Abstract
The 2.2 Mb long dystrophin (DMD) gene, the largest gene in the human genome, corresponds to roughly 0.1% of the entire human DNA sequence. Mutations in this gene cause Duchenne muscular dystrophy and other milder X-linked, recessive dystrophinopathies. Using a custom-made tiling array, specifically designed for the DMD locus, we identified a variety of novel long non-coding RNAs (lncRNAs), both sense and antisense oriented, whose expression profiles mirror that of DMD gene. Importantly, these transcripts are intronic in origin and specifically localized to the nucleus and are transcribed contextually with dystrophin isoforms or primed by MyoD-induced myogenic differentiation. Furthermore, their forced ectopic expression in both human muscle and neuronal cells causes a specific and negative regulation of endogenous dystrophin full length isoforms and significantly down-regulate the activity of a luciferase reporter construct carrying the minimal promoter regions of the muscle dystrophin isoform. Consistent with this apparently repressive role, we found that, in muscle samples of dystrophinopathic female carriers, lncRNAs expression levels inversely correlate with those of muscle full length DMD isoforms. Overall these findings unveil an unprecedented complexity of the transcriptional pattern of the DMD locus and reveal that DMD lncRNAs may contribute to the orchestration and homeostasis of the muscle dystrophin expression pattern by either selective targeting and down-modulating the dystrophin promoter transcriptional activity.
Highlights
DMD Gene Micro Fluidic Card (FluiDMD v1.1) Analysis We explored all transcripts originating from the DMD locus, including the long non-coding RNAs (lncRNAs) identified by our array as well as the whole exome of the dystrophin gene, using a slightly modified design of our FluiDMD card already reported [57]
Data were normalized in accordance with the Agilent Quality Controls probes (Spike-in), as reported in the literature [58] 90th percentile analysis of fluorescence intensities on both DMD-GEx Sense and Antisense arrays identified as statistically significant a total of 14 poly-adenylated transcripts, (Figure 1 B), which were named according to their intron of origin
Architecture, Compartmentalisation and Conservation of Long Non-coding RNAs in the DMD Gene non-coding RNAs (ncRNAs) are currently categorised on the basis of their structure, and the transcripts we identified show several structural features common to many previously characterised lncRNAs
Summary
DMD is the largest gene in the human genome; it is 2.2 Mb long, and accounts for approximately 0.1% of the entire human DNA sequence. It consists of 79 exons, 78 introns and of 7 promoters, giving rise to 7 isoforms that are finely regulated in terms of tissue specificity [1]. Mutations in the DMD gene lead to muscle wasting, and two main phenotypes have been defined according to Monaco’s reading-frame theory: the severe Duchenne Muscular Dystrophy, due to out-of-frame mutations, and the milder Becker Muscular Dystrophy, associated with in-frame mutations [3]. Heterozygous females for dystrophin mutations are generally asymptomatic, but rarely they can be affected with variable disease severity ranging from mild muscle weakness to a Duchenne-like phenotype [5]. At variance from what historically thought, the symptomatic condition is not related to the X inactivation ratio but seems to be due to other still unraveled expression regulatory mechanisms [6]
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
