Konik

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Das Pferd gehört zu den wenigen domestizierten Tierarten, deren direkter Vorfahre ausgestorben ist.

Was heute unter „Wildpferd“ bekannt ist, hat gänzlich andere Wurzeln als unser Hauspferd.

Thomas Druml und Gertrud Grilz-Seger spüren der wechselhaften und abenteuerlichen Geschichte

von Tarpan & Co nach.

Mit freundlicher Genehmigung der PferdeRevue download

Esel

Der weiße österreichisch-ungarische Barockesel ist eine Rarität, bei dem wie beim italienischen Asinara Esel, die weiße Fellfarbe ein wichtiges Rassemerkmal ist. Die Rassengeschichte des Barockesels ist noch nicht gänzlich geklärt. Es ist bekannt, dass weiße Esel bis ins 19. Jahrhundert in privaten Adelsgestüten gezüchtet wurden. Im Habsburger Hofgestüt Kladrub wurde eine kleine Eselherde zum Zwecke der Maultierzucht gehalten (Grilz-Seger und Druml, 2011), wobei ein Hinweis auf eine explizite Zucht auf weiße Fellfarben bislang fehlt. Während bei den österreichischen Pferderassen das Interesse an deren Zucht und Erhaltung im Laufe des 20. Jahrhundert ungebrochen war, setzte eine intensivere Auseinandersetzung mit den Barockeseln erst in den 1980ern ein. Die Wiederentdeckung einer weißen und morphologisch einheitlichen Eselpopulation im Zoo Herberstein und eines Esels in Ungarn war der Ausgangspunkt für die Revitalisierung dieser Rasse. Dabei wurden zwei Pärchen aus der Nukleus Herde von Herberstein in den Erfurter Zoo transferiert, diese Esel gelangten mit ihrer Nachzucht in weiterer Folge in den Stralsunder Zoo, wo bis heute eine Herde besteht (Altmann, 2002). In Österreich wurde in den 1990er Jahren eine bis heute bestehende Zuchtherde im Nationalpark Neusiedlersee/Illmitz etabliert. Gegenwärtig gibt es in Österreich drei Nukleus Herden (Zoo Herberstein, Schlosshof, National Park Neusiedler See und mehrere private Zuchtstätten). Rund 257 Tiere sind im Verein zur Erhaltung der Weißen Barockesel registriert.

Der italienische Asinara Esel, eine halbwild auf der gleichnamigen sardonischen Insel gehaltene Eselrasse, weist einen dem österreich-ungarischen Barockesel ähnlichen Farbphänotyp auf, der durch unpigmentierte Haut und Haare, weiße Hufe und blaue Augen charakterisiert ist (Utzeri, 2015). Während als genetische Ursache für die weiße Farbe des Asinara Esels eine rezessiv vererbte Mutation (c.604C>G) im Tyrosinase (TYR) Gen identifiziert wurde (Utzeri et al., 2015), ist der genetische Hintergrund der weißen Fellfarbe beim österreichisch-ungarischen Barockesel noch ungeklärt.

Artikel: Grilz-Seger, Gertrud & Utzeri, Valerio & Ribani, Anisa & Taurisano, Valeria & Fontanesi, Luca & Brem, Gottfried. (2020). Known loci in the KIT and TYR genes do not explain the depigmented white coat colour of Austro-Hungarian Baroque donkey. Italian Journal of Animal Science. 19. 739-743. 10.1080/1828051X.2020.1790997.

F Aquileja

Fellfarben unterliegen in der Pferdezucht einem starken Selektionsdruck, der sich je nach Zuchtzielvorgabe unterschiedlich auf die Farbverteilung und damit auf die Allelfrequenzen der verantwortlichen Gene ausprägt. Mit der staatlichen österreichischen Lipizzaner​herde liegt eine Untersuchungspopulation vor, die über langfristige Aufzeichnungen bis Mitte des 18. Jahrhunderts verfügt. Mittels Genotypisierung einzelner bekannter Farbloci ( MC1R, ASIP , STX17 , SLC45A2 / MATP , PMEL17/SILV, SLC36A1, PAXC70Y und SB1) und der Phänotypisierung von Abzeichen mit anschließender Varianzkomponentenschätzung wurde in dieser Studie die phänotypische und genetische Variabilität von Farbmerkmalen erhoben und mit historischen Aufzeichnungen verglichen. Der Anteil der homozygoten Schimmel (98,1% der Population) lag bei 80,6%. Unter der Schimmeldecke waren 81,1% der Pferde Braun, 18,9% Rappen, drei Tiere waren heterozygote Falben. Drei Pferde zeigten phänotypisch Scheckungsmerkmale und waren zumindest heterozygot am Dominant White Locus ( W20 Allel). Bei den Abzeichen variierten die Heritabilitäten je nach Lokalisation zwischen 23% und 71%. Im Vergleich zum 18. Jahrhundert hat sich außer der Tendenz zur Fixierung des Schimmelgens bei den Grundfarben eine Verschiebung in Richtung Braun auf Kosten der Rappen ergeben. Die Ergebnisse dieser Studie demons​trieren, dass selbst nach 150 Jahren intensiver Selektion auf einen einheitlichen Farb​phänotyp, immer noch eine gewisse genetische Varianz in Hinblick auf die Fellfarben in der Population vorhanden ist, die züchterisch eine Erweiterung der phänotypischen Farb​palette des Lipizzaners ermöglichen würde.

Artikel: Grilz-Seger G., Dobretsberger M, Brem G., Druml T. (2020): Untersuchungen zum Allelstatus einzelner Farbloci und Abzeichen beim Lipizzaner, Züchtungskunde 92, (2) S. 76-86.

 

 

 

Distribution of runs of homozygosity ROH on ECA3

Overlapping runs of homozygosity (ROH islands) shared by the majority of a population are hypothesized to be the result of selection around a target locus. In this study we investigated the impact of selection for coat color within the Noriker horse on autozygosity and ROH patterns. We analyzed overlapping homozygous regions (ROH islands) for gene content in fragments shared by more than 50% of horses. Long‐term assortative mating of chestnut horses and the small effective population size of leopard spotted and tobiano horses resulted in higher mean genome‐wide ROH coverage (SROH) within the range of 237.4–284.2 Mb, whereas for bay, black and roan horses, where rotation mating is commonly applied, lower autozygosity (SROH from 176.4–180.0 Mb) was determined. We identified seven common ROH islands considering all Noriker horses from our dataset. Specific islands were documented for chestnut, leopard spotted, roan and bay horses. The ROH islands contained, among others, genes associated with body size (ZFAT, LASP1 and LCORL/NCAPG), coat color (MC1R in chestnut and the factor PATN1 in leopard spotted horses) and morphogenesis (HOXB cluster in all color strains except leopard spotted horses). This study demonstrates that within a closed population sharing the same founders and ancestors, selection on a single phenotypic trait, in this case coat color, can result in genetic fragmentation affecting levels of autozygosity and distribution of ROH islands and enclosed gene content.

Article: Grilz-Seger G., Neuditschko M., Mesaric M. et al. (2019): Analysis of ROH patterns in the Noriker horse breed reveals signatures of selection for coat color and body size, Animal genetics 59(2). DOI: 10.1111/age.12797

 

Intensive artificial and natural selection have shaped substantial variation among European horse breeds. Whereas most equine selection signature studies employ divergent genetic population structures in order to derive specific inter-breed targets of selection, we screened a total of 1476 horses originating from 12 breeds for the loss of genetic diversity by runs of homozygosity (ROH) utilizing a 670,000 single nucleotide polymorphism (SNP) genotyping array. Overlapping homozygous regions (ROH islands) indicating signatures of selection were identified by breed and similarities/dissimilarities between populations were evaluated. In the entire dataset, 180 ROH islands were identified, whilst 100 islands were breed specific, all other overlapped in 36 genomic regions with at least one ROH island of another breed.

chr11 Copyright grilz

Furthermore, two ROH hot spots were determined at horse chromosome 3 (ECA3) and ECA11. Besides the confirmation of previously documented target genes involved in selection for coat color (MC1R, STX17, ASIP), body size (LCORL/NCAPG, ZFAT, LASP1, HMGA2), racing ability (PPARGC1A), behavioral traits (GRIN2B, NTM/OPCML) and gait patterns (DMRT3), several putative target genes related to embryonic morphogenesis (HOXB), energy metabolism (IGFBP-1, IGFBP-3), hair follicle morphogenesis (KRT25, KRT27, INTU) and autophagy (RALB) were highlighted. Furthermore, genes were pinpointed which might be involved in environmental adaptation of specific habitats (UVSSA, STXBP4, COX11, HLF, MMD).

Article: Grilz-Seger G, Neuditschko M, Ricard A, Velie B, Lindgren G, Mesarič M, Cotman M, Horna M, Dobretsberger M, Brem G, Druml T. Genome-Wide Homozygosity Patterns and Evidence for Selection in a Set of European and Near Eastern Horse Breeds. Genes. 2019; 10(7):491.

 

The sample ascertainment bias due to complex population structures remains a major challenge in genome-wide investigations of complex traits. In this study we derived the high-resolution population structure and levels of autozygosity of 377 Lipizzan horses originating from five different European stud farms utilizing the SNP genotype information of the high density 700k Affymetrix Axiom™ Equine genotyping array. Scanning the genome for overlapping runs of homozygosity (ROH) shared by more than 50% of horses, we identified homozygous regions (ROH islands) in order to investigate the gene content of those candidate regions by gene ontology and enrichment analyses.

Results

The high-resolution population network approach revealed well-defined substructures according to the origin of the horses (Austria, Slovakia, Croatia and Hungary). The highest mean genome coverage of ROH (SROH) was identified in the Austrian (SROH=342.9), followed by Croatian (SROH=214.7), Slovakian (SROH=205.1) and Hungarian (SROH=171.5) subpopulations. ROH island analysis revealed five common islands on ECA11 and ECA14, hereby confirming a closer genetic relationship between the Hungarian and Croatian as well as between the Austrian and Slovakian samples.

 

 

Populationstructure

 

 

 

 Private islands were detected for the Hungarian and the Austrian Lipizzan subpopulations. All subpopulations shared a homozygous region on ECA11, nearly identical in position and length containing among other genes the homeobox-B cluster, which was also significantly (p<0.001) highlighted by enrichment analysis. Gene ontology terms were mostly related to biological processes involved in embryonic morphogenesis and anterior/posterior specification. Around the STX17 gene (causative for greying), we identified a ROH island harbouring the genes NR4A3, STX17, ERP44 and INVS. Within further islands on ECA14, ECA16 and ECA20 we detected the genes SPRY4, NDFIP1, IMPDH2, HSP90AB1, whereas SPRY4 and HSP90AB1 are involved in melanoma metastasis and survival rate of melanoma patients in humans.

Conclusions

We demonstrated that the assessment of high-resolution population structures within one single breed supports the downstream genetic analyses (e.g. the identification of ROH islands). By means of ROH island analyses, we identified the genes SPRY4, NDFIP1, IMPDH2, HSP90AB1, which might play an important role for further studies on equine melanoma. Furthermore, our results highlighted the impact of the homeobox-A and B cluster involved in morphogenesis of Lipizzan horses.

 

Article: G. Grilz-Seger, T. Druml, M. Neuditschko, M. Dobretsberger, M. Horna and G. Brem (2019): High-resolution population structure and runs of homozygosity reveal the genetic architecture of complex traits in the Lipizzan horse, BMC Genomics 20/1. DOI: 10.1186/s12864-019-5564-x.

 

GGs

 

Long consecutive homozygous genotype segments, runs of homozygosity (ROH), are a result of parents transmitting identical haplotypes, which can be used to estimate autozygosity. Based on 612K singlenucleotide polymorphisms, we computed three ROH parameters (genome length covered by ROH, SROH; number of ROH, NROH; and autozygosity, FROH) to investigate different scenarios in contemporary horse breeding: limited census (Bosnian mountain horse), conservation breeding (Posavje horse), and selection within closed studbook (Haflinger). The ROH parameters revealed well-defined differences between breeds. SROH was highest in the Bosnian mountain horse with 296.32 Mb, followed by the Haflinger sample (SROH 270.35 Mb) and the Posavje sample with 192.68 Mb. The highest number of ROH segments (ROHs) was observed within the Haflinger sample followed by the Posavje sample. FROH ranged at a population level from 8.59% in Posavje, over the Haflinger (mean FROH 12.05%) to 13.21% in the Bosnian mountain horse breed. Bottlenecks were detected for Bosnian mountain horse and Haflinger, whereas for the Posavje, a positive effect of the conservation breeding program was documented.
Investigating the distribution of ROHs across the genome, we detected four common ROH islands on equine chromosomes ECA 6, ECA 11, and ECA 17, which were present in all breeds. On breed level, the Bosnian mountain horses contained 10, the Posavje, four, and the Haflinger, 11 distinct ROH islands (containing the MC1R locus on ECA 3). With this analysis, we were able to compare genomic levels of inbreeding between breeds differing in management, pedigree completeness, and genes under selection.

Authors: Grilz-Seger G., Mesaric M., Cotman M., Neuditschko M., Druml T.and Brem G. (2018): Runs of Homozygosity and Population History of Three Horse Breeds With Small Population Size. Journal of Equine Verterinary science 71, 24-34.

Within the framework of genome‐wide analyses using the novel Axiom® genotyping array, we investigated the distribution of two previously described coat color patterns, namely sabino1 (SBI), associated with the KIT gene (KI16+1037A), and splashed white, associated with the PAX3 gene (ECA6:g.11429753C>T; PAX3C70Y), including a total of 899 horses originating from eight different breeds (Achal Theke, Purebred Arabian, Partbred Arabian, Anglo‐Arabian, Shagya Arabian, Haflinger, Lipizzan and Noriker). Based on the data we collected we were able to demonstrate that, besides Quarter horses, the PAX3C70Y allele is also present in Noriker (seven out of 189) and Lipizzan (three out of 329) horses. The SB1 allele was present in three breeds (Haflinger, 14 out of 98; Noriker, four out of 189; Lipizzan one out of 329). Furthermore, we examined the phenotypes of SB1‐ and PAX3C70Y‐carrier horses for their characteristic white spotting patterns. None of the SB1/sb1‐carrier horses met the criteria defining the Sabino1 pattern according to current applied protocols. From 10 heterozygous PAX3C70Y‐carrier horses, two had nearly a splashed white phenotype. The results of this large‐scale experiment on the genetic association of white spotting patterns in horses underline the influence of gene interactions and population differences on complex traits such as Sabino1 and splashed white.

Article: Druml et al. (2018), Novel insights into Sabino1 and splashed white coat color patterns in horses, Anim Genet., doi: 10.1111/age.12657

 

 

 

Shape model for phenotyping the horses On the Lipizzan stallion a 31 single landmarks

Crossbreeding between individuals of different breeds and introgression, the transfer of genes between breeds and/or populations mediated primarily by backcrossing, have been characteristic tools used in the refinement or optimisation of practical horse breeding. In this study we analysed the genetic contribution of the Arabian horse to the gene pool of the Lipizzan horse and its association with the overall type via shape regression analysis in 158 Lipizzan horses from the Austrian federal stud farm of Piber and the Spanish Riding School. Although crossbreeding with Arabian horses took place between 1776 and 1945, we found a significant association between Lipizzan body shape (p < 0.003) and individual coefficients of Arabian gene proportion, which varied from 21 to 29 %. In order to compare and interpret the estimated Lipizzan shape transitions from Iberian type towards the oriental type, we included a sample of 32 Shagya Arabians from the Slovak National stud farm Topol'ćianky. The estimated shape transitions in Lipizzans due to an increasing proportion of Arabian genes are similar to those we observed in the population comparison study of Lipizzan and Shagya Arabian horses. The main morphometric differences due to increasing Arabian genetic contributions in Lipizzans were found in the conformation of head, neck, withers, and legs. Although selection in the Austrian Lipizzan breed favours the Iberian type, Arabian shape characteristics are still present, indicating the segregation of Arabian founder haplotypes in the population. We also demonstrated that techniques of shape analysis are able to differentiate phenotypes associated with the gene pool and can be applied for phenotypic evaluation and prediction in crossbreeding programs.

Article: Thomas Druml, Michaela Horna, Gertrud Grilz-Seger, Maximilian Dobretsberger und G.
Brem (2018):Association of body shape with amount of Arabian genetic contribution in the Lipizzan horse,
Archives of Animal Breeding, 61, 79-83
 
 
 

Within the scope of current genetic diversity analyses, population structure and homozygosity measures are independently analysed and interpreted. To enhance analytical power, we combined the visualization of recently described high-resolution population networks with runs of homozygosity (ROH). In this study, we demonstrate that this approach enabled us to reveal important aspects of the breeding history of the Haflinger horse. We collected high-density genotype information of 531 horses originating from seven populations which were involved in the formation of the Haflinger, namely 32 Italian Haflingers, 78 Austrian Haflingers, 190 Noriker, 23 Bosnian Mountain Horses, 20 Gidran, 33 Shagya Arabians, and 155 Purebred Arabians. Model-based cluster analysis identified substructures within Purebred Arabian, Haflinger and Noriker that reflected distinct genealogy (Purebred Arabian), geographic origin (Haflinger) and coat colour patterns (Noriker). Analysis of ROH revealed that the two Arabian populations (Purebred and Shagya Arabians), Gidran and the Bosnian Mountain Horse had the highest genome proportion covered by ROH segments (306Mb - 397Mb). The Noriker and the Austrian Haflinger showed the lowest ROH coverage (228Mb, 282Mb). Our combined visualization approach made it feasible to clearly identify outbred (admixture) and inbred (ROH segments) horses. Genomic inbreeding coefficients (FROH) ranged from 10.1% (Noriker) to 17.7% (Purebred Arabian). Finally it could be demonstrated, that the Austrian Haflinger sample has a lack of longer ROH segments and a deviating ROH spectrum, which is associated with past bottleneck events and the recent mating strategy favouring out-crosses within the breed.

 

Druml T., Neuditschko M., Grilz-Seger G., Horna M., Ricard A., Mesarič M., Cotman M., Pausch H.and Brem, G. (2017): Population networks associated with runs of homozygosity reveal new insights into the breeding history of the Haflinger horse, Journal of Heredityhttps://doi.org/10.1093/jhered/esx114