David Gamm, MD, PhD – Slide of the Week

David Gamm, MD, PhD - Slide of the Week

Title: Investigating Cone Photoreceptor Development using Patient-Derived NRL Null Retinal Organoids

Legend: The transcription factor NRL is required for normal rod photoreceptor development. In retinal organoids derived from wildtype, NRL+/+ iPSCs (c-h), 80% of photoreceptors are rods (o) organized in a 4-6 nuclei deep rod layer that is also positive for the rod marker NR2E3 (g). Just outside of the multiple rows of rods is a single row of ARR3+ cone photoreceptors (f), about 5% of which are S Opsin+ (e and p). In the absence of NRL (NRL null retinal organoids derived from a patient with a childhood-onset form of retinitis pigmentosa, i-n), the rod program is silent (q), NR2E3+ rod nuclei are not detected (m and o), and the cells occupying the rod photoreceptor layer express the cone markers ARR3 (l) and S Opsin (k and p).

Citation: Alyssa Kallman, Elizabeth E. Capowski, Jie Wang, Aniruddha M. Kaushik, Alex D. Jansen, Kimberly L. Edwards, Liben Chen, Cynthia A. Berlinicke, M. Joseph Phillips, Eric A. Pierce, Jiang Qian, Tza-Huei Wang, David M. Gamm, Donald J. Zack. Manuscript accepted for publication by Communications Biology.

Abstract: Loss of photoreceptors through disease or injury is a leading cause of vision loss. Emerging stem cell-based strategies aimed at treating these conditions would benefit from an improved understanding of the complex gene-expression patterns directing photoreceptor development.  Neural retina leucine zipper (NRL) is a key transcription factor involved in rod photoreceptor genesis, and NRL mutations in humans are known to cause enhanced S-cone syndrome and retinitis pigmentosa. By performing histological and single-cell transcriptomic analysis of human organoid models of retinal development in the presence and absence of NRL, we molecularly defined the developmental alterations occurring in a human model of NRL loss.  Consistent with the function of NRL in directing photoreceptors toward a rod fate, human retinal organoids lacking NRL develop S-opsin dominant photoreceptor populations. We report the generation of two distinct S-opsin expressing populations in NRL null retinal organoids and identify MEF2C as a candidate regulator of cone development.

About the Lab: David Gamm’s laboratory at the Waisman Center uses stem cell technology to investigate the cellular and molecular events that occur during human retinal differentiation and to generate cells for use in human retinal disease modeling and cell-based rescue or replacement strategies. To meet these goals, Gamm utilizes a variety of human cell types, including ES and iPS cells, which have the capacity to mimic retinal development and disease, as well as to delineate the genetic “checkpoints” necessary to produce particular retinal cell types. By understanding the behavior of these cell types in vitro and in vivo, Gamm hopes to optimize strategies to delay or reverse the effects of blinding disorders such as retinitis pigmentosa and age–related macular degeneration.

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