Ethanol Causes Cell Death and Neuronal Differentiation Defect During Initial Neurogenesis of the Neural Retina by Disrupting Calcium Signaling in Human Retinal Organoids

Fetal Alcohol Syndrome (FAS) affects a significant proportion, exceeding 90%, of afflicted children, leading to severe ocular aberrations such as microphthalmia and optic nerve hypoplasia. During the early stages of pregnancy, the commencement of neural retina neurogenesis represents a critical period for human eye development, concurrently exposing the developing retinal structures to the highest risk of prenatal ethanol exposure due to a lack of awareness. Despite the paramount importance of this period, the precise influence and underlying mechanisms of short-term ethanol exposure on the developmental process of the human neural retina have remained largely elusive. In this study, we utilize the human embryonic stem cells derived retinal organoids (hROs) to recapitulate the initial retinal neurogenesis and find that 1% (v/v) ethanol slows the growth of hROs by inducing robust cell death and retinal ganglion cell differentiation defect. Bulk RNA-seq analysis and two-photon microscope live calcium imaging reveal altered calcium signaling dynamics derived from ethanol-induced down-regulation of RYR1 and CACNA1S. Moreover, the calcium-binding protein RET, one of the downstream effector genes of the calcium signaling pathway, synergistically integrates ethanol and calcium signals to abort neuron differentiation and cause cell death. To sum up, our study illustrates the effect and molecular mechanism of ethanol on the initial neurogenesis of the human embryonic neural retina, providing a novel interpretation of the ocular phenotype of FAS and potentially informing preventative measures for susceptible populations.

Automated summary

Fetal Alcohol Syndrome (FAS) significantly affects more than 90% of affected children, causing severe ocular aberrations. This study used human embryonic stem cells derived retinal organoids (hROs) to simulate the initial neurogenesis of the human embryonic neural retina and found that 1% ethanol slows down the growth of hROs, leading to cell death and retinal ganglion cell differentiation defect. The study also identified the calcium-binding protein RET as a key player in the ethanol-induced neurogenesis disruption. Overall, this study provides insights into the effects and molecular mechanisms of ethanol exposure on the development of the human neural retina and may inform preventative measures for FAS.