The Joint Annual Scientific Meetings of the Endocrine Society of Australia and the Society for Reproductive Biology 2018

Expression of olfactory signalling proteins in spermatozoa (#295)

Yuliya Makeyeva 1 2 3 , William Ledger 4 , Christopher Nicol 5 , David K Ryugo 3
  1. Sydney Children’s Hospital, Sydney, NSW, Australia
  2. Westfield Research Laboratory, Royal Hospital for Women, Sydney, NSW, Australia
  3. Garvan Institute of Medical Research, Sydney, NSW, Australia
  4. Fertility and Research Centre, UNSW, Sydney, NSW, Australia
  5. NSW Health Pathology – Andrology, Royal Hospital for Women, Sydney, NSW, Australia

The olfactory signalling cascade begins when an odorant binds to the olfactory receptor (OR) on the olfactory sensory neuron and activates the olfactory G-protein (Golf) and Ca2+-calmodulin-sensitive adenylyl cyclase (AC3). Olfactory Marker Protein (OMP) is an abundant, soluble acidic protein that is expressed in mature olfactory sensory neurons throughout vertebrates and immunologically co-localises with ORs. The expression of OMP in specific cell types of non-olfactory tissue suggests that it might reveal OR-mediated chemoreception in other functional systems.

We tested the hypothesis that chemoreceptors from the olfactory system could play a role in sperm chemotaxis if sperm were guided by factors secreted from the egg. Using light microscopic immunocytochemistry, we studied OMP, Golf, and AC3 in spermatozoa of rats and humans. In rats, expression of these proteins was documented in epididymal spermatozoa. In humans, expression was investigated in ejaculated spermatozoa in three modes of activation (control, activated, and hyper-activated).

OMP expression was evident in compartment-specific locations of rat and human spermatozoa with some species-specific differences.  OMP expression in the acrosomal cap of hyper-activated spermatozoa implies guidance of the sperm to the egg, whereas its presence in the equatorial segment suggests a role for the binding of the sperm to the egg after it undergoes its 90 degree rotation. The role of OMP in the connecting piece where the centriole is located and along the tail remains unknown.  In epididymal spermatozoa, Golf and AC3 were immunolocalised to the acrosome head and equatorial segment, the connecting piece, and along the tail. 

OMP appears a reliable indicator of OR-mediated chemoreception and is heavily involved in reproductive biology. Much remains to be determined about the ligands that activate ORs but the resulting knowledge will have direct significance to understanding human fertility.