Biology subjects

Coomer, C. E.

Publications and source records attributed to Coomer, C. E..

3 recordsLinked to original sources

bioRxiv2025

Her9 is required for the migration, differentiation, and survival of neural crest cells

Neural crest cells (NCC) are vertebrate-specific multipotent progenitor cells that arise from the neural plate border and go on to contribute to a wide variety of morphological structures such as the jaw and palate, enteric nervous system (ENS), and pigment cells. Defects in essential steps in neural crest cell development have been associated with a wide variety of congenital disorders, collectively referred to as neurocristopathies. Her9/Hes4 is a bHLH-O transcriptional repressor that has been shown to regulate neural crest cell and craniofacial development in Xenopus and zebrafish, however the extent of Her9 function in other neural crest cell lineages has not been investigated. In this study, we characterized NCC phenotypes in her9 mutant zebrafish. We show that loss of Her9 perturbs the development of several NCC derivatives. Her9 mutants display a variety of NCC defects, including craniofacial abnormalities, alterations in pigment cell lineages, and improper formation of the gut. These phenotypes are associated with defects in neural crest cell specification, migration, and differentiation, as well as an upregulation in expression of BMP ligand genes. Furthermore, loss of Her9 leads to apoptosis of NCC derivatives. Collectively, our results show that Her9 functions in neural crest development by regulating members of the NCC gene regulatory network (GRN) to control NCC specification, migration, differentiation and survival.

developmental biology↗

bioRxiv2019

Her9/HES4 is required for retinal photoreceptor development, maintenance, and survival

The intrinsic and extrinsic factors that regulate vertebrate photoreceptor specification and differentiation are complex, and our understanding of all the players is far from complete. Her9, the zebrafish ortholog of human HES4, is a basic helix-loop-helix-orange (bHLH-O) transcriptional repressor that regulates neurogenesis in several developmental contexts. We have previously shown that her9 is upregulated during chronic rod photoreceptor degeneration and regeneration in adult zebrafish, but little is known about the role of her9 during retinal development. To better understand the function of Her9 in the retina, we generated zebrafish her9 CRISPR mutants. Her9 homozygous mutants displayed striking retinal phenotypes, including decreased numbers of rods and red/green cones, whereas blue and UV cones were relatively unaffected. The reduction in rods and red/green cones correlated with defects in photoreceptor subtype lineage specification. The remaining rods and double cones displayed abnormally truncated outer segments, and elevated levels of apoptosis. In addition to the photoreceptor defects, her9 mutants also possessed a reduced proliferative ciliary marginal zone, and decreased and disorganized Muller glia. Mutation of her9 was larval lethal, with no mutants surviving past 13 days post fertilization. Our results reveal a previously undescribed role for Her9/Hes4 in photoreceptor differentiation, maintenance, and survival.

developmental biology↗

bioRxiv2018

Capn5 expression in the healthy and regenerating zebrafish retina

PurposeAutosomal dominant neovascular inflammatory vitreoretinopathy (ADNIV) is a devastating inherited autoimmune disease of the eye that displays features commonly seen in other eye diseases, such as retinitis pigmentosa and diabetic retinopathy. ADNIV is caused by a gain of function mutation in Calpain-5 (CAPN5), a calcium dependent cysteine protease. Very little is known about the normal function of Capn5 in the adult retina, and there are conflicting results regarding its role during mammalian embryonic development. The zebrafish (Danio rerio) is an excellent animal model for studying vertebrate development and tissue regeneration, and represents a novel model to explore the function of Capn5 in the eye.\n\nMethodsWe characterized the expression of Capn5 in the developing zebrafish central nervous system (CNS) and retina, in the adult zebrafish retina, and in response to photoreceptor degeneration and regeneration using whole mount in situ hybridization, fluorescent in situ hybridization (FISH), and immunohistochemistry.\n\nResultsIn zebrafish, capn5 is strongly expressed in the developing embryonic brain, early optic vesicles, and in newly differentiated retinal photoreceptors. We found that expression of capn5 co-localized with cone specific markers in the adult zebrafish retina. We observed an increase in expression of Capn5 in a zebrafish model of chronic rod photoreceptor degeneration and regeneration. Acute light damage to the zebrafish retina, was accompanied by an increase in expression of Capn5 in the surviving cones and in a subset of Muller glia.\n\nConclusionsThese studies suggest that Capn5 may play a role in CNS development, photoreceptor maintenance, and photoreceptor regeneration.

developmental biology↗