Mu Gains Continued NIH Funding to Study Retinal Development

The knowledge obtained from the study will serve as guidance in future endeavors of developing preventive and therapeutic measures for eye diseases such as glaucoma, optic neuritis and ischemic optic neuropathy.

Despite significant progress, a clear understanding of the genetic mechanism underlying formation of the cellular diversity of the central nervous system is lacking, notes Mu, principal investigator on the grant.

“We use the mouse neural retina to address this question. Our long-term goal is to understand how transcription factors regulate gene expression globally to orchestrate the formation of the various retinal cell types.”

The research focuses on the fate-specification and differentiation of retinal ganglion cells (RGCs), which are essential to human vision; damages to them are implicated in various eye diseases.

As with other retinal cell types, RGC development initiates from native multipotent retinal progenitor cells (RPCs), progresses in a stepwise fashion and is regulated by a hierarchical gene regulatory network (GRN).

Within this GRN, three transcription factors — Atoh7 (also known as Math5), Isl1 and Pou4f2 — occupy key node positions at two different stages of RGC development, Mu says.

Past studies by the Mu lab and others have established that these transcription factors are critical for RGC formation. Atoh7 is upstream and is required for RPCs to gain competence for an RGC fate, whereas Isl1 and Pou4f2 are downstream and function collaboratively to initiate and maintain the gene expression program in RGC specification and differentiation.

However, how these transcription factors actually do their job to specify the RGC fate and promote differentiation, key aspects of RGC development, remains unknown, according to Mu.

“Our overarching hypothesis is that changes in the epigenetic landscape are the major mechanism underlying the progression of RGC genesis through the different phases,” Mu says. “Thus, investigating how the epigenetic landscape shifts to influence gene expression during RGC formation will be the central theme of this study.”

The team will conduct its research using state-of-the-art technologies, including in vivo genetic labeling, genomics and epigenomics analysis and bioinformatics tools.

The research’s specific aims include:

• investigation of the properties of RGC-competent RPCs by clonal lineage analysis, expression profiling and epigenomic survey
• survey of the progression of the epigenetic landscape throughout RGC differentiation and identification of RGC-specific enhancers in the genome
• evaluation and characterization of the function of RGC-specific enhancers

“Collectively, these experiments address the genetic and epigenetic basis underlying RGC formation,” Mu says.

“The results will expand our knowledge about the molecular events during the transition from RPCs to RGCs in retinal development,” he adds. “They will also help us to define the requirement for reprogramming stem cells into RGCs, which is highly pertinent to developing treatment for RGC-related diseases.”

“Thus, our proposed research is significant in both advancing basic research on retinal development and providing knowledge for clinical applications.”

The five-year, $2 million R01 grant from the National Eye Institute is a continuation of a previous five-year NIH grant.

Co-investigators from the University at Buffalo are:

• Tao Liu, PhD, assistant professor of biochemistry
• Zihua Hu, PhD, bioinformatics computational scientist, Center for Computational Research