Richard I. Gregory, PhD
Harvard Medical School
The laboratory research focus is to understand the pathways of how small regulatory RNAs are generated, how they exert their gene regulatory function, and their role in the self-renewal and pluripotency of embryonic stem (ES) cells. RNA interference (RNAi) describes the recently identified phenomenon whereby small non-coding RNAs can silence gene expression. It is emerging that cells possess a wide repertoire of tiny regulatory RNAs that are critical for a variety of biological pathways and can repress genes via numerous mechanisms. For posttranscriptional gene silencing, microRNAs (miRNAs), and small inhibitory RNAs (siRNAs), function as guide molecules inducing mRNA degradation or translational repression.
We apply biochemical and molecular biological approaches to identify the molecular machinery of RNAi. Previously we isolated the 'Microprocessor' complex that we found to be necessary and sufficient for processing long primary miRNA transcripts (pri-miRNAs) to hairpin-shaped precursor miRNA (pre-miRNA) intermediates. Additionally, isolation of a Dicer-containing complex revealed that processing of pre-miRNAs to the final ~22 nucleotide miRNA duplexes is physically and functionally coupled with assembly of an active RNA-induced silencing complex (RISC).
A fundamental question in stem cell biology is what determines the self-renewal and pluripotency of stem cells? Recent data indicate that RNAi may play an important role in these processes. We aim to understand the role of small regulatory RNAs in the self-renewal and pluripotency of ES cells. Although ES cell-specific miRNAs have been identified, the genes that they regulate have so far remained elusive. We plan to systematically investigate the function of individual miRNAs in ES cells and identify their target genes. Moreover, we have identified particular miRNAs that are likely candidate genes for several human diseases. We are characterizing the expression profiles of these miRNAs, and in collaboration with appropriate laboratories, will perform DNA sequence analysis on patient samples in order to identify mutations in the miRNA gene that may contribute to the disease phenotype. Subsequently, we will identify the target mRNAs that are deregulated by abrogated miRNA function.