ESA-SRB-AOTA 2019

Epididymal CRISPs regulates efficient flagellar waveform and optimal sperm function (#163)

Avinash S. Gaikwad 1 , Ashwin Nandagiri 2 , David Potter 3 , Ranganathan Prabhakar 4 , Sameer Jadhav 5 , Julio Soria 6 , Moira K. O'Bryan 1
  1. School of Biological Sciences, Monash Univeristy, Clayton, VIC, Australia
  2. IITB-Monash Research Academy, Indian Institute of Technology-Bombay, Mumbai, Maharashtra, India
  3. Monash Micro Imaging - Advanced Optical Microscopy, Monash University, Clayton, Victoria, Australia
  4. Department of Mechanical & Aerospace Engineering, Monash University, Clayton, Victoria, Australia
  5. Department of Chemical Engineering, Indian Institute of Technology-Bombay, Mumbai, Maharashtra, India
  6. Laboratory for Turbulence Research in Aerospace and Combustion (LTRAC), Department of Mechanical & Aerospace Engineering, Monash Univeristy, Melbourne, VIC, Australia

The oscillatory waveform generated by flagella dictates the ability of sperm to achieve fertilization and is a critical determinant of reproductive success. Indeed, even minor deviations away from optimal flagellar waveform are predicted to affect fertility. The Cysteine-RIch Secretory Proteins (CRISPs) are highly expressed in the epididymis and are hypothesized to be involved in establishing optimal functional competence. Previously, it has been shown that CRISPs can regulate ion flow via various sperm ion channels, and thus potentially regulate sperm function, including motility. We use image-analysis and hydrodynamic calculations to show here that epididymal CRISP1 and CRISP4 indeed influence sperm flagellar beating significantly. This was achieved by developing an image-analysis algorithm on MATLAB which utilizes proper orthogonal decomposition to study the complex dynamics and beating pattern of the sperm flagella. Sperm from wildtype (WT) mice exhibited rhythmic and sinusoidal flagella beating. By contrast, the Crisp1-/- and Crisp4-/- sperm displayed asymmetric flagellar beating. The changes observed between genotypes were characterized by reconstructing an average beat cycle, which revealed that Crisp1-/- sperm possessed an inflexible mid-piece and a highly asymmetric waveform at the distal regions of the flagella. By contrast, the Crisp4-/- sperm was constrained along the entire length of the flagella. We found that Crisp1-/- and Crisp4-/- sperm had altered periodicity of flagellar oscillations between cycles and lowered flagellar amplitude compared to WT. The oscillating frequency of the flagella was reduced in Crisp1-/- and Crisp4-/-sperm and that loss of CRISP1 or 4 led to reduced rates of energy dissipation along the flagella. Excitingly, these deficits could be largely rescued by the addition of recombinant CRISPs to sperm, thus suggesting that their use may be of benefit in assisted reproductive technologies. Collectively, the data reveal that CRISPs play a significant role in establishing efficient sperm flagella waveform and function and thus, fertility.