The molecular etiology of human congenital eye disorders remains largely unknown. The objective of this revised competitive renewal application is to identify defects in the MAP3K1-EGFR axis that lead to murine developmental eye disorders. Our previous studies have shown that embryonic eyelid closure, an essential morphogenetic event of the mammalian eye, is a developmental threshold trait that is regulated by the interaction of an exceptionally complex genetic network and certain environmental conditions. We have identified MAP3 kinase 1 (MAP3K1) as an integral component of this network. Specifically, Map3k1 heterozygosity can render the eyelid closure program more vulnerable to perturbation by genetic and environmental insults. Importantly in this context, we have identified a human patient, who carries a MAP3K1 allele deletion and displays congenital eyelid and eye movement abnormalities. We hypothesize that Map3k1 allelic lesion is a genetic risk that predisposes the developmental programs to eyelid closure defect and congenital eye disorders. Based on preliminary data in mice and humans, we postulate that MAP3K1 and EGFR form a molecularly integrated network such that the combination of genetic variants and environmental insults that perturb the network signals will cause defective eyelid closure as the underlying mechanism of congenital eye anomalies. We propose two Specific Aims.
Aim 1 will investigate the genetic contributions to defective eyelid closure. We will examine whether Map3k1 hemizygosity in combination with genetic mutants of the EGFR pathway leads to failure of eyelid closure as the underlying mechanisms of congenital eye anomalies. The approach is using genetically modified mice to generate digenic or polygenic mutants and examining whether the epistatic interactions affect eyelid closure program, and using novel 3-D imaging tool to characterize the eye abnormalities in the mutants in order to uncover novel structural and functional information with particular relevance to human pathobiology.
Aim 2 will elucidate the mechanisms of gene-environment interaction that lead to defective eyelid closure. We will use Map3k1 as the model gene and organochlorinated dioxin-like compounds, which are ubiquitous environmental contaminants, as the model compounds. We will examine whether in utero exposure to the compounds results in defective eyelid closure in Map3k1 hemizygotes but not wild type pups and whether the defect is associated with inactivation of the MAP3K1-EGFR axis. The proposed work is our ongoing effort to delineate the genesis of congenital eye abnormalities using mouse embryonic eyelid closure as a model. Completion of the work will provide novel mechanistic insights into the multifactorial etiology of eyelid closure defect in mice. This information will serve as a basis to uncover the origins of human congenital eye disorders related to this defect. The experimental paradigm that studies gene-gene and gene-environment interaction mechanisms is applicable to all the multifactorial birth defects; hence, this work will chart a path to test for these gene-environment connections.
This project will use mouse embryonic eyelid closure, a developmental program conserved in mammals, as a model to investigate gene-gene and gene-environmental interaction mechanisms that control epithelium morphogenesis and eye development. Results will help us to better understand the mechanisms underlying similar developmental processes, such as fusion of optic fissure, palate and neural tube, where an epithelial hole has to close by morphogenetic force; they will also lead to uncover the genesis of congenital eye anomaly and facilitate the identification of high-risk populations for targeted prevention and intervention.
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