Gibbons have experienced extensive karyotype rearrangements during evolution and represent an ideal model for studying the underlying molecular mechanism of evolutionary chromosomal rearrangements. It is anticipated that the cloning and sequence characterization of evolutionary chromosomal breakpoints will provide vital insights into the molecular force that has driven such a radical karyotype reshuffle in gibbons. We constructed and characterized a high-quality fosmid li- brary of the white-cheeked gibbon （Nomascus leucogenys） containing 192,000 non- redundant clones with an average insert size of 38 kb and 2.5-fold genome coverage. By end sequencing of 100 randomly selected fosmid clones, we generated 196 se- quence tags for the library. These end-sequenced fosmid clones were then mapped onto the chromosomes of the white-cheeked gibbon by fluorescence in situ hy- bridization~ and no spurious chimeric clone was detected. BLAST search against the human genome showed a good correlation between the number of hit clones and the number of chromosomes, an indication of unbiased chromosomal distribu- tion of the fosmid library. The chromosomal distribution of the mapped clones is also consistent with the BLAST search result against human and white-cheeked gibbon genomes. The fosmid library and the mapped clones will serve as a valu- able resource for further studying gibbons＇ chromosomal rearrangements and the underlying molecular mechanism as well as for comparative genomic study in the lesser apes.
Liping ChenJianping YeYan LiuJinghuan WangWeiting SuFengtang YangWenhui Nie
Recent molecular cytogenetic studies demonstrate that extensive centromere-telomere fusions are the main chromosomal rearrangements underlying the karyotypic evolution of extant muntjacs. Although the molecular mechanism of tandem fusions remains unknown, satellite DNA is believed to have facilitated chromosome fusions by non-allelic homologous recombination. Previous studies detected non-random hybridization signals of cloned satellite DNA at the postulated fusion sites on the chromosomes in Indian and Chinese muntjacs. But the genomic distribution and organization of satellite DNAs in other muntjacs have not been investigated. In this study, we have isolated four satellite DNA clones （BMCS, BM700, BM 1.1 k and FM700） from the black muntjac （Muntiacus crinifrons） and Fea＇s muntjac （M. feae）, and hybridized these four clones onto chromosomes of four muntjac species （M. reevesi, M. crinifrons, M. gongshanenisis and M. feae）. Besides the predominant centromeric signals, non-random interstitial hybridization signals from satellite I and II DNA clones （BMC5, BM700 and FM700） were also observed on the arms of chromosomes of these four muntjacs. Our results provide additional support for the notion that the karyotypes of M. crinifrons, M. feae and M. gongshanensis have evolved from a 2n = 70 ancestral karyotype by a series of chromosome fusions.
