EFTBA Veterinary Newsletter 30

Home , Equid hybrid, Hinny, Mule, Telegony (theory)

April 2019

The Conventional . For centuries, breeders won- maternal dered whether the maternal versus grandsire effect grandsire may have an effect sympathetic on the offspring. - training . To answer such questions, wishful thinking geneticists investigated the or reality? parent-of-origin identification of genes in reciprocal hybrids

Races asine et chevaline de Poitou (Bonheur) (mules an hinnies).

. The results of this research

allow to explain that some Welcome to EFTBA’s veterinary newsletter genes skip a generation.

Dear Breeder, cation issues to name but a few. In many cases those in the position of This is normally a great time of year power are not fully understanding of for breeders as with each new foal our industry, when drafting and imple- born, we wonder if this is the one menting legislation, which can impin- “Many thanks to Mrs. which will put our name in lights; as ge our industry and livelihood negate- being a champion, or a big sale vely. These are some of the issues we Eva-Maria Bucher- horse (for those in the commercial should discuss at the upcoming EFTBA sector). We then worry if it will fulfil its Haefner, Moyglare 2019 AGM. genetic plan of being a successful, Stud Farm, for her correct and sound race horse. In the face of Brexit, I led a group of To this end, Hanspeter Meier will ex- concerned breeders, including mem- valued sponsorship plain how it works. bers of the EFTBA Executive and Paul Marie Gadot of France Galop to Brus- of this newsletter.” In the latest edition of the EFTBA sels on 22nd February 2019, during Veterinar y Newsletter Hanspeter laid which EU Lobbyist Michael Treacy had out in plain language how the ge- arranged a series of strategic mee- netic map will or should guide a tings with EU Commissioner Phil Hogan new born thoroughbred through its and senior EU officials who were part young life, how it develops to reach of the BREXIT negotiation team. It pro- its potential. There are many mile ved to be a beneficial delegation in stones, pitfalls, which may or may terms of highlighting the concerns of not be encountered that are be- European breeders and offering possi- yond the control of breeders or ble solutions in terms of free move- guardians, including safe birth, bio- ment of High Health Horses. Commis- security issues, scour, lameness as sioner Hogan, along with Dr. Alf-Eck- well as external factors such as poor bert Fussel, EU Commission’s Directo- husbandry and horsemanship, all of rate General on Animal Health as well which we hope to avoid with our as David Bruck, Donal O’Donnell, Tom stock. Tynan and Bernard Van Goethe have In the current climate of world ra- a good understanding of what is re- cing, our sport, our racing and as- quired and seemed willing to foster sociated way of life has never been and advance these requirements to under so much threat. The deve- facilitate continued movement and lopments at Santa Anita, welfare is- trade of bloodstock after the UK exits sues, taxational funding, or lack the- from the EU. 1 reof, changing of jockey rules, medi-

Please be reassured your federation is working to stay on top of these and other issues challenging Genomic imprinting is an epigenetic phenome- our industry. If there are any questions you would non that causes genes to be expressed in a pa- like raised in advance of the AGM, please do not rent-of-origin-specific manner. Forms of genomic hesitate to contact me. I look forward to welcom- imprinting have been demonstrated in fungi, ing you to Kildare, Ireland on 24th May 2019. plants and animals. There are about 150 imprinted genes known in the mouse and about half Best regards that in humans. Genomic imprinting is an inheritance process in- Joe Hernon dependent of the classical Mendelian inheritan- Chairman, EFTBA ce. It is an epigenetic process without altering the genetic sequence. These epigenetic marks Editorial are established ("imprinted") in the germ-line (sperm or egg cells) of the parents and are main- In our last newsletter, we looked at results of genetic tained through mitotic cell divisions in the soma- studies in our time and possible connections with Oftic course, cells of these an organism scientists (Wikipedia). were above all interested traditional views on possible peculiarities of horse- breeding. There, our subjects were the mitochond- May these discoveries now help us breeders to ex- rial DNA and the dam-line in pedigrees. In this issue plain the “maternal grandsire effect” where traits now, we discuss the role of paternally expressed ge- may only be seen in later generations? – But first, let nes in the placenta of the mare. Is there an influen- us review some endeavors in investigating a pos- ce of the maternal grandsire on the offspring? Are sible role of the broodmare sire in the history of hor- the modern genetic findings in accordance with se breeding and the Thoroughbred. views of our ancestors on this subject? Let’s have a look at some publications on these questions in ear- The “maternal grandsire effect” in the lier times and scientific discoveries of today. history of breeding

Dr Hanspeter Meier Presumptions of individual hereditary influences by EFTBA veterinary advisor & Newsletter editor the dam or the sire, most probably are as old as horse breeding itself. For instance, in the 18th century already, Prizelius (1777) expressed the opinion that the stallion contributes more to the procreation Introduction of a foal than the mare (“Die Erfahrung lehret es, Six years ago, Wang and co-workers from Cornell dass der Bescheler mehr zur Zeugung eines Füllens University (NY) published a very comprehensive beyträgt als eine Stute”). And - most interestingly - study with the title “Paternally expressed genes pre- he also added the remark that a foal exceptionally dominate in the placenta” and referred to earlier may present itself like an ancestor further back (“… studies with mouse embryos which had allowed the wobey jedoch, wiewohl selten, eine Ausnahme discovery that the paternal genome – by means of statt findet, indem ein Füllen auf das dritte Glied genomic imprinting – has a major influence on pla- zurück schlagen kann”). Although Prizelius just men- cental development. tioned personal experience(s), the history tells us that his remarks had a great influence on many Of course, these scientists were above all intere- breeders. sted to find out whether the phenomenon of genomic imprinting also exists in other mammals – and it Comparable notes e.g. are reported by Sir Charles certainly was a brilliant idea to select equids for the Leicester in his book ‘Bloodstock Breeding’; he had research in this field. With them, one is able to in- heard breeders of hunters in England and Ireland vestigate reciprocal hybrids of the horse and the aver that if they mated their broodmares to a Shire donkey - mules and hinnies. Here, genotypic differ- or other heavy horse in the first instance, the sub- rences allow the parent-of-origin identification of sequent foals by thoroughbred sires would be up to most expressed genes. more weight than if they had not followed this course. According to Sir Charles, this attitude was so in- Using this approach, the scientists identified a core grained amongst farmer breeders of hunters in ear- group of 15 ancient imprinted genes, of which 10 lier times that a Thoroughbred sire as a first mate were paternally expressed (Wang et al., 2013). was rarely tried (Wright, 1983).

At the beginning of the 19th, such considerations ced a bay foal with a black dorsal line and a few were known under the conception “telegony”. dark (quagga like) stripes on its forehand and legs. To a subsequent mating to the same horse, she pro- Telegony was a theory in heredity, holding that duced another similarly marked foal. On discove- offspring can inherit the characteristics of a pre- ring this, Lord Morton sent details to the Royal Socie- vious mate of the female parent; thus the off- ty, whereupon many learned members of this insti- spring of a female might partake of traits of a tution accepted the facts as indisputable proof of previous sexual partner. the existence of telegony (Wright, 1983). Telegony was a very popular theory in the first However, other experts weren’t convinced of such th half of the 19 century among biologists, but a simple explanation and later, Sir Charles Leicester was largely dismissed with the arrival of Mende- mentioned photographs of two different pony foals lian genetics (1866). with similar but more abundant stripes. Neither of Experiments in the late 19th century on several the dams of these two pony foals had ever been species failed to provide evidence that off- near a quagga or zebra. The fact is that in some spring would inherit any character from their breeds of horses – and Sir Charles believes espe- mother's previous mates. However, in 2014 the cially amongst Norwegian ponies – these zebra evolutionary ecologists A.J. Crean and collea- stripes are sometimes seen. In his opinion, it was gues reported a similar phenomenon – passing pure coincidence that the peculiarity showed itself environmental (non-genetic) traits in a species in the two horses bred from Lord Morton’s mare of fly (Telostylinus angusticollis) (Wikipedia). (Wright, 1983).

The most famous case of this alleged theory was Since those far-off days there have been innume- the following: In about 1815, Lord Morton mated a rable attempts to produce a similar result both by quagga stallion (a quagga is of the zebra species) crossing zebras etc., with mares and by other hybrid to a mare of seven/eights Arabian blood with the matings but all have failed. It was around the years result that she foaled a hybrid quagga/horse. A pic- 1894-95, when Scottish zoologist, James Cossar ture of the mare’s produce by the quagga and by Ewart began his Penicuik Experiments in animal the Arab sire was painted by Agasse and found its breeding on his private experimental farm where he way into the Royal College of Surgeons’ Museum conducted many pioneering investigations in gene- (Fig. 1). It shows the animal to be of undoubted tics. However, the quagga species had become Arab type with no detectable sign of quagga con- extinct by that time, wherefore he decided to use a formation - but the peculiar quagga-like stripes are Burchell’s zebra stallion which served several differ- plainly discernible. rent breeds of mares (West Highland, Shetland, Iceland, Irish and other Ponies and Thoroughbreds) which produced striped hybrid foals (Fig. 2).

Fig. 1 Lord Morton's Quagga-Arab-cross by Jacques Laurent Agasse (Courtesy of the Royal College of Surgeons) (Wikipedia)

He then sold the mare to Sir Gore Ougeley who put Fig. 2 James Cossar Ewart and one of his her to an Arab stallion. From this mating she produ- striped hybrid foals, called “Tartan Cuddies” 3

Their conclusion was: “It thus appears that the evi- foaled by the Shire dam grew to resemble the Shire dence in support of the belief that Lord Morton’s breed (Fig. 3). mare was “infected” by the quagga is at the best far from satisfactory” (Ewart & Lord Arthur Cecil, In their book ‘Genetics of the Horse’, Jones and 1899). Bogart (1971) referred to the work of Hammond and Walton in the chapter ‘Maternal Inheritance’. An investigation by means of reciprocal crosses (in By using crosses between breeds of horses that principle the same method which has been used contained some drastic differences, Hammond and by Wang et al., 2013) was already chosen by John Walton showed that the foal inherited more of its Hammond and A. Walton in Cambridge in 1938. dam’s size characteristics than its sire’s (Fig. 3). This They also wanted to know more about the parent- allowed the statement that the chromosomes are of-origin specific manner of inheritance and studied not the only important element determining inheri- the intra-uterine growth of the fetus in Shire- and tance and did shed light on epigenetic factors. Shetland Pony-mares Jones and Bogart (1971) did agree that each pa- The results of these crosses showed that the proge- rent contributed equally to the diploid autosome ny foaled by the Shetland dam grew to resemble complement of an embryo and that they only differ more closely the Shetland breed; but the progeny in contribution with respect to the sex chromoso-

Fig. 3 Hammond’s and Walton’s reciprocal crosses between Shires and Shetland Ponies. The progeny from the Shire mares were three times the size of those from the Shetland mares (Jones and Bogart, 1971) mes. They meant that there is a big difference bet- serum of mares between days 35 and 41 of gesta- ween spermatozoon and egg, as the first is almost tion. Maximum levels occur at about day 60 and entirely void of cytoplasmatic substances, in con- the hormone often disappears from the serum by trast to the egg which also contains a mitochond- day 130. PMSG is produced by uterine structures rion. They thought that the cytoplasm contains known as endometrial cups which form in a circle some structures or substances which affect the around the developing foetal sac. These areas are overall conformation and function of the horse’s only present in the pregnant animal; they are maxi- body (Jones and Bogart, 1971). mally developed by about day 70 and then dege- nerate rapidly. Allen (1969) noticed now that the Research on pregnancies of horse, donkey, mule concentrations of PMSG in mares which had been and hinny also occurred in the 1960s in Newmarket. mated to a jack donkey were much lower than in The article ‘Factors influencing Pregnant Mare mares carrying a horse foetus. Thus, the paternal Serum Gonadotrophin Production’ was published by genotype appeared to have a dominant influence W.R. Allen in 1969. This research primarily concentra- on PMSG (today ‘eCG’) production and the pla- ted on the hormone ‘Pregnant Mare Serum Gona- cental development. dotropin’ (PMSG), which is first detected in the 4

The subject of the broodmare sire was also dealt que epigenetic signature for each placenta. This with by Matthew Binns and Tony Morris (2010). They variation presents a central importance of the pla- mentioned it in the chapter ‘Nicks and Broodmare centa and the opportunity for natural selection ge- Sires’ and among the several different types of nerally.

‘nick’, they consider the sire-broodmare nick as the In the case of reciprocal horse-donkey hybrids, the only one where there is at least a close enough mule (donkey father) and hinny (horse father) differ relationship between the individuals involved for physiologically and in temperament, despite sha- certain gene combinations to be reproduced in a ring nuclear genomes, leading to speculation that fair proportion of the offspring. Their opinion is foun- these phenotypic differences might be attributable ded by also referring to the studies on mice in the to the action of imprinted genes. Evidence suggests mid-1980s in England, that it did matter from which that genome-wide methylation does not undergo parent an individual animal inherited different forms any organizational alteration in interspecific hybrids of a gene: genes which were transmitted in a of placental mammals; therefore, the mule and “switched-off” (inactivated) form from one sex, hinny may provide a model for the identification of whilst the other sex passed on an active form of the further imprinted genes. gene - the phenomenon of ‘genomic imprinting’. Such a positive statement of these great experts Wang concluded that their results confirm what certainly motivates us to occupy ourselves with this past findings suggested and that the methods used phenomenon. Especially as they added that nick- may also help breeders. Doug Antczak (one of the ing remains an interesting idea that could become co-authors) added: “This discovery explains what verified with increasing amounts of molecular gene- breeders call the maternal grandsire effect. Some tic information on Thoroughbreds in the future. genes skip a generation and only express in grand- children if their carrier was a certain sex. We’ve developed a new approach that can identify imprin- Paternally expressed genes predominate ted genes that may be linked to racehorse traits in the placenta and which could help breeders’ decision-making.” (Hodes and Shtessel, 2013). The presumptions of Binns and Morris (2010) be- came reality very soon, with the study of Wang and co-workers at Cornell University (Ithaca NY) in 2013. References These scientists referred both to the discovery of genomic imprinting through studies of manipulated Allen W.R. (1969) Factors influencing pregnant mare mouse embryos (in 1984 & 1986) but also to the serum gonadotrophin production. Nature 223 work of Allen (1969 - by now 50 years ago!) on (5201):64–66. equine Chorionic Gonadotropin (eCG - the new Binns M. and Morris T. (2010): Thoroughbred Bree- expression for the former ‘PMSG’) in the horse, the ding Pedigree Theories And The Science Of Gene- donkey and their hybrids. There, the peak serum tics. J.A.Allen, London, 160-166 concentrations of eCG were markedly higher when the sire was a horse than in pregnancies in which Ewart J.C. and Lord Arthur Cecil (1899): Experimen- the sire was a donkey. tal Contributions to the Theory of Heredity. A. Tele-

Wang et al. (2013) consider the results of Allen gony. Experiments with West Highland Ponies, Shet- (1969) as consistent with the action of paternally ex- land, Iceland, Irish, Thoroughbred and other Ponies. pressed imprinted genes in mice 15 years later and Hammond J. and Walton A. (1938): Rate of Intra- their own results. uterine Growth. Proc. of the Royal Society, B, 125, They also followed the approach of Allen (1969) by 311 using hybrids and used the method of RNA se- quencing to placental tissues (trophoblast) of mules Hodes C. and Shtessel L. (2013): Placental study and hinnies. This combination allowed the parent- helps explain maternal grandsire effect in breeding. Horsetalk.co.nz, August 11, September 28 of-origin identification of most expressed genes. They identified a core group of 15 ancient imprint- Jones W.E. and Bogart R. (1971): Genetics of the ted genes, of which 10 were paternally expressed. Horse. Edwards Brothers, Inc., Ann Arbor, Michigan. Additional 78 candidate imprinted genes also sho- P. 105-107 wed paternal bias. These genes displayed expression in the placenta but not in the fetus. Some Prizelius J.G. (1777): Vollständige Pferdewissen- showed individual variability which results in a uni- schaft. Weidmanns Erben und Reich, Leipzig

Wang X., Miller D.C., Harman R., Antczak D.F., Clark Wright H. (1983): Sir Charles Leicester Bloodstock A.G. (2013): Paternally expressed genes predomi- Breeding. J.A.Allen & Co. Ltd. London, 44-57 nate in the placenta. Proc Natl Acad Sci USA Jun

25;110(26):10705-10. Doi: 10.1073/pnas.1308998110. Epub 2013 Jun 10.

Mules and hinnies as hybrids are once more fantastic helpers for genetic studies in our times. However, mules already had been most reliable companions for us for centuries (photo: Schmid, Valais 1944)

If there is any aera you would like covered in these very informative newsletters you should contact Kerry on [email protected] and she will forward your request on.

Joe Hernon, Chairman EFTBA

European Federation of Thoroughbred Breeders’ Associations EFTBA c/o Irish Thoroughbred Breeders’ Association ITBA HQ, Greenhills, Kill, Co. Kildare, IRELAND Tel: +353 45 877 543 Fax: + 353 45 877 429 E-Mail: [email protected] Web Site www.eftba.eu

April 2019 ● Issue 30 ● EFTBA