Loading...
Journal Title
Readers/Advisors
Journal Title
Term and Year
Publication Date
2025
Book Title
Publication Volume
Publication Issue
Publication Begin
Publication End
Number of pages
Files
Daniel Larbi Approved Thesis 7-17-2025_anonymous.pdf
Adobe PDF, 19.49 MB
- Embargoed until 2030-01-01
Research Projects
Organizational Units
Journal Issue
Abstract
"Müller glia (MG) are the predominant glia in the retina, critical for maintaining retinal homeostasis, however MG respond to retinal injury by becoming reactive in a series of changes referred to as gliosis. microRNAs (miRNAs) have been shown to be key regulators of MG function, but their role in MG reactivity and its impact in neurodegeneration is unknown. To investigate how MG miRNAs contribute to retinal health and pathology, we generated two MG- specific conditional Dicer1 knockout (cKO) mouse strains (Rlbp- CreER:tdTomato:Dicer-cKO and Glast-CreER:tdTomato:Dicer-cKO), allowing the targeted deletion of Dicer and therefore mature miRNAs in MG. Using optical coherence tomography (OCT), electroretinography (ERG), and histological analyses, we characterized the structural and functional changes following Dicer1 deletion in vivo (Aim 1).
Loss of Dicer in MG led to a progressive and severe photoreceptor degeneration over six months, mirroring features seen in retinal diseases such as retinitis pigmentosa and age-related macular degeneration. Chronologically, MG Dicer loss caused early impairments in the external limiting membrane (ELM) to retinal pigment epithelium (RPE) region, followed by cone photoreceptor dysfunction at three months, and retinal remodeling and inner retinal functional loss by three to six months. Of note, cone dysfunction preceded measurable rod impairments, emphasizing a critical role for MG miRNAs in supporting cone health. In the Rlbp-CreER:DicercKO strain, we found accelerated rod degeneration relative to the Glast-CreER:DicercKO, suggesting Dicer1 loss in RPE increases overall photoreceptor vulnerability.
Given that MG with reduced miRNAs did not upregulate GFAP, a hallmark of reactive gliosis, in late state after Dicer1 loss, we hypothesized that reactivity attenuation might lessen secondary neurodegeneration after injury. To test this, we subjected three-month-old Dicer-cKO (both Rlbp-CreER and Glast-CreER) and wildtype mice to moderate light damage (~5000 lux, 4 h), a model that induces gradual photoreceptor loss and functional decline over 28 days (Aim 2). Structural and functional assessments revealed that naïve mice exhibited a steady degeneration, with 70% outer nuclear layer (ONL) thinning and a 60% decline in ERG function by 28 days. Interestingly, Dicer-cKO mice displayed a less severe functional decline at 14 days post-injury, and in the RlbpCreER:DicercKO strain, this preservation persisted until 28 days. Although initial ONL thinning was similar between groups, cKO mice showed a slower rate of degeneration. In RlbpCreER:DicercKO 14 days post-injury, we found significantly less GFAP upregulation compared to naïve mice. These findings suggest that MG miRNAs regulate glial reactivity and their depletion up to a specific time point (in this case- 3months), confers partial protection against light-induced retinal injury.
We have profiled miRNA and mRNA expression in reactive MG 7 days after intense light damage (10,000 lux, 8 h) using Nanostring and microarray technologies. We found that the majority of MG miRNAs declined after light damage, mirroring the miRNA profile of Dicer-depleted MG suggesting a common regulatory mechanism for MG reactivity involving miRNAs
Together, these findings demonstrate that MG miRNAs are critical for retinal stability under both physiological and injury conditions. MG miRNAs are important for cone health and their long term depletion has detrimental effects on overall retinal health. However, MG lacking miRNAs 3-months post deletion are less reactive after light damage and confer neuroprotection after injury.
"