Ten percent of congenital blindness results from microphthamia, anophthalmia and coloboma. The genetic basis for most forms of microphthalmia, anophthalmia and coloboma remain unknown but it is hypothesized that the initial pathologic processes result from faulty embryonic development of the optic vesicle and optic cup. A critical event in eye development is closure of the optic fissure on the ventral surface of the optic cup. It has been observed that seventy percent of patients with microphthalmia, anophthalmia and coloboma have evidence of defective optic fissure closure. The overarching goal of this proposal is to identify transcripts that participate in the process of optic fissure closure. Through a thorough understanding of the list of transcriptional regulators controlling optic fissure closure, we can determine the underlying basis of optic fissure closure defects. In mouse and zebrafish models, Pax2 expression supports optic fissure closure while loss of Pax2 expression results in optic fissure closure failure. Using total RNA transcripts from both Pax2 expressing and Pax2 null embryonic optic cup and stalk containing tissue, a group of 66 differentially expressed transcripts were identified by microarray analysis. We propose to validate these transcripts to develop a list of Pax2 Eye Regulated Transcripts (PERTs) (Aim 1). Individual PERT function will be assessed in a zebrafish based forward genetic screen using anti-sense technology to identify optic fissure closure defective phenotypes (Aim 2). We will determine the capacity for each individual PERT to rescue the pax2a optic fissure closure defect in zebrafish (Aim 3). These studies would result in a greater understanding of optic fissure closure and provide a resource for the zebrafish community to study optic fissure closure with the ultimate programmatic goal of identifying the genetic basis of microphthalmia, anophthalmia and coloboma.
Microphthamia (small eye), anophthalmia (nearly absent eye) and coloboma (cleft eye) are significant birth defects causing ten percent of childhood blindness. It is estimated that two in every ten thousand babies are born with microphthalmia, anophthamia or coloboma. For most families impacted by this group of birth defects, a causative genetic explanation remains unavailable. We propose to use zebrafish as a model organism to help discover the genes responsible for microphthalmia, anophthalmia and coloboma and to provide the zebrafish model as a resource to the research community to allow greater understanding of this group of birth defects.