# Hedgehog Signaling in Optic Fissure Morphogenesis and Coloboma

> **NIH NIH R01** · UTAH STATE HIGHER EDUCATION SYSTEM--UNIVERSITY OF UTAH · 2024 · $385,000

## Abstract

Uveal coloboma, a condition estimated to occur in ~1:10,000 live births, is a significant cause of blindness
worldwide. It is characterized by a hole or cleft in the eye, and results from defective formation or closure of the
optic fissure, a transient, yet vital structure through which retinal axons exit and vasculature enters the eye.
Despite its importance, we have a poor understanding of the cellular and molecular mechanisms governing optic
fissure development, especially the crucial initial step of formation: if the fissure does not form correctly, it will
not undergo closure. The conserved Hedgehog (Hh) signaling pathway is crucial: in Gorlin Syndrome, overactive
Hh signaling, in the context of the PTCH mutant (ptch2 in zebrafish) causes coloboma.
 In the past funding cycle, we determined the cell movements underlying optic fissure formation, using 4-
dimensional imaging and cell tracking. Surprisingly, we found that a previously undescribed folding event in the
ventral eye drives optic fissure formation, however, the underlying cell shape changes and rearrangements are
unknown. In the ptch2 mutant, we uncovered key mechanisms by which overactive Hh signaling perturbs this
process and found that downstream targets of Hh signaling are responsible for disrupting cell movements.
Therefore, we performed single-cell RNA-seq to identify Hh target genes controlling optic fissure formation:
matrix proteoglycans (agrin, dystroglycan, and syndecan-4) and mitochondria genes have informed our new
directions. Here we take advantage of the unique optical transparency and rapid development of zebrafish
embryos to directly examine optic fissure formation in vivo. We recently developed imaging and computational
approaches to visualize and quantitatively analyze dynamics of cell movements, shape, and orientation driving
optic fissure formation for the first time, as well as molecular genetic methods to perturb signaling pathways. In
this proposal, we will uncover the cellular mechanisms directly responsible for optic fissure formation, as well as
the role of tissue-tissue interactions with the olfactory placode, and intrinsic metabolic activity.
 Our hypothesis is that active cell shape changes and reorientation drive optic fissure formation, and
this process relies on mechanical coupling with the olfactory placode via matrix proteoglycans, as well
as intracellular mitochondrial dynamics. Combining molecular genetics, live imaging, custom computational
methods and quantitative image analyses, we will test this hypothesis in the following specific aims: (1) establish
the morphogenetic mechanisms driving optic fissure formation and its disruption in coloboma; (2) determine the
cellular and molecular mechanisms by which the olfactory placode influences optic fissure formation; and (3)
determine how mitochondrial dynamics contribute to optic fissure formation and its disruption in coloboma.
 Our proposed mechanistic experiments will expand the coloboma gene regu...

## Key facts

- **NIH application ID:** 10897924
- **Project number:** 5R01EY025378-07
- **Recipient organization:** UTAH STATE HIGHER EDUCATION SYSTEM--UNIVERSITY OF UTAH
- **Principal Investigator:** Kristen M Kwan
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2024
- **Award amount:** $385,000
- **Award type:** 5
- **Project period:** 2015-04-01 → 2027-07-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10897924

## Citation

> US National Institutes of Health, RePORTER application 10897924, Hedgehog Signaling in Optic Fissure Morphogenesis and Coloboma (5R01EY025378-07). Retrieved via AI Analytics 2026-05-24 from https://api.ai-analytics.org/grant/nih/10897924. Licensed CC0.

---

*[NIH grants dataset](/datasets/nih-grants) · CC0 1.0*