Expression of 8-oxoguanine DNA glycosylase (Ogg1) in mouse retina.
OBJECTIVE
The retina is highly exposed to oxidative stress due to the high level of oxygen consumption in this tissue and its exposure to light. The main DNA base lesion generated by oxygen free radicals is 8-oxoguanine (8-oxoG). However, its presence in retinal cells and the mechanisms underlying its repair remain undetermined.


METHODS
8-oxoguanine DNA glycosylase (Ogg1) gene expression and messenger localization in adult mouse ocular tissues was analyzed by RT-PCR and in situ hybridization. Using immunohistochemistry, we determined the localization of Ogg1 protein and three base excision repair (BER) enzymes: apurinic/apyrimidic endonuclease (APE1), DNA polymerase beta, and X-ray repair cross-complementation group 1 (XRCC1). Ogg1 and AP-lyase activities in the neuroretina were obtained using double-stranded oligonucleotides harboring either an 8-oxoG residue or a tetrahydrofuran.


RESULTS
We report here that 8-oxoG is abundant in the retina. Ogg1, the enzyme responsible for the recognition and excision of the oxidized base, is present in its active form and found mainly in ganglion cells and photoreceptor inner segments. We show that APE1 and DNA polymerase beta, two BER proteins involved in 8-oxoG repair, are also present in these cells. The cellular distribution of these proteins was similar to that of Ogg1. XRRC1 is present in both inner nuclear and ganglion cells layers; however, this protein is absent from photoreceptor inner segments.


CONCLUSIONS
This is the first study to demonstrate the presence of a functional 8-oxoG BER pathway in retinal neurons. The study of three BER proteins involved in 8-oxoG elimination demonstrates that XRCC1 localization differs from those of Ogg1, APE1, and DNA polymerase beta. This result suggests that the elimination of 8-oxoG is coordinated through two pathways, which differ slightly according to the cellular localization of the abnormally oxidized guanine.
Bigot
Karine
K
Université Paris-Descartes, CERTO, Centre de Recherche Thérapeutique en Ophtalmologie, Paris, France.
Leemput
Julia
J
Vacher
Monique
M
Campalans
Anna
A
Radicella
J Pablo
JP
Lacassagne
Emmanuelle
E
Provost
Alexandra
A
Masson
Christel
C
Menasche
Maurice
M
Abitbol
Marc
M
D000704:Analysis of Variance; D000818:Animals; D045647:DNA Glycosylases / Q000235:genetics* / Q000378:metabolism*; D019951:DNA Polymerase beta / Q000235:genetics / Q000378:metabolism; D004260:DNA Repair / Q000235:genetics; D043603:DNA-(Apurinic or Apyrimidinic Site) Lyase / Q000235:genetics / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D005123:Eye / Q000378:metabolism; D015870:Gene Expression; D020869:Gene Expression Profiling / Q000379:methods; D007150:Immunohistochemistry; D017403:In Situ Hybridization; D051379:Mice; D016133:Polymerase Chain Reaction; D012160:Retina / Q000378:metabolism*; D000076105:X-ray Repair Cross Complementing Protein 1
D004268:DNA-Binding Proteins; D000076105:X-ray Repair Cross Complementing Protein 1; C000619352:Xrcc1 protein, mouse; D019951:DNA Polymerase beta; D045647:DNA Glycosylases; C485990:Ogg1 protein, mouse; C486216:Apex1 protein, mouse; D043603:DNA-(Apurinic or Apyrimidinic Site) Lyase