Abstract
ABSTRACTThe Rab11 apical recycling endosome pathway is a well-established regulator of polarity and lumen formation; however, Rab11-vesicular trafficking also directs a diverse array of other cellular processes, raising the question of how Rab11 vesicles achieve specificity in space, time and content of cargo delivery. In part, this specificity is achieved through effector proteins, yet the role of Rab11 effector proteins in vivo remains vague. Here, we use CRISPR/Cas9 gene editing to study the role of the Rab11 effector Fip5 during zebrafish intestinal development. Zebrafish contain two paralogous genes, fip5a and fip5b, that are orthologs of human FIP5. We find that fip5a- and fip5b-mutant fish show phenotypes characteristic of microvillus inclusion disease, including microvilli defects and lysosomal accumulation. Single and double mutant analyses suggest that fip5a and fip5b function in parallel and regulate trafficking pathways required for assembly of keratin at the terminal web. Remarkably, in some genetic backgrounds, the absence of Fip5 triggers protein upregulation of a closely related family member, Fip1. This compensation mechanism occurs both during zebrafish intestinal development and in tissue culture models of lumenogenesis. In conclusion, our data implicate the Rab11 effectors Fip5 and Fip1 in a trafficking pathway required for apical microvilli formation.
Highlights
Development of many organs, such as the gastrointestinal system, kidneys and respiratory tract, requires morphogenetic remodeling of cells to form a hollow tube, or lumen (Jewett and Prekeris, 2018)
We first examined the degree to which zebrafish Fip5 protein was conserved with human and dog FIP5 protein, as most work on FIP5 during cell polarization has been performed in Madin Darby Canine Kidney (MDCK) cells
To determine where fip5a and fip5b were expressed in zebrafish larvae during development, we performed in situ hybridization on 4 dpf larvae
Summary
Development of many organs, such as the gastrointestinal system, kidneys and respiratory tract, requires morphogenetic remodeling of cells to form a hollow tube, or lumen (Jewett and Prekeris, 2018). Whereas the mechanisms cells use to form a lumen vary by organ, a common feature is that cells adopt a highly polarized conformation including establishment of apical structures such as primary cilia, motile cilia or microvilli (Apodaca and Gallo, 2013). Intestinal epithelia are one of the few vertebrate cell types to lack primary cilia, but their apical cell surface is covered with a brush border composed of actin-rich membrane protrusions called microvilli to aid in nutrient absorption (Apodaca and Gallo, 2013). The molecular basis of cell polarization is well defined, but much less is understood about how trafficking pathways govern formation of these apical structures, especially in vivo.
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
