Abstract
Purpose :
Hyaloid vasculature is a transient circulatory system formed during early oculogenesis that regresses during mid-gestation in humans and postnatally in mice. Failure of the hyaloid vasculature to regress leads to persistent fetal vasculature (PFV) and can result in clinical presentations affecting cornea, lens and the retina. Tremendous research has been performed to understand the pathophysiology of PFV. However, not much is known about the failure of the hyaloid vasculature to form properly during early embryogenesis.
The Mediator complex is an integral part of the transcriptional machinery driven by RNA Polymerase II, where it acts as a molecular bridge between different components of the transcriptional apparatus. Deleting one of the Mediator subunits, Med23, in mice results in both craniofacial and vascular defects. To understand the role of Med23 in vasculature, we generated endothelial cell-specific deletion mutants using Tek-Cre. Med23fx/fx;Tek-Cre embryos exhibit vascular defects such as edema and hemorrhage as well as microphthalmia and congenital cataracts. Based on the phenotypic data, we hypothesized that deletion of Med23 in the endothelial cells results in abnormal hyaloid vasculature formation which leads to molecular changes in the lens and thus leads to cataracts.
Methods :
To test this hypothesis we analyzed the Med23fx/fx;Tek-Cre mutant lenses using bright field imaging as well as immunostaining with endothelial cell marker, Pecam1. Lastly we performed spatial transcriptomics using the CosMx platform.
Results :
Bright field imaging of the Med23fx/fx;Tek-Cre mutant lenses with the vasculature indicates a perturbed vascular network compared to controls. Pecam1 staining suggests that the number of endothelial cells is significantly reduced in the hyaloid vasculature of the Med23fx/fx;Tek-Cre mutants. In addition, spatial transcriptomics data indicates that Cryab is significantly reduced in the mutant lenses, mutations in which has previously been shown to cause congenital cataracts.
Conclusions :
We are currently investigating the mechanism by which loss of hyaloid vasculature leads to downregulation of Cryab in the lens. Our data from investigating the Med23fx/fx;Tek-Cre mutants suggests that 1) Med23fx/fx;Tek-Cre mutants exhibit cataracts as a result of reduced perturbed hyaloid vasculature 2) Med23 links vascular and ocular development during embryogenesis.
This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.