title: Arf4 is required for Mammalian development but dispensable for ciliary assembly.
abstract: The primary cilium is a sensory organelle, defects in which cause a wide range of human diseases including retinal degeneration, polycystic kidney disease and birth defects. The sensory functions of cilia require specific receptors to be targeted to the ciliary subdomain of the plasma membrane. Arf4 has been proposed to sort cargo destined for the cilium at the Golgi complex and deemed a key regulator of ciliary protein trafficking. In this work, we show that Arf4 binds to the ciliary targeting sequence (CTS) of fibrocystin. Knockdown of Arf4 indicates that it is not absolutely required for trafficking of the fibrocystin CTS to cilia as steady-state CTS levels are unaffected. However, we did observe a delay in delivery of newly synthesized CTS from the Golgi complex to the cilium when Arf4 was reduced. Arf4 mutant mice are embryonic lethal and die at mid-gestation shortly after node formation. Nodal cilia appeared normal and functioned properly to break left-right symmetry in Arf4 mutant embryos. At this stage of development Arf4 expression is highest in the visceral endoderm but we did not detect cilia on these cells. In the visceral endoderm, the lack of Arf4 caused defects in cell structure and apical protein localization. This work suggests that while Arf4 is not required for ciliary assembly, it is important for the efficient transport of fibrocystin to cilia, and also plays critical roles in non-ciliary processes.
authors.affiliation: Program in Molecular Medicine, University of Massachusetts Medical School, Biotech II, Worcester, Massachusetts, United States of America.
authors.forename: John A
authors.initials: JA
authors.lastname: Follit
authors.affiliation: Program in Molecular Medicine, University of Massachusetts Medical School, Biotech II, Worcester, Massachusetts, United States of America.
authors.forename: Jovenal T
authors.initials: JT
authors.lastname: San Agustin
authors.affiliation: Department of Microbiology and Physiological Systems, University of Massachusetts Medical School, Worcester, Massachusetts, United States of America.
authors.forename: Julie A
authors.initials: JA
authors.lastname: Jonassen
authors.affiliation: Department of Cell and Developmental Biology, University of Massachusetts Medical School, Worcester, Massachusetts, United States of America.
authors.forename: Tingting
authors.initials: T
authors.lastname: Huang
authors.affiliation: Department of Cell and Developmental Biology, University of Massachusetts Medical School, Worcester, Massachusetts, United States of America.
authors.forename: Jaime A
authors.initials: JA
authors.lastname: Rivera-Perez
authors.affiliation: Department of Veterinary and Animal Sciences, University of Massachusetts, Amherst, Amherst, Massachusetts, United States of America.
authors.forename: Kimberly D
authors.initials: KD
authors.lastname: Tremblay
authors.affiliation: Program in Molecular Medicine, University of Massachusetts Medical School, Biotech II, Worcester, Massachusetts, United States of America.
authors.forename: Gregory J
authors.initials: GJ
authors.lastname: Pazour
mesh_terms: D020727:ADP-Ribosylation Factors / Q000235:genetics* / Q000378:metabolism; D000818:Animals; D002462:Cell Membrane; D002923:Cilia / Q000235:genetics / Q000648:ultrastructure; D004622:Embryo, Mammalian / Q000378:metabolism; D047108:Embryonic Development / Q000235:genetics*; D018507:Gene Expression Regulation, Developmental; D006056:Golgi Apparatus / Q000235:genetics / Q000378:metabolism; D006801:Humans; D051379:Mice; D017044:Polycystic Kidney, Autosomal Recessive / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D011956:Receptors, Cell Surface / Q000235:genetics / Q000378:metabolism*
chemical_list: C484365:Pkhd1 protein, mouse; D011956:Receptors, Cell Surface; D020727:ADP-Ribosylation Factors; C571368:ARF4 protein, mouse