Non protein coding RNAs have emerged as a major regulatory mechanism in eukaryotic genomes. While there are a few well studied examples in model organisms, the evolutionary trajectory and function of noncoding RNAs in sex chromosome biology and sexual development is largely unknown. Here we utilise our unique access to iconic Australian mammals to investigate the role of noncoding RNAs in mammalian sex chromosome biology and reproduction to answer fundamental questions about how noncoding RNAs function in mammalian sexual development.
We have identified an array of sex linked and autosomal lncRNAs with restricted temporal and spatial gonadal expression profiles (Necsulea et al, Nature 2014) which are currently being tested for chromatin and chromatin modifier associations and gene regulatory roles during male and female monotreme meiosis and sex specific gene regulation. For example, the fascinating 10kb+ lncRNA Psx displays female only expression, X-chromosome linkage, monoallelic expression, all traits consistent with functions in dosage compensation. On the other hand transcriptome analysis showed the lack of chromosome wide dosage compensation in monotremes (Julien et al, PLoS Biol 2012) and we observed no coating of X chromosomes with PSX. We are currently investigating the genomic structure, expression and potential functions of Psx in more detail. We also discovered a number of testis specific lncRNAs with nuclear and subnuclear expression foci in restricted meiosis I cells. We hypothesise that the fast paced evolution of expression patterns of some mammalian noncoding RNAs is a result of functional specialisations in specific tissue types and therefore are working to investigate the structure and function of these novel lncRNAs in monotreme sex chromosome organisation and reproduction.