Spermatogenesis

Exploratorium

Male fertility requires the successful development of sperm. Developing male germ cells undergo dramatic changes in cell shape. They go from small round cells to incredibly long motile cells specialized for fertilizing an egg. We are studying sperm formation in the fruit fly, Drosophila melanogaster. Using Drosophila genetics, we identified genes required for different stages of sperm development. Because much of spermatogenesis is conserved across species, what we learn will have implications for understanding human male infertility and may also lead to the design of novel therapeutic approaches for birth control.

Adapted from M. Fuller

Ref: Patterson 1943

Courtesy: G. Hime

Spermatogenesis is a stem cell-mediated process. A germ line stem cell undergoes asymmetric division to yield a new stem cell and a founder gonial blast. This gonial cell undergoes four rounds of mitotic amplification division, giving rise to a cyst of 16 primary spermatocytes. Each primary spermatocyte then undergoes two meiotic divisions, giving rise to a cyst of 64 haploid spermatids. These spermatids elongate and differentiate into mature sperm.

Stage 1

Stage 2

Stage 3

Stage 4

The different stages of spermatogenesis are present in rough temporal order in the adult Drosophila testis. These are phase micrographs illustrating four stages of sperm development.

Stage 1. Primary spermatocyte with a large pale nucleus and prominant nucleolus.
Stage 2. Cells undergoing cytokinesis during meiosis II.
Stage 3. Early round haploid spermatids with a light nucleus and a dark mitochondrial derivative.
Stage 4. Early elongating spermatids.