NINL and DZANK1 Co-function in Vesicle Transport and Are Essential for Photoreceptor Development in Zebrafish

Abstract

Ciliopathies are Mendelian disorders caused by dysfunction of cilia, ubiquitous organelles involved in fluid propulsion (motile cilia) or signal transduction (primary cilia). Retinal dystrophy is a common phenotypic characteristic of ciliopathies since photoreceptor outer segments are specialized primary cilia. These ciliary structures heavily rely on intracellular minus-end directed transport of cargo, mediated at least in part by the cytoplasmic dynein 1 motor complex, for their formation, maintenance and function. Ninein-like protein (NINL) is known to associate with this motor complex and is an important interaction partner of the ciliopathy-associated proteins lebercilin, USH2A and CC2D2A. Here, we scrutinize the function of NINL with combined proteomic and zebrafish in vivo approaches. We identify Double Zinc Ribbon and Ankyrin Repeat domains 1 (DZANK1) as a novel interaction partner of NINL and show that loss of Ninl, Dzank1 or both synergistically leads to dysmorphic photoreceptor outer segments, accumulation of trans-Golgi-derived vesicles and mislocalization of Rhodopsin and Ush2a in zebrafish. In addition, retrograde melanosome transport is severely impaired in zebrafish lacking Ninl or Dzank1. We further demonstrate that NINL and DZANK1 are essential for intracellular dynein-based transport by associating with complementary subunits of the cytoplasmic dynein 1 motor complex, thus shedding light on the structure and stoichiometry of this important motor complex. Altogether, our results support a model in which the NINL-DZANK1 protein module is involved in the proper assembly and folding of the cytoplasmic dynein 1 motor complex in photoreceptor cells, a process essential for outer segment formation and function.

Mutagenesis of putative ciliary genes with the CRISPR/Cas9 system in zebrafish identifies genes required for retinal development

“…In our study, we discovered 3 genes ( vps28, ran , and sec13 ) that encode proteins for protein transport (27, 31, 48) are required for retinal development. This is consistent with previous observations that photoreceptor development is sensitive to defects in intracellular transport (49), especially nuclear protein transport (27). Niu et al .…”

The cytoplasmic dynein transport machinery and its many cargoes

“…In zebrafish lacking the protein ninein-like (NINL), melanosome transport is severely impaired. NINL interacts with components of the dynein and dynactin complex as shown via mass spectrometry experiments 97,98 , and human NINL is an activating adaptor 98 , suggesting that NINL is the activating adaptor for melanosome motility.…”

Ataluren for the Treatment of Usher Syndrome 2A Caused by Nonsense Mutations

“…The long USH2A isoform b is a transmembrane protein composed of a signal peptide, a large extracellular domain with several functional subdomains, such as FN3 (fibronectin type II motif) domains, a laminin G-like domain (LamGL), several laminin-type EGF (epidermal growth factor)-like modules (EGF-LAM) and two laminin G domains (LamG), a transmembrane domain, and the intracellular cytoplasmic tail domain containing a PDZ-binding motif (PBM) ( Figure 2A). The PBM links the USH2A protein to several other proteins, such as whirlin (USH2D) and ninein-like protein (NINL) [24,25]. The USH2A protein is essential in the maintenance of photoreceptor cells and the normal development of cochlear hair cells [26] ( Figure 2A).…”