Disc1 regulates both ß-catenin-mediated and noncanonical Wnt signaling during vertebrate embryogenesis.

Disc1 is a schizophrenia risk gene that engages multiple signaling pathways during neurogenesis and brain development. Using the zebrafish as a tool, we analyze the function of zebrafish Disc1 (zDisc1) at the earliest stages of brain and body development. We define a "tool" as a biological system that gives insight into mechanisms underlying a human disorder, although the system does not phenocopy the disorder. A zDisc1 peptide binds to GSK3ß, and zDisc1 directs early brain development and neurogenesis, by promoting ß-catenin-mediated Wnt signaling and inhibiting GSK3ß activity. zDisc1 loss-of-function embryos additionally display a convergence and extension phenotype, demonstrated by abnormal movement of dorsolateral cells during gastrulation, through changes in gene expression, and later through formation of abnormal, U-shaped muscle segments, and a truncated tail. These phenotypes are caused by alterations in the noncanonical Wnt pathway, via Daam and Rho signaling. The convergence and extension phenotype can be rescued by a dominant negative GSK3ß construct, suggesting that zDisc1 inhibits GSK3ß activity during noncanonical Wnt signaling. This is the first demonstration that Disc1 modulates the noncanonical Wnt pathway and suggests a previously unconsidered mechanism by which Disc1 may contribute to the etiology of neuropsychiatric disorders.

Brain activity patterns in high-throughput electrophysiology screen predict both drug efficacies and side effects.

Neurological drugs are often associated with serious side effects, yet drug screens typically focus only on efficacy. We demonstrate a novel paradigm utilizing high-throughput in vivo electrophysiology and brain activity patterns (BAPs). A platform with high sensitivity records local field potentials (LFPs) simultaneously from many zebrafish larvae over extended periods. We show that BAPs from larvae experiencing epileptic seizures or drug-induced side effects have substantially reduced complexity (entropy), similar to reduced LFP complexity observed in Parkinson's disease. To determine whether drugs that enhance BAP complexity produces positive outcomes, we used light pulses to trigger seizures in a model of Dravet syndrome, an intractable genetic epilepsy. The highest-ranked compounds identified by BAP analysis exhibit far greater anti-seizure efficacy and fewer side effects during subsequent in-depth behavioral assessment. This high correlation with behavioral outcomes illustrates the power of brain activity pattern-based screens and identifies novel therapeutic candidates with minimal side effects.

First evidence of prothymosin alpha in a non-mammalian vertebrate and its involvement in the spermatogenesis of the frog Rana esculenta.

A cDNA clone encoding for a Prothymosin alpha (Prot-alpha) has been isolated and characterized from the testis of the frog Rana esculenta. Frog Prothymosin alpha (fProt-alpha) predicted a 109 amino acid protein with a high homology to the mammalian Prot-alpha. fProt-alpha contains 28 aspartic and 25 glutamic acid residues and presents the typical basic KKQK amino acid sequence in the close carboxyl terminal region. Northern blot analysis revealed that fProt-alpha is highly expressed in the testis. A different expression of fProt-alpha transcript was found during the frog reproductive cycle with a peak in September/October in concomitance with germ cell maturation, strongly suggesting a role for this protein in the testicular activity. In situ hybridization evidenced that the only germ cells expressing fProt-alpha are the primary and secondary spermatocytes; in addition, the hybridization signal was stronger in the October testis. Taken together, our findings indicate that fProt-alpha might contribute to the efficiency of frog spermatogenesis with a role during the meiosis. This study is the first report on the isolation and characterization of a Prot-alpha in a non-mammalian vertebrate. In addition, our results indicate that the testis of the frog R. esculenta may be a useful model to increase the knowledge concerning the physiological role of Prot-alpha in vertebrates.

Extracellular vesicles modulate the glioblastoma microenvironment via a tumor suppression signaling network directed by miR-1.

Extracellular vesicles have emerged as important mediators of intercellular communication in cancer, including by conveying tumor-promoting microRNAs between cells, but their regulation is poorly understood. In this study, we report the findings of a comparative microRNA profiling and functional analysis in human glioblastoma that identifies miR-1 as an orchestrator of extracellular vesicle function and glioblastoma growth and invasion. Ectopic expression of miR-1 in glioblastoma cells blocked in vivo growth, neovascularization, and invasiveness. These effects were associated with a role for miR-1 in intercellular communication in the microenvironment mediated by extracellular vesicles released by cancer stem-like glioblastoma cells. An extracellular vesicle-dependent phenotype defined by glioblastoma invasion, neurosphere growth, and endothelial tube formation was mitigated by loading miR-1 into glioblastoma-derived extracellular vesicles. Protein cargo in extracellular vesicles was characterized to learn how miR-1 directed extracellular vesicle function. The mRNA encoding Annexin A2 (ANXA2), one of the most abundant proteins in glioblastoma-derived extracellular vesicles, was found to be a direct target of miR-1 control. In addition, extracellular vesicle-derived miR-1 along with other ANXA2 extracellular vesicle networking partners targeted multiple pro-oncogenic signals in cells within the glioblastoma microenvironment. Together, our results showed how extracellular vesicle signaling promotes the malignant character of glioblastoma and how ectopic expression of miR-1 can mitigate this character, with possible implications for how to develop a unique miRNA-based therapy for glioblastoma management.

Efficient shRNA-mediated inhibition of gene expression in zebrafish.

Despite the broad repertoire of loss of function (LOF) tools available for use in the zebrafish, there remains a need for a simple and rapid method that can inhibit expression of genes at later stages. RNAi would fulfill that role, and a previous report (Dong et al. 2009) provided encouraging data. The goal of this study was to further address the ability of expressed shRNAs to inhibit gene expression. This included quantifying RNA knockdown, testing specificity of shRNA effects, and determining whether tissue-specific LOF could be achieved. Using an F0 transgenic approach, this report demonstrates that for two genes, wnt5b and zDisc1, each with described mutant and morphant phenotypes, shRNAs efficiently decrease endogenous RNA levels. Phenotypes elicited by shRNA resemble those of mutants and morphants, and are reversed by expression of cognate RNA, further demonstrating specificity. Tissue-specific expression of zDisc1 shRNAs in F0 transgenics demonstrates that conditional LOF can be readily obtained. These results suggest that shRNA expression presents a viable approach for rapid inhibition of zebrafish gene expression.

Zebrafish homologs of genes within 16p11.2, a genomic region associated with brain disorders, are active during brain development, and include two deletion dosage sensor genes.

Deletion or duplication of one copy of the human 16p11.2 interval is tightly associated with impaired brain function, including autism spectrum disorders (ASDs), intellectual disability disorder (IDD) and other phenotypes, indicating the importance of gene dosage in this copy number variant region (CNV). The core of this CNV includes 25 genes; however, the number of genes that contribute to these phenotypes is not known. Furthermore, genes whose functional levels change with deletion or duplication (termed 'dosage sensors'), which can associate the CNV with pathologies, have not been identified in this region. Using the zebrafish as a tool, a set of 16p11.2 homologs was identified, primarily on chromosomes 3 and 12. Use of 11 phenotypic assays, spanning the first 5 days of development, demonstrated that this set of genes is highly active, such that 21 out of the 22 homologs tested showed loss-of-function phenotypes. Most genes in this region were required for nervous system development - impacting brain morphology, eye development, axonal density or organization, and motor response. In general, human genes were able to substitute for the fish homolog, demonstrating orthology and suggesting conserved molecular pathways. In a screen for 16p11.2 genes whose function is sensitive to hemizygosity, the aldolase a (aldoaa) and kinesin family member 22 (kif22) genes were identified as giving clear phenotypes when RNA levels were reduced by ∼50%, suggesting that these genes are deletion dosage sensors. This study leads to two major findings. The first is that the 16p11.2 region comprises a highly active set of genes, which could present a large genetic target and might explain why multiple brain function, and other, phenotypes are associated with this interval. The second major finding is that there are (at least) two genes with deletion dosage sensor properties among the 16p11.2 set, and these could link this CNV to brain disorders such as ASD and IDD.

Common DISC1 polymorphisms disrupt Wnt/GSK3ß signaling and brain development.

Disrupted in Schizophrenia-1 (DISC1) is a candidate gene for psychiatric disorders and has many roles during brain development. Common DISC1 polymorphisms (variants) are associated with neuropsychiatric phenotypes including altered cognition, brain structure, and function; however, it is unknown how this occurs. Here, we demonstrate using mouse, zebrafish, and human model systems that DISC1 variants are loss of function in Wnt/GSK3ß signaling and disrupt brain development. The DISC1 variants A83V, R264Q, and L607F, but not S704C, do not activate Wnt signaling compared with wild-type DISC1 resulting in decreased neural progenitor proliferation. In zebrafish, R264Q and L607F could not rescue DISC1 knockdown-mediated aberrant brain development. Furthermore, human lymphoblast cell lines endogenously expressing R264Q displayed impaired Wnt signaling. Interestingly, S704C inhibited the migration of neurons in the developing neocortex. Our data demonstrate DISC1 variants impair Wnt signaling and brain development and elucidate a possible mechanism for their role in neuropsychiatric phenotypes.

Characterization and classification of zebrafish brain morphology mutants.

The mechanisms by which the vertebrate brain achieves its three-dimensional structure are clearly complex, requiring the functions of many genes. Using the zebrafish as a model, we have begun to define genes required for brain morphogenesis, including brain ventricle formation, by studying 16 mutants previously identified as having embryonic brain morphology defects. We report the phenotypic characterization of these mutants at several timepoints, using brain ventricle dye injection, imaging, and immunohistochemistry with neuronal markers. Most of these mutants display early phenotypes, affecting initial brain shaping, whereas others show later phenotypes, affecting brain ventricle expansion. In the early phenotype group, we further define four phenotypic classes and corresponding functions required for brain morphogenesis. Although we did not use known genotypes for this classification, basing it solely on phenotypes, many mutants with defects in functionally related genes clustered in a single class. In particular, Class 1 mutants show midline separation defects, corresponding to epithelial junction defects; Class 2 mutants show reduced brain ventricle size; Class 3 mutants show midbrain-hindbrain abnormalities, corresponding to basement membrane defects; and Class 4 mutants show absence of ventricle lumen inflation, corresponding to defective ion pumping. Later brain ventricle expansion requires the extracellular matrix, cardiovascular circulation, and transcription/splicing-dependent events. We suggest that these mutants define processes likely to be used during brain morphogenesis throughout the vertebrates. Anat Rec, 2009. (c) 2008 Wiley-Liss, Inc.

The expression level of frog relaxin mRNA (fRLX), in the testis of Rana esculenta, is influenced by testosterone.

Frog relaxin (fRLX) belongs to the relaxin/insulin gene family present in the testis of Rana esculenta and is specifically expressed by Leydig cells. Since the expression of fRLX transcript changes during the reproductive cycle and is more abundant when circulating levels of androgens are relatively high, we investigated the effect(s) of testosterone and its antagonist (cyproterone acetate, CPA) on its expression pattern, in the testis of the frog Rana esculenta. Results from in vivo and in vitro experiments demonstrate that testosterone strongly induces a significant increase of fRLX mRNA expression in frog testes and, this effect is counteracted by CPA, supporting the existence of intratesticular (autocrine/paracrine) mechanisms of action. Interestingly, in both the control and testosterone-treated testes, fRLX mRNA expression was markedly decreased 24 h post-treatment, as compared to that measured at 2 h and 8 h post-treatment, suggesting that factor(s), other than testosterone, may act(s) in controlling its expression. In addition, RT-PCR analysis and in situ hybridization performed on frog testis injected with CPA for 15 days, on alternate days, showed a strong decrease of fRLX expression, suggesting that CPA counteracts the effect of testosterone on fRLX expression. Taken together our results strongly indicate that changes in the production, by the Leydig cells, of both testosterone and fRLX may represent a marker for the study of Leydig cell activity in the testis of the frog Rana esculenta.

Ethane 1,2-dimethane sulphonate is a useful tool for studying cell-to-cell interactions in the testis of the frog, Rana esculenta.

Ethane 1,2-dimethane sulphonate (EDS), a toxin which specifically destroys Leydig cells (LC), has been used to study cellular interactions in the testis of the frog Rana esculenta. Animals received three consecutive EDS injections and were sacrificed on day 4, 8, and 28 from the first injection. No significant morphological differences were observed between present observation and that obtained, in a previous experiment, after four consecutive EDS injections. In fact, on day 4, in the germinal tubules adjacent to apparently normal LC, Sertoli cells surrounding primary spermatogonia (I SPG) show heterochromatic nuclei and loss of cellular adhesion. Interestingly, I SPG surrounded by the heterochromatic Sertoli cells present grossly swollen mitochondria with ballooned cristae. On day 8, sometimes in the interstitium many LC appear strongly damaged and the germinal tubules appear disorganized; the only cell type still distinguishable is the I SPG. On day 28 from the first EDS injection a new population of LC reappear in the interstitium and spermatogenesis normalizes. These data confirm the close relationship between the interstitial and the geminal compartments. Immunocytochemical data obtained using a polyclonal antibody anticonnexin-43 (Cx-43, the most abundant Cx found in mammalian testis) demonstrate the presence of Cx-43 in the frog testis. In particular, Cx-43 is present between LC in the interstitium, between Sertoli and germ cells in the cysts and between Sertoli cells and I SPG. Cx-43 immunopositivity sharply decreases on day 4 from the first EDS injection simultaneously with the loss of cellular adhesion between Sertoli and germ cells. On day 8 and 28 from the first EDS injection Cx-43, immunopositivity is restored and, this data is also supported by Western blot analysis. Our data provide, for the first time, evidence that Cx-43 protein is present in the frog testis and confirm that EDS is a useful tool for studying cellular communication at the paracrine pathway or through direct contact depending on the gap junctional pathway in R. esculenta testis

Effects of melatonin treatment on Leydig cell activity in the testis of the frog Rana esculenta.

This study was conducted to verify the effect(s) of melatonin treatment on frog Leydig cells. Morphological observation after melatonin treatment indicates that many frog Leydig cells show degenerative changes (i.e. heterochromatic nuclei, loss of cellular adhesion) while in adjacent germinal tubules several Sertoli cells show heterochromatic nuclei, confirming the presence of a paracrine effect between interstitial and germinal compartments. The effect of melatonin on frog Leydig cell steroidogenesis was investigated in in vitro experiments; after 6 h of incubation melatonin severely inhibits both control and GnRH-induced testosterone secretion. In addition, in order to verify the effect of indolamine on frog Leydig cell activity, we investigated, by in situ hybridization, the presence of frog relaxin (fRLX, a transcript specifically expressed by these cells) in the testes of melatonin-injected animals after 48 h. fRLX signal completely disappeared from the testis of melatonin- injected frogs. The results of the present study indicate that melatonin treatment provokes Leydig cell morphological changes, blocks GnRH-antagonist-induced testosterone secretion and decreases fRLX expression. Taken together these results strongly indicate that melatonin acts on Leydig cells in the testis of the frog Rana esculenta.

Temporal and spatial localization of prothymosin alpha transcript in the Harderian gland of the frog, Rana esculenta.

The Harderian gland (hg) is the only orbital gland of the frog Rana esculenta, and it has the essential function of lubricating the eyes. The hg secretory activity is seasonal, showing the highest value in summer. There is, at present, no data on gene expression of the frog hg. This study reports, for the first time, on the temporal and spatial expression of a cDNA clone encoding for the prothymosin alpha (Prot-alpha), a highly acidic nuclear protein present in virtually all mammalian cells. Northern blot analysis revealed a single 1.7 kb transcript detected in the frog hg throughout the year, with a lowest expression in September in concomitance with the minimum secretory activity. In situ hybridization indicated that hg secretory cells express Prot-alpha transcript, and the hybridization signal was less intense in the September gland. The constant expression of the frog Prot-alpha mRNA during the whole year suggests a constitutive role for this molecule in the hg. In addition, taking into account that, in mammals, many immunomodulatory functions have been attributed to this protein, it is suggested that frog Prot-alpha might contribute to the hg immunity processes, probably acting as a protective agent against infections of the eyeball. Interestingly, although the presence of Prot-alpha gene in animals other than mammals has been considered to be highly unlikely, the present paper confirms the presence of Prot-alpha transcript in a nonmammalian vertebrate, the frog R. esculenta.