Genomic organization of the mouse Surfeit locus and comparison with the organization of the Fugu Surfeit genes at three separate loci. (A) Organization of the mouse Surfeit locus. The relative orientation of the genes and their intergenic distances are shown (adapted from Garson et al. 1995). The continuous line represents genomic DNA. The direction of transcription of each gene (Surf-1 to Surf-6) is indicated by arrows, and the 5′ end of each gene can be seen to be associated with a CpG island (▪). In human the ASS gene is located ∼2–4 Mb from the Surfeit locus 3′ to the Surf-6 gene. The human EST00098 has been mapped to chromosome 9 but is not found within 50 kb either side of Surfeit locus as determined by PCR. These features have not been determined in mouse. (B) Cosmid contig construction demonstrates that the Fugu Surfeit gene homologs are located at three separate loci (modified from Gilley et al. 1997). Cosmid contigs were constructed around each of the three Fugu genomic loci; (i) containing the Fugu Surf-3/rpL7a, Surf-1, and Surf-6 gene homologs, (ii) containing the FuguSurf-2, Surf-4, and ASS gene homologs and sequences homologous to human EST00098, and (iii) containing the Fugu Surf-5 gene homolog only. In each case, Fugu genomic DNA is represented as a thick horizontal line, and, above, the direction of transcription and position of each of gene is expanded for clarity. Intergenic distances between Fugu Surfeit genes are shown. Cosmid contigs are highlighted below the genomic DNA with each cosmid clone shown as a thin horizontal line. Each cosmid is labeled with its original Fugu cosmid library clone number. Cosmids in each contig were isolated and arranged relative to one another using restriction and hybridization analyses. None of the cosmids overlap with cosmids from either of the other two contigs. The approximate distance that each contig stretches either side of the FuguSurfeit gene loci is shown in kilobases below the genomic DNA. Each contig shows only informative cosmids. Additional cosmids in contigi are 006I18, 041C23, 059G12, 070P11, 111D07, 111M11, 111N11, 117M14, 194B16, and 194C20, and additional cosmids in contigii are 007P02, 028B15, 044B19, 139G10, 186G08, and 196C01. No additional cosmids could be identified for locus iii, owing to the probable presence of numerous repetitive elements.
