Our lab studies the cellular and molecular mechanisms underlying tissue morphogenesis: the process by which a group of cells achieves its proper cellular organization and shape. Using the vertebrate eye as a model, we want to understand how the cells that comprise the vertebrate optic cup – neural retina, retinal pigmented epithelium, and lens – form the stereotyped structure that is critical for visual function. Developmental defects in eye morphogenesis represent a common cause of serious visual impairment in newborns.
Using confocal microscopy and a custom-built software suite for tracking cell behaviors in four dimensions, we have previously generated a map encompassing all cellular movements and divisions during zebrafish optic cup morphogenesis. We found that a complex set of cell movements, coordinated between different tissues, is responsible for shaping the eye. Using this unprecedented dataset as a reference point, our current studies focus on the molecular mechanisms underlying eye morphogenesis. Our studies make use of zebrafish molecular genetics, cell biology, and live imaging, and include the following projects:
We found that the extracellular matrix component laminin is required for eye morphogenesis: in laminin-α1 mutants, optic stalk constriction and optic vesicle invagination are impaired. In addition, establishment of apicobasal polarity is impaired. However, we still do not understand how disrupted polarity leads to this phenotype, how polarity is initially established, or the signaling pathway downstream of laminin.
We found that the extracellular matrix component laminin is required for eye morphogenesis: in laminin-α1 mutants, optic stalk constriction and optic vesicle invagination are impaired. In addition, establishment of apicobasal polarity is impaired. However, we still do not understand how disrupted polarity leads to this phenotype, how polarity is initially established, or the signaling pathway downstream of laminin.
While signaling pathways such as Shh and Wnt are known to play a role in patterning the optic vesicle, their role in morphogenesis itself is unknown. By performing 4-dimensional cell tracking on zebrafish mutants and morphants, we will quantitatively determine the contributions of different developmental signaling pathways to eye morphogenesis.
While signaling pathways such as Shh and Wnt are known to play a role in patterning the optic vesicle, their role in morphogenesis itself is unknown. By performing 4-dimensional cell tracking on zebrafish mutants and morphants, we will quantitatively determine the contributions of different developmental signaling pathways to eye morphogenesis.
During eye morphogenesis, we find that retinal progenitors have unexpectedly motile behaviors despite their epithelial polarization. Such behaviors are frequently regulated by Rho-family small GTPases, and we will investigate the involvement of these signaling molecules in coordinating the motility of single cells and the morphogenesis of entire sheets if tissue.
During eye morphogenesis, we find that retinal progenitors have unexpectedly motile behaviors despite their epithelial polarization. Such behaviors are frequently regulated by Rho-family small GTPases, and we will investigate the involvement of these signaling molecules in coordinating the motility of single cells and the morphogenesis of entire sheets if tissue.
Our 4D analysis suggests that coordination of cell movements between tissues is critical for eye morphogenesis. In addition, in a forward genetic screen, Kristen isolated a mutant, O15, in which extremely tight adhesion between the optic vesicle and the overlying ectoderm impairs invagination of both the optic vesicle and lens. We are isolating the underlying mutation and will determine the nature of the tissue-tissue interactions regulated by O15.
Our 4D analysis suggests that coordination of cell movements between tissues is critical for eye morphogenesis. In addition, in a forward genetic screen, Kristen isolated a mutant, O15, in which extremely tight adhesion between the optic vesicle and the overlying ectoderm impairs invagination of both the optic vesicle and lens. We are isolating the underlying mutation and will determine the nature of the tissue-tissue interactions regulated by O15.
Nandamuri SP, Lusk S, Kwan KM (2022) Loss of zebrafish dzip1 reults in inappropriate recruitment of periocular mesenchyme to the optic fissure and ocular coloboma. PLOS One 10.1371/journal.pone.0265327
Casey MA, Hill JT, Hoshijima K, Bryan CD, Gribble SL, Brown JT, Chien CB, Yost HJ, Kwan KM (2021) Shutdown corner, a large deletion mutant isolated from a haploid mutagenesis screen in zebrafish. G3 10.1093/g3journal/jkab442
Lusk S and Kwan KM (2021) Pax2a, but not pax2b, influences cell survival and periocular mesenchyme localization to facilitate zebrafish optic fissure closure. Developmental Dynamics dvdy.422
Lusk S, Casey MA, Kwan KM (2021) 4-Dimensional Imaging of Zebrafish Optic Cup Morphogenesis. Journal of Visualized Experiments 10.3791/62155
Casey MA, Lusk S, Kwan KM (2021) Build me up optic cup: Intrinsic and extrinsic mechanisms of vertebrate eye morphogenesis. Developmental Biology j.ydbio.2021.03.023
Bryan CD, Casey MA, Pfeiffer RL, Jones BW, Kwan KM (2020) Optic cup morphogenesis requires neural crest-mediated basement membrane assembly. Development dev.181420
Carney KR, Bryan CD, Gordon HB, Kwan KM (2020) LongAxis: A MATLAB-based program for 3D quantitative analysis of epithelial cell shape and orientation. Developmental Biology j.ydbio.2019.09.016
Gordon HB*, Lusk S*, Carney KR, Wirick EO, Murray BF, Kwan KM (2018) Hedgehog signaling regulates cell motility and optic fissure and stalk formation during vertebrate eye formation. Development dev.165068
Bryan CD, Chien CB, Kwan KM (2016) Loss of laminin alpha 1 results in multiple structural defects and divergent effects on adhesion during vertebrate optic cup morphogenesis. Developmental Biology 416:324-37
Kwan KM (2014) Coming into focus: The role of extracellular matrix in vertebrate optic cup morphogenesis. Developmental Dynamics 243:1242-8
Kwan KM, Otsuna H, Kidokoro H, Carney KR, Saijoh Y, Chien CB (2012) A complex choreography of cell movements shapes the vertebrate eye. Development 139:359-72
Kwan KM (2010) 25 years on, Developmental Biology remains dynamic, competent, and instructive (book review). Developmental Dynamics 239:3506-7
Kwan KM, Fujimoto E, Grabher C, Mangum BD, Hardy ME, Campbell DS, Parant JM, Yost HJ, Kanki JP, Chien C-B (2007) The Tol2kit: a multisite-gateway based construction kit for Tol2 transposon transgenesis constructs. Developmental Dynamics 236:3088-99
NIH/NEI
Knights Templar Eye Foundation
March of Dimes Basil O’Connor Starter Scholar Award
University of Utah Research Foundation
