Knockdown of poc1b causes abnormal photoreceptor sensory cilium and vision impairment in zebrafish

Abstract

Proteomic analysis of the mouse photoreceptor sensory cilium identified a set of cilia proteins, including Poc1 centriolar protein b (Poc1b). Previous functional studies in human cells and zebrafish embryos implicated that Poc1b plays important roles in centriole duplication and length control, as well as ciliogenesis. To study the function of Poc1b in photoreceptor sensory cilia and other primary cilia, we expressed a tagged recombinant Poc1b protein in cultured renal epithelial cells and rat retina. Poc1b was localized to the centrioles and spindle bundles during cell cycle progression, and to the basal body of photoreceptor sensory cilia. A morpholino knockdown and complementation assay of poc1b in zebrafish showed that loss of poc1b led to a range of morphological anomalies of cilia commonly associated with human ciliopathies. In the retina, the development of retinal laminae was significantly delayed and the length of photoreceptor outer segments was shortened. Visual behavior studies revealed impaired visual function in the poc1b morphants. In addition, ciliopathy-associated developmental defects, such as small eyes, curved body axis, heart defects, and shortened cilia in Kupffer's vesicle, were observed as well. These data suggest that poc1b is required for normal development and ciliogenesis of retinal photoreceptor sensory cilia and other cilia. Furthermore, this conclusion is supported by recent findings that mutations in POC1B gene have been identified in patients with inherited retinal dystrophy and syndromic retinal ciliopathy.

Phenotypical Characteristics ofPOC1B-Associated Retinopathy in Japanese Cohort: Cone Dystrophy With Normal Funduscopic Appearance

“…37 A morpholino oligomer knockdown of poc1b translation in zebrafish resulted in a dosedependent small-eye phenotype, impaired optokinetic responses, and decreased length of the photoreceptor outer segments. 40 These findings suggested that poc1b is required for the normal development and ciliogenesis of the retinal photoreceptor sensory cilia. 40 Homozygous or compound heterozygous mutations of the POC1B gene in three Turkish patients and a Dutch subject with COD and CORD were reported in 2014.…”

“…40 These findings suggested that poc1b is required for the normal development and ciliogenesis of the retinal photoreceptor sensory cilia. 40 Homozygous or compound heterozygous mutations of the POC1B gene in three Turkish patients and a Dutch subject with COD and CORD were reported in 2014. 29 The three mutations were located in a highly conserved residue within the WD40 domain.…”

Versatile Genome Engineering Techniques Advance Human Ocular Disease Researches in Zebrafish

“…This molecular process is critical for cilia formation and thus affects ocular development. In addition, controlling the expression of another cilia-related gene, poc1b, with MO knockdown resulted in similar photoreceptor sensory cilium defects as those observed in the inpp5e morphant (Roosing et al, 2014 ; Zhang et al, 2015 ). The MO knockdown technique has underpinned the initial growth of gene discovery, which was valuable for human ocular disease studies in zebrafish.…”

“…By combining the MO knockdown technique with the fast-developing zebrafish, researchers have identified a dozen genes associated with JBTS. JBTS-causing genes, including AHI (Elsayed et al, 2015 ), CC2D2A (Bachmann-Gagescu et al, 2011 , 2015 ), CEP290 (Baye et al, 2011 ), CSPP1 (Tuz et al, 2014 ), INPP5E (Luo et al, 2012 ; Xu et al, 2017 ), PDE6D (Thomas S. et al, 2014 ), and POC1B (Roosing et al, 2014 ; Zhang et al, 2015 ), have been verified in zebrafish models. Specifically, knocking down inpp5e by MOs lead to microphthalmia, pronephros cysts and pericardial effusion in zebrafish.…”

Zebrafish: a vertebrate tool for studying basal body biogenesis, structure, and function

“…Knockdown of the zebrafish orthologue Poc1b using MOs results in phenotypic similarities to cilia deficient mutants, including visual impairment. Cilia motility and length is hindered in Poc1b morphant zebrafish embryos [ 53 – 55 ]. Recently, mutations in POC1B have been identified in patients displaying ciliopathy features [ 54 , 56 , 57 ].…”