O'Carroll Group
Non-coding RNA function in mammalian development and physiology
Figure 1: A. Single cell visualization of the miR-144/451 locus activity in E8.5 mouse embryos. A miR-144/451 EGFP BAC transgenic E8.5 mouse embryo is shown, DAPI in blue and EGFP in green. EGFP expression is found in the nascent blood islands.
B. Sylamer analysis of transcriptomes from wildtype and miR-144/451 -/- erythroblasts reveals miR-451 targets and the importance of miR-451 within the miR-144/451 locus (Collaboration with Enright Group).
C. Nuclear Miwi2 localization in gonadocytes from fetal testis of Slicer-inactive Mili ADH mice. DAPI in blue and Miwi2 in green.
The O’Carroll group studies mouse blood cell formation, embryology and germ cell development using state-of-the-art genetic strategies and high-throughput sequencing approaches.
Previous and current research
The aim of the group is to understand the mechanisms by which non-coding RNAs contribute to mammalian development and physiology with an emphasis on mouse hematopoiesis, embryology and germ cell development. We address our challenges using state-of-the-art mouse genetic strategies coupled with high throughput sequencing approaches.
Members of the Argonaute family are highly conserved small-RNA-binding proteins with diverse functions ranging from the regulation of post-transcriptional gene expression, anti-viral defense, and transposon silencing to the establishment of heterochromatin domains. In mammals two subclades of Argonaute proteins exist, the Ago and Piwi sub-families. MicroRNAs (miRNAs) and short-interfering RNAs (siRNA) are small non-coding RNA molecules that are potent negative regulators of gene expression. MiRNA/siRNA-mediated gene silencing is executed by the multi-protein RNA-induced silencing complex (RISC). At the core of RISC is an Ago protein that binds a small-RNA and executes their function. Our current RISC interests now focus on the physiological importance of Ago2 post-translational regulation in vivo.
Piwi proteins bind a class of small non-coding RNAs known as Piwi-interacting RNAs (piRNAs) that are believed to act as guides for targeting of the respective ribonuclear particles. In the mammalian male germline, the members of the Piwi subclade of the Argonaute family, Mili and Miwi2, are essential for de novo DNA methylation of transposons and spermatogenesis. We currently address several basic questions on the intrinsic mechanism and function of mammalian Piwi proteins in and beyond transposon silencing.
Transcriptome sequencing has established long non-coding RNAs (lncRNAs) as a distinct class of genes that encompass abundant and diverse classes of cellular RNAs, mostly of unknown function. The defining feature of lncRNAs is simply that their length exceeds 200 nucleotides. These RNAs are derived from both intergenic or genic regions of the genome. Similar to their coding counterparts lncRNAs can undergo extensive processing, such as capping, splicing, trans-splicing and polyadenylation. LncRNAs have been shown to affect gene expression via epigenetic, transcriptional or post-transcriptional mechanisms. We currently investigate the role of these newly identified genomic outputs in germ cell development and homeostasis.
Selected publications
The endonuclease activity of Mili fuels piRNA amplification that silences LINE1 elements. De Fazio, S., Bartonicek, N., Di Giacomo, M., Abreu-Goodger, C., Sankar, A., Funaya, C., Antony, C., Moreira, P.N., Enright, A.J. & O'Carroll, D. Nature. 2011 Oct 23. doi: 10.1038/nature10547.
The miR-144/451eGFP allele, a novel tool for resolving the erythroid potential of hematopoietic precursors. Rasmussen, K.D. & O'Carroll, D. Blood. 2011 Jul 25.
Conserved vertebrate mir-451 provides a platform for Dicer-independent, Ago2-mediated microRNA biogenesis. Yang, J.S., Maurin, T., Robine, N., Rasmussen, K.D., Jeffrey, K.L., Chandwani, R., Papapetrou, E.P., Sadelain, M., O'Carroll, D. & Lai, E.C. Proc Natl Acad Sci U S A. 2010 Aug 24;107(34):15163-8. Epub 2010 Aug 10.
The miR-144/451 locus is required for erythroid homeostasis. Rasmussen, K.D., Simmini, S., Abreu-Goodger, C., Bartonicek, N., Di Giacomo, M., Bilbao-Cortes, D., Horos, R., Von Lindern, M., Enright, A.J. & O'Carroll, D. J Exp Med. 2010 May 31.
A Slicer-independent role for Argonaute 2 in hematopoiesis and the microRNA. O'Carroll, D., Mecklenbrauker, I., Das, P.P., Santana, A., Koenig, U., Enright, A.J., Miska, E.A. & Tarakhovsky, A. Genes Dev. 2007 Aug 15;21(16):1999-2004. Epub 2007 Jul 12.
Future projects and goals
- Determine the in vivo significance of post-translational modifications of Ago2.
- Explore the function of Miwi2 and Mili during spermatogenesis beyond transposon silencing.
- Understand the contribution of lncRNAs to germ cell development and homeostasis.