ABSTRACT
A critical barrier in the treatment of endosomal and lysosomal diseases is the lack of understanding of the in vivo functions of the putative causative genes. We addressed this by investigating a key pair of endocytic adaptor proteins, PH domain-containing endocytic trafficking adaptor 1 and 2 (PHETA1/2; also known as FAM109A/B, Ses1/2, IPIP27A/B), which interact with the protein product of OCRL, the causative gene for Lowe syndrome. Here, we conducted the first study of PHETA1/2 in vivo, utilizing the zebrafish system. We found that impairment of both zebrafish orthologs, pheta1 and pheta2, disrupted endocytosis and ciliogenesis in renal tissues. In addition, pheta1/2 mutant animals exhibited reduced jaw size and delayed chondrocyte differentiation, indicating a role in craniofacial development. Deficiency of pheta1/2 resulted in dysregulation of cathepsin K, which led to an increased abundance of type II collagen in craniofacial cartilages, a marker of immature cartilage extracellular matrix. Cathepsin K inhibition rescued the craniofacial phenotypes in the pheta1/2 double mutants. The abnormal renal and craniofacial phenotypes in the pheta1/2 mutant animals were consistent with the clinical presentation of a patient with a de novo arginine (R) to cysteine (C) variant (R6C) of PHETA1. Expressing the patient-specific variant in zebrafish exacerbated craniofacial deficits, suggesting that the R6C allele acts in a dominant-negative manner. Together, these results provide insights into the in vivo roles of PHETA1/2 and suggest that the R6C variant is contributory to the pathogenesis of disease in the patient.
This article has an associated First Person interview with the first author of the paper.
Footnotes
Competing interests
The authors declare no competing or financial interests.
Author contributions
Conceptualization: K.M.A., Y.A.P., G.B.G., H.F.-S.; Methodology: K.M.A., T.W., T. Moreland, R.V.-K., M.M., P.A., W.W., H.-G.K., L.A.W., J.S., D.R.A., T. Markello, C.J.T., R.S., W.A.G., G.B.G., M.C.M., H.F.-S., Y.A.P.; Software: M.M.; Validation: K.M.A., Y.A.P.; Formal analysis: K.M.A., Y.A.P.; Investigation: K.M.A., T.W., T. Moreland, R.V.-K., M.M., C.J., P.A., W.W., H.-G.K., L.A.W., J.S., D.R.A., T. Markello, C.J.T., W.A.G., G.B.G., M.C.M., H.F.-S., Y.A.P.; Writing - original draft: K.M.A., Y.A.P.; Writing - review & editing: K.M.A., G.B.G., M.C.M., H.-G.K., J.S., W.A.G., H.F.-S., Y.A.P.; Visualization: K.M.A., Y.A.P.; Supervision: Y.A.P.; Project administration: Y.A.P.; Funding acquisition: H.-G.K., G.B.G., Y.A.P., H.F.-S.
Funding
This work was supported by the National Institutes of Health (GM119016 to H.-G.K., G.B.G. and Y.A.P.; GM086524 to H.F.-S.), the Commonwealth Research Commercialization Fund (ER14S-001-LS to Y.A.P.), Augusta University, and Virginia Polytechnic Institute and State University.
Data availability
The data discussed in this publication are available at GEO under accession number GSE142673.
Supplementary information
Supplementary information available online at http://dmm.biologists.org/lookup/doi/10.1242/dmm.041913.supplemental
- Received August 8, 2019.
- Accepted February 27, 2020.
- © 2020. Published by The Company of Biologists Ltd
This is an Open Access article distributed under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution and reproduction in any medium provided that the original work is properly attributed.
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