Mutations in vacuolar H+-ATPase subunits lead to biliary developmental defects in zebrafish

• Published in: Developmental biology 2012-05, Vol.365 (2), p.434-444
• Main Authors: EauClaire, Steven F., Cui, Shuang, Ma, Liyuan, Matous, James, Marlow, Florence L., Gupta, Tripti, Burgess, Harold A., Abrams, Elliott W., Kapp, Lee D., Granato, Michael, Mullins, Mary C., Matthews, Randolph P.
• Format: Article
• Language: English
• Subjects: Animals; Biliary Tract - abnormalities; Biliary Tract - enzymology; Danio rerio; Freshwater; Gene Expression Regulation, Developmental; Gene Knockdown Techniques; Hepatobiliary; Membrane Proteins - genetics; Membrane Proteins - metabolism; Mutagenesis screen; Mutation; Protein Subunits - genetics; Protein Subunits - metabolism; Trafficking; Vacuolar Proton-Translocating ATPases - genetics; Vacuolar Proton-Translocating ATPases - metabolism; Zebrafish; Zebrafish - abnormalities; Zebrafish - genetics; Zebrafish Proteins - genetics; Zebrafish Proteins - metabolism
• ISSN: 0012-1606; 1095-564X
• DOI: 10.1016/j.ydbio.2012.03.009

We identified three zebrafish mutants with defects in biliary development. One of these mutants, pekin (pn), also demonstrated generalized hypopigmentation and other defects, including disruption of retinal cell layers, lack of zymogen granules in the pancreas, and dilated Golgi in intestinal epithelial cells. Bile duct cells in pn demonstrated an accumulation of electron dense bodies. We determined that the causative defect in pn was a splice site mutation in the atp6ap2 gene that leads to an inframe stop codon. atp6ap2 encodes a subunit of the vacuolar H+-ATPase (V-H+-ATPase), which modulates pH in intracellular compartments. The Atp6ap2 subunit has also been shown to function as an intracellular renin receptor that stimulates fibrogenesis. Here we show that mutants and morphants involving other V-H+-ATPase subunits also demonstrated developmental biliary defects, but did not demonstrate the inhibition of fibrogenic genes observed in pn. The defects in pn are reminiscent of those we and others have observed in class C VPS (vacuolar protein sorting) family mutants and morphants, and we report here that knockdown of atp6ap2 and vps33b had an additive negative effect on biliary development. Our findings suggest that pathways which are important in modulating intracompartmental pH lead to defects in digestive organ development, and support previous studies demonstrating the importance of intracellular sorting pathways in biliary development. ► We report the identification of three novel zebrafish biliary mutants. ► Pekin is caused by mutation in the vacuolar H+-ATPase subunit gene atp6ap2. ► Pekin also demonstrates hypopigmentation and defects in pancreas and intestine. ► Other V-H+-ATPase mutants have similar defects. ► Inhibition of atp6ap2 and the trafficking gene vps33b is additive.