Principal Investigator Harvey Lodish
Researchers are interested in microRNA -mediated regulation of erythropoiesis. Currently, one aspect of his research focuses on the identification and functional characterization of functionally important microRNAs that regulate erythroid terminal differentiation, including enucleation. Using Johan Flygare’s RNA-seq deep sequencing data, he found that the majority of microRNAs present in CFU-E erythroid progenitors are downregulated during terminal erythroid differentiation. Taking advantage of our in vitro erythrocyte progenitor culture and differentiation system, Lingbo used retrovirus infection to overexpress many erythroid lineage – enriched microRNAs in mouse fetal liver erythroid progenitors, followed by FACS analysis after two days of culture.
Of the predominant developmentally down-regulated miRNAs, ectopic overexpression only of miR-191 blocked erythroid enucleation but had minor effects on proliferation or erythroid differentiation. Lingbo further identified two developmentally upregulated genes, Riok3 and Mxi1, as direct targets of miR-191. More importantly, he found that the upregulation of Riok3 and Mxi1 are required for chromatin condensation and enucleation. Either overexpression of miR-191 or knockdown of Riok3 or Mxi1 impaired the normal downregulation of histone acetyltransferase Gcn5 (whose downregulation is required for histone deacetylation and chromatin condensation). Thus normal down-regulation of miR-191 is essential for erythroid chromatin condensation and enucleation by allowing up-regulation of Riok3 and Mxi1 and downregulation of Gcn5. Since our understanding of erythropoiesis regulation is still limited, this is a good example to illustrate how we may be able to uncover novel protein coding genes regulating erythropoiesis through identification of microRNA target genes. In all, these discoveries will shed light on post-transcriptional regulation of erythropoiesis.
In addition to microRNA- mediated posttranscriptional regulation, Lingbo Zhang is also interested in the identification of protein and gene based regulatory networks governing erythropoiesis through computational biology approaches. In contrast to wet lab experiments, such as Chip-seq, Lingbo is trying to decipher this regulatory network by public databases, such as Gene Expression Omnibus (GEO), and data mining, followed by rigorous experimental validation.