title: A rare complex DNA rearrangement in the murine Steel gene results in exon duplication and a lethal phenotype.
abstract: Kit ligand (Kitl), encoded by the Steel (Sl) locus, plays an essential role in hematopoiesis, gametogenesis, and melanogenesis during both embryonic and adult life. We have characterized a new spontaneous mutant of the Sl locus in mice designated KitlSl-20J that arose in the breeding colony at Jackson Laboratories. Heterozygous KitlSl-20J mice display a white belly spot and intercrossing results in an embryonic lethal phenotype in the homozygous state. Analysis of homozygous embryos demonstrated a significant reduction in fetal liver cellularity, colony forming unit-erythroid (CFU-E) progenitors, and a total absence of germ cells. Although expressed in vivo, recombinant mutant protein demonstrated loss of bioactivity that was correlated with lack of receptor binding. Analysis of the Sl gene transcripts in heterozygous KitlSl-20J mice revealed an in-frame tandem duplication of exon 3. A long-range polymerase chain reaction (PCR) strategy using overlapping primers in exon 3 amplified an approximately 7-kilobase (kb) product from DNA isolated from heterozygous KitlSl-20J mice but not from wild-type DNA that contained sequences from both introns 2 and 3 and an inverted intron 2 sequence, suggesting a complex rearrangement as the mechanism of the mutation. "Complexity analysis" of the sequence of the amplified product strongly suggests that local DNA motifs may have contributed to the generation of this spontaneous KitlSl-20J allele, likely mediated by a 2-step process. The KitlSl-20J mutation is a unique KitlSl allele and represents an unusual mechanism of mutation.
authors.affiliation: Division of Experimental Hematology, Cincinnati Children's Hospital, Medical Center, 3333 Burnet Ave, Cincinnati, OH 45229, USA.
authors.forename: Saurabh
authors.initials: S
authors.lastname: Chandra
authors.forename: Reuben
authors.initials: R
authors.lastname: Kapur
authors.forename: Nadia
authors.initials: N
authors.lastname: Chuzhanova
authors.forename: Victoria
authors.initials: V
authors.lastname: Summey
authors.forename: David
authors.initials: D
authors.lastname: Prentice
authors.forename: Jane
authors.initials: J
authors.lastname: Barker
authors.forename: David N
authors.initials: DN
authors.lastname: Cooper
authors.forename: David A
authors.initials: DA
authors.lastname: Williams
mesh_terms: D000818:Animals; D015672:Erythroid Precursor Cells; D005091:Exons; D020440:Gene Duplication; D015321:Gene Rearrangement; D005804:Genes, Lethal / Q000235:genetics*; D005854:Germ Cells; D007438:Introns; D008099:Liver / Q000166:cytology; D051379:Mice; D008810:Mice, Inbred C57BL; D008817:Mice, Mutant Strains; D009154:Mutation; D010641:Phenotype; D011485:Protein Binding / Q000235:genetics; D019009:Proto-Oncogene Proteins c-kit / Q000378:metabolism; D019089:Stem Cell Factor / Q000096:biosynthesis / Q000235:genetics* / Q000378:metabolism
chemical_list: D019089:Stem Cell Factor; D019009:Proto-Oncogene Proteins c-kit