Diagram of a human spermatozoa showing the acrosome
Theacrosome is anorganelle that develops over theanterior (front) half of the head in thespermatozoa (sperm cells) of humans and many other animals. It is a cap-like structure derived from theGolgi apparatus. Inplacental mammals, the acrosome contains degradativeenzymes (includinghyaluronidase andacrosin).[1] These enzymes break down the outer membrane of theovum,[2] called thezona pellucida, allowing thehaploidnucleus in the sperm cell to join with the haploid nucleus in the ovum.This shedding of the acrosome, known as theacrosome reaction, can be stimulatedin vitro by substances that a sperm cell may encounter naturally, such asprogesterone[3] orfollicular fluid, as well as the more commonly used calciumionophore A23187.[4] This can be done to serve as a positive control when assessing the acrosome reaction of a sperm sample byflow cytometry[5] orfluorescence microscopy. This is usually done after staining with a fluoresceinatedlectin such as FITC-PNA, FITC-PSA, FITC-ConA, or fluoresceinated antibody such as FITC-CD46.[6]
