title: Presence of the Gpr179(nob5) allele in a C3H-derived transgenic mouse.
abstract: OBJECTIVE
  To identify the mutation responsible for an abnormal electroretinogram (ERG) in a transgenic mouse line (tg21) overexpressing erythropoietin (Epo). The tg21 line was generated on a mixed (C3H; C57BL/6) background and lacked the b-wave component of the ERG. This no-b-wave (nob) ERG is seen in other mouse models with depolarizing bipolar cell (DBC) dysfunction and in patients with the complete form of congenital stationary night blindness (cCSNB). We determined the basis for the nob ERG phenotype and screened C3H mice for the mutation to evaluate whether this finding is important for the vision research community.
  
  
  METHODS
  ERGs were used to examine retinal function. The retinal structure of the transgenic mice was investigated using histology and immunohistochemistry. Inverse PCR was performed to identify the insertion site of the Epo transgene in the mouse genome. Affected mice were backcrossed to follow the inheritance pattern of the nob ERG phenotype. Quantitative real-time PCR (qRT PCR), Sanger sequencing, and immunohistochemistry were used to identify the mutation causing the defect. Additional C3H sublines were screened for the detected mutation.
  
  
  RESULTS
  Retinal histology and blood vessel structure were not disturbed, and no loss of DBCs was observed in the tg21 nob mice. The mutation causing the nob ERG phenotype is inherited independently of the tg21 transgene. The qRT PCR experiments revealed that the nob ERG phenotype reflected a mutation in Gpr179, a gene involved in DBC signal transduction. PCR analysis confirmed the presence of the Gpr179(nob5) insertional mutation in intron 1 of Gpr179. Screening for mutations in other C3H-derived lines revealed that C3H.Pde6b(+) mice carry the Gpr179 (nob5) allele whereas C3H/HeH mice do not.
  
  
  CONCLUSIONS
  We identified the presence of the Gpr179(nob5) mutation causing DBC dysfunction in a C3H-derived transgenic mouse line. The nob phenotype is not related to the presence of the transgene. The Gpr179(nob5) allele can be added to the list of background alleles that impact retinal function in commonly used mouse lines. By providing primers to distinguish between Gpr179 mutant and wild-type alleles, this study allows investigators to monitor for the presence of the Gpr179(nob5) mutation in other mouse lines derived from C3H.
authors.affiliation: Department of Ophthalmology, Inselspital, University of Bern, Switzerland ; Graduate School for Cellular and Biomedical Sciences, University of Bern, Switzerland.
authors.forename: Jasmin
authors.initials: J
authors.lastname: Balmer
authors.affiliation: Department of Biochemistry and Molecular Biology, University of Louisville, KY.
authors.forename: Rui
authors.initials: R
authors.lastname: Ji
authors.affiliation: Department of Biochemistry and Molecular Biology, University of Louisville, KY.
authors.forename: Thomas A
authors.initials: TA
authors.lastname: Ray
authors.affiliation: Department of Ophthalmology, Inselspital, University of Bern, Switzerland.
authors.forename: Fabia
authors.initials: F
authors.lastname: Selber
authors.affiliation: Institute of Veterinary Physiology, University of Zürich, Switzerland.
authors.forename: Max
authors.initials: M
authors.lastname: Gassmann
authors.affiliation: Department of Ophthalmic Research, Cole Eye Institute, Cleveland Clinic, Cleveland OH ; Research Service, Louis Stokes Cleveland VA Medical Center, Cleveland OH ; Department of Ophthalmology, Cleveland Clinic Lerner College of Medicine of Case Western Reserve University, Cleveland OH.
authors.forename: Neal S
authors.initials: NS
authors.lastname: Peachey
authors.affiliation: Department of Biochemistry and Molecular Biology, University of Louisville, KY.
authors.forename: Ronald G
authors.initials: RG
authors.lastname: Gregg
authors.affiliation: Department of Ophthalmology, Inselspital, University of Bern, Switzerland.
authors.forename: Volker
authors.initials: V
authors.lastname: Enzmann
mesh_terms: D000483:Alleles; D000818:Animals; D003433:Crosses, Genetic; D004195:Disease Models, Animal; D004596:Electroretinography; D004921:Erythropoietin / Q000235:genetics* / Q000378:metabolism; D005260:Female; D018703:Founder Effect; D015870:Gene Expression; D006801:Humans; D008297:Male; D051379:Mice; D008809:Mice, Inbred C3H; D008822:Mice, Transgenic; D016254:Mutagenesis, Insertional; D009755:Night Blindness / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D043562:Receptors, G-Protein-Coupled / Q000235:genetics* / Q000378:metabolism; D051245:Retinal Bipolar Cells / Q000378:metabolism* / Q000473:pathology; D015398:Signal Transduction; D019076:Transgenes
chemical_list: C554270:EPO protein, human; C575060:GPR179 protein, mouse; D043562:Receptors, G-Protein-Coupled; D004921:Erythropoietin