All ETDs from UAB

Advisory Committee Chair

Elizabet Sztul

Document Type


Date of Award


Degree Name by School

Doctor of Philosophy (PhD) Heersink School of Medicine


This thesis focuses on two key questions: 1) how are bone development and regeneration regulated by the CREB3L1 transcription factor; and 2) what is the mechanism of action of the endoplasmic reticulum resident protein JAGN1, which when dysregulated, causes severe congenital neutropenia (SCN)? CREB3L1 regulates bone development and regeneration in mammalian models by facilitating the expression of COL1A1 and components of the secretory pathway required for collagen secretion. We generated two zebrafish models of Creb3l1 dysfunction (creb3l1ΔbZIP/ΔbZIP and creb3l1TA+/TA+). Both models showed that Creb3l1 functions in regulating col1a1a transcription and overall regenerate size are conserved in zebrafish. However, we also uncovered that Creb3l1 regulates patterning during development and regeneration by intersecting with the Sonic Hedgehog signaling pathway. This novel finding in zebrafish provides a foundation for future studies to explore CREB3L1 effects on Hedgehog signaling during healing of bone fractures in mammalian models. JAGN1 mutations cause Severe Congenital Neutropenia (SCN) in patients and knocking-out JAGN1 leads to embryonic lethality in mice. JAGN1 has domains that suggest an “escort” function in transport of cargo proteins at the ER-Golgi interface. Unlike mammals, zebrafish have two jagn1 (jagn1a and jagn1b) genes. To determine the effects of their dysfunction, we separately knocked out each jagn1. The jagn1a-/- fish survived to become healthy adults but exhibited defects in brain activity. In contrast, the jagn1b-/- fish died between 10- and 14-days post fertilization, recapitulating the lethality seen in mammals. Our zebrafish models will be key in future analyses of tissue-specific roles for jagn1. To probe cellular function(s) of JAGN1, we used CRISPR/Cas9 to generate mouse embryonic fibroblasts expressing different forms of dysfunctional JAGN1. Interestingly, Jagn1 mutant cells exhibited dramatic delay in spreading and adhesion, a novel role for JAGN1 in an ubiquitous cellular process. The molecular underpinnings of the spreading defect remain to be determined, but preliminary Bio-ID analyses suggest that JAGN1 may impact trafficking of adhesion molecules and/or affect actin cytoskeleton dynamics. Based on the findings presented in this thesis, we propose a novel role for CREB3L1 in patterning during bone regeneration, and a novel function for JAGN1 in cell adhesion. Our findings broaden the knowledge of bone regeneration and inform on the possible molecular lesion responsible for JAGN1-linked neutropenia.



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