title: An unstable targeted allele of the mouse Mitf gene with a high somatic and germline reversion rate.
abstract: The mouse Mitf gene encodes a transcription factor that is regulated by serine phosphorylation and is critical for the development of melanin-containing pigment cells. To test the role of phosphorylation at a particular serine, S73 in exon 2 of Mitf, we used a standard targeting strategy in mouse embryonic stem cells to change the corresponding codon into one encoding an alanine. By chance, we generated an allele in which 85,222 bp of wild-type Mitf sequence are duplicated and inserted into an otherwise correctly targeted Mitf gene. Depending on the presence or absence of a neomycin resistance cassette, this genomic rearrangement leads to animals with a white coat with or without pigmented spots or a gray coat with obligatory white and black spots. Several independent, genetically stable germline revertants that lacked the duplicated wild-type sequence but retained the targeted codon were then derived. These animals were normally pigmented, indicating that the serine-to-alanine mutation is not deleterious to melanocyte development. The fact that mosaic coat reversions occur in all mice lacking the neo-cassette and that approximately 1% of these transmit a reverted allele to their offspring places this mutation among those with the highest spontaneous reversion rates in mammals.
authors.affiliation: Mammalian Development Section, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland 20892-3706, USA.
authors.forename: Keren
authors.initials: K
authors.lastname: Bismuth
authors.forename: Susan
authors.initials: S
authors.lastname: Skuntz
authors.forename: Jón H
authors.initials: JH
authors.lastname: Hallsson
authors.forename: Evgenia
authors.initials: E
authors.lastname: Pak
authors.forename: Amalia S
authors.initials: AS
authors.lastname: Dutra
authors.forename: Eiríkur
authors.initials: E
authors.lastname: Steingrímsson
authors.forename: Heinz
authors.initials: H
authors.lastname: Arnheiter
mesh_terms: D000409:Alanine / Q000235:genetics; D000483:Alleles; D019943:Amino Acid Substitution / Q000187:drug effects; D000818:Animals; D004351:Drug Resistance / Q000187:drug effects; D005260:Female; D005455:Fluorescent Antibody Technique; D005786:Gene Expression Regulation / Q000187:drug effects; D018390:Gene Targeting; D018095:Germ-Line Mutation / Q000235:genetics*; D006720:Homozygote; D017404:In Situ Hybridization, Fluorescence; D007438:Introns / Q000235:genetics; D008297:Male; D051379:Mice; D051739:Microphthalmia-Associated Transcription Factor / Q000235:genetics*; D016254:Mutagenesis, Insertional / Q000187:drug effects; D009355:Neomycin / Q000494:pharmacology; D010641:Phenotype; D010858:Pigmentation / Q000187:drug effects; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D017422:Sequence Analysis, DNA; D012694:Serine / Q000235:genetics
chemical_list: D051739:Microphthalmia-Associated Transcription Factor; D012333:RNA, Messenger; D012694:Serine; D009355:Neomycin; D000409:Alanine