Project description:East African cichlid fishes have radiated in an explosive fashion. The (epi)genetic basis for the abundant phenotypic diversity of these fishes remains largely unknown. As transposable elements (TEs) contribute extensively to genome evolution, we reasoned that TEs may have fuelled cichlid radiations. While TE-derived genetic and epigenetic variability has been associated with phenotypic traits, TE expression and epigenetic silencing remain unexplored in cichlids. Here, we profiled TE expression in African cichlids, and describe dynamic expression patterns during embryogenesis and according to sex. Most TE silencing factors are conserved and expressed in cichlids. We describe an expansion of two truncated Piwil1 genes in Lake Malawi/Nyasa cichlids, encoding a Piwi domain with catalytic potential. To further dissect epigenetic silencing of TEs, we focused on small RNA-driven epigenetic silencing. We detect a small RNA population in gonads consistent with an active Piwi-interacting RNA (piRNA) pathway targeting TEs. We uncover fluid genomic origins of piRNAs in closely related cichlid species. This, along with signatures of positive selection in piRNA pathway factors, points towards fast co-evolution of TEs and the piRNA pathway. Our study is the first step to understand the contribution of ongoing TE-host arms races to the cichlid radiations in Africa.
Project description:The manuscript by D. Licastro and colleagues “Promiscuity of enhancer, coding and non-coding transcription functions in ultraconserved sequence elements” presents an overview of experimental and computational approaches employed by the authors to perform a multi-facet characterization of ultraconserved elements (UCEs). The authors present an interesting analysis where they investigate the transcription of UCEs in mouse development at different stages by conductin an microarray experiment. Some of these results are further verified by RT-PCR.
Project description:The manuscript by D. Licastro and colleagues “Promiscuity of enhancer, coding and non-coding transcription functions in ultraconserved sequence elements” presents an overview of experimental and computational approaches employed by the authors to perform a multi-facet characterization of ultraconserved elements (UCEs). The authors present an interesting analysis where they investigate the transcription of UCEs in mouse development at different stages by conductin an microarray experiment. Some of these results are further verified by RT-PCR. 12 Samples, 4 groups 3 samples per group.
