Importantly, this work generates new hypothesis on potential regulators of horn development, which linkage studies have mapped to chromosome 1.
First, we identified genes whose expression in the context of horn development could be expected given existing insights into the developmental biology of horns, and knowledge about the function of these genes in other organisms.
The location and size of horn development differs between species and sexes in both genera, and also depends on the nutritional status of the male.
Studies are now under way documenting and quantifying changes in cell shape and orientation during the pupal remodeling stage of horn development.
Secondly, we identified genes that although functionally well characterized in Drosophila or elsewhere, would not readily be expected to be expressed in the context of horn development.
The first such study used restriction-digest mapping of mitochondrial DNA (mtDNA) ribosomal region to find weak support (maximum parsimony bootstrap support of 57%) for the extant rhinoceros phylogeny as outlined on the basis of horn morphology [ 7].
Although there has been no recent study on the physiology of the horn development in cattle, many of the features of horn morphogenesis maybe viewed as equivalent processes to cattle hoof development.
In the present study we substantially increase the number of candidate genes now available to investigate the role of these pathways in horn development and evolution (Table 4).
The age of the buffalo was estimated in years on the basis of dental wear patterns, number of erupted incisor teeth, body size, and horn development [8], [30].
