, while its paralogue Hoxb2 is not required. On the contrary, in zebrafish Hoxa2 and Hoxb2 are functionally redundant for hyoid arch patterning. Here, we show that in Xenopus embryos morpholino-induced functional knockdown of Hoxa2 is sufficient to induce homeotic changes of the second arch cartilage. Moreover, Hoxb2 is downregulated in the BA2 of Xenopus embryos, even though initially expressed in second arch NCCs, similar to mouse and unlike in zebrafish. Finally, Xbap, a gene involved in jaw joint formation, is selectively upregulated in the BA2 of Hoxa2 knocked-down frog embryos, supporting a hyoid to mandibular change of NCC identity. Thus, in Xenopus Hoxa2 does not act redundantly with Hoxb2 for BA2 patterning, similar to mouse and unlike in fish. These data bring novel insights into the regulation of Hox PG2 genes and hyoid patterning in vertebrate evolution and suggest that Hoxa2 function is required at late stages of BA2 development.

XHas2 activity is required during somitogenesis and precursor cell migration in Xenopus development

In vertebrates, hyaluronan biosynthesis is regulated by three transmembrane catalytic enzymes denoted Has1, Has2 and Has3. We have previously cloned the Xenopus orthologues of the corresponding genes and defined their spatiotemporal distribution during development. During mammalian embryogenesis, Has2 activity is known to be crucial, as its abrogation in mice leads to early embryonic lethality. Here, we show that, in Xenopus,morpholino-mediated loss-of-function of XHas2 alters somitogenesis by causing a disruption of the metameric somitic pattern and leads to a defective myogenesis. In the absence of XHas2, early myoblasts underwent apoptosis, failing to complete their muscle differentiation programme. XHas2 activity is also required for migration of hypaxial muscle cells and trunk neural crest cells (NCC). To approach the mechanism whereby loss of HA,following XHas2 knockdown, could influence somitogenesis and precursor cell migration, we cloned the orthologue of the primary HA signalling receptor CD44 and addressed its function through an analogous knockdown approach. Loss of XCD44 did not disturb somitogenesis, but strongly impaired hypaxial muscle precursor cell migration and the subsequent formation of the ventral body wall musculature. In contrast to XHas2,loss of function of XCD44 did not seem to be essential for trunk NCC migration, suggesting that the HA dependence of NCC movement was rather associated with an altered macromolecular composition of the ECM structuring the cells' migratory pathways. The presented results, extend our knowledge on Has2 function and, for the first time, demonstrate a developmental role for CD44 in vertebrates. On the whole, these data underlie and confirm the emerging importance of cell-ECM interactions and modulation during embryonic development.

Molecular cloning and characterization of UDP-glucose dehydrogenase from the amphibian Xenopus laevis and its involvement in hyaluronan synthesis

UDP-glucose dehydrogenase (UGDH) supplies the cell with UDP-glucuronic acid (UDP-GlcUA), a precursor of glycosaminoglycan and proteoglycan synthesis. Here we reported the cloning and the characterization of the UGDH from the amphibian Xenopus laevis that is one of the model organisms for developmental biology. We found that X. laevis UGDH (xUGDH) maintained a very high degree of similarity with other known UGDH sequences both at the genomic and the protein levels. Also its kinetic parameters are similar to those of UGDH from other species. During X. laevis development, UDGH is always expressed but clearly increases its mRNA levels at the tail bud stage (i.e. 30 h post-fertilization). This result fits well with our previous observation that hyaluronan, a glycosaminoglycan that is synthesized using UDP-GlcUA and UDP-N-acetylglucosamine, is abundantly detected at this developmental stage. The expression of UGDH was found to be related to hyaluronan synthesis. In human smooth muscle cells the overexpression of xUGDH or endogenous abrogation of UGDH modulated hyaluronan synthesis specifically. Our findings were confirmed by in vivo experiments where the silencing of xUGDH in X. laevis embryos decreased glycosaminoglycan synthesis causing severe embryonic malformations because of a defective gastrulation process.

5-HT2B-mediated serotonin signaling is required for eye morphogenesis in Xenopus

In this paper, we show that serotonin, via 5-HT2B receptor, is involved in Xenopus retinal histogenesis and eye morphogenesis by supporting cell proliferation and survival. To analyze the 5-HT2B function in retinal development, we performed a loss-of-function study using both a pharmacological and a morpholino antisense oligonucleotide approach. Gain-of-function experiments were made by microinjecting 5-HT2B mRNA. Misregulation of the 5-HT2B receptor activity causes alterations in the proliferation rate and survival of retinal precursors, resulting in abnormal retinal morphology, where lamination is severely compromised. Clones derived from lipofected retinoblasts that overexpress 5-HT2B show an increase in the relative percentage of ganglion cells, possibly due to protection from apoptosis. This effect is reversed in clones lipofected with a 5-HT2B-specific morpholino. We hypothesize that the survival of the correct number of ganglion cells is controlled by 5-HT/5-HT2B signaling. Serotonin, acting as a neurotrophic factor, may contribute by refining retinal connectivity and cytoarchitecture.

Regulated gene expression of hyaluronan synthases during Xenopus laevis development

Here reported is the developmental gene expression pattern of the three known vertebrate hyaluronan synthases (XHas1, XHas2 and XHas3) and a comparative analysis of their mRNAs spatio-temporal distribution during Xenopus laevis development. We found that while XHas2 shows a steady-state expression from gastrula to late tailbud stage, XHas1 is mainly present in the early phases of development while XHas3 is predominantly transcribed in tailbud embryos. XHas1, XHas2 and XHas3 show distinct tissue expression patterns. In particular, XHas1 is localized in ectodermal derivatives and in cranial neural crest cells, whereas XHas2 is mainly found in mesoderm-derived structures and in trunk neural crest cells. Moreover, the expression pattern of XHas2 overlaps that of MyoD in cells committed to a muscle fate. Unlike the other hyaluronan synthases, XHas3 mRNA distribution is very restricted. In particular, XHas3 is expressed in the otic vesicles and closely follows the inner ear development. In conclusion, XHas1, XHas2 and XHas3 mRNAs have distinct and never overlapping spatial expression domains, which would suggest that these three enzymes may play different roles during embryogenesis.

Molecular cloning, genomic organization and developmental expression of the Xenopus laevis hyaluronan synthase 3

The content of hyaluronan (HA), a polymer of the extracellular matrix involved in a variety of physiological and pathological processes, depends on the activity of synthetic (HAS) and degrading enzymes. Since HA is also involved in embryogenesis, we have used Xenopus as a model organism because information is available for HAS1 and HAS2, but not for HAS3. We report the sequence of xlHAS3 mRNA, its genomic organization and its expression in adult tissues as well as during embryonic development. Interestingly, evidence from in situ hybridization indicates that xlHAS3 expression is restricted to the developing inner ear and cement gland. In addition, we have correlated the expression pattern of the enzymes involved in HA metabolism with the HA content during development.

Expression of 5-HT2B and 5-HT2C receptor genes is associated with proliferative regions of Xenopus developing brain and eye

Here we clone the Xenopus 5-HT2B receptor cDNA and describe its spatio-temporal mRNA expression within the developing larval brain and visual system. Expression of the 5-HT2B transcripts is compared to that of 5-HT2C as well as proliferation and neurogenic markers. In developing brain and retina, 5-HT2B and 2C mRNAs are mainly expressed in proliferative regions. We suggest that these receptors may play a role in the larval secondary neurogenesis by mediating mitogenic effects of serotonin.

Identification of circadian brain photoreceptors mediating photic entrainment of behavioural rhythms in lizards

We have shown previously that in ruin lizards (Podarcis sicula) the ablation of all known photoreceptive structures (lateral eyes, pineal and parietal eye) in the same individual animal does not prevent entrainment of their circadian locomotor rhythms to light. The present study was aimed at identifying the circadian brain photoreceptors mediating entrainment. For this purpose, we looked for opsin expression in the brain by means of immunocytochemistry. Using anti-cone-opsin antiserum CERN 874 we have localized photoreceptors in the periventricular area of hypothalamus, near the third cerebral ventricle. We also cloned a brain opsin cDNA that, on the basis of the deduced amino acid sequence, appears to belong to the RH2 class of cone-opsins. We named the cloned cone-opsin Ps-RH2. To examine whether brain cone-opsins mediate photic entrainment of circadian locomotor rhythms, we performed post-transcriptional inactivation experiments by injecting an expression eukaryotic vector transcribing the antisense cone-opsin Ps-RH2 mRNA in the third cerebral ventricle of pinealectomized-retinectomized lizards previously entrained to a light-dark (LD) cycle. Injections of the antisense construct abolished photic entrainment of circadian locomotor rhythms of pinealectomized-retinectomized lizards to the LD cycle for 6-9 days. CERN 874 completely failed to label cells within the periventricular area of hypothalamus of brains injected with antisense construct. Thus, abolishment of photic entrainment is due to inactivation of endogenous brain cone-opsins mRNA. The present results demonstrate for the first time in a vertebrate that brain cone-opsins are part of a true circadian brain photoreceptor participating in photic entrainment of behavioural rhythms.

mRNA expression of serotonin receptors of type 2C and 5A in human resting lymphocytes

We investigated the presence of mRNA for serotonin receptors of type 2C (5-HT(2C)) in resting lymphocytes by means of RT-PCR and Southern blotting analyses, given their possible role in the pathophysiology of anxiety and eating disorders. At the same time, we explored also the presence of the specific mRNA for 5-HT(5A) receptors, a novel subtype for which still no functional data exist. Healthy subjects and patients with obsessive-compulsive or bipolar disorders were included in the study. The results showed the presence of the specific mRNAs for both 5-HT(2C) and 5-HT(5A) receptors in resting lymphocytes of the three groups of subjects. An additional band was also observed after the amplification of the 5-HT(5A) cDNA in each sample. These findings, while revealing the presence of 5-HT(2C) and 5-HT(5A) receptor mRNAs in an easily available tissue, can be considered preliminary for future quantitative analyses in patients with different psychiatric conditions.

Ectopic Hoxa2 induction after neural crest migration results in homeosis of jaw elements in Xenopus

Hox genes are required to pattern neural crest (NC) derived craniofacial and visceral skeletal structures. However, the temporal requirement of Hox patterning activity is not known. Here, we use an inducible system to establish Hoxa2 activity at distinct NC migratory stages in Xenopus embryos. We uncover stage-specific effects of Hoxa2 gain-of-function suggesting a multistep patterning process for hindbrain NC. Most interestingly, we show that Hoxa2 induction at postmigratory stages results in mirror image homeotic transformation of a subset of jaw elements, normally devoid of Hox expression, towards hyoid morphology. This is the reverse phenotype to that observed in the Hoxa2 knockout. These data demonstrate that the skeletal pattern of rhombomeric mandibular crest is not committed before migration and further implicate Hoxa2 as a true selector of hyoid fate. Moreover, the demonstration that the expression of Hoxa2 alone is sufficient to transform the upper jaw and its joint selectively may have implications for the evolution of jaws.

Distribution and cellular localization of the serotonin type 2C receptor messenger RNA in human brain

The regional and cellular distribution of serotonin type 2C receptor messenger RNA was investigated in autopsy samples of human brain by in situ hybridization histochemistry. The main sites of serotonin receptor type 2C messenger RNA expression were the choroid plexus, cerebral cortex, hippocampus, amygdala, some components of the basal ganglia, the substantia nigra, the substantia innominata and the ventromedial hypothalamus, suggesting that this receptor might be involved in the regulation of different brain functions. Interestingly, in all regions examined, the serotonin type 2C receptor messenger RNA was always restricted to subpopulations of cells, suggesting a specific role, perhaps determined by regionality. A comparison of the in situ hybridization results with those previously obtained by means of radioligand binding experiments suggested that in most of the areas analysed the serotonin type 2C receptors were located at axon terminals.

Protective effect of L-arginine on hypercholesterolemia-enhanced renal ischemic injury

The effects of hypercholesterolemia on ischemic renal failure were evaluated in rats subjected to 60 min of left renal artery clamping and contralateral nephrectomy. One group of rats (HC) was kept on a cholesterol-supplemented diet for 3 weeks before renal injury and compared to a group fed a regular diet (ND). Two days after renal ischemia, inulin clearance (C(in), ml/min per 100 g BW) was lower in HC-rats (0.033 +/- 0.011) than in ND-rats (0.227 +/- 0.037; P < 0.01). indicating that hypercholesterolemia potentiated renal ischemic injury. Twenty-one days after renal ischemia the C(in) of HC-rats did not differ from ND-rats, suggesting that hypercholesterolemia did not limit late recovery. Since nitric oxide production is impaired in HC, L-arginine (50 mg/kg BW i.v.) was administered immediately after ischemia. Two days after ischemia, L-arg did not protect ND-rats from ischemia, while the C(in) and renal blood flow were higher in L-arg-treated HC rats than in untreated HC rats (C(in) = 0.125 +/- 0.013 rats vs. 0.033 +/- 0.011; P < 0.001) (RBF = 3.96 +/- 0.64 vs. 2.40 +/- 0.20 ml/min per 100 g BW; P < 0.05), indicating that L-arg protects HC rats from renal ischemia. The administration of D-arginine to ND rats induced a significant decrease of the C(in) and a significant increase of FE H2O, FE Na and FE K compared to the L-arginine and not treated groups. Cultures of inner medullary collecting duct cells from ND rats were resistant to 24-h hypoxia. In contrast, IMCD cell cultures from HC rats showed higher LDH release after 24-h hypoxia than normoxic cells (69.2 +/- 3.4 vs. 30.9 +/- 3.6%, P < 0.001); 1 mM L-arg added to the medium attenuated LDH release (44.3 +/- 2.4%, P < 0.01). These data demonstrate that HC predisposes renal tubular cells to hypoxic injury and L-arg protects cells of HC.

Distribution of the 5-HT5A serotonin receptor mRNA in the human brain

The 5-HT5A receptor is a member of a new subfamily of serotonin [5-hydroxytryptamine (5-HT)] receptors recently cloned from the human and rodent brain. The role of this receptor in normal brain functions as well as its possible involvement in pathological states is still to be determined. We therefore studied the regional distribution and cellular localization of 5-HT5A receptor mRNA in human brain sections from autopsy samples by in situ hybridization histochemistry, in order to obtain anatomical information which might be useful in formulating hypotheses on possible functions subserved by this receptor in the central nervous system (CNS). Our results showed that the main sites of 5-HT5A mRNA expression were the cerebral cortex, hippocampus and cerebellum. In the neocortical regions, the 5-HT5A receptor mRNA was mainly distributed in the layers II-III and V-VI. In the hippocampus, the dentate gyrus and the pyramidal cell layer of the CA1 and CA3 fields expressed 5-HT5A mRNA at high levels. The broad distribution in the neocortex and hippocampus supports the view that the 5-HT5A receptor in these areas might be implicated in high cortical and limbic functions. The 5-HT5A mRNA was widely distributed in the cerebellum where it was highly expressed in the Purkinje cells, in the dentate nucleus and, at a lower level, in the granule cells. Since the cerebellum receives diffuse serotonergic afferents, this finding suggests that the 5-HT5A receptor may have an important role in mediating the effects of 5-HT on cerebellar functions.

Nephrotoxicity of amphotericin B is attenuated by solubilizing with lipid emulsion

Nephrotoxicity is the major adverse effect of conventional amphotericin B (AMB/D), often limiting administration of full dosage. The new liposomal amphotericin B seems to be less toxic. The new liposomal amphotericin B seems to be less toxic. In this study, it is proposed that solubilizing the standard AMB/D preparation with 10% lipid emulsion will attenuate nephrotoxicity. Rats were injected with either AMB/D (Fungizone), AMB, AMB/D plus lipid emulsion (AMB/D/LE), or sodium deoxycholate (D). Renal function studies were performed on day 5. To assess a direct tubular toxic effect, isolated rat proximal tubule suspensions and inner medullary collecting duct cells in culture were exposed to AMB/D, AMB, AMB/D/LE, liposomal amphotericin B, and D for 60 min in normoxia. Lactate dehydrogenase (LDH) release was assessed as an index of cell injury. Creatinine clearance (ml/min per 100 g) averaged 0.79 +/- 0.04 in control rats, 0.29 +/- 0.09 in AMB rats (P < 0.001 versus control), 0.38 +/- 0.04 in AMB/D rats, 0.46 +/- 0.05 in D rats, and 0.78 +/- 0.03 in AMB/LE rats. Renal blood flow (ml/min per 100 g) was 3.45 +/- 0.31 in control, 1.29 +/- 0.28 in AMB, 1.42 +/- 0.23 in AMB/D, 3.03 +/- 0.39 in D, and 2.71 +/- 0.21 in AMB/D/LE rats. The fractional excretion of potassium (%) was 27.3 +/- 1.18 in control rats, 61.6 +/- 7.00 in AMB/D rats, 58.4 +/- 15.32 in AMB rats, and 37.9 +/- 2.06 in AMB/D/LE rats. LDH release (%) in proximal tubules incubated with AMB/D and D was 43.6 +/- 3.39 and 58.6 +/- 4.20, respectively. Addition of lipid emulsion decreased LDH release: 21.6 +/- 1.22 for AMB/D/LE and 26.4 +/- 3.03 for deoxycholate plus lipid emulsion. AMB did not demonstrate any toxic effect in proximal tubule suspensions. D was not toxic to inner medullary collecting duct cells at 0.16 mg/ml, whereas D at a higher dose and AMB induced a significant LDH release. Addition of lipid emulsion did not affect the antifungal activity as assessed by the Etest method. In conclusion, an alternative way of administering standard AMB with reduced nephrotoxicity is proposed.

[Inhibitory effect of serum from rats with acute and chronic renal insufficiency on phagocytic activity in vitro]

The effect of serum obtained from rats with acute and chronic renal failure on phagocytosis was evaluated in macrophages cultured "in vitro". The erythrophagocytosis of these cells was lower after incubation with serum from rats with acute and chronic renal failure when compared to normal plasma. This inhibitory process persisted when the serum was previously filtered through a Millipore filter PM-30, but it was abolished when the serum was filtered through a Millipore filter PM-10. These data suggest that uremic plasma displays a inhibitory factor of phagocytic cells of a molecular weight between 10.000 and 30.000 daltons.