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Axonemal doublet microtubules can split into two complete singlets in human sperm flagellum tips
Davide Zabeo1, Jacob T Croft1, Johanna L Höög1
1Department of Chemistry and Molecular Biology, University of Gothenburg, Gothenburg, Sweden.
FEBS Letters
|April 9, 2019
Summary
Human sperm flagella have a unique tip structure, forming complete singlet microtubules from both A- and B-tubules. This finding differs from model organisms and highlights the need for direct human flagella research in health and disease.
Area of Science:
- Cell Biology
- Human Reproduction
- Microscopy
Background:
- Motile flagella are essential for human fertility and embryonic development.
- The flagellar distal tip is critical for growth and intra-flagellar transport.
- Most model organisms exhibit a 'singlet region' at the flagellar tip where doublet microtubules terminate.
Purpose of the Study:
- To investigate the structure of the human sperm flagellar tip.
- To determine how microtubules are arranged at the human flagellar tip.
Main Methods:
- Cryo-electron tomography was employed to visualize the human sperm flagellar tip structure.
- High-resolution imaging techniques were used to analyze microtubule arrangements.
Main Results:
- Human spermatozoa exhibit a distinct flagellar tip structure compared to model organisms.
- Complete singlet microtubules (sMT) are formed from both the A-tubule and B-tubule of doublet microtubules (dMT) at the human flagellar tip.
- This contrasts with the typical termination of dMTs and extension of only A-tubules as sMTs in other species.
Conclusions:
- The human sperm flagellar tip possesses a unique microtubule arrangement.
- Direct investigation of human flagella is necessary to understand their function in human health and disease.
- Findings necessitate re-evaluation of flagellar tip models based on non-human organisms.
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