The Bohnsack Laboratory focuses on cranial neural crest biology in the context of the development of the anterior segment of the eye. We are specifically interested in the genetics and molecular pathways that underlie congenital eye disease pathogenesis. We utilize both in vivo (zebrafish) and in vitro (human embryonic stem cells) systems to model various eye diseases. We take advantage of the accessibility of zebrafish embryos to study in real-time the molecular regulation of the ocular neural crest, a transient population of stem cells that gives rise to portions of the cornea, iris, and aqueous humor drainage system in the anterior segment of the eye. In addition, we use human embryonic stem cells, which harbor known congenital eye disease-causing mutations, as a model that mirrors the human condition, yet is genetically accessible. These programs are improving our understanding of the genetic regulation of eye development and the pathophysiology of these blinding diseases which is importantly laying the groundwork for molecularly targeted treatments that aim to prevent blindness and restore vision in affected children.
Congenital Eye Diseases
Human Embryonic Stem Cells
Brenda L. Bohnsack
DEFINING CRANIOFACIAL AND OCULAR NEURAL CREST CELL POPULATIONS
The cranial neural crest is a transient embryonic stem cell population that ultimately give rise to the bone, cartilage, and connective tissue of the jaw and mid face, and within the eye contribute to the corneal endothelium and stroma, iris stroma, ciliary body stroma and muscles, aqueous outflow pathways, and sclera. Due to the common origin of these tissues, congenital eye anomalies are often associated with congenital facial defects, indicating underlying disruption of the cranial neural crest. We are investigating key molecular and cellular differences between craniofacial and ocular neural crest cells. Using transgenic zebrafish, we have done extensive fate mapping to define different neural crest cell populations through the embryonic, larval, juvenile, and adult stages. Further, we have used a combined fluorescence-activated cell sorting (FACS) and RNA-Seq approach to identify novel genes within the craniofacial and ocular neural crest cell populations. Through this we have gained a better understand of the signaling networks that contribute to ocular anterior segment development.
NEURAL CREST REGULATION OF OCULAR FISSURE CLOSURE
Colobomas arise from failure of the ocular fissure to close during embryogenesis. The inferior ocular fissure arises from the invagination of the neural epithelial-derived optic vesicle to form the double-layered optic cup. Although colobomas may be isolated findings, these congenital defects can be associated with anomalies due to disruption of the neural crest. We hypothesize that neural crest cells that surround the optic cup are essential for regulating various steps of ocular fissure closure. We are using various mutant and CRISPR/Cas9 zebrafish to study the signaling pathways within neural crest cells and in the optic cup that regulate fissure closure. This information is helping us better understand coloboma disease pathogenesis and ultimately may lead to vision-saving therapies.
USING HUMAN EMBRYONIC STEM CELLS TO STUDY CONGENITAL DISEASES
Human embryonic stem cells (hESCs) afford a unique opportunity to study human development and congenital disease pathogenesis. Using disease-specific hESC lines that were derived from families with genetic diseases, we are investigating the role of certain genes including PAX6 and COL2A1 in ocular and neural crest development. With these hESC lines we are able to investigate differences in optic cup and neural crest cell differentiation in human tissues. These cells allow us to study human disease pathogenesis and is the first step in creating stem cell therapies for these congenital diseases.
As an academic pediatric ophthalmologist and developmental biologist, Brenda L. Bohnsack, MD, PhD, focuses on the clinical aspects and underlying basic science of congenital eye diseases. Clinically, Dr. Bohnsack specializes in the medical and surgical management of congenital and complex pediatric eye diseases such as primary congenital glaucoma, Peters Anomaly, Axenfeld-Rieger syndrome, aniridia, microphthalmia, and congenital ectropion uvea. Her clinical research concentrates on identifying new genes associated with congenital eye diseases and the outcomes of children with these diseases. Her basic science research program utilizes both in vivo (zebrafish) and in vitro (human embryonic stem cells) systems to model various congenital eye diseases in order to better understand disease pathogenesis and ultimately develop new therapeutic options that prevent vision loss.