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Who We Are

Our work would not be possible without our incredible team. 

Committee Members

William Holt

I am currently a Visiting Professor at the University of Sheffield, an Honorary Research Associate of the Smithsonian Institution in Washington, DC, and an Honorary Research Associate of the Institute of Zoology, Zoological Society of London. I obtained my PhD in 1979 through the Royal Veterinary College (London) and spent most of my professional life at the Zoological Society of London (ZSL). I retired in 2011: however, I still hold a position as Secretary of the ZSL Ethics Committee for Animal Research. In 2012 I was awarded the Setchell medal by the British Andrology Society, and then in January 2018 the Society for Reproduction and Fertility awarded me their Marshall medal.

In my research I have tried to combine studies of basic reproductive biology in various species, including many wild species, with some practical developments of reproductive technologies and their applications to wildlife conservation. Research in semen cryopreservation and semen assessment in both wild and agricultural species led me into many international collaborations; notably with Steve Johnston at the University of Queensland (Australia), where we attempted to solve the intractable problem of freezing wallaby, kangaroo and koala sperm. More recently I have collaborated with Dr Fran Otero-Ferrer and Professor Marisol Izquierdo at the University of Las Palmas, Gran Canaria, studying how the quality of paternal diet affects placental function and offspring survival in seahorses. (Seahorses are very unusual because the males not only produce sperm; they become pregnant as well!). We showed that offspring growth and fitness are adversely affected if the male seahorse’s diet is even slightly restricted before conception and during early pregnancy [1].   

Bill Holt 2022 for Nature's Safe.jpg

From the late 1990s onwards, I have collaborated with Professor Alireza Fazeli (Universities of Sheffield and Tartu) on various projects to study the interactions between oviductal cells and spermatozoa. One crucial experiment led to a really important finding: namely, that after insemination, the mouse female reproductive tract modifies its gene expression profile and upregulates a new set of genes [2]. This work was subsequently extended to the pig reproductive tract [3] and we were able to show that the same effects occurred. More recent studies have revealed that the pig reproductive tract exerts powerful influences over sperm selection and transport [4,5]. These developments have since been taken forward and confirmed by others, and it was a revelation to find out recently that some of the mammalian female tract genes upregulated after insemination are the same as those upregulated in the pouch of the pregnant seahorse [6]!  


  1. Holt, W.V.; Fazeli, A.; Otero-Ferrer, F. Sperm transport and male pregnancy in seahorses: An unusual model for reproductive science. Anim. Reprod. Sci. 2021, 106854, doi:

  2. Fazeli, A.; Affara, N.A.; Hubank, M.; Holt, W.V. Sperm-induced modification of the oviductal gene expression profile after natural insemination in mice. Biol. Reprod. 2004, 71, 60-65, doi:10.1095/biolreprod.103.026815.

  3. Holt, W.V.; Fazeli, A. The oviduct as a complex mediator of mammalian sperm function and selection. Mol Reprod Dev 2010, 77, 934-943, doi:10.1002/mrd.21234.

  4. Almiñana, C.; Caballero, I.; Heath, P.R.; Maleki-Dizaji, S.; Parrilla, I.; Cuello, C.; Gil, M.A.; Vazquez, J.L.; Vazquez, J.M.; Roca, J.; et al. The battle of the sexes starts in the oviduct: modulation of oviductal transcriptome by X and Y-bearing spermatozoa. BMC Genomics 2014, 15, 293, doi:10.1186/1471-2164-15-293.

  5. Holt, W.V.; Fazeli, A. Do sperm possess a molecular passport? Mechanistic insights into sperm selection in the female reproductive tract. Mol. Human Reprod. 2015, 21, 491-501, doi:10.1093/molehr/gav012.

  6. Whittington, C.M.; Griffith, O.W.; Qi, W.; Thompson, M.B.; Wilson, A.B. Seahorse brood pouch transcriptome reveals common genes associated with vertebrate pregnancy. Mol. Biol. Evol. 2015, 32, 3114-3131, doi:10.1093/molbev/msv177.

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