Regulated functional alternative splicing in Drosophila

Université Montpellier 2, UMR 5535, Institut de Génétique Moléculaire de Montpellier, CNRS, 1919 Route de Mende, 34293 Montpellier cedex 05, France.
Nucleic Acids Research (Impact Factor: 9.11). 09/2011; 40(1):1-10. DOI: 10.1093/nar/gkr648
Source: PubMed


Alternative splicing expands the coding capacity of metazoan genes, and it was largely genetic studies in the fruit-fly Drosophila melanogaster that established the principle that regulated alternative splicing results in tissue- and stage-specific protein isoforms
with different functions in development. Alternative splicing is particularly prominent in germ cells, muscle and the central
nervous system where it modulates the expression of various proteins including cell-surface molecules and transcription factors.
Studies in flies have given us numerous insights into alternative splicing in terms of upstream regulation, the exquisite
diversity of their forms and the key differential cellular functions of alternatively spliced gene products. The current inundation
of transcriptome sequencing data from Drosophila provides an unprecedented opportunity to gain a comprehensive view of alternative splicing.

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Available from: Jamal Tazi
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    • "Alternative ''cassette'' exon splicing is thought to represent the most frequent type of AS in animals in which splice sites in primary transcripts are differentially utilized to produce different protein isoforms, often in a developmental or tissue-specific manner. The multilevel splicing cascade that regulates sex determination and sex-specific development in Drosophila is the best-characterized system of AS during cell differentiation (Lalli et al. 2003; Salz and Erickson 2010; Venables et al. 2012). In this system, the primary determinant of sex is the ratio of X chromosomes to sets of autosomes (X:A), which leads to a cascade of sexspecific differential mRNA splicing events initiated by the splicing factor SXL. Thus, SXL acts as a binary switch that determines whether a fruit fly will develop as a male or a female. "
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    • "This makes Drosophila particularly well-suited to modeling and studying muscular disorders (García-López et al., 2008; Lloyd and Taylor, 2010; Mosqueira et al., 2010; Timmerman and Sanyal, 2012). Regarding alternative splicing, although important functional conservation occurs between Drosophila and mammals (Venables et al., 2012), dissimilarities have also been described (Mount et al., 1992; Irion, 2012). Results obtained here from the DM1 spliceosensor flies suggested, in this specific condition, that there were only slight alternative splicing machinery differences, hence, still allowing for robust disease mirroring. "
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    ABSTRACT: Alternative splicing of pre-messenger RNAs is an important mechanism to achieve correct cellular function in higher eukaryotes. It is known that a growing number of human genetic diseases involve important splicing defects directly connected to pathologic signs. In myotonic dystrophy type 1 (DM1) it is proposed that several clinical manifestations are consequence of tissue-specific missplicing of numerous genes, triggered by a RNA gain-of-function and resultant deregulation of specific RNA-binding factors, being remarkable the nuclear sequestration of muscleblind-like family factors (MBNL1-3). Thus, identification of chemical modulators of splicing events is thought to have beneficial impacts towards the development of first valid therapy for DM1 patients. For this purpose, we generated and validated transgenic flies, which contained a luciferase reporter-based system coupled to the expression of MBNL1-reliant splicing events deregulated in DM1 patients on a relevant disease tissue (spliceosensor flies). We then developed an innovative 96-well plate screening platform to carry out in vivo high throughput pharmacological screening (HTS) with the spliceosensor model. After a large-scale evaluation (>16,000 chemical entities) several reliable splicing modulators (hits) were identified. Hit validation steps recognized separate DM1-linked therapeutic traits for some of them, which corroborated the feasibility of the approach described herein for revealing promising drug candidates by indirect improving of DM1 missplicing. The powerful Drosophila-based tool for innovative chemical screening is suitable for its use with other disease models displaying abnormal alternative splicing coupled to a luminescent reporter-based system as final read-out, thus offering widespread uses in drug discovery.
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    • "First, the central nervous system of many species is highly complex in architecture and is a rich source of alternative transcripts [17]. Additionally, the Drosophila sex determination hierarchy is a classical model of regulated alternative splicing [18]. Three members of this hierarchy, Sex-lethal (Sxl), transformer (tra), and male specific lethal 2 (msl-2) encode broadly expressed alternatively spliced mRNAs. "
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