Morphogenetic aspects of deer antler development

Deer antlers are unique mammalian appendages that have potential for application as a valuable model for biomedical research, such as organ regeneration, bone development and growth control. In this review we described the morphogenetic aspects of antler development, by summarizing relevant information accumulated over the course of our antler research in combine with other published papers. Antler development consists of two distinct phenomena: generation and regeneration. Generation starts with the initiation of a pair of pedicles, permanent bony protuberances on the skull of a male deer, when the animal approaches puberty; proceeds to transformation to antlers when the pedicles reach a species-specific height (around 5 cm in red deer); and terminates with total antler calcification and velvet (antler skin) shedding. Regeneration commences in the spring of the subsequent year with the initiation of new soft antlers growing from the pedicle stumps that remain following the casting of the previous hard antlers; proceeds to the elaboration of multi-branched antlers in summer; and ends up with total antler calcification and velvet shedding in autumn, resulting in the formation of hard bony antlers in winter. Therefore, this paper not only lays the foundation for further development of this valuable biomedical model, but also provides comprehensive background knowledge that will be of use to readers when reading the papers featured in this special issue.