A Mutation in Syne2 Causes Early Retinal Defects in Photoreceptors, Secondary Neurons, and Müller Glia.

Purpose: The purpose of this study was to identify the molecular basis and characterize the pathological consequences of a spontaneous mutation named cone photoreceptor function loss 8 (cpfl8) in a mouse model with a significantly reduced cone electroretinography (ERG) response.

Methods: The chromosomal position for the recessive cpfl8 mutation was determined by DNA pooling and by subsequent genotyping with simple sequence length polymorphic markers in an F2 intercross phenotyped by ERG. Genes within the candidate region of both mutants and controls were directly sequenced and compared.

A novel allele of Alx4 results in reduced Fgf10 expression and failure of eyelid fusion in mice.

Normal fusion of developing eyelids requires coordination of inductive signals from the eyelid mesenchyme with migration of the periderm cell layer and constriction of the eyelids across the eye. Failure of this process results in an eyelids open at birth (EOB) phenotype in mice. We have identified a novel spontaneous allele of Alx4 that displays EOB, in addition to polydactyly and cranial malformations.

An allele of microtubule-associated protein 1A (Mtap1a) reduces photoreceptor degeneration in Tulp1 and Tub Mutant Mice.

Purpose: To identify genes that modify photoreceptor cell loss in the retinas of homozygous Tulp1(tm1Pjn) and Tub(tub) mice, which exhibit juvenile retinitis pigmentosa.

Methods: Modifier loci were identified by genetic quantitative trait locus analysis. F2 Tulp1(tm1Pjn/tm1Pjn) mutant mice from a B6-Tulp1(tm1Pjn/tm1Pjn) × AKR/J intercross were genotyped with a panel of single nucleotide polymorphism markers and phenotyped by histology for photoreceptor nuclei remaining at 9 weeks of age.

An ENU-induced mutation in the Mertk gene (Mertknmf12) leads to a slow form of retinal degeneration.

Purpose: To determine the basis and to characterize the phenotype of a chemically induced mutation in a mouse model of retinal degeneration.

Methods: Screening by indirect ophthalmoscopy identified a line of N-ethyl-N-nitrosourea (ENU) mutagenized mice demonstrating retinal patches. Longitudinal studies of retinal histologic sections showed photoreceptors in the peripheral retina undergoing slow, progressive degeneration.

Retina-specific GTPase accelerator RGS11/G beta 5S/R9AP is a constitutive heterotrimer selectively targeted to mGluR6 in ON-bipolar neurons.

Members of the R7 family of the regulators of G-protein signaling (R7 RGS) proteins form multi-subunit complexes that play crucial roles in processing the light responses of retinal neurons. The disruption of these complexes has been shown to lead to the loss of temporal resolution in retinal photoreceptors and deficient synaptic transmission to downstream neurons. Despite the well established role of one member of this family, RGS9-1, in controlling vertebrate phototransduction, the roles and organizational principles of other members in the retina are poorly understood.

Allelic variance between GRM6 mutants, Grm6nob3 and Grm6nob4 results in differences in retinal ganglion cell visual responses.

An electroretinogram (ERG) screen identified a mouse with a normal a-wave but lacking a b-wave, and as such it was designated no b-wave3 (nob3). The nob3 phenotype mapped to chromosome 11 in a region containing the metabotropic glutamate receptor 6 gene (Grm6). Sequence analyses of cDNA identified a splicing error in Grm6, introducing an insertion and an early stop codon into the mRNA of affected mice (designated Grm6(nob3)).

Generation, identification and functional characterization of the nob4 mutation of Grm6 in the mouse.

We performed genome-wide chemical mutagenesis of C57BL/6J mice using N-ethyl-N-nitrosourea (ENU). Electroretinographic screening of the third generation offspring revealed two G3 individuals from one G1 family with a normal a-wave but lacking the b-wave that we named nob4. The mutation was transmitted with a recessive mode of inheritance and mapped to chromosome 11 in a region containing the Grm6 gene, which encodes a metabotropic glutamate receptor protein, mGluR6.

The mouse vesicular inhibitory amino acid transporter gene: expression during embryogenesis, analysis of its core promoter in neural stem cells and a reconsideration of its alternate splicing.

The vesicular inhibitory amino acid transporter, VIAAT (also known as vesicular GABA transporter VGAT) transports GABA or glycine into synaptic vesicles. To initiate an analysis of the expression and regulation of VIAAT during neurogenesis we have cloned and characterized the mouse Viaat gene. We find that the mouse Viaat coding sequence is encoded by two exons spanning 5.

Induction of cystine-glutamate transporter xc- by human immunodeficiency virus type 1 transactivator protein tat in retinal pigment epithelium.

Purpose: The transactivator protein Tat encoded by the human immunodeficiency virus-1 (HIV-1) genome reduces glutathione levels in mammalian cells. Because the retina contains large amounts of glutathione, a study was undertaken to determine the influence of Tat on glutathione levels, gamma-glutamyl transpeptidase activity, and the expression and activity of the cystine-glutamate transporter xc- in the human retinal pigment epithelial cell line ARPE-19 and in retina from Tat-transgenic mice.

Methods: The transport function of xc- was measured as glutamate uptake in the absence of Na+.

Osmoregulation of taurine transporter function and expression in retinal pigment epithelial, ganglion, and müller cells.

Purpose: To determine whether taurine transporter (TauT) activity and expression are regulated by hyperosmolarity in RPE, ganglion, and Müller cells.

Methods: Uptake of taurine was measured in ARPE-19 cells cultured in DMEM-F12 medium without or with the addition of 50 mM NaCl or 100 mM mannitol. The kinetics of the transport were analyzed.

Reduced-folate carrier (RFC) is expressed in placenta and yolk sac, as well as in cells of the developing forebrain, hindbrain, neural tube, craniofacial region, eye, limb buds and heart.

Background: Folate is essential for cellular proliferation and tissue regeneration. As mammalian cells cannot synthesize folates de novo, tightly regulated cellular uptake processes have evolved to sustain sufficient levels of intracellular tetrahydrofolate cofactors to support biosynthesis of purines, pyrimidines, and some amino acids (serine, methionine). Though reduced-folate carrier (RFC) is one of the major proteins mediating folate transport, knowledge of the developmental expression of RFC is lacking.

Human sodium-coupled citrate transporter, the orthologue of Drosophila Indy, as a novel target for lithium action.

NaCT (sodium-coupled citrate transporter) is an Na(+)-coupled citrate transporter identified recently in mammals that mediates the cellular uptake of citrate. It is expressed predominantly in the liver. NaCT is structurally and functionally related to the product of the Indy (I'm not dead yet) gene in Drosophila, the dysfunction of which leads to lifespan extension.

Analysis of sigma receptor (sigmaR1) expression in retinal ganglion cells cultured under hyperglycemic conditions and in diabetic mice.

The type 1 sigma receptor (sigmaR1) is a nonopiate and nonphencyclidine binding site that has numerous pharmacological and physiological functions. In some studies, agonists for sigmaR1 have been shown to afford neuroprotection against overstimulation of the NMDA receptor. sigmaR1 expression has been demonstrated recently in retinal ganglion cells (RGC).

Structure, function, and expression pattern of a novel sodium-coupled citrate transporter (NaCT) cloned from mammalian brain.

Citrate plays a pivotal role not only in the generation of metabolic energy but also in the synthesis of fatty acids, isoprenoids, and cholesterol in mammalian cells. Plasma levels of citrate are the highest ( approximately 135 microm) among the intermediates of the tricarboxylic acid cycle. Here we report on the cloning and functional characterization of a plasma membrane transporter (NaCT for Na+ -coupled citrate transporter) from rat brain that mediates uphill cellular uptake of citrate coupled to an electrochemical Na+ gradient.