Neuronal cell type-specific promoter of the α CaM kinase II gene is activated by Zic2, a Zic family zinc finger protein

The Wnt/β-catenin/TCF/Sp5/Zic4 Gene Network That Regulates Head Organizer Activity in Hydra Is Differentially Regulated in Epidermis and Gastrodermis

Hydra head formation depends on an organizing center in which Wnt/β-catenin signaling, that plays an inductive role, positively regulates Sp5 and Zic4, with Sp5 limiting Wnt3/β-catenin expression and Zic4 triggering tentacle formation. Using transgenic lines in which the HySp5 promoter drives eGFP expression in either the epidermis or gastrodermis, we show that Sp5 promoter activity is differentially regulated in each epithelial layer. In intact animals, epidermal HySp5:GFP activity is strong apically and weak along the body column, while in the gastrodermis, it is maximal in the tentacle ring region and maintained at a high level along the upper body column. During apical regeneration, HySp5:GFP is activated early in the gastrodermis and later in the epidermis. Alsterpaullone treatment induces a shift in apical HySp5:GFP expression towards the body column where it forms transient circular figures in the epidermis. Upon β-catenin(RNAi), HySp5:GFP activity is down-regulated in the epidermis while bud-like structures expressing HySp5:GFP in the gastrodermis develop. Sp5(RNAi) reveals a negative Sp5 autoregulation in the epidermis, but not in the gastrodermis. These differential regulations in the epidermis and gastrodermis highlight the distinct architectures of the Wnt/β-catenin/TCF/Sp5/Zic4 network in the hypostome, tentacle base and body column of intact animals, as well as in the buds and apical and basal regenerating tips.

Emerging Perspectives on Gene Therapy Delivery for Neurodegenerative and Neuromuscular Disorders

Neurodegenerative disorders (NDDs), such as Alzheimer's disease (AD) and Parkinson's Disease (PD), are a group of heterogeneous diseases that mainly affect central nervous system (CNS) functions. A subset of NDDs exhibit CNS dysfunction and muscle degeneration, as observed in Gangliosidosis 1 (GM1) and late stages of PD. Neuromuscular disorders (NMDs) are a group of diseases in which patients show primary progressive muscle weaknesses, including Duchenne Muscular Dystrophy (DMD), Pompe disease, and Spinal Muscular Atrophy (SMA). NDDs and NMDs typically have a genetic component, which affects the physiological functioning of critical cellular processes, leading to pathogenesis. Currently, there is no cure or efficient treatment for most of these diseases. More than 200 clinical trials have been completed or are currently underway in order to establish safety, tolerability, and efficacy of promising gene therapy approaches. Thus, gene therapy-based therapeutics, including viral or non-viral delivery, are very appealing for the treatment of NDDs and NMDs. In particular, adeno-associated viral vectors (AAV) are an attractive option for gene therapy for NDDs and NMDs. However, limitations have been identified after systemic delivery, including the suboptimal capacity of these therapies to traverse the blood-brain barrier (BBB), degradation of the particles during the delivery, high reactivity of the patient's immune system during the treatment, and the potential need for redosing. To circumvent these limitations, several preclinical and clinical studies have suggested intrathecal (IT) delivery to target the CNS and peripheral organs via cerebrospinal fluid (CSF). CSF administration can vastly improve the delivery of small molecules and drugs to the brain and spinal cord as compared to systemic delivery. Here, we review AAV biology and vector design elements, different therapeutic routes of administration, and highlight CSF delivery as an attractive route of administration. We discuss the different aspects of neuromuscular and neurodegenerative diseases, such as pathogenesis, the landscape of mutations, and the biological processes associated with the disease. We also describe the hallmarks of NDDs and NMDs as well as discuss current therapeutic approaches and clinical progress in viral and non-viral gene therapy and enzyme replacement strategies for those diseases.

Link between the causative genes of holoprosencephaly: Zic2 directly regulates Tgif1 expression

One of the causal genes for holoprosencephaly (HPE) is ZIC2 (HPE5). It belongs to the zinc finger protein of the cerebellum (Zic) family of genes that share a C2H2-type zinc finger domain, similar to the GLI family of genes. In order to clarify the role of Zic2 in gene regulation, we searched for its direct target genes using chromatin immunoprecipitation (ChIP). We identified TGIF1 (HPE4), another holoprosencephaly-causative gene in humans. We identified Zic2-binding sites (ZBS) on the 5′ flanking region of Tgif1 by in vitro DNA binding assays. ZBS were essential for Zic2-dependent transcriptional activation in reporter gene assays. Zic2 showed a higher affinity to ZBS than GLI-binding sequences. Zic2-binding to the cis-regulatory element near the Tgif1 promoter may be involved in the mechanism underlying forebrain development and incidences of HPE.

Zebrafish Zic Genes Mediate Developmental Signaling

The introduction of genomics into the field of developmental biology led to a vast expansion of knowledge about developmental genes and signaling mechanisms they are involved in. Unlike mammals, the zebrafish features seven Zic genes. This provides an interesting insight into Zic gene evolution. In addition, an unprecedented bioimaging capability of semitransparent zebrafish embryos turns to be a crucial factor in medium- to large-scale analysis of the activity of potential regulatory elements. The Zic family of zinc finger proteins plays an important, relatively well-established, role in the regulation of stem cells and neural development and, in particular, during neural fate commitment and determination. At the same time, some Zic genes are expressed in mesodermal lineages, and their deficiency causes a number of developmental defects in axis formation, establishing body symmetry and cardiac morphogenesis. In stem cells, Zic genes are required to maintain pluripotency by binding to the proximal promoters of pluripotency genes (Oct4, Nanog, Sox2, etc.). During embryogenesis, the dynamic nature of Zic transcriptional regulation is manifested by the interaction of these factors with distal enhancers and other regulatory elements associated with the control of gene transcription and, in particular, with the Nodal and Wnt signaling pathways that play a role in establishing basic organization of the vertebrate body. Zic transcription factors may regulate development through acting alone as well as in combination with other transcription factors. This is achieved due to Zic binding to sites adjacent to the binding sites of other transcription factors, including Gli. This probably leads to the formation of multi-transcription factor complexes associated with enhancers.

The role of Zic genes in inner ear development in the mouse: Exploring mutant mouse phenotypes

BACKGROUND

Murine Zic genes (Zic1-5) are expressed in the dorsal hindbrain and in periotic mesenchyme (POM) adjacent to the developing inner ear. Zic genes are involved in developmental signaling pathways in many organ systems, including the ear, although their exact roles haven't been fully elucidated. This report examines the role of Zic1, Zic2, and Zic4 during inner ear development in mouse mutants in which these Zic genes are affected.

RESULTS

Zic1/Zic4 double mutants don't exhibit any apparent defects in inner ear morphology. By contrast, inner ears from Zic2(kd/kd) and Zic2(Ku/Ku) mutants have severe but variable morphological defects in endolymphatic duct/sac and semicircular canal formation and in cochlear extension in the inner ear. Analysis of otocyst patterning in the Zic2(Ku/Ku) mutants by in situ hybridization showed changes in the expression patterns of Gbx2 and Pax2.

CONCLUSIONS

The experiments provide the first genetic evidence that the Zic genes are required for morphogenesis of the inner ear. Zic2 loss-of-function doesn't prevent initial otocyst patterning but leads to molecular abnormalities concomitant with morphogenesis of the endolymphatic duct. Functional hearing deficits often accompany inner ear dysmorphologies, making Zic2 a novel candidate gene for ongoing efforts to identify the genetic basis of human hearing loss.

Zic2 regulates retinal ganglion cell axon avoidance of ephrinB2 through inducing expression of the guidance receptor EphB1

The navigation of retinal axons to ipsilateral and contralateral targets in the brain depends on the decision to cross or avoid the midline at the optic chiasm, a critical guidance maneuver that establishes the binocular visual pathway. Previous work has identified a specific guidance receptor, EphB1, that mediates the repulsion of uncrossed axons away from its ligand, ephrinB2, at the optic chiasm midline (Williams et al., 2003), and a transcription factor Zic2, that, like EphB1, is required for formation of the ipsilateral retinal projection (Herrera et al., 2003). Although the reported similarities in localization implicated that Zic2 regulates EphB1 (Herrera et al., 2003; Williams et al., 2003; Pak et al., 2004), whether Zic2 drives expression of EphB1 protein has not been elucidated. Here we show that EphB1 protein is expressed in the growth cones of axons from ventrotemporal (VT) retina that project ipsilaterally and that repulsion by ephrinB2 is determined by the presence of this receptor on growth cones. Moreover, ectopic delivery of Zic2 into explants from non-VT retina induces expression of EphB1 mRNA and protein. The upregulated EphB1 receptor protein is localized to growth cones and is functional, because it is sufficient to change retinal ganglion cell axon behavior from extension onto, to avoidance of, ephrinB2 substrates. Our results demonstrate that Zic2 upregulates EphB1 expression and define a link between a transcription factor and expression of a guidance receptor protein essential for axon guidance at the vertebrate midline.

Molecular Mechanism of Learning and Memory Based on the Research for Ca2+/Calmodulin-dependent Protein Kinase II

In the central nervous system (CNS), the synapse is a specialized junctional complex by which axons and dendrites emerging from different neuron intercommunicates. Changes in the efficiency of synaptic transmission are important for a number of aspects of neural function. Much has been learned about the activity-dependent synaptic modifications that are thought to underlie memory storage, but the mechanism by which these modifications are stored remains unclear. Thus, it is important to find and characterize "memory molecules," and "memory apparatus or memory forming apparatus." A good candidate for the storage mechanism is Ca(2+)/calmodulin-dependent protein kinase II (CaM kinase II). CaM kinase II is one of the most prominent protein kinases, present in essentially every tissue but most concentrated in the brain. Neuronal CaM kinase II regulates important neuronal functions, including neurotransmitter synthesis, neurotransmitter release, modulation of ion channel activity, cellular transport, cell morphology and neurite extension, synaptic plasticity, learning and memory, and gene expression. Studies concerning this kinase open a door of the molecular basis of nerve function, especially learning and memory, and indicate one direction for the studies in the field of neuroscience. This review presents molecular structure, properties and functions of CaM kinase II, as a major component of neuron, which are mainly developed in our laboratory.

Emerging roles for zic genes in early development

Members of the Zic family of zinc finger transcription factors play critical roles in a variety of developmental processes. They are involved in development of neural tissues and the neural crest, in left-right axis patterning, in somite development, and in formation of the cerebellum. In addition to their roles in cell-fate specification, zic genes also promote cell proliferation. Further, they are expressed in postmitotic cells of the cerebellum and in retinal ganglion cells. Efforts to determine the role of individual zic genes within an array of developmental and cellular processes are complicated by overlapping patterns of zic gene expression and strong sequence conservation within this gene family. Nevertheless, substantial progress has been made. This review summarizes our knowledge of the molecular events that govern the activities of zic family members, including emerging relationships between upstream signaling pathways and zic genes. In addition, advancements in our understanding of the molecular events downstream of Zic transcription factors are reviewed. Despite significant progress, however, much remains to be learned regarding the mechanisms through which zic genes exert their function in a variety of different contexts.

Array-based profiling of reference-independent methylation status (aPRIMES) identifies frequent promoter methylation and consecutive downregulation of ZIC2 in pediatric medulloblastoma

Existing microarray-based approaches for screening of DNA methylation are hampered by a number of shortcomings, such as the introduction of bias by DNA copy-number imbalances in the test genome and negligence of tissue-specific methylation patterns. We developed a method designated array-based profiling of reference-independent methylation status (aPRIMES) that allows the detection of direct methylation status rather than relative methylation. Array-PRIMES is based on the differential restriction and competitive hybridization of methylated and unmethylated DNA by methylation-specific and methylation-sensitive restriction enzymes, respectively. We demonstrate the accuracy of aPRIMES in detecting the methylation status of CpG islands for different states of methylation. Application of aPRIMES to the DNA from desmoplastic medulloblastomas of monozygotic twins showed strikingly similar methylation profiles. Additional analysis of 18 sporadic medulloblastomas revealed an overall correlation between highly methylated tumors and poor clinical outcome and identified ZIC2 as a frequently methylated gene in pediatric medulloblastoma.

Rat leucine-rich protein binds and activates the promoter of the beta isoform of Ca2+/calmodulin-dependent protein kinase II gene

We previously found the neuronal cell-type specific promoter and binding partner of the beta isoform of Ca(2+)/calmodulin-dependent protein kinase II (beta CaM kinase II) in rat brain [Donai, H., Morinaga, H., Yamauchi, T., 2001. Genomic organization and neuronal cell type specific promoter activity of beta isoform of Ca(2+)/calmodulin-dependent protein kinase II of rat brain. Mol. Brain Res. 94, 35-47]. In the present study, we purified a protein that binds specifically a promoter region of beta CaM kinase II gene from a nuclear extract of the rat cerebellum using DEAE-cellulose column chromatography, ammonium sulfate fractionation, gel filtration and polyacrylamide gel electrophoresis. The purified protein was identified as rat leucine-rich protein 157 (rLRP157) using tandem mass spectrometry. Then, we prepared its cDNA by reverse transcriptase-polymerase chain reaction (RT-PCR) from poly(A)(+)RNA of rat cerebellum. The rLRP157 cDNA was introduced into mouse neuroblastomaxrat glioma hybrid NG108-15 cells, and cells stably expressing rLRP157 (NG/LRP cells) were isolated. Binding of rLRP157 with the promoter sequence was confirmed by electrophoretic mobility shift assay using nuclear extract of NG/LRP cells. A luciferase reporter gene containing a promoter of beta CaM kinase II was transiently expressed in NG/LRP cells. Under the conditions, the promoter activity was enhanced about 2.6-fold in NG/LRP cells as compared with wild-type cells. The expression of rLRP157 mRNA was paralleled with that of beta CaM kinase II in the adult and embryo rat brain detected by in situ hybridization. Nuclear localization of rLRP157 was confirmed using GFP-rLRP157 fusion protein investigated under a confocal microscope. These results indicate that rLRP157 is one of the proteins binding to, and regulating the activity of, the promoter of beta CaM kinase II.