A novel cDNA corresponding to transcripts expressed in retina post-mitotic neurons

CEP162 deficiency causes human retinal degeneration and reveals a dual role in ciliogenesis and neurogenesis

Defects in primary or motile cilia result in a variety of human pathologies, and retinal degeneration is frequently associated with these so-called ciliopathies. We found that homozygosity for a truncating variant in CEP162, a centrosome and microtubule-associated protein required for transition zone assembly during ciliogenesis and neuronal differentiation in the retina, caused late-onset retinitis pigmentosa in 2 unrelated families. The mutant CEP162-E646R*5 protein was expressed and properly localized to the mitotic spindle, but it was missing from the basal body in primary and photoreceptor cilia. This impaired recruitment of transition zone components to the basal body and corresponded to complete loss of CEP162 function at the ciliary compartment, reflected by delayed formation of dysmorphic cilia. In contrast, shRNA knockdown of Cep162 in the developing mouse retina increased cell death, which was rescued by expression of CEP162-E646R*5, indicating that the mutant retains its role for retinal neurogenesis. Human retinal degeneration thus resulted from specific loss of the ciliary function of CEP162.

Genetic determinants of ammonia-induced acute lung injury in mice

In this study, a genetically diverse panel of 43 mouse strains was exposed to ammonia, and genome-wide association mapping was performed employing a single-nucleotide polymorphism (SNP) assembly. Transcriptomic analysis was used to help resolve the genetic determinants of ammonia-induced acute lung injury. The encoded proteins were prioritized based on molecular function, nonsynonymous SNP within a functional domain or SNP within the promoter region that altered expression. This integrative functional approach revealed 14 candidate genes that included Aatf, Avil, Cep162, Hrh4, Lama3, Plcb4, and Ube2cbp, which had significant SNP associations, and Aff1, Bcar3, Cntn4, Kcnq5, Prdm10, Ptcd3, and Snx19, which had suggestive SNP associations. Of these genes, Bcar3, Cep162, Hrh4, Kcnq5, and Lama3 are particularly noteworthy and had pathophysiological roles that could be associated with acute lung injury in several ways.

QN1/KIAA1009: a new essential protein for chromosome segregation and mitotic spindle assembly

We previously reported the involvement of QN1 (quail neuroretina 1) protein in cell cycle control during retinal development. We show here that QN1 is an ATPase conserved through evolution, from fugu to humans. We show that chicken/quail QN1 protein is orthologous to the KIAA1009 protein in humans, the function of which was not known. We demonstrate here for the first time that QN1/KIAA1009 protein is located at the spindle poles of the mitotic apparatus and at centrosomes during mitosis. The siRNA-mediated depletion of KIAA1009 led to abnormal mitosis with chromosome segregation defects and abnormal centrosome separation leading to the death of PC12 and MCF7 cells. Thus, QN1/KIAA1009 is a new microtubule-associated ATPase involved in cell division.

Cloning and characterization of a novel transcription factor involved in cellular proliferation arrest: PATF

Cell cycle withdrawal involves several transcription factors such as E2Fs members that play a key role in cell growth control. Here we describe a novel putative bZIP transcription factor isolated from the retina and involved in neuronal proliferation arrest at the terminal differentiation: PATF (Proliferation Arrest Transcription Factor). We show that PATF associates with E2F4 protein and interacts with the E2F consensus site. PATF expression increases with establishment of quiescent state. Furthermore, the nuclear PATF localization like E2F4, depends on cell growth arrest. The decrease of PATF amount, using a retroviral antisense strategy, results in pursued neuroretina cell mitosis. Our results indicate that PATF could be a new molecular signal implicated in the final neuronal cell cycle withdrawal.

Role of QN1 protein in cell proliferation arrest and differentiation during the neuroretina development

In this report, we describe the involvement of the quail neuroretina 1 (QN1) protein in retinal development. The Qn1 cDNA was isolated as a gene specifically expressed at the onset of neuronal cell cycle withdrawal (Bidou et al., Mech. Dev. 43 (1993) 159). Qn1 is located in the cytoplasm in proliferating cells during the early stages of the development. Its distribution changes, becoming predominantly nuclear, in neurons during establishment of the quiescent state upon the differentiation. We decreased the amount of QN1 protein by an antisense strategy in vitro or in vivo. This decrease of the amount of QN1 protein results in additional mitosis and in severe abnormalities such as retinal dysplasia. Our results suggest that QN1 plays a key role at the onset of neuronal cell cycle withdrawal.

Nectinepsin: a new extracellular matrix protein of the pexin family. Characterization of a novel cDNA encoding a protein with an RGD cell binding motif

We report the isolation and characterization of a novel cDNA from quail neuroretina encoding a putative protein named nectinepsin. The nectinepsin cDNA identifies a major 2.2-kilobase mRNA that is detected from ED 5 in neuroretina and is increasingly abundant during embryonic development. A nectinepsin mRNA is also found in quail liver, brain, and intestine and in mouse retina. The deduced nectinepsin amino acid sequence contains the RGD cell binding motif of integrin ligands. Furthermore, nectinepsin shares substantial homologies with vitronectin and structural protein similarities with most of the matricial metalloproteases. However, the presence of a specific sequence and the lack of heparin and collagen binding domains of the vitronectin indicate that nectinepsin is a new extracellular matrix protein. Furthermore, genomic Southern blot studies suggest that nectinepsin and vitronectin are encoded by different genes. Western blot analysis with an anti-human vitronectin antiserum revealed, in addition to the 65- and 70-kDa vitronectin bands, an immunoreactive protein of about 54 kDa in all tissues containing nectinepsin mRNA. It seems likely that the form of vitronectin found in chick egg yolk plasma by Nagano et al. ((1992) J. Biol. Chem. 267, 24863-24870) is the protein that corresponds to the nectinepsin cDNA. This new protein could be an important molecule involved in the early steps of the development.

Target preference of embryonic retina cells and retinal cell lines is cell-autonomous, position-specific, early determined and heritable

Retinal ganglion cells (RGCs) form the topographic connection between retina and optic tectum in the developing avian embryo. In vitro, neurons with the morphological traits and marker expression of RGCs were found both in single-cell cultures from embryonic day (E) 6 chick retina and in retinal cell lines derived from E3.5 quail retina. Rapid and substantial differentiation of RGC-like cells could be induced in the lines by addition of fibroblast growth factor aFGF or bFGF. RGC-like cells were examined with respect to their target discrimination properties as single cells in the stripe carpet assay. In this assay system, alternating stripes of membrane vesicles prepared from the anterior and posterior tectum are offered to growing axonal processes as a substrate. Temporal RGC-like cells, both primary cells prepared from the temporal retina and immortalized cells of those retinal lines derived from the temporal retina, avoid stripes of membrane vesicles from posterior tectum; they prefer to grow on membrane vesicles from the anterior tectum, which is their in vivo target. Nasal RGC-like cells did not exhibit a target preference, in accordance with previous findings. Together the experiments show that target preference of RGCs is a cell-autonomous and heritable mechanism that is determined early and is position-dependent.

Generation of cell lines from embryonic quail retina capable of mature neuronal differentiation

The avian embryonic retina is widely used as a model system for cellular and molecular studies on central nervous system neurons. We aimed at the generation of cell lines from the early embryonic quail retina by retroviral oncogene transduction. For this, we made use of the retina organ culture system which exhibits both proliferation, necessary for stable oncogene transduction, and initial neuronal differentiation, a prerequisite for the generation of cell lines with mature neuronal properties. The oncogene myc was chosen as it is both proliferation-inducing and differentiation-compatible. A chimeric gene, mycER, containing v-myc and the hormone-binding domain of the estrogen receptor, was used for transduction in order to allow for hormone regulation of myc activity. Transduced organ-cultured cells from temporal and nasal retina were passaged into sparse single cell cultures. From these, colonies of rapidly dividing cells were isolated and the progeny expanded as cell lines. The lines contained cells with features of neuroepithelial cells, showing vimentin and A2B5. They also contained spontaneously differentiated neuronal cells showing neurofilament L and N-CAM180. A subpopulation of the neuronal cells exhibited the morphological characteristics of retinal ganglion cells, i.e., large pear-shaped somata each emitting one long process with a distinct growth cone. In addition, they showed the marker profile of retinal ganglion cells, i.e., expression of Thy-1, G4, DM-GRASP, Nr-CAM, neurofilament H, and tau. Neuronal differentiation could be induced by the addition of db cAMP and retinoic acid. The mature neuronal features of the lines open new possibilities to study properties of retinal neurons, including ganglion cells, in a defined and manipulable experimental system.

Developmental control of transcription of a retina-specific gene, QR1, during differentiation: involvement of factors from the POU family

Developmental control of gene expression often results from the coupling of growth arrest with the establishment of differentiation programs. QR1 is a gene specifically expressed in retinas during the late phase of embryogenesis. At this stage neuroectodermal precursors have reached terminal mitosis and are undergoing differentiation into distinct cell types. Transcription of the QR1 gene is tightly regulated during retinal development: this gene is expressed between embryonic day 9 (ED9) and ED17 and is completely repressed at hatching in quail. Moreover, QR1 transcription is downregulated when postmitotic neural retina cells are induced to proliferate by pp60v-src. We studied the stage-dependent transcriptional control of this gene during quail neural retina (QNR) cell development. Transient transfection experiments with QR1/CAT constructs at various stages of development showed that a region located between -935 and -1265 bp upstream of the transcription start site is necessary to promote transcription in retina cells during the late phase of embryonal development (QNR9, corresponding to ED9). By in vivo footprinting assays we identified at least two elements that are occupied by DNA-protein complexes in QNR cells: the A and B boxes. The A box allows formation of several biochemically distinct complexes: C1, C2, C3, and C4. Formation of the C2 complex mainly during early stages (ED7) and of C2, C3, and C4 complexes during postnatal life correlates with repression of QR1 transcription, whereas the C1 complex is strongly induced at ED11 when the QR1 gene is expressed. We previously showed that C1 was involved in downregulation of QR1 transcription by pp60v-src. Several complexes are also formed on the B box. We show that these complexes are exclusively present in neural tissues and that they involve members of the POU family of transcription factors. Mutations of each one of the two regions which abolish the binding of the C1 factor(s) on the A box and of the POU factor(s) on the B box also prevent stimulation of QR1 transcription in QNR9. Therefore, both elements appear to be required for the stage-specific transcription of the QR1 gene. We also show that the regulatory region from position -1265 to position -935 is able to confer stage-specific transcription upon a heterologous promoter (thymidine kinase). Indeed, this region stimulates transcription in differentiating retinas (QNR9) and represses transcription in terminally differentiated retinas (QNR17, corresponding to postnatal life). Our results suggest that cell growth regulation and developmental control are coordinated through the A and B boxes in regulating QR1 transcription during retinal differentiation.