THE SPERMATID PLASMA-MEMBRANE COMES OF AGE

Spermiogenesis affords a unique opportunity to examine the formation o f plasma membrane domains. Recent attempts to chart the life cycles of well-characterized integral plasma membrane proteins during spermioge nesis have suggested that spermatids are at least as adept as epitheli al cells or neurons at establishing their plasma membrane domains. The y appear to expand upon the standard recipe involving concurrent domai n-specific protein targeting and diffusion barriers by using a combina tion of intracellular storage within the secretory pathway development ally-regulated delivery to provisional plasma membrane domains, large- scale redistributions of diffusion barriers and integral plasma membra ne proteins, and the shedding of an entire plasma membrane domain.