IoO Seminar Series

Bob Johnston

Department of Biology, John Hopkins at UCL Institute of Ophthalmology

My research focuses on understanding the mechanisms that specify neuronal fates during development. As a graduate student in the laboratory of Oliver Hobert at Columbia University/HHMI, I identified the first microRNA to play a role in neuronal development and described the regulatory network controlling a laterally asymmetric fate decision in worms. As a post-doc in the lab of Claude Desplan at New York University, I studied the interplay of activating and repressing inputs controlling stochastic gene expression during fly eye development and discovered a critical role for interchromosomal regulation in this process. I also described the gene network that dictates the fates of colour- and motion-detecting photoreceptors.

In 2013, I established my laboratory at Johns Hopkins University. The Johnston lab differentiates human retinal organoids to determine the mechanisms controlling the specification of photoreceptors and retinal ganglion cells. The Johnston lab also uses fly-eye as a model system to study stochastic fate specifications during development and the physical association and regulation of genes between chromosomes. Our lab described how enhancers integrate combinatorial transcription factor input, feedback, and redundancy to generate cell-type-specific levels of expression in post-mitotic neurons. We studied how natural variation impacts stochastic photoreceptor specification and colour preference. We also identified chromatin structures that facilitate the pairing of chromosomes and interchromosomal gene regulation. Finally, our studies of human retinal organoids revealed a temporal mechanism controlling cone subtype specification in humans. This work advanced organoids as a model for determining mechanisms of human development with promising utility for therapeutics and vision repair