Assessment of spermatogenesis through staging of seminiferous tubules.

Male germ cells in all mammals are arranged within the seminiferous epithelium of the testicular tubules in a set of well-defined cell associations called stages. The cellular associations found in these stages and characteristics of the cells used to identify the stages have been well described. Here we present a binary decision key roadmap for identifying stages and present several examples of how staging tubules can be used to better assess the developmental profile of gene expression during spermatogenesis and defects in spermatogenesis arising in pathological conditions resulting from genetic mutations in mice. In particular, when one or more cells of a cellular association cannot be clearly identified or are missing, the cell types that should be present can be precisely identified by knowledge of the approximate or exact stage of the tubule cross section.