title: Abrupt onset of mutations in a developmentally regulated gene during terminal differentiation of post-mitotic photoreceptor neurons in mice.
abstract: For sensitive detection of rare gene repair events in terminally differentiated photoreceptors, we generated a knockin mouse model by replacing one mouse rhodopsin allele with a form of the human rhodopsin gene that causes a severe, early-onset form of retinitis pigmentosa. The human gene contains a premature stop codon at position 344 (Q344X), cDNA encoding the enhanced green fluorescent protein (EGFP) at its 3' end, and a modified 5' untranslated region to reduce translation rate so that the mutant protein does not induce retinal degeneration. Mutations that eliminate the stop codon express a human rhodopsin-EGFP fusion protein (hRho-GFP), which can be readily detected by fluorescence microscopy. Spontaneous mutations were observed at a frequency of about one per retina; in every case, they gave rise to single fluorescent rod cells, indicating that each mutation occurred during or after the last mitotic division. Additionally, the number of fluorescent rods did not increase with age, suggesting that the rhodopsin gene in mature rod cells is less sensitive to mutation than it is in developing rods. Thus, there is a brief developmental window, coinciding with the transcriptional activation of the rhodopsin locus, in which somatic mutations of the rhodopsin gene abruptly begin to appear.
authors.affiliation: Verna and Marrs McLean Department of Biochemistry and Molecular Biology, Houston, Texas, United States of America.
authors.forename: Ivette M
authors.initials: IM
authors.lastname: Sandoval
authors.affiliation: Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas, United States of America.
authors.forename: Brandee A
authors.initials: BA
authors.lastname: Price
authors.affiliation: Department of Vision Science, University of Alabama Birmingham, Birmingham, Alabama, United States of America.
authors.forename: Alecia K
authors.initials: AK
authors.lastname: Gross
authors.affiliation: Verna and Marrs McLean Department of Biochemistry and Molecular Biology, Houston, Texas, United States of America.
authors.forename: Fung
authors.initials: F
authors.lastname: Chan
authors.affiliation: Department of Vision Science, University of Alabama Birmingham, Birmingham, Alabama, United States of America.
authors.forename: Joshua D
authors.initials: JD
authors.lastname: Sammons
authors.affiliation: Verna and Marrs McLean Department of Biochemistry and Molecular Biology, Houston, Texas, United States of America; Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas, United States of America.
authors.forename: John H
authors.initials: JH
authors.lastname: Wilson
authors.affiliation: Verna and Marrs McLean Department of Biochemistry and Molecular Biology, Houston, Texas, United States of America.
authors.forename: Theodore G
authors.initials: TG
authors.lastname: Wensel
mesh_terms: D000375:Aging / Q000235:genetics; D000818:Animals; D002454:Cell Differentiation; D002478:Cells, Cultured; D004195:Disease Models, Animal; D018507:Gene Expression Regulation, Developmental; D055879:Gene Knock-In Techniques; D049452:Green Fluorescent Proteins / Q000235:genetics; D006801:Humans; D051379:Mice; D008810:Mice, Inbred C57BL; D008856:Microscopy, Fluorescence; D009154:Mutation; D012160:Retina / Q000473:pathology; D017948:Retinal Rod Photoreceptor Cells / Q000166:cytology*; D012174:Retinitis Pigmentosa / Q000235:genetics*; D012243:Rhodopsin / Q000235:genetics*; D015533:Transcriptional Activation / Q000235:genetics
chemical_list: C485184:enhanced green fluorescent protein; D049452:Green Fluorescent Proteins; D012243:Rhodopsin