(A) A proposed model of the gorilla evolutionary translocation t(4;19). FISH results showed that the GGO 19 breakpoint maps between BAC clones RP11–640I15 and CTD-3157E16, at the border between LCR17pA/B and LCR17pA/D. The BLAST analysis of this junction in human (indicated with solid arrows) revealed several fission fragments scattered within proximal 17p (border between yellow and green rectangles depicted with dotted arrows), suggesting evolutionary unequal crossing-over constraint on this junction. Such genomic misalignments might have led to chromosome breakage and the origination of the evolutionary gorilla translocation t(4;19). Note the presence of a Charlie3 transposon at the edge of the SMS-REP fragment identified by sequencing the GGO 19 breakpoint and the sequence IMAGE:5265056 likely expressed in the human brain (hippocampus). (B) PCR confirmation analysis of the breakpoint of the gorilla translocation t(4;19). PCR primers spanning the t(4;19) were designed from gorilla BAC genomic clone CHORI-255–413A16 sequence. Genomic DNA from Homo sapiens (HSA), Pan troglodytes (PTR), Gorilla gorilla (GGO), and Pongo pygmaeus (PPY) was subjected to PCR amplification. A 444-bp product was obtained only in gorilla genomic DNA, indicating the translocation is unique to this genus. (C) Schematic diagram of human chromosomes 5 and 17 and gorilla translocation chromosomes 4 “der(HSA17)” and 19 “der(HSA5)”. Vertical bars represent the breakpoint spanning clones. (D,E). FISH analysis of gorilla BACs. (D) Human metaphase spread with human BAC probe RP11–90A9 (red), which hybridizes to chromosome 5 (this clone spans the evolutionary breakpoint but doesn't show a signal on chromosome 17 because the breakpoint is very close to the end of the BAC), and gorilla BAC probe CHORI 255–413A16 (green), which hybridizes to chromosomes 5 and 17, suggesting this clone spans the t(4;19) breakpoint in gorilla. (E) Gorilla metaphase spread with human BAC probe RP11–90A9 (red), which hybridizes to chromosome 19, and gorilla BAC probe CHORI 255–413A16 (green), which hybridizes to chromosomes 4 and 19. (F) The BLAST analysis of the gorilla BAC clone 413A16 spanning the t(4;19) breakpoint revealed a complex rearrangement on the HSA17 portion of this clone. Note the presence of DNA sequences from HSA 17p11.2, 17p13.2, and 17q23.2.
