Predicted and Observed Spatial Prepatterns in (Hair) Wool Follicle Bulbs

Abstract

It is now well established both theoretically (see the review by Murray 1989) and experimentally (Ouyang & Swinney 1991) that reaction-diffusion (RD) systems, of the type originally proposed by Turing (1952), are able to spontaneously produce stable spatial wave-like patterns in an otherwise completely homogeneous medium. It has been argued that these wavelike spatial patterns have considerable potential to function as spatial prepatterns controlling the differentiation of groups of cells during biological development (Nagorcka 1989). The particular interest of this paper is the proposal that a 2-component RD system present in the epidermis and epithelium, the two chemical components being denoted here as U and V, is responsible for the regulation of many aspects of wool (hair) follicle initiation and development as well as the formation of the fibre in the mature wool (hair) follicle bulb (Nagorcka & Mooney 1989; Nagorcka 1989). Our research is currently aimed at experimentally testing this proposal. To date these tests have included: (i) experiments designed to observe prepatterns predicted to arise but not yet observed. For example, particular spatial patterns of mitotic activity have been predicted to arise in early stage follicles during follicle development (Mooney & Nagorcka 1985), and in follicle bulbs during fibre formation (discussed in this paper), but these patterns have not previously been observed or reported. (ii) experiments to alter prepatterns by changing the diffusion rates and hence the characteristic wavelength of the RD system. (iii) experiments to alter the prepattern by mechanical manipulation of tissue size and shape.