Physical Mapping Of Chicken Functional Genes By Fluorescence In Situ Hybridization (FISH) And Comparative Genomic Study Of Chicken

Using BAC DNA as probes for fluorescence in-situ hybridization (FISH), 20 functional chicken genes have been localized to chicken metaphase chromosomes prepared from embryo fibroblast cells with an air-drying method. The gene position was identified by FLpter (fractional length, the ratio between the distance from hybridization signal to the p-arm telomere and the full length of the chromosome) and comparison with the international standardized G-banded ideogram of chicken. The positions of 19 genes were identified. Of the 19 genes, 12 genes have not been mapped previously, and their chromosomal positions are as follows: ALVEB5, lp26-24; ACO2, 1pl6-14; LGAL4, 1pl5-14; HSP108, Ipl4-13; CD4, 1q11; HSD3B, 1q11-12; SOD1,1lq14-21; LAMP1, 1q24-31; P2Y5, lq35-36; EN2, 2p33; NPY, 2pl4-13 and CA2, 2q31-32.Although another gene HBB was not identified positively, its physical mapping to chicken chromosomes indicated that the W chromosome, q-arm telomere of chromosome 1, p-arm telomere of chromosome 2, and the centromeres of chromosome 3 and 5 contained abundant heterochromatin or repeat sequences.Twelve functional chicken genes mapped newly in this study enriched the comparative maps between chicken, human and mouse. Comparative mapping analysis of these genes in chicken, human and mouse provided additional cytogenetic evidence for several conserved chromosomal segments. At the same time, a new conserved homologous segment was found between chicken and mouse, and it is lqll in chicken, corresponding to 6F3 in mouse. Now this segment includes two genes SCNN1A and CD4.Comparative chromosome karyotype and G-bands among chicken, duck and ostrich indicated that their first largest 3 pairs of chromosomes were all the type of M, SM/M, and ST/T, which is the typical characteristic of primitive karyotype. Futhermore, G-bands of the 3 pairs of chromosomes had high homology among chicken, duck and ostrich.The above BAC clones of 20 chicken genes were hybridized by FISH with duck and ostrich metaphase chromosomes prepared from embryo fibroblasts. Only two genes, IGF1 and SCNN1A, were hybridized to Ipl4-13 and lqll in duck, respectively. The two genes were also localized at 1p14-13 and lqll in chicken, which revealed that the chromosomal fragment of 1p14-1q11 was conserved homologous between chicken and duck. AN the 20 BAC clones did not show hybridization signals on ostrich chromosomes, which indicated that these BAC clone sequences had poor homology between chicken and ostrich.The PCR products of two functional ostrich genes, SPIN and RAG-], were mapped comparatively in ostrich, chicken and duck. The hybridization results revealed some anonymous chromosomal segments of ostrich were homologous with some those on chicken chromosome 1 and 2, which were not present on the ostrich chromosome 1 or 2.