Disruption of Visc-2, a Brain-Expressed Conserved Long Noncoding RNA, Does Not Elicit an Overt Anatomical or Behavioral Phenotype.

Peter L Oliver,Rebecca A Chodroff,Zoltán Molnár,Julio Gomez-Rodriguez,Eric D Green,Amrit Gosal,Tom Lickiss,Chris P Ponting,Francis Szele,Lisa J Garrett,Amanda F.P Cheung,Gene Elliot,Benjamin Edwards

doi:10.1093/cercor/bhu196

Abstract

Although long noncoding RNAs (lncRNAs) are proposed to play essential roles in mammalian neurodevelopment, we know little of their functions from their disruption in vivo. Combining evidence for evolutionary constraint and conserved expression data, we previously identified candidate lncRNAs that might play important and conserved roles in brain function. Here, we demonstrate that the sequence and neuronal transcription of lncRNAs transcribed from the previously uncharacterized Visc locus are conserved across diverse mammals. Consequently, one of these lncRNAs, Visc-2, was selected for targeted deletion in the mouse, and knockout animals were subjected to an extremely detailed anatomical and behavioral characterization. Despite a neurodevelopmental expression pattern of Visc-2 that is highly localized to the cortex and sites of neurogenesis, anomalies in neither cytoarchitecture nor neuroproliferation were identified in knockout mice. In addition, no abnormal motor, sensory, anxiety, or cognitive behavioral phenotypes were observed. These results are important because they contribute to a growing body of evidence that lncRNA loci contribute on average far less to brain and biological functions than protein-coding loci. A high-throughput knockout program focussing on lncRNAs, similar to that currently underway for protein-coding genes, will be required to establish the distribution of their organismal functions.

Highlights

The full range and complexity of RNA species that are transcribed in mammals are becoming increasingly apparent as a result of large-scale cDNA cloning and transcriptome sequencing projects (Okazaki et al 2002; Carninci et al 2005; Birney et al 2007; Derrien et al 2012)
We shall refer to the locus as Visc, chosen to reflect the known expression of expressed sequence tags (ESTs) in the region in the visual cortex, and to these 2 Visc long noncoding RNAs (lncRNAs) as Visc-1 and Visc-2
Despite a highly localized neurodevelopmental expression pattern in the subventricular zone (SVZ), rostral migratory stream (RMS), olfactory bulb (OB), and cortex, no defects in neuronal migration or anatomy were identified in Visc-2−/− animals, and no abnormal anxiety or cognitive behavioral phenotypes were observed

Summary

Introduction

The full range and complexity of RNA species that are transcribed in mammals are becoming increasingly apparent as a result of large-scale cDNA cloning and transcriptome sequencing projects (Okazaki et al 2002; Carninci et al 2005; Birney et al 2007; Derrien et al 2012). A substantial proportion of these transcripts are not translated: in addition to a myriad of small regulatory RNAs such as microRNAs (miRNAs), many thousands of long noncoding RNAs (lncRNAs) have been identified (Guttman et al 2009; Derrien et al 2012). These larger transcripts, defined as being over 200 nucleotides in length, are found within, or anti-sense to, protein-coding genes, and in intergenic regions (Khalil et al 2009). Potential functional significance has been inferred from expression patterns of lncRNAs; for example, recent next-generation sequencing studies of mRNAs in the mammalian cortex have identified transcripts with a layer-specific distribution (Belgard et al 2011)

Methods

Results

Conclusion