Tumor suppressor gene BRCA-1 is expressed by embryonic and adult neural stem cells and involved in cell proliferation

Germline BRCA2 pathogenic variants in pediatric ganglioglioma: Case report and review of the literature

BACKGROUND

BRCA1 and BRCA2 are tumor suppressor genes associated with increased risk of breast and ovarian cancer in adulthood. Patients with germline pathogenic variants in these genes have also been reported to develop brain tumors, although it is unclear whether these syndromes are associated with significant increased risk of brain tumor formation.

RESULTS

Here, we report a case of a child with germline BRCA2 pathogenic variant presenting with a symptomatic ganglioglioma. To our knowledge, this is the first such patient to be reported. We discuss prior cases of brain tumors in BRCA1/2 patients and evidence for a potential role for BRCA1/2 pathogenic variants in brain tumor formation.

CONCLUSION

BRCA2 germline variants may increase the risk of developing some types of pediatric brain tumors, but further study is needed to determine its effect on low-grade glioma formation.

MicroRNA networks linked with BRCA1/2, PTEN, and common genes for Alzheimer's disease and breast cancer share highly enriched pathways that may unravel targets for the AD/BC comorbidity treatment

MicroRNAs (miRNAs) are involved in the regulation of various cellular processes including pathological conditions. MiRNA networks have been extensively researched in age-related degenerative diseases, such as cancer, Alzheimer's disease (AD), and heart failure. Thus, miRNA has been studied from different approaches, in vivo, in vitro, and in silico including miRNA networks. Networks linking diverse biomedical entities unveil information not readily observable by other means. This work focuses on biological networks related to Breast cancer susceptibility 1 (BRCA1) in AD and breast cancer (BC). Using various bioinformatics approaches, we identified subnetworks common to AD and BC that suggest they are linked. According to our results, miR-107 was identified as a potentially good candidate for both AD and BC treatment (targeting BRCA1/2 and PTEN in both diseases), accompanied by miR-146a and miR-17. The analysis also confirmed the involvement of the miR-17-92 cluster, and miR-124-3p, and highlighted the importance of poorly researched miRNAs such as mir-6785 mir-6127, mir-6870, or miR-8485. After filtering the in silico analysis results, we found 49 miRNA molecules that modulate the expression of at least five genes common to both BC and AD. Those 49 miRNAs regulate the expression of 122 genes in AD and 93 genes in BC, from which 26 genes are common genes for AD and BC involved in neuron differentiation and genesis, cell differentiation and migration, regulation of cell cycle, and cancer development. Additionally, the highly enriched pathway was associated with diabetic complications, pointing out possible interplay among molecules underlying BC, AD, and diabetes pathology.

Efficacy and safety of PARP inhibitors in the treatment of BRCA-mutated breast cancer: an updated systematic review and meta-analysis of randomized controlled trials

INTRODUCTION

Poly-ADP-ribose polymerase inhibitors (PARPis) have emerged as a new class of therapeutic agents for breast cancer patients with breast cancer susceptibility gene (BRCA) mutations. However, the efficacy and toxicity of PARPis have not been clearly established.

METHODS

This study comprehensively evaluated the efficacy and safety of PARPis in patients with BRCA-mutated breast cancer. Online databases were systematically searched, and six clinical trials were included. The primary endpoint of efficacy was progression-free survival (PFS), whereas the secondary endpoints were overall survival (OS) and objective response rate (ORR). Additionally, we assessed the safety of PARPis.

RESULTS

The results of the meta-analysis showed that PARPis can effectively improve the PFS and OS in patients compared with the control group. The pooled HR (PARPi vs control groups) was 0.63 (95% CI, 0.55 - 0.73) and 0.83 (95% CI, 0.73 to -0.95) for PFS and OS, respectively. In safety, PARPis demonstrated controllable adverse reactions. There were no significant differences in overall AEs or grade ≥3 AEs between the PARP inhibitor and control arms.

CONCLUSIONS

Our results confirm the efficacy and safety of PARPis in patients with BRCA-mutated breast cancer, and more specifically clarify the efficacy of PARPis alone or in combination with other chemotherapy drugs. [Figure: see text].

Brca1 Is Regulated by the Transcription Factor Gata3, and Its Silencing Promotes Neural Differentiation in Retinal Neurons

Previous studies have indicated that Brca1 (Breast cancer suppressor gene 1) plays an important role in neural development and degenerative diseases. However, the bioactivity and regulatory mechanism of Brca1 expression in retinal neurocytes remain unclear. In the present study, our data indicated that Brca1 maintains the state of neuronal precursor cells. Brca1 silencing induces differentiation in 661W cells. Nestin, a marker of precursor cells, was significantly decreased in parallel with Brca1 silencing in 661W cells, whereas Map2 (Microtubule associated protein 2), a marker of differentiated neurons, was significantly increased. Neurite outgrowth was increased by ~4.0-fold in Brca1-silenced cells. Moreover, DNA affinity purification assays and ChIP assays demonstrated that Gata3 (GATA binding protein 3) regulates Brca1 transcription in 661W cells. Silencing or overexpressing Gata3 could significantly regulate the expression of Brca1 and affect its promoter inducibility. Furthermore, the expression of Gata3 generally occurred in parallel with that of Brca1 in developing mouse retinas. Both Gata3 and Brca1 are expressed in the neonatal mouse retina but are developmentally silenced with age. Exogenous Gata3 significantly inhibited neural activity by decreasing synaptophysin and neurite outgrowth. Thus, this study demonstrated that Brca1 is transcriptionally regulated by Gata3. Brca1/Gata3 silencing is involved in neuronal differentiation and maturation.

Mammalian tumor-like organs. 1. The role of tumor-like normal organs and atypical tumor organs in the evolution of development (carcino-evo-devo)

Background

Earlier I hypothesized that hereditary tumors might participate in the evolution of multicellular organisms. I formulated the hypothesis of evolution by tumor neofunctionalization, which suggested that the evolutionary role of hereditary tumors might consist in supplying evolving multicellular organisms with extra cell masses for the expression of evolutionarily novel genes and the origin of new cell types, tissues, and organs. A new theory—the carcino-evo-devo theory—has been developed based on this hypothesis.

Main text

My lab has confirmed several non-trivial predictions of this theory. Another non-trivial prediction is that evolutionarily new organs if they originated from hereditary tumors or tumor-like structures, should recapitulate some tumor features in their development. This paper reviews the tumor-like features of evolutionarily novel organs. It turns out that evolutionarily new organs such as the eutherian placenta, mammary gland, prostate, the infantile human brain, and hoods of goldfishes indeed have many features of tumors. I suggested calling normal organs, which have many tumor features, the tumor-like organs.

Conclusion

Tumor-like organs might originate from hereditary atypical tumor organs and represent the part of carcino-evo-devo relationships, i.e., coevolution of normal and neoplastic development. During subsequent evolution, tumor-like organs may lose the features of tumors and the high incidence of cancer and become normal organs without (or with almost no) tumor features.

Breast cancer type 1 and neurodegeneration: consequences of deficient DNA repair

Numerous cellular processes, including toxic protein aggregation and oxidative stress, have been studied extensively as potential mechanisms underlying neurodegeneration. However, limited therapeutic efficacy targeting these processes has prompted other mechanisms to be explored. Previous research has emphasized a link between cellular senescence and neurodegeneration, where senescence induced by excess DNA damage and deficient DNA repair results in structural and functional changes that ultimately contribute to brain dysfunction and increased vulnerability for neurodegeneration. Specific DNA repair proteins, such as breast cancer type 1, have been associated with both stress-induced senescence and neurodegenerative diseases, however, specific mechanisms remain unclear. Therefore, this review explores DNA damage-induced senescence in the brain as a driver of neurodegeneration, with particular focus on breast cancer type 1, and its potential contribution to sex-specific differences associated with neurodegenerative disease.

ASPM promotes homologous recombination-mediated DNA repair by safeguarding BRCA1 stability

DNA double-strand break (DSB) repair by homologous recombination (HR) is essential for ensuring genome stability. Abnormal spindle-like microcephaly-associated (ASPM) gene encodes a spindle protein that is commonly implicated in primary microcephaly. We found that ASPM is recruited to sites of DNA damage in a PARP2-dependent manner. ASPM interacts with BRCA1 and its E3 ligase HERC2, preventing HERC2 from accessing to BRCA1 and ensuring BRCA1 stability. Inhibition of ASPM expression promotes HERC2-mediated BRCA1 degradation, compromises HR repair efficiency and chromosome stability, and sensitizes cancer cells to ionizing radiation. Moreover, we observed a synergistic effect between ASPM and PARP inhibition in killing cancer cells. This research has uncovered a novel function for ASPM in facilitating HR-mediated repair of DSBs by ensuring BRCA1 stability. ASPM might constitute a promising target for synthetic lethality-based cancer therapy.

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ASPM is recruited to sites of DNA damage in a PARP2-dependent manner.

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ASPM promotes DSB-end resection to facilitate HR repair.

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ASPM prevents HERC2 from accessing to BRCA1 and ensuring BRCA1 stability.

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Inhibition of ASPM sensitizes cancer cells to ionizing radiation and PARP inhibitor.

De novo mutation of cancer-related genes associates with particular neurodevelopmental disorders

Epidemiological studies have shown an increased prevalence of cancer in some patients with neurodevelopmental disorder (NDD); however, the genetic mechanisms regarding how cancer-related genes (CRGs) contribute to NDD remain unclear. We performed bioinformatic analyses on 219 CRGs from OMIM and de novo mutations (DNMs) from 16,498 patients with different NDDs and 3391 controls. Our results showed that autism spectrum disorder, undiagnosed neurodevelopmental disorder, congenital heart disease and intellectual disability, but not epileptic encephalopathy and schizophrenia, harboured significantly more putative functional DNMs in CRGs, compared with controls, providing genetic evidence supporting previous epidemiological surveys. We further detected 26 CRGs with recurrent putative functional DNMs that showed high expression in the human brain during the prenatal stage and in non-brain organs in adults. The proteins coded by the 26 CRGs and known NDD candidate genes formed a functional network that is involved in brain development and tumorigenesis. Overall, we proposed 39 cancer-targeting drugs that could be investigated for treating patients with NDD, which would be potentially cost-effective. In conclusion, DNMs contribute to specific NDDs and there may be a shared genetic basis between NDDs and cancer, highlighting the importance of considering cancer-targeting drugs with potential curative effects in patients with NDDs. KEY MESSAGES: • The contribution of DNMs in NDD is consistent with epidemiological surveys. • We highlighted 26 CRGs, including nine genes with more than five functional DNMs. • Specific expression patterns underlie the genetic mechanism of CRGs in NDD. • Specific functional networks underlie the genetic mechanism of CRGs in NDD. • The shared genetic aetiology suggests potential mutual treatment strategies.

Beyond Trophic Factors: Exploiting the Intrinsic Regenerative Properties of Adult Neurons

Injuries and diseases of the peripheral nervous system (PNS) are common but frequently irreversible. It is often but mistakenly assumed that peripheral neuron regeneration is robust without a need to be improved or supported. However, axonal lesions, especially those involving proximal nerves rarely recover fully and injuries generally are complicated by slow and incomplete regeneration. Strategies to enhance the intrinsic growth properties of reluctant adult neurons offer an alternative approach to consider during regeneration. Since axons rarely regrow without an intimately partnered Schwann cell (SC), approaches to enhance SC plasticity carry along benefits to their axon partners. Direct targeting of molecules that inhibit growth cone plasticity can inform important regenerative strategies. A newer approach, a focus of our laboratory, exploits tumor suppressor molecules that normally dampen unconstrained growth. However several are also prominently expressed in stable adult neurons. During regeneration their ongoing expression “brakes” growth, whereas their inhibition and knockdown may enhance regrowth. Examples have included phosphatase and tensin homolog deleted on chromosome ten (PTEN), a tumor suppressor that inhibits PI3K/pAkt signaling, Rb1, the protein involved in retinoblastoma development, and adenomatous polyposis coli (APC), a tumor suppressor that inhibits β-Catenin transcriptional signaling and its translocation to the nucleus. The identification of several new targets to manipulate the plasticity of regenerating adult peripheral neurons is exciting. How they fit with canonical regeneration strategies and their feasibility require additional work. Newer forms of nonviral siRNA delivery may be approaches for molecular manipulation to improve regeneration.

DNA repair fidelity in stem cell maintenance, health, and disease

Stem cells are a sub population of cell types that form the foundation of our body, and have the potential to replicate, replenish and repair limitlessly to maintain the tissue and organ homeostasis. Increased lifetime and frequent replication set them vulnerable for both exogenous and endogenous agents-induced DNA damage compared to normal cells. To counter these damages and preserve genetic information, stem cells have evolved with various DNA damage response and repair mechanisms. Furthermore, upon experiencing irreparable DNA damage, stem cells mostly prefer early senescence or apoptosis to avoid the accumulation of damages. However, the failure of these mechanisms leads to various diseases, including cancer. Especially, given the importance of stem cells in early development, DNA repair deficiency in stem cells leads to various disabilities like developmental delay, premature aging, sensitivity to DNA damaging agents, degenerative diseases, etc. In this review, we have summarized the recent update about how DNA repair mechanisms are regulated in stem cells and their association with disease progression and pathogenesis.

Overexpression of BRCA1 in Neural Stem Cells Enhances Cell Survival and Functional Recovery after Transplantation into Experimental Ischemic Stroke

Transplantation of neural stem cells (NSCs) is a promising therapy for ischemic stroke. However, the effectiveness of this approach is limited by grafted cell death. Breast cancer susceptibility protein 1 (BRCA1) could suppress apoptosis in neural progenitors and modulate oxidative stress in neurons. In this study, we found that BRCA1 was upregulated by oxygen-glucose deprivation/reoxygenation (OGD/R). Overexpression of BRCA1 in NSCs reduced cell apoptosis and oxidative stress after OGD/R insult. The molecule overexpression also stimulated cellular proliferation in OGD/R NSCs and increased the survival rate of grafted cells. Further, the transplantation of BRCA1-transfected NSCs into mice with ischemic stroke increased brain-derived neurotropic factor and nerve growth factor expression in the brain and elicited neurological function improvement. In addition, we found that RING finger domain and BRCT domain of BRCA1 could physically interact with p53 in NSCs. The cross talk between BRCA1 RING finger domain and p53 was responsible for p53 ubiquitination and degradation. Our findings indicate that modification with BRCA1 could enhance the efficacy of NSCs transplantation in ischemic stroke.

Breast cancer susceptibility protein 1 (BRCA1) rescues neurons from cerebral ischemia/reperfusion injury through NRF2-mediated antioxidant pathway

Cellular oxidative stress plays a vital role in the pathological process of neural damage in cerebral ischemia/reperfusion (I/R). The breast cancer susceptibility protein 1 (BRCA1), a tumor suppressor, can modulate cellular antioxidant response and DNA repair. Yet the role of BRCA1 in cerebral I/R injury has not been explored. In this study, we observed that BRCA1 was mainly expressed in neurons and was up-regulated in response to I/R insult. Overexpression of BRCA1 attenuated reactive oxygen species production and lipid peroxidation. Enhanced BRCA1 expression promoted DNA double strand break repair through non-homologous end joining pathway. These effects consequently led to neuronal cell survival and neurological recovery. Mechanically, BRCA1 can interact with the nuclear factor (erythroid-derived 2)-like 2 (NRF2) through BRCA1 C-terminal (BRCT) domain. The cross-talk between BRCT and NRF2 activated the NRF2/Antioxidant Response Element signaling pathway and thus protected injured neurons during cerebral I/R. In conclusion, enhanced BRCA1 after cerebral I/R injury may attenuate or prevent neural damage from I/R via NRF2-mediated antioxidant pathway. The finding may provide a potential therapeutic target against ischemic stroke.

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BRCA1 was up-regulated after cerebral ischemia/reperfusion injury.

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Up-regulated BRCA1 attenuated cerebral ischemia/reperfusion injury and cognitive impairment.

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BRCA1 binding to NRF2 via BRCT domain triggered NRF2-mediated antioxidant response.

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BRCA1 promoted DSBs repair via non-homologous end joining-pathway.

Brca1 Is Upregulated by 5-Aza-CdR and Promotes DNA Repair and Cell Survival, and Inhibits Neurite Outgrowth in Rat Retinal Neurons

Previous studies have reported that Brca1 acts as a “hinge” in the development of the central nervous system (CNS). However, the precise role of Brca1 in rat retinal neurons remains unclear. Here, we found that Brca1 is developmentally downregulated and silenced in adult retina. Brca1 was upregulated in rat primary retinal neurons by 5-Aza-2′-deoxycytidine (5-Aza-CdR) treatment. Moreover, the upregulation of Brca1 by both 5-Aza-CdR and transgenic Brca1 promoted genomic stability and improved cell viability following exposure to ionizing radiation (IR). Furthermore, transgenic Brca1 significantly inhibited neurite outgrowth of retinal neurons, which implicates that Brca1 silencing promotes cell differentiation and determines neuronal morphology. Taken together, our results reveal a biological function of Brca1 in retinal development.

Brca1 is expressed in human microglia and is dysregulated in human and animal model of ALS

Background

There is growing evidence that microglia are key players in the pathological process of amyotrophic lateral sclerosis (ALS). It is suggested that microglia have a dual role in motoneurone degeneration through the release of both neuroprotective and neurotoxic factors.

Results

To identify candidate genes that may be involved in ALS pathology we have analysed at early symptomatic age (P90), the molecular signature of microglia from the lumbar region of the spinal cord of hSOD1^G93A mice, the most widely used animal model of ALS. We first identified unique hSOD1^G93A microglia transcriptomic profile that, in addition to more classical processes such as chemotaxis and immune response, pointed toward the potential involvement of the tumour suppressor gene breast cancer susceptibility gene 1 (Brca1). Secondly, comparison with our previous data on hSOD1^G93A motoneurone gene profile substantiated the putative contribution of Brca1 in ALS. Finally, we established that Brca1 protein is specifically expressed in human spinal microglia and is up-regulated in ALS patients.

Conclusions

Overall, our data provide new insights into the pathogenic concept of a non-cell-autonomous disease and the involvement of microglia in ALS. Importantly, the identification of Brca1 as a novel microglial marker and as possible contributor in both human and animal model of ALS may represent a valid therapeutic target. Moreover, our data points toward novel research strategies such as investigating the role of oncogenic proteins in neurodegenerative diseases.

Electronic supplementary material

The online version of this article (doi:10.1186/s13024-015-0023-x) contains supplementary material, which is available to authorized users.

[Gliomas and BRCA genes mutations: fortuitous association or imputability?]

BRCA is a tumor suppressor gene implicated in the major mechanisms of cellular stability in every type of cell. Its mutations are described in numerous cancers, mainly breast and ovarian in women. It was also found an increase of lifetime risk of pancreas, colon, prostate cancer or lymphoma in men carriers. We report the cases of two female patients aged 40 and 58-years-old female patients and one 35-years-old male patient, with brain or medullar gliomas, carriers of a germline mutation of BRCA gene. Those gliomas were particularly aggressive and were not responding to the standard treatment, with chemo and radiotherapy. The very unusual characteristics in location and evolutive profile of these central nervous system tumors raise the question of a genetical underlying mechanism, maybe linked to the BRCA gene mutation that carry these patients. In addition, a non-fortuitous association between germline mutation of BRCA and occurrence of a glioma can be evoked according to the embryological, epidemiological and biomolecular findings noted in the literature. Other clinical and experimental studies are necessary to precise the physiopathological link existing between BRCA mutations and the occurrence of a glioma; this could have therapeutical and clinical implications in the future.

BRCA1 silencing is associated with failure of DNA repairing in retinal neurocytes

Retinal post-mitotic neurocytes display genomic instability after damage induced by physiological or pathological factors. The involvement of BRCA1, an important factor in development and DNA repair in mature retinal neurocytes remains unclear. Thus, we investigated the developmental expression profile of BRCA1 in the retina and defined the role of BRCA1 in DNA repair in retinal neurocytes. Our data show the expression of BRCA1 is developmentally down-regulated in the retinas of mice after birth. Similarly, BRCA1 is down-regulated after differentiation induced by TSA in retinal precursor cells. An end-joining activity assay and DNA fragmentation analysis indicated that the DNA repair capacity is significantly reduced. Moreover, DNA damage in differentiated cells or cells in which BRCA1 is silenced by siRNA interference is more extensive than that in precursor cells subjected to ionizing radiation. To further investigate non-homologous end joining (NHEJ), the major repair pathway in non-divided neurons, we utilized an NHEJ substrate (pEPI-NHEJ) in which double strand breaks are generated by I-SceI. Our data showed that differentiation and the down-regulation of BRCA1 respectively result in a 2.39-fold and 1.68-fold reduction in the total NHEJ frequency compared with that in cells with normal BRCA1. Furthermore, the analysis of NHEJ repair junctions of the plasmid substrate indicated that BRCA1 is involved in the fidelity of NHEJ. In addition, as expected, the down-regulation of BRCA1 significantly inhibits the viability of retina precursor cells. Therefore, our data suggest that BRCA1 plays a critical role in retinal development and repairs DNA damage of mature retina neurocytes.

Role of BRCA1 in brain development

Breast cancer susceptibility gene 1 (BRCA1) is a breast and ovarian cancer tumor suppressor whose loss leads to DNA damage and defective centrosome functions. Despite its tumor suppression functions, BRCA1 is most highly expressed in the embryonic neuroepithelium when the neural progenitors are highly proliferative. To determine its functional significance, we deleted BRCA1 in the developing brain using a neural progenitor-specific driver. The phenotype is characterized by severe agenesis of multiple laminated cerebral structures affecting most notably the neocortex, hippocampus, cerebellum, and olfactory bulbs. Major phenotypes are caused by excess apoptosis, as these could be significantly suppressed by the concomitant deletion of p53. Certain phenotypes attributable to centrosomal and cell polarity functions could not be rescued by p53 deletion. A double KO with the DNA damage sensor kinase ATM was able to rescue BRCA1 loss to a greater extent than p53. Our results suggest distinct apoptotic and centrosomal functions of BRCA1 in neural progenitors, with important implications to understand the sensitivity of the embryonic brain to DNA damage, as well as the developmental regulation of brain size.

Transgenic expression of BRCA1 disturbs hematopoietic stem and progenitor cells quiescence and function

The balance between quiescence and proliferation of HSCs is an important regulator of hematopoiesis. Loss of quiescence frequently results in HSCs exhaustion, which underscores the importance of tight regulation of proliferation in these cells. Studies have indicated that cyclin-dependent kinases are involved in the regulation of quiescence in HSCs. BRCA1 plays an important role in the repair of DNA double-stranded breaks, cell cycle, apoptosis and transcription. BRCA1 is expressed in the bone marrow. However, the function of BRCA1 in HSCs is unknown. In our study, we generated BRCA1 transgenic mice to investigate the effects of BRCA1 on the mechanisms of quiescence and differentiation in HSCs. The results demonstrate that over-expression of BRCA1 in the bone marrow impairs the development of B lymphocytes. Furthermore, BRCA1 induced an increase in the number of LSKs, LT-HSCs, ST-HSCs and MPPs. A competitive transplantation assay found that BRCA1 transgenic mice failed to reconstitute hematopoiesis. Moreover, BRCA1 regulates the expression of p21(waf1)/cip1 and p57(kip2), which results in a loss of quiescence in LSKs. Together, over-expression of BRCA1 in bone marrow disrupted the quiescent of LSKs, induced excessive accumulation of LSKs, and disrupted differentiation of the HSCs, which acts through the down-regulated of p21(waf1)/cip1 and p57(kip2).

Hepatocyte growth factor activator inhibitor-1 is induced by bone morphogenetic proteins and regulates proliferation and cell fate of neural progenitor cells

Background

Neural progenitor cells (NPCs) in the developing neuroepithelium are regulated by intrinsic and extrinsic factors. There is evidence that NPCs form a self-supporting niche for cell maintenance and proliferation. However, molecular interactions and cell-cell contacts and the microenvironment within the neuroepithelium are largely unknown. We hypothesized that cellular proteases especially those associated with the cell surface of NPCs play a role in regulation of progenitor cells in the brain.

Methodology/Principal Findings

In this work, we show that NPCs, isolated from striatal anlage of developing rat brain, express hepatocyte growth factor activator inhibitor-1 and -2 (HAI-1 and HAI-2) that are cell surface-linked serine protease inhibitors. In addition, radial glia cells derived from mouse embryonic stem cells also express HAI-1 and HAI-2. To study the functional significance of HAI-1 and HAI-2 in progenitor cells, we modulated their levels using expression plasmids or silencing RNA (siRNA) transfected into the NPCs. Data showed that overexpression of HAI-1 or HAI-2 decreased cell proliferation of cultured NPCs, whilst their siRNAs had opposite effects. HAI-1 also influenced NPC differentiation by increasing the number of glial fibrillary acidic protein (GFAP) expressing cells in the culture. Expression of HAI-1 in vivo decreased cell proliferation in developing neuroepithelium in E15 old animals and promoted astrocyte cell differentiation in neonatal animals. Studying the regulation of HAI-1, we observed that Bone morphogenetic protein-2 (BMP-2) and BMP-4 increased HAI-1 levels in the NPCs. Experiments using HAI-1-siRNA showed that these BMPs act on the NPCs partly in a HAI-1-dependent manner.

Conclusions

This study shows that the cell-surface serine protease inhibitors, HAI-1 and HAI-2 influence proliferation and cell fate of NPCs and their expression levels are linked to BMP signaling. Modulation of the levels and actions of HAI-1 in NPCs may be of a potential value in stem cell therapies in various brain diseases.

Cell cycle proteins in brain in mild cognitive impairment: insights into progression to Alzheimer disease

Recent studies have demonstrated the re-emergence of cell cycle proteins in brain as patients progress from the early stages of mild cognitive impairment (MCI) into Alzheimer's disease (AD). Oxidative stress markers present in AD have also been shown to be present in MCI brain suggesting that these events occur in early stages of the disease. The levels of key cell cycle proteins, such as CDK2, CDK5, cyclin G1, and BRAC1 have all been found to be elevated in MCI brain compared to age-matched control. Further, peptidyl prolyl cis-trans isomerase (Pin1), a protein that plays an important role in regulating the activity of key proteins, such as CDK5, GSK3-β, and PP2A that are involved in both the phosphorylation state of Tau and in the cell cycle, has been found to be oxidatively modified and downregulated in both AD and MCI brain. Hyperphosphorylation of Tau then results in synapse loss and the characteristic Tau aggregation as neurofibrillary tangles, an AD hallmark. In this review, we summarized the role of cell cycle dysregulation in the progression of disease from MCI to AD. Based on the current literature, it is tempting to speculate that a combination of oxidative stress and cell cycle dysfunction conceivably leads to neurodegeneration.

BRCA1 tumour suppression occurs via heterochromatin-mediated silencing

Mutations in tumor suppressor BRCA1 lead to breast and/or ovarian cancer. Here we show that loss of BRCA1 in mice results in transcriptional derepression of the tandemly repeated satellite DNA. BRCA1 deficiency is accompanied by reduction of condensed DNA regions in the genome and loss of ubiquitylation of histone H2A at satellite repeats. BRCA1 binds to satellite DNA regions in vivo and ubiquitylates H2A in vitro. Ectopic expression of an H2A fused to ubiquitin reverses the effects of BRCA1 loss, suggesting that BRCA1 maintains heterochromatin structure via ubiquitylation of histone H2A. Satellite DNA derepression was also observed mouse and human BRCA1 deficient breast cancers. Ectopic expression of satellite DNA can phenocopy BRCA1 loss in centrosome amplification, cell cycle checkpoint defects, DNA damage and genomic instability. We propose that the role of BRCA1 in maintaining global heterochromatin integrity accounts for many of its tumor suppressor functions.

The origins and evolution of genetic disease risk in modern humans

Patterns and risks of human disease have evolved. In this article, I review evidence regarding the importance of recent adaptive evolution, positive selection, and genomic conflicts in shaping the genetic and phenotypic architectures of polygenic human diseases. Strong recent selection in human populations can create and maintain genetically based disease risk primarily through three processes: increased scope for dysregulation from recent human adaptations, divergent optima generated by intraspecific genomic conflicts, and transient or stable deleterious by-products of positive selection caused by antagonistic pleiotropy, ultimately due to trade-offs at the levels of molecular genetics, development, and physiology. Human disease due to these processes appears to be concentrated in three sets of phenotypes: cognition and emotion, reproductive traits, and life-history traits related to long life-span. Diverse, convergent lines of evidence suggest that a small set of tissues whose pleiotropic patterns of gene function and expression are under especially strong selection-brain, placenta, testis, prostate, breast, and ovary-has mediated a considerable proportion of disease risk in modern humans.

Evolutionary genomics of human intellectual disability

Previous studies have postulated that X-linked and autosomal genes underlying human intellectual disability may have also mediated the evolution of human cognition. We have conducted the first comprehensive assessment of the extent and patterns of positive Darwinian selection on intellectual disability genes in humans. We report three main findings. First, as noted in some previous reports, intellectual disability genes with primary functions in the central nervous system exhibit a significant concentration to the X chromosome. Second, there was no evidence for a higher incidence of recent positive selection on X-linked than autosomal intellectual disability genes, nor was there a higher incidence of selection on such genes overall, compared to sets of control genes. However, the X-linked intellectual disability genes inferred to be subject to recent positive selection were concentrated in the Rho GTP-ase pathway, a key signaling pathway in neural development and function. Third, among all intellectual disability genes, there was evidence for a higher incidence of recent positive selection on genes involved in DNA repair, but not for genes involved in other functions. These results provide evidence that alterations to genes in the Rho GTP-ase and DNA-repair pathways may play especially-important roles in the evolution of human cognition and vulnerability to genetically-based intellectual disability.

Brca1 is required for embryonic development of the mouse cerebral cortex to normal size by preventing apoptosis of early neural progenitors

The extent of apoptosis of neural progenitors is known to influence the size of the cerebral cortex. Mouse embryos lacking Brca1, the ortholog of the human breast cancer susceptibility gene BRCA1, show apoptosis in the neural tube, but the consequences of this for brain development have not been studied. Here we investigated the role of Brca1 during mouse embryonic cortical development by deleting floxed Brca1 using Emx1-Cre, which leads to conditional gene ablation specifically in the dorsal telencephalon after embryonic day (E) 9.5. The postnatal Brca1-ablated cerebral cortex was substantially reduced in size with regard to both cortical thickness and surface area. Remarkably, although the thickness of the cortical layers (except for the upper-most layer) was decreased, cortical layering as such was essentially unperturbed. High levels of apoptosis were found at E11.5 and E13.5, but dropped to near-control levels by E16.5. The apoptosis at the early stage of neurogenesis occurred in both BrdU pulse-labeled neural progenitors and the neurons derived therefrom. No changes were observed in the mitotic index of apical (neuroepithelial, radial glial) progenitors and basal (intermediate) progenitors, indicating that Brca1 ablation did not affect cell cycle progression. Brca1 ablation did, however, result in the nuclear translocation of p53 in neural progenitors, suggesting that their apoptosis involved activation of the p53 pathway. Our results show that Brca1 is required for the cerebral cortex to develop to normal size by preventing the apoptosis of early cortical progenitors and their immediate progeny.

Growth of cancer cell lines under stem cell-like conditions has the potential to unveil therapeutic targets

Malignant tumors comprise a small proportion of cancer-initiating cells (CIC), capable of sustaining tumor formation and growth. CIC are the main potential target for anticancer therapy. However, the identification of molecular therapeutic targets in CIC isolated from primary tumors is an extremely difficult task. Here, we show that after years of passaging under differentiating conditions, glioblastoma, mammary carcinoma, and melanoma cell lines contained a fraction of cells capable of forming spheroids upon in vitro growth under stem cell-like conditions. We found an increased expression of surface markers associated with the stem cell phenotype and of oncogenes in cell lines and clones cultured as spheroids vs. adherent cultures. Also, spheroid-forming cells displayed increased tumorigenicity and an altered pattern of chemosensitivity. Interestingly, also from single retrovirally marked clones, it was possible to isolate cells able to grow as spheroids and associated with increased tumorigenicity. Our findings indicate that short-term selection and propagation of CIC as spheroid cultures from established cancer cell lines, coupled with gene expression profiling, represents a suitable tool to study and therapeutically target CIC: the notion of which genes have been down-regulated during growth under differentiating conditions will help find CIC-associated therapeutic targets.

Differential effects of Th1, monocyte/macrophage and Th2 cytokine mixtures on early gene expression for glial and neural-related molecules in central nervous system mixed glial cell cultures: neurotrophins, growth factors and structural proteins

Background

In multiple sclerosis, inflammatory cells are found in both active and chronic lesions, and it is increasingly clear that cytokines are involved directly and indirectly in both formation and inhibition of lesions. We propose that cytokine mixtures typical of Th1 or Th2 lymphocytes, or monocyte/macrophages each induce unique molecular changes in glial cells.

Methods

To examine changes in gene expression that might occur in glial cells exposed to the secreted products of immune cells, we have used gene array analysis to assess the early effects of different cytokine mixtures on mixed CNS glia in culture. We compared the effects of cytokines typical of Th1 and Th2 lymphocytes and monocyte/macrophages (M/M) on CNS glia after 6 hours of treatment.

Results

In this paper we focus on changes with potential relevance for neuroprotection and axon/glial interactions. Each mixture of cytokines induced a unique pattern of changes in genes for neurotrophins, growth and maturation factors and related receptors; most notably an alternatively spliced form of trkC was markedly downregulated by Th1 and M/M cytokines, while Th2 cytokines upregulated BDNF. Genes for molecules of potential importance in axon/glial interactions, including cell adhesion molecules, connexins, and some molecules traditionally associated with neurons showed significant changes, while no genes for myelin-associated genes were regulated at this early time point. Unexpectedly, changes occurred in several genes for proteins initially associated with retina, cancer or bone development, and not previously reported in glial cells.

Conclusion

Each of the three cytokine mixtures induced specific changes in gene expression that could be altered by pharmacologic strategies to promote protection of the central nervous system.

BRCA1 may modulate neuronal cell cycle re-entry in Alzheimer disease

In Alzheimer disease, neuronal degeneration and the presence of neurofibrillary tangles correlate with the severity of cognitive decline. Neurofibrillary tangles contain the antigenic profile of many cell cycle markers, reflecting a re-entry into the cell cycle by affected neurons. However, while such a cell cycle re-entry phenotype is an early and consistent feature of Alzheimer disease, the mechanisms responsible for neuronal cell cycle are unclear. In this regard, given that a dysregulated cell cycle is a characteristic of cancer, we speculated that alterations in oncogenic proteins may play a role in neurodegeneration. To this end, in this study, we examined brain tissue from cases of Alzheimer disease for the presence of BRCA1, a known regulator of cell cycle, and found intense and specific localization of BRCA1 to neurofibrillary tangles, a hallmark lesion of the disease. Analysis of clinically normal aged brain tissue revealed systematically less BRCA1, and surprisingly in many cases with apparent phosphorylated tau-positive neurofibrillary tangles, BRCA1 was absent, yet BRCA1 was present in all cases of Alzheimer disease. These findings not only further define the cell cycle reentry phenotype in Alzheimer disease but also indicate that the neurofibrillary tangles which define Alzheimer disease may have a different genesis from the neurofibrillary tangles of normal aging.

A t(1;19)(q10;p10) mediates the combined deletions of 1p and 19q and predicts a better prognosis of patients with oligodendroglioma

Combined deletion of chromosomes 1p and 19q is associated with improved prognosis and responsiveness to therapy in patients with anaplastic oligodendroglioma. The deletions usually involve whole chromosome arms, suggesting a t(1;19)(q10;p10). Using stem cell medium, we cultured a few tumors. Paraffin-embedded tissue was obtained from 21 Mayo Clinic patients and 98 patients enrolled in 2 North Central Cancer Treatment Group (NCCTG) low-grade glioma trials. Interphase fusion of CEP1 and 19p12 probes detected the t(1;19). 1p/19q deletions were evaluated by fluorescence in situ hybridization. Upon culture, one oligodendroglioma contained an unbalanced 45,XX,t(1;19)(q10;p10). CEP1/19p12 fusion was observed in all metaphases and 74% of interphase nuclei. Among Mayo Clinic oligodendrogliomas, the prevalence of fusion was 81%. Among NCCTG patients, CEP1/19p12 fusion prevalence was 55%, 47%, and 0% among the oligodendrogliomas, mixed oligoastrocytomas, and astrocytomas, respectively. Ninety-one percent of NCCTG gliomas with 1p/19q deletion and 12% without 1p/19q deletion had CEP1/19p12 fusion (P < 0.001, chi(2) test). The median overall survival (OS) for all patients was 8.1 years without fusion and 11.9 years with fusion (P = 0.003). The median OS for patients with low-grade oligodendroglioma was 9.1 years without fusion and 13.0 years with fusion (P = 0.01). Similar significant median OS differences were observed for patients with combined 1p/19q deletions. The absence of alterations was associated with a significantly shorter OS for patients who received higher doses of radiotherapy. Our results strongly suggest that a t(1;19)(q10;p10) mediates the combined 1p/19q deletion in human gliomas. Like combined 1p/19q deletion, the 1;19 translocation is associated with superior OS and progression-free survival in low-grade glioma patients.

Positive selection in the evolution of cancer

We hypothesize that forms of antagonistic coevolution have forged strong links between positive selection at the molecular level and increased cancer risk. By this hypothesis, evolutionary conflict between males and females, mothers and foetuses, hosts and parasites, and other parties with divergent fitness interests has led to rapid evolution of genetic systems involved in control over fertilization and cellular resources. The genes involved in such systems promote cancer risk as a secondary effect of their roles in antagonistic coevolution, which generates evolutionary disequilibrium and maladaptation. Evidence from two sources: (1) studies on specific genes, including SPANX cancer/testis antigen genes, several Y-linked genes, the pem homebox gene, centromeric histone genes, the breast cancer gene BRCA1, the angiogenesis gene ANG, cadherin genes, cytochrome P450 genes, and viral oncogenes; and (2) large-scale database studies of selection on different functional categories of genes, supports our hypothesis. These results have important implications for understanding the evolutionary underpinnings of cancer and the dynamics of antagonistically-coevolving molecular systems.

Glucocorticoid hormones decrease proliferation of embryonic neural stem cells through ubiquitin-mediated degradation of cyclin D1

Corticosteroids can influence brain function, and glucocorticoid hormone receptors (GRs) are present in brain tissue. We observed that GR and also mineralocorticoid receptor (MR) are expressed by embryonic rat neural stem cells (NSCs). NSCs in developing ventricular epithelium were positive for GR. Stimulation of cultured NSCs with the specific receptor ligands dexamethasone and corticosterone reduced cell proliferation, shown by 5'-bromo-2-deoxy-uridine labeling. The effect of the hormones was dose dependent and inhibited by the GR blocker mifepristone but not by spironolactone, blocking MR. Dexamethasone inhibited the cell cycle by decreasing the levels of cyclin D1 in NSCs. The hormone-induced decline was inhibited by MG132 (benzyloxycarbonyl-leucyl-leucyl-leucinal), showing an involvement of the ubiquitin proteasome system, In keeping with this, dexamethasone increased the ubiquitination of cyclin D1. In embryonic brain, dexamethasone inhibited cell proliferation of NSCs. This demonstrates that embryonic NSCs are critically influenced by glucocorticoids, which can have long-term effects in the brain.

Inhibition of AF116909 gene expression enhances the differentiation of neural stem cells

OBJECTIVES

Neural stem cells (NSCs) are self-renewed, pluripotent cells that can differentiate into neurons, astrocytes and oligodendrocytes. Such multipotency that allows production of specific types of nerve cells for basic research and therapeutic purposes depends on how these cells are directed in their differentiation. Here, we investigate the function of the AF116909 gene in the differentiation of NSC.

METHODS

NSC culture was isolated from the striatum corpora of embryonic brain tissues in a 14-day pregnant rat. A constructed RNAi (RNA-mediated interference) vector was transfected to knock down the expression of this gene. Afterwards, RT-PCT was applied to examine the presence of endogenous AF116909 mRNA and the effect of RNA interference.

RESULTS

After the knockdown of this gene, we detected that the differentiation rate of cells was enhanced to 80% on the 11th day in comparison with 12% in the control cells transfected with the expression vector alone.

DISCUSSION

These findings suggest that AF116909 functions in inhibiting the differentiation of NSCs, and AF116909 gene-targeting by RNAi provides a useful method to study the differentiation mechanisms of NSCs.

19-Nortestosterone influences neural stem cell proliferation and neurogenesis in the rat brain

Abuse of androgenic anabolic steroids can affect brain function leading to behavioural changes. In this study, the effects of the testosterone analogue, 19-nortestosterone, on rat neural stem cells was examined. The androgen receptor is expressed by cultured embryonic and adult neural stem cells, and is also present in the ventricular epithelium during development and in the adult brain in, among others, dentate gyrus. In neural stem cells stimulated with epidermal growth factor, nandrolone reduced cell proliferation, especially in adult ones. The decrease was abolished by flutamide, a receptor antagonist. Nandrolone also decreased the BrdU labelling of neural stem cells in the dentate gyrus, demonstrating an effect of the hormone on cell proliferation in vivo. The effect of nandrolone was observed with both female and male rats but it was more pronounced in pregnant rats, indicating an involvement of oestrogen in nandrolone action. Nandrolone also decreased the number of newly born neuronal cells in the dentate gyrus of male rats. The results show that nandrolone has important effects on the proliferation and differentiation of neural stem cells expressing the cognate androgen receptor. The data show that the use of nandrolone may severely affect the formation of neural stem cells and could therefore have long-term negative consequences in the brain.

Chromatin remodeling and histone modification in the conversion of oligodendrocyte precursors to neural stem cells

We showed previously that purified rat oligodendrocyte precursor cells (OPCs) can be induced by extracellular signals to convert to multipotent neural stem-like cells (NSLCs), which can then generate both neurons and glial cells. Because the conversion of precursor cells to stem-like cells is of both intellectual and practical interest, it is important to understand its molecular basis. We show here that the conversion of OPCs to NSLCs depends on the reactivation of the sox2 gene, which in turn depends on the recruitment of the tumor suppressor protein Brca1 and the chromatin-remodeling protein Brahma (Brm) to an enhancer in the sox2 promoter. Moreover, we show that the conversion is associated with the modification of Lys 4 and Lys 9 of histone H3 at the same enhancer. Our findings suggest that the conversion of OPCs to NSLCs depends on progressive chromatin remodeling, mediated in part by Brca1 and Brm.

Choroid plexus ependymal cells host neural progenitor cells in the rat

We previously demonstrated that choroid plexus epithelial (modified ependymal) cells (CPECs) differentiated into astrocytes after grafting into the spinal cord. In the present study, we examined whether CPECs from rats at postnatal 1 day (P1), 7 day (P7), and 8 weeks (P8W) can function as neural progenitor cells that give rise to neurons and glial cells. Cell spheres were produced in cultures of whole tissue of the choroid plexus from the fourth ventricle of rats at each postnatal period. beta-tubulin class III (Tuj-1), glial fibrillary acid protein (GFAP)-, and O4-positive cells differentiated from cell spheres in the differentiation medium. We produced a monoclonal antibody 3E6 specifically labeling microvilli of CPECs. Using this monoclonal antibody, CPECs were isolated from the choroid plexus of P8W rats by cell sorter (FACS). Immunocytochemistry confirmed that there was no contamination from fibroblasts, endothelial cells, macrophages, or Schwann cells in the FACS-isolated 3E6-labeled cells. Cell spheres formed in the cultures of these 3E6-labeled CPECs. After expansion, these cell spheres gave rise to Tuj-1- (5%), GFAP- (45%), and O4-positive cells (0.16%). The remaining cells (45%) were unlabeled neural or glial markers. Some CPECs of the P8W rat were immunohistochemically stained with lineage-associated markers of Musashi-1 and epidermal growth factor-receptor (EGF-R). In addition, infusion of EGF or fibroblast growth factor-2 (FGF2) into the ventricle increased the number of bromodeoxyuridine (BrdU)-positive cells among CPECs from 0.03% (untreated) to 1.14% (38-fold, EGF) and 1.03% (35-fold, FGF2), respectively. These findings indicate that neural progenitor cells exist among CPECs in the rat.

BRCA1 functions as a breast stem cell regulator

BRCA1 is an important susceptibility gene for breast cancer, which confers substantial lifetime risks of breast cancer, particularly in the pre-menopausal age group. Typically, carriers of BRCA1 mutations develop breast tumours that grow rapidly and are high grade and oestrogen receptor negative. They also possess a basal epithelial phenotype, as defined by cytokeratin expression, that is not present in most breast cancers. It has recently been proposed that the adult breast stem cell expresses only basal keratins. Others have indicated a CD44 positive, CD24 negative phenotype for breast cancer stem cells. In this paper, I argue that the biology of human BRCA1 and its rodent homologues and the clinicopathological features of breast cancer related to BRCA1 support the notion that one of the key functions of BRCA1 is to act as a stem cell regulator. This has implications for the management of carriers of mutations of BRCA1, in part because support for the role of BRCA1 as a stem cell regulator would emphasise the distinct nature of breast cancer related to BRCA1.

Cystatin-B is expressed by neural stem cells and by differentiated neurons and astrocytes

Mutation in the gene encoding cystatin-B (CSTB) has been shown to cause progressive myoclonus epilepsy. Mice with a gene deletion of CSTB exhibit increased apoptosis of specific neurons but the physiological role of CSTB in brain cells is not fully understood. In the present study, we have examined the expression of CSTB in neural stem cells (NSC) and in differentiating mature brain cells. The results show that CSTB is present in embryonic and adult NSC and in the neuroepithelium. CSTB was expressed by both neurons and glial cells differentiated from NSC and in hippocampal cultures. CSTB localized mainly to the nucleus in NSC and in neurons, whilst in astrocytes CSTB was also in the cytoplasm. Double labeling showed that CSTB was present in the lysosomes in glial cells. The results demonstrate a nuclear expression of CSTB in NSC and in neurons, suggesting novel function for this molecule.