Heads You Lose

The head of a sperm carries genetic information towards an egg, colliding in a high speed head butt that results in fertilisation. Their determined swim is powered by mitochondria in the sperm’s tail. But with acephalic spermatozoa syndrome (a rare, genetic disorder), detachment of the head from the tail leaves sperm immobile, leading to infertility. In this human sperm, super-resolution fluorescence microscopy highlights an interesting structure between its head (with its DNA highlighted in blue) and tail (green). A protein called SUN5 (orange) is part of a lattice of proteins on the lower surface of the nuclear envelope – forming a sort of collar which helps the head stay attached. SUN5 is often found mutated in acephalic spermatozoa syndrome, suggesting a possible target for drugs aiming to help the sperm keep its head.

Written by John Ankers

John Ankers

Writer

A former researcher in systems biology, John is now an online biology tutor and professional coach supporting the wellbeing of scientists and NHS professionals. He's writing, too, of course.

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• Video from work by Jonas Moecking and colleagues
• Bijvoet Centre for Biomolecular Research, Department of Chemistry, Utrecht University, Utrecht, The Netherlands
• Video originally published with a Creative Commons Attribution – NonCommercial – NoDerivs (CC BY-NC-ND 4.0)
• Published in Proceedings of the National Academy of Science (PNAS), March 2026