Expression of p53/HGF/c-met/STAT3 signal in fetuses with neural tube defects

Teratogenicity of valproic acid and its constitutional isomer, amide derivative valnoctamide in mice

OBJECTIVES

The anticonvulsant valproic acid (VPA) has a known teratogenic effect capable of inducing major congenital malformations and developmental disorders. A comparative teratogenicity study of VPA and its analog valnoctamide (VCD), which is a new generation candidate antiepileptic drug, was carried out using Swiss Vancouver (SWV) mice.

METHODS

Pregnant SWV dams were treated with either a single intraperitoneal injection of VPA (1.8 and 2.7 mmol/kg), VCD (1.8 and 2.7 mmol/kg), or vehicle on E8:12 (gestational day:hour). The numbers of implantation and resorption, viable and dead fetuses, and the presence of gross fetal visceral and skeletal abnormalities were determined (E18). Real-time Polymerase chain reaction (RT-PCR) arrays were used to analyze the expression of 84 genes related to the processes of neurogenesis and neural stem cell differentiation.

RESULTS

Significant decreases in pregnancy weight gain and the number of live fetuses were observed when VPA was administered at the high dose, whereas the percentage of exencephalic fetuses was significantly increased in VPA treated compared with an equivalent VCD dosage group. There was a dose-related increase in visceral defects in the VPA-exposed fetuses. Missing skull bones and fused vertebrae in fetuses occurred at the high dose of VPA. Three genes (Mtap2, Bmp8b, and Stat3) were significantly upregulated and one (Heyl) was downregulated in samples from VPA-treated dams.

CONCLUSIONS

The study demonstrates that the teratogenicity of VPA was significantly greater than that of an equimolar dose of VCD. Four genes (Mtap2, Bmp8b, Stat3, and Heyl) represent candidate target genes for the underlying teratogenic mechanism responsible for VPA-induced malformations.

Apoptosis, Expression of PAX3 and P53, and Caspase Signal in Fetuses with Neural Tube Defects

BACKGROUND

Neural tube defects (NTDs) are among the most common and severe congenital malformations of the central nervous system. Animal studies have shown that apoptosis is involved in the development of NTDs. However, little evidence is available from human studies. We aim to examine the level of apoptosis and expression of apoptosis-regulating proteins of human terminated fetuses.

METHODS

A total of 37 NTD cases and 21 controls from pregnancy terminations were recruited. Tissues of the central nervous system were obtained through autopsy. Apoptosis of neuroepithelial cells was examined by terminal deoxynucleotidyl transferase-mediated deoxyuridinetriphosphate nick end-labeling (TUNEL) assay. Expression of PAX3, p53, and caspase 3/8/9 in central nervous tissue was measured using Western blotting.

RESULTS

More TUNEL-positive apoptosis cells were observed in the central nervous tissue of NTD cases than those of controls (p < 0.05). In spinal cord tissue, lower PAX3 expression, higher p53 expression, and increased levels of cleaved caspase 3(17kD) and cleaved caspase 8 (18kD) were found in anencephaly cases but not in spina bifida cases when compared with controls. In brain tissue, levels of PAX3 were significantly reduced in both encephalocele and spina bifida subtypes; the expression levels of cleaved caspase 3(17 kD) of encephalocele cases and cleaved caspase 8(47/45 kD) in spina bifida cases were higher than in controls; no difference was found in the expression of p53 or caspase 9 between NTDs and controls.

CONCLUSION

These findings provide some evidence that excessive apoptosis in fetal central nervous tissues may be associated with the development of human NTDs. Birth Defects Research 109:1596-1604, 2017. © 2017 Wiley Periodicals, Inc.

STAT3 and apoptosis regulators: Bak and Bcl-xL in endometrioid adenocarcinomas of different estrogen receptor-α immunoprofile

Estrogen receptor (ER) is a major feature of endometrioid adenocarcinoma. It has a significant impact on constitution of estrogen-responsiveness of this endometrial malignancy, in which STAT3 (signal transducer and activator of transcription) becomes hyperactivated. The aim of our study was to detect immunohistochemically and compare expressions of STAT3 with apoptosis regulators (Bak and Bcl-xL) in regard to different pathological features and variably pronounced ER-α immunoprofile in 78 endometrioid adenocarcinomas. STAT3 was abundantly detected in nuclei of cancer cells in 54 cases, thus pointing at its activation as an universal nuclear transcriptional factor. Bcl-xL and Bak were expressed in cytoplasm of malignant cells in 62 and 20 cancers, respectively. STAT3 correlated both with Bcl-xL (p = 0.001, r = 0.365) and Bak (p  < 0.001, r = 0.436) in all of endometrioid adenocarcinomas and variably in different subgroups of these tumours segregated in regard to grading, staging and patients' age. Remarkably, only ER-α positive cancers retained these correlations in opposition to ER-α negative tumours with negativity defined as an immunoreactivity below 10%. ER-α receptor probably enhances interactions between STAT3 and Bcl-xL to be present in statistically significant manner. Presence of ER-α receptor seems to be crucial for relationships among Bcl-xL and STAT3 to occur in endometrioid adenocarcinomas.

MicroRNA gene expression signatures in the developing neural tube

BACKGROUND

Neurulation requires precise, spatio-temporal expression of numerous genes and coordinated interaction of signal transduction and gene regulatory networks, disruption of which may contribute to the etiology of neural tube defects (NTDs). MicroRNAs (miRNAs) are key modulators of cell and tissue differentiation. To define potential roles of miRNAs in development of the murine neural tube (NT), miRNA microarray analysis was conducted to establish expression profiles, and identify miRNA target genes and functional gene networks.

METHODS

The miRNA expression profiles in murine embryonic NTs derived from gestational days 8.5, 9.0, and 9.5 were defined and compared utilizing miRXplore microarrays from Miltenyi Biotec GmbH, Bergisch Gladbach, Germany. Gene expression changes were verified by TaqMan quantitative Real-Time PCR. The clValid R package and the UPGMA (hierarchical) clustering method were utilized for cluster analysis of the microarray data. Functional associations among selected miRNAs were examined via Ingenuity Pathway Analysis.

RESULTS

The miRXplore chips enabled examination of 609 murine miRNAs. Expression of approximately 12% of these was detected in murine embryonic NTs. Clustering analysis revealed several developmentally regulated expression clusters among these expressed genes. Target analysis of differentially expressed miRNAs enabled identification of numerous target genes associated with cellular processes essential for normal NT development. Utilization of Ingenuity Pathway Analysis revealed interactive biologic networks which connected differentially expressed miRNAs with their target genes, and highlighted functional relationships.

CONCLUSIONS

The present study defined unique gene expression signatures of a range of miRNAs in the developing NT during the critical period of NT morphogenesis. Analysis of miRNA target genes and gene interaction pathways revealed that specific miRNAs might direct expression of numerous genes encoding proteins, which have been shown to be indispensable for normal neurulation. This study is the first to identify miRNA expression profiles and their potential regulatory networks in the developing mammalian NT.

Endogenous hepatocyte growth factor is a niche signal for subventricular zone neural stem cell amplification and self-renewal

Neural stem cells persist in the adult mammalian brain, within the subventricular zone (SVZ). The endogenous mechanisms underpinning SVZ neural stem cell proliferation, self-renewal, and differentiation are not fully elucidated. In the present report, we describe a growth-stimulatory activity of liver explant-conditioned media on SVZ cell cultures and identify hepatocyte growth factor (HGF) as a major player in this effect. HGF exhibited a mitogenic activity on SVZ cell cultures in a mitogen-activated protein kinase (MAPK) (ERK1/2)-dependent manner as U0126, a specific MAPK inhibitor, blocked it. Combining a functional neurosphere forming assay with immunostaining for c-Met, along with markers of SVZ cells subtypes, demonstrated that HGF promotes the expansion of neural stem-like cells that form neurospheres and self-renew. Immunostaining, HGF enzyme-linked immunosorbent assay and Madin-Darby canine kidney cell scattering assay indicated that SVZ cell cultures produce and release HGF. SVZ cell-conditioned media induced proliferation on SVZ cell cultures, which was blocked by HGF-neutralizing antibodies, hence implying that endogenously produced HGF accounts for a major part in SVZ mitogenic activity. Brain sections immunostaining revealed that HGF is produced by nestin-expressing cells and c-Met is expressed within the SVZ by immature cells. HGF intracerebroventricular injection promoted SVZ cell proliferation and increased the ability of these cells exposed in vivo to HGF to form neurospheres in vitro, whereas intracerebroventricular injection of HGF-neutralizing antibodies decreased SVZ cell proliferation. The present study unravels a major role, both in vitro and in vivo, for endogenous HGF in SVZ neural stem cell growth and self-renewal.

[Recent perspectives on the development of the central nervous system and the genetic background of neural tube defects]

Neural tube defects are rare and mostly lethal malformations. The pattern of inheritance of these malformations is multifactorial, rendering the identification of the underlying causes. Numerous studies have been conducted to elucidate the genetic basis of the development of the central nervous system. Essential signaling pathways of the development of the central nervous system include the planar cell polarity pathway, which is important for the initiation of neural tube closure as well as sonic hedgehog pathway, which regulates the neural plate bending. Genes and their mutations influencing the different stages of neurulation have been investigated for their eventual role in the development of these malformations. Among the environmental factors, folic acid seems to be the most important modifier of the risk of human neural tube defects. Genes of the folate metabolism pathways have also been investigated to identify mutations resulting in increased risk of NTDs. In this review the author has attempted to summarize the knowledge on neural tube defects, with special regard to genetic factors of the etiology.

Recent perspectives on the genetic background of neural tube defects with special regard to iniencephaly

Iniencephaly is a rare and mostly lethal type of neural tube defect. The pattern of inheritance of this group of malformations is multifactorial, rendering the identification of the underlying causes. Numerous studies have been conducted to elucidate the genetic basis of human neurulation. Essential signaling pathways of the development of the CNS include the planar cell polarity pathway, which is important for the initiation of neural tube closure, as well as the sonic hedgehog pathway, which regulates the neural plate bending. Genes influencing the different stages of neurulation have been investigated for their eventual role in the development of these malformations. Among the environmental factors, folic acid seems to be the most important modifier of the risk of human neural tube defects. Genes of the folate metabolism pathways have also been investigated to identify mutations resulting in increased risk of neural tube defects. In this review we have attempted to summarize the knowledge on iniencephaly and neural tube defects, with special regard to genetic factors of the etiology.

[Differentially expressed genes in diabetes-induced embryopathy]

To determine molecular mechanism in hyperglycemia induced congenital neural tube defects, yolk sac cells were harvested at gestational day 12 from streptozotocin (STZ) -induced diabetic rats with congenital neural tube defects in offspring, STZ-induced diabetic rats without neural tube defects and normal control group. We analyzed gene expression profiles in yolk sac cells using a DNA microarray technique. Changes in apoptotic and MAP Kinase signaling pathways were detected by Western blotting analyses. Comparison of genes in yolk sac cells with a total of 1 200 genes in the control cells, 79 genes differently expressed between the two groups were detected. Forty-two of them were up-regulated and 37 were down-regulated. There was strong characteristic apoptotic DNA ladder in yolk sac cells in embryopathic offspring from experimentally-induced diabetic rats. The activity of ERK1/2 was dramatically decreased and the activity of JNK1/2 was significantly increased. Differentially expressed genes, MAP Kinase, and apoptotic signal pathways play very important roles in hyperglycemia induced neural tube defects. We hope that these could provide useful hallmark to rapid identification of early diabetic embryopathy.

The tumour-suppressor p53 is not required for pancreatic beta cell death during diabetes and upon irradiation

Immune-independent diabetes often occurs via pancreatic beta cell dysfunction. However, the role of the tumour suppressor p53 that regulates cellular life and death in multiple tissues, in pancreatic cell death and diabetes has not been clarified. We have therefore utilized an established mouse model for diabetes in which the MHC class I antigen is overexpressed in pancreatic beta cells under the rat insulin promoter, to investigate the role of p53. We show that pancreatic beta cell death, as determined by TUNEL staining, is elevated in transgenic mice compared to wild-type mice. However, there was no increase in immuno-reactivity towards anti-p53 antibodies in the pancreas of transgenic mice over the course of diabetes formation and beta cell death, suggesting that p53 may not be involved in these processes. Interestingly, p53 expression was also not induced in pancreas upon gamma-irradiation, which resulted in a massive increase in the number of TUNEL-positive cells, suggesting that the p53 pathway may not be causally involved in pancreatic cell death. To further confirm these findings, we generated MHC class I transgenic mice lacking p53 expression. Absence of p53 did not result in any significant changes in pancreatic morphology or affect cell death levels. Importantly, p53 absence did not rescue the diabetic phenotype of the transgenic mice. The results therefore demonstrate that p53 may not be causally involved in pancreatic beta cell death, and suggests that the classical cell death pathway dependent on p53 may not be operating in pancreatic beta cells.