In situ hybridization analysis of gibbon chromosomes suggests that amplification of alpha satellite DNA in the telomere region is confined to two of the four genera.

The siamang (Symphalangus syndactylus), a species of the family Hylobatidae (gibbons), carries large blocks of constitutive heterochromatin in the telomere region of chromosomes. We recently found that alpha satellite DNA constitutes these heterochromatin blocks as a main component. Alpha satellite DNA, tandem repeat sequences of 171-bp repeat units, is a major component of centromeres in primates. In addition to the siamang, the white-cheeked gibbon (Nomascus leucogenys) was previously found to carry the alpha satellite DNA in the telomere region, although not as large a scale as the siamang. Gibbons comprise four genera: Hoolock, Hylobates, Nomascus, and Symphalangus. Here, we report that the amplification of alpha satellite DNA in the telomere region is probably confined to two genera: Nomascus and Symphalangus. We examined one species of Hoolock and four species of Hylobates and obtained evidence against such an amplification event in these species. The phylogenetic relationship of the four gibbon genera remains unclear. One simple explanation for the current distribution of the telomere region alpha satellite DNA would be that Nomascus and Symphalangus are relatively closely related and the amplification occurred in their common ancestor.