Selection signatures in goats reveal copy number variants underlying breed-defining coat color phenotypes

Taurine pangenome uncovers a segmental duplication upstream of KIT associated with depigmentation in white-headed cattle

Cattle have been selectively bred for coat color, spotting, and depigmentation patterns. The assumed autosomal dominant inherited genetic variants underlying the characteristic white head of Fleckvieh, Simmental, and Hereford cattle have not been identified yet, although the contribution of structural variation upstream of the KIT gene has been proposed. Here, we construct a graph pangenome from 24 haplotype assemblies representing seven taurine cattle breeds to identify and characterize the white-head-associated locus for the first time based on long-read sequencing data and pangenome analyses. We introduce a pangenome-wide association mapping approach that examines assembly path similarities within the graph to reveal an association between two most likely serial alleles of a complex structural variant (SV) 66 kb upstream of KIT and facial depigmentation. The complex SV contains a variable number of tandemly duplicated 14.3 kb repeats, consisting of LTRs, LINEs, and other repetitive elements, leading to misleading alignments of short and long reads when using a linear reference. We align 250 short-read sequencing samples spanning 15 cattle breeds to the pangenome graph, further validating that the alleles of the SV segregate with head depigmentation. We estimate an increased count of repeats in Hereford relative to Simmental and other white-headed cattle breeds from the graph alignment coverage, suggesting a large under-assembly in the current Hereford-based cattle reference genome, which had fewer copies. Our work shows that exploiting assembly path similarities within graph pangenomes can reveal trait-associated complex SVs.

Genetic advancements and future directions in ruminant livestock breeding: from reference genomes to multiomics innovations

Ruminant livestock provide a rich source of products, such as meat, milk, and wool, and play a critical role in global food security and nutrition. Over the past few decades, genomic studies of ruminant livestock have provided valuable insights into their domestication and the genetic basis of economically important traits, facilitating the breeding of elite varieties. In this review, we summarize the main advancements for domestic ruminants in reference genome assemblies, population genomics, and the identification of functional genes or variants for phenotypic traits. These traits include meat and carcass quality, reproduction, milk production, feed efficiency, wool and cashmere yield, horn development, tail type, coat color, environmental adaptation, and disease resistance. Functional genomic research is entering a new era with the advancements of graphical pangenomics and telomere-to-telomere (T2T) gap-free genome assembly. These advancements promise to improve our understanding of domestication and the molecular mechanisms underlying economically important traits in ruminant livestock. Finally, we provide new perspectives and future directions for genomic research on ruminant genomes. We suggest how ever-increasing multiomics datasets will facilitate future studies and molecular breeding in livestock, including the potential to uncover novel genetic mechanisms underlying phenotypic traits, to enable more accurate genomic prediction models, and to accelerate genetic improvement programs.

Selection Signatures in Italian Goat Populations Sharing the "facciuto" Phenotype

Background: The presence of light-pigmented facial stripes, parallel on both sides of the cranial region, is a widespread characteristic in various goat breeds of European origin and beyond. In Italy, this phenotype is relatively common from the north to the south of the peninsula. The availability of genotypic data at single-nucleotide polymorphism (SNP) loci for breeds and populations characterized by such a pigmentation pattern enabled us to study the genomic regions potentially correlated with this phenotype, for simplicity referred to as "facciuto". Methods: We adopted an FST-outlier approach to detect signals of differential selection in 18 pairwise comparisons, each involving 6 genetic goat types with the "facciuto" phenotype (Facciuta Lucana, Facciuta della Valnerina, Valfortorina, Teramana, Capestrina, and Roccaverano) contrasted with each of 3 "non-facciuto" goat breeds selected as reference populations (Red Mediterranean, light brown; Saanen, white; Malagueña, mahogany solid). Results: The analysis of the region ±200 kbps upstream and downstream of the two significant signals on chromosome 13 and 15 allowed us to identify, among the annotated genes, ASIP, AHCY, ITCH, DYNLRB1, MAP1LC3A, PIGU, LOC102177263, and DTX4, whose functions could be related to several mechanisms underlying the phenotype under investigation. Conclusions: This study confirmed the fundamental role of ASIP in pigmentation, although additional pathways may concurrently contribute to the determinism of the considered "facciuto" phenotype in Italian goats.

Deciphering genomic basis of unique adaptation of Ladakhi cattle to Trans-Himalayan high-altitude region of Leh-Ladakh in India

In this study, whole genome sequence data of Ladakhi cattle from high altitude region of Leh-Ladakh and Sahiwal cattle from arid, semi-arid tropical region were compared. To gain a deeper understanding of the selective footprints in the genomes of Ladakhi and Sahiwal cattle, two strategies namely run of homozygosity (ROH), and fixation index (FST) were employed. A total of 975 and 1189 ROH regions were identified in Ladakhi and Sahiwal cattle, respectively. Several genes associated with high-altitude adaptation were enriched in many of the ROH hot spots in genome of Ladakhi cattle such as; HIF1A, VEGFA, VEGFC, EPHB1, ZEB1, CAV3, TEK, SENP2, GATA6, RAD51 and ADAMTSL4 etc.. The FST value of 0.32 also indicated strong genetic differentiation between Ladakhi and Sahiwal cattle. A total of 3616 genomic regions were identified to be under selection in the two cattle breeds. The FST selection signature analysis led to identification of several genes such as HIF1A, VEGFC, ZEB1, SOD1, EGLN3, EPAS1, ZNF, DYSF, ADAM, SENP2, MMP16, and CDK2 etc., that could be associated with high altitude adaptation in Ladakhi cattle. Additionally, several signalling pathways found in Ladakhi cattle like HIF1A, VEGF, DNA repair, and angiogenesis, which are associated with adaptation to high-altitude hypoxic environments. The phylogenetic, PCA and admixture analysis separated the individuals of Ladakhi and Sahiwal cattle according to their geographic origin. In the present study, the WGS data has helped to identify key genes and genic regions that contribute to high altitude adaptation in Ladakhi cattle.

Climate resilience in goats: a comprehensive review of the genetic basis for adaptation to varied climatic conditions

The sustainability of livestock systems is widely acknowledged to be threatened by climate change on a worldwide scale. There are worries about the effects this phenomenon may have on the productivity and performance of native livestock species due to its influence on environmental stresses, such as the frequency and severity of unfavorable weather occurrences and the ongoing changes in the agro-ecological landscape. Among the most climatically tolerant livestock animals, goats can survive in a range of environments, from deserts to alpine areas. The domestic goat has undergone significant phenotypic changes in terms of shape, behavior, physiological adaptation, reproduction, and production over their evolutionary journey. It will be possible to better understand the genetic mechanisms underlying successful domestication and the practical breeding strategies leading to the improvement in productivity and resilience to environmental challenges by identifying the genes underlying these modifications. This review explores current knowledge on goat adaptation strategies, emphasizing gene expression patterns, epigenetic modifications, and whole-genome selection signatures. It examines how these molecular mechanisms enable goats to endure heat stress, hypoxia, and other environmental challenges. Furthermore, the review highlights the potential of epigenetic markers and selection signatures in developing climate-resilient goat breeds through marker-assisted selection and genome editing, offering actionable insights into sustainable goat production in the context of global climate change.

Telomere-to-telomere genome assembly of a male goat reveals variants associated with cashmere traits

A complete goat (Capra hircus) reference genome enhances analyses of genetic variation, thus providing insights into domestication and selection in goats and related species. Here, we assemble a telomere-to-telomere (T2T) gap-free genome (2.86 Gb) from a cashmere goat (T2T-goat1.0), including a Y chromosome of 20.96 Mb. With a base accuracy of >99.999%, T2T-goat1.0 corrects numerous genome-wide structural and base errors in previous assemblies and adds 288.5 Mb of previously unresolved regions and 446 newly assembled genes to the reference genome. We sequence the genomes of five representative goat breeds for PacBio reads, and use T2T-goat1.0 as a reference to identify a total of 63,417 structural variations (SVs) with up to 4711 (7.42%) in the previously unresolved regions. T2T-goat1.0 was applied in population analyses of global wild and domestic goats, which revealed 32,419 SVs and 25,397,794 SNPs, including 870 SVs and 545,026 SNPs in the previously unresolved regions. Also, our analyses reveal a set of selective variants and genes associated with domestication (e.g., NKG2D and ABCC4) and cashmere traits (e.g., ABCC4 and ASIP).

Structural variations in livestock genomes and their associations with phenotypic traits: a review

Genomic structural variation (SV) refers to differences in gene sequences between individuals on a genomic scale. It is widely distributed in the genome, primarily in the form of insertions, deletions, duplications, inversions, and translocations. Due to its characterization by long segments and large coverage, SVs significantly impact the genetic characteristics and production performance of livestock, playing a crucial role in studying breed diversity, biological evolution, and disease correlation. Research on SVs contributes to an enhanced understanding of chromosome function and genetic characteristics and is important for understanding hereditary diseases mechanisms. In this article, we review the concept, classification, main formation mechanisms, detection methods, and advancement of research on SVs in the genomes of cattle, buffalo, equine, sheep, and goats, aiming to reveal the genetic basis of differences in phenotypic traits and adaptive genetic mechanisms through genomic research, which will provide a theoretical basis for better understanding and utilizing the genetic resources of herbivorous livestock.

Whole-genome resequencing reveals new mutations in candidate genes for Beichuan-white goat prolificacya

In this study, we evaluated the copy number variation in the genomes of two groups of Beichuan-white goat populations with large differences in litter size by FST method, and identified 1739 genes and 485 missense mutations in the genes subject to positive selection. Through functional enrichment, ITGAV, LRP4, CDH23, TPRN, RYR2 and CELSR1 genes, involved in embryonic morphogenesis, were essential for litter size trait, which received intensive attention. In addition, some mutation sites of these genes have been proposed (ITGAV: c.38C > T; TPRN: c.133A > T, c.1192A > G, c.1250A > C; CELSR1: c.7640T > C), whose allele frequencies were significantly changed in the high fecundity goat group. Besides, we found that new mutations at these sites altered the hydrophilicity and 3D structure of the protein. Candidate genes related to litter size in this study and their missense mutation sites were identified. These candidate genes are helpful to understand the genetic mechanism of fecundity in Beichuan white goat, and have important significance for future goat breeding.

Genetic characterization of cashmere goat (Capra hircus) populations in Mongolia

Objective

Characterization studies of the phenotypic and genetic diversity of Mongolian goats are limited, despite several goat breeds being registered in the country. This study aimed to evaluate the phenotypic and genetic diversity of 14 cashmere goat populations in Mongolia, consisting largely of identified goat breeds.

Methods

Body weight, cashmere quality, and coat color were the phenotypic traits considered in this study. A linear model was used to fit body weight and cashmere traits, and least squares means (LSMs) were estimated for the region and location classes. Genetic diversity and structure were assessed using a goat 50K SNP array.

Results

The studied populations exhibited greater phenotypic diversity at the regional level. A very small overall differentiation index (Fst: 0.017) was revealed by Wright's Fst and a very small overall inbreeding index (F ROH1 :0.019) was revealed based on runs of homozygosity. Genetic clustering of populations by principal components showed large variances for the two goat populations of the Russian admixture (Gobi Gurvan Saikhan and Uuliin Bor), and smaller but differentiated clusters for the remaining populations. Similar results were observed in the admixture analysis, which identified populations with the highest (Govi Gurvan Saikhan and Uuliin Bor) and lowest (Tsagaan Ovoo Khar) exotic admixtures. A genomewide association study (GWAS) of body weight and cashmere traits identified a few significant variants on chromosomes 2, 4, 5, 9, and 15, with the strongest variant for cashmere yield on chromosome 4. The GWAS on coat color yielded nine significant variants, with the strongest variants located on chromosomes 6, 13, and 18 and potential associations with KIT, ASIP, and MC1R genes. These signals were also found in other studies on coat color and patterns in goats.

Conclusion

Mongolian cashmere goats showed relatively low genetic differentiation and low inbreeding levels, possibly caused by the traditional pastoral livestock management system and the practice of trading breeding bucks across provinces, along with a recent increase in the goat population. Further investigation of cashmere traits using larger samples and alternative methods may help identify the genes or genomic regions underlying cashmere quality in goats.

Caprine and Ovine Genomic Selection-Progress and Application

The advancement of sequencing technology and molecular breeding methods has provided technical support and assurance for accurate breeding. Genomic Selection (GS) utilizes genomic information to improve livestock breeding, and it is more accurate and more efficient than traditional selection methods. GS has been widely applied in domestic animal breeding, especially in cattle. However, there are still limited studies on the application and research of GS in sheep and goats. This paper outlines the principles, analysis methods, and influential factors of GS and elaborates on the research progress, challenges, and prospects of applying GS in sheep and goat breeding. Through the review of these aspects, this paper is expected to provide valuable references for the implementation of GS in the field of sheep and goat breeding.

Genome-wide copy number variant analysis reveals candidate genes associated with milk production traits in water buffalo (Bubalus bubalis)

Buffaloes are vital contributors to the global dairy industry. Understanding the genetic basis of milk production traits in buffalo populations is essential for breeding programs and improving productivity. In this study, we conducted whole-genome resequencing on 387 buffalo genomes from 29 diverse Asian breeds, including 132 river buffaloes, 129 swamp buffaloes, and 126 crossbred buffaloes. We identified 36,548 copy number variants (CNV) spanning 133.29 Mb of the buffalo genome, resulting in 2,100 CNV regions (CNVR), with 1,993 shared CNVR being found within the studied buffalo types. Analyzing CNVR highlighted distinct genetic differentiation between river and swamp buffalo subspecies, verified by evolutionary tree and principal component analyses. Admixture analysis grouped buffaloes into river and swamp categories, with crossbred buffaloes displaying mixed ancestry. To identify candidate genes associated with milk production traits, we employed 3 approaches. First, we used Vst-based population differentiation, revealing 11 genes within CNVR that exhibited significant divergence between different buffalo breeds, including genes linked to milk production traits. Second, expression quantitative loci analysis revealed differentially expressed CNVR-derived genes (DECG) associated with milk production traits. Notably, known milk production-related genes were among these DECG, validating their relevance. Last, a GWAS identified 3 CNVR significantly linked to peak milk yield. Our study provides comprehensive genomic insights into buffalo populations and identifies candidate genes associated with milk production traits. These findings facilitate genetic breeding programs aimed at increasing milk yield and improving quality in this economically important livestock species.

A new Finnish flavor of feline coat coloration, "salmiak," is associated with a 95-kb deletion downstream of the KIT gene

Cats with a distinctive white hair pattern of unknown molecular cause have been discovered in the Finnish domestic cat population. Based on the unique appearance of these cats, we have named this phenotype salmiak ("salty licorice"). The use of a commercially available panel test to genotype four salmiak-colored cats revealed the absence of all known variants associated with white-haired phenotypic loci: full White (W), Spotting (Ws) and the Birman white Gloves associated (wg) allele of the KIT proto-oncogene (KIT) gene. Whole-genome sequencing on two salmiak-colored cats was conducted to search for candidate causal variants in the KIT gene. Despite a lack of coding variants, visual inspection of the short read alignments revealed a large ~95 kb deletion located ~65 kb downstream of the KIT gene in the salmiak cats. Additional PCR genotyping of 180 domestic cats and three salmiak-colored cats confirmed the homozygous derived variant genotype fully concordant with the salmiak phenotype. We suggest the newly identified variant be designated as wsal for "w salmiak".

Genomic analysis reveals the association of KIT and MITF variants with the white spotting in swamp buffaloes

BACKGROUND

Swamp-type buffaloes with varying degrees of white spotting are found exclusively in Tana Toraja, South Sulawesi, Indonesia, where spotted buffalo bulls are highly valued in accordance with the Torajan customs. The white spotting depigmentation is caused by the absence of melanocytes. However, the genetic variants that cause this phenotype have not been fully characterized. The objective of this study was to identify the genomic regions and variants responsible for this unique coat-color pattern.

RESULTS

Genome-wide association study (GWAS) and selection signature analysis identified MITF as a key gene based on the whole-genome sequencing data of 28 solid and 39 spotted buffaloes, while KIT was also found to be involved in the development of this phenotype by a candidate gene approach. Alternative candidate mutations included, in addition to the previously reported nonsense mutation c.649 C > T (p.Arg217*) and splice donor mutation c.1179 + 2T > A in MITF, a nonsense mutation c.2028T > A (p.Tyr676*) in KIT. All these three mutations were located in the genomic regions that were highly conserved exclusively in Indonesian swamp buffaloes and they accounted largely (95%) for the manifestation of white spotting. Last but not the least, ADAMTS20 and TWIST2 may also contribute to the diversification of this coat-color pattern.

CONCLUSIONS

The alternative mutations identified in this study affect, at least partially and independently, the development of melanocytes. The presence and persistence of such mutations may be explained by significant financial and social value of spotted buffaloes used in historical Rambu Solo ceremony in Tana Toraja, Indonesia. Several de novo spontaneous mutations have therefore been favored by traditional breeding for the spotted buffaloes.

Coat colour in marsupials: genetic variants at the ASIP locus determine grey and black fur of the brushtail possum

The possession of fur or hair is a defining characteristic of mammals and can occur in a variety of colours and patterns. While genetic determinants of coat colour are well described in eutherian 'placental' mammals, the other major mammalian infraclass, marsupials, is grossly understudied. The fur of the common brushtail possum (Trichosurus vulpecula), an iconic native mammal found throughout Australia and introduced into Aotearoa New Zealand, possesses two main colour morphs: grey and black. To identify genetic variants associated with coat colour, we performed a genome-wide association study (GWAS) with genotype by sequencing (GBS) data. Single nucleotide variants (SNVs) on chromosome 3, close to the agouti signalling protein (ASIP) gene that controls the temporal and spatial distribution of pigments in eutherian mammals, were identified. Fine-mapping identified a C>T variant at chr3:100483705 that results in a ASIP:p.Arg115Cys missense substitution, and animals homozygous for this variant have black fur. In addition to uncovering the first genetic determinant of coat colour in a natural marsupial population, comparative analysis of ASIP in divergent marsupial species identified the dasyurids as having accelerated evolution, reflecting their well described diversity of coat colour and pattern.

Genomic regions associated with coat color in Gir cattle

Indicine cattle breeds are adapted to the tropical climate, and their coat plays an important role in this process. Coat color influences thermoregulation and the adhesion of ectoparasites and may be associated with productive and reproductive traits. Furthermore, coat color is used for breed qualification, with breeders preferring certain colors. The Gir cattle is characterized by a wide variety of coat colors. Therefore, we performed genome-wide association studies to identify candidate genes for coat color in Gir cattle. Different phenotype scenarios were considered in the analyses and regions were identified on eight chromosomes. Some regions and many candidate genes are influencing coat color in the Gir cattle, which was found to be a polygenic trait. The candidate genes identified have been associated with white spotting patterns and base coat color in cattle and other species. In addition, a possible epistatic effect on coat color determination in the Gir cattle was suggested. This is the first published study that identified genomic regions and listed candidate genes associated with coat color in Gir cattle. The findings provided a better understanding of the genetic architecture of the trait in the breed and will allow to guide future fine-mapping studies for the development of genetic markers for selection.

Copy number variant detection using next-generation sequencing in EYS-associated retinitis pigmentosa

Retinitis pigmentosa (RP) is the most common inherited retinal dystrophy and a major cause of blindness. RP is caused by several variants of multiple genes, and genetic diagnosis by identifying these variants is important for optimizing treatment and estimating patient prognosis. Next-generation sequencing (NGS), which is currently widely used for diagnosis, is considered useful but is known to have limitations in detecting copy number variations (CNVs). In this study, we re-evaluated CNVs in EYS, the main causative gene of RP, identified via NGS using multiplex ligation-dependent probe amplification (MLPA). CNVs were identified in NGS samples of eight patients. To identify potential CNVs, MLPA was also performed on samples from 42 patients who were undiagnosed by NGS but carried one of the five major pathogenic variants reported in Japanese EYS-RP cases. All suspected CNVs based on NGS data in the eight patients were confirmed via MLPA. CNVs were found in 2 of the 42 NGS-undiagnosed RP cases. Furthermore, results showed that 121 of the 661 patients with RP had EYS as the causative gene, and 8.3% (10/121 patients with EYS-RP) had CNVs. Although NGS using the CNV calling criteria utilized in this study failed to identify CNVs in two cases, no false-positive results were detected. Collectively, these findings suggest that NGS is useful for CNV detection during clinical diagnosis of RP.

Coloration in Equine: Overview of Candidate Genes Associated with Coat Color Phenotypes

Variation in coat color among equids has attracted significant interest in genetics and breeding research. The range of colors is primarily determined by the type, concentration, and distribution of melanin pigments, with the balance between eumelanin and pheomelanin influenced by numerous genetic factors. Advances in genomic and sequencing technologies have enabled the identification of several candidate genes that influence coat color, thereby clarifying the genetic basis of these diverse phenotypes. In this review, we concisely categorize coat coloration in horses and donkeys, focusing on the biosynthesis and types of melanin involved in pigmentation. Moreover, we highlight the regulatory roles of some key candidate genes, such as MC1R, TYR, MITF, ASIP, and KIT, in coat color variation. Moreover, the review explores how coat color relates to selective breeding and specific equine diseases, offering valuable insights for developing breeding strategies that enhance both the esthetic and health aspects of equine species.

Genetic Association Analysis of Copy Number Variations for Meat Quality in Beef Cattle

Meat quality is an economically important trait for global food production. Copy number variations (CNVs) have been previously implicated in elucidating the genetic basis of complex traits. In this article, we detected a total of 112,198 CNVs and 10,102 CNV regions (CNVRs) based on the Bovine HD SNP array. Next, we performed a CNV-based genome-wide association analysis (GWAS) of six meat quality traits and identified 12 significant CNV segments corresponding to eight candidate genes, including PCDH15, CSMD3, etc. Using region-based association analysis, we further identified six CNV segments relevant to meat quality in beef cattle. Among these, TRIM77 and TRIM64 within CNVR4 on BTA29 were detected as candidate genes for backfat thickness (BFT). Notably, we identified a 34 kb duplication for meat color (MC) which was supported by read-depth signals, and this duplication was embedded within the keratin gene family including KRT4, KRT78, and KRT79. Our findings will help to dissect the genetic architecture of meat quality traits from the aspects of CNVs, and subsequently improve the selection process in breeding programs.

Whole-Genome Resequencing Reveals Selection Signatures of Abigar Cattle for Local Adaptation

Over time, indigenous cattle breeds have developed disease resistance, heat tolerance, and adaptability to harsh environments. Deciphering the genetic mechanisms underlying adaptive traits is crucial for their improvement and sustainable utilization. For the first time, we performed whole-genome sequencing to unveil the genomic diversity, population structure, and selection signatures of Abigar cattle living in a tropical environment. The population structure analysis revealed that Abigar cattle exhibit high nucleotide diversity and heterozygosity, with low runs of homozygosity and linkage disequilibrium, suggesting a genetic landscape less constrained by inbreeding and enriched by diversity. Using nucleotide diversity (Pi) and population differentiation (FST) selection scan methods, we identified 83 shared genes that are likely associated with tropical adaption. The functional annotation analysis revealed that some of these genes are potentially linked to heat tolerance (HOXC13, DNAJC18, and RXFP2), immune response (IRAK3, MZB1, and STING1), and oxidative stress response (SLC23A1). Given the wider spreading impacts of climate change on cattle production, understanding the genetic mechanisms of adaptation of local breeds becomes crucial to better respond to climate and environmental changes. In this context, our finding establishes a foundation for further research into the mechanisms underpinning cattle adaptation to tropical environments.

Phenotypic and Genomic Characterization of the Comune di Sicilia Goat: Towards the Conservation of an Endangered Local Breed

The Comune di Sicilia, a local goat breed from Sicily (Italy), is currently undergoing recognition as a distinct breed. This study aims to characterize the population both phenotypically and genomically to advance its recognition process. A total of 78 subjects from two locations were enrolled, and their phenotypic data, including qualitative traits and morphometric measurements of adult animals, were recorded and statistically analyzed. The goats were genotyped using the Illumina 50 k Goat SNPchip, comparing them with 473 goats from 15 Italian breeds. Population structure, phylogenetic relationships, admixture, and genomic inbreeding were analyzed. Additionally, subjects with different morphological traits were compared using FST and runs of homozygosity, leading to the identification of potential candidate genes associated with anotia and wattle presence in goats. The Comune di Sicilia breed exhibited distinctive genomic and phenotypic features, setting it apart from other breeds in the same region. However, moderate variability, possibly influenced by selection practices, was also observed. To ensure the breed's preservation and prevent excessive inbreeding, a comprehensive approach considering both morphology and genomic background is recommended. This study contributes valuable insights into the genetic peculiarities of the Comune di Sicilia goat, supporting its recognition as a unique and valuable breed.

Genomic selection pressure discovery using site-frequency spectrum and reduced local variability statistics in Pakistani Dera-Din-Panah goat

BACKGROUND

Population geneticists have long sought to comprehend various selection traces accumulated in the goat genome due to natural or human driven artificial selection through breeding practices, which led the wild animals to domestication, so understanding evolutionary process may helpful to utilize the full genetic potential of goat genome.

METHODS AND RESULTS

As a step forward to pinpoint the selection signals in Pakistani Dera-Din-Panah (DDP) goat, whole-genome pooled sequencing (n = 12) was performed, and 618,236,192 clean paired-end reads were mapped against ARS1 reference goat assembly. Five different selection signature statistics were applied using four site-frequency spectrum (SFS) methods (Tajima's D ([Formula: see text]), Fay and Wu's H ([Formula: see text]), Zeng's E ([Formula: see text]), [Formula: see text]) and one reduced local variability approach named pooled heterozygosity ([Formula: see text]). The under-selection regions were annotated with significant threshold values of [Formula: see text]≥4.7, [Formula: see text]≥6, [Formula: see text]≥2.5, Pool-HMM ≥ 12, and [Formula: see text]≥5 that resulted in accumulative 364 candidate gene hits. The highest genomic selection signals were observed on Chr. 4, 6, 10, 12, 15, 16, 18, 20, and 27 and harbor ADAMTS6, CWC27, RELN, MYCBP2, FGF14, STIM1, CFAP74, GNB1, CALML6, TMEM52, FAM149A, NADK, MMP23B, OPN3, FH, MFHAS1, KLKB1, RRM1, KMO, SPEF2, F11, KIT, KMO, ERI1, ATP8B4, and RHOG genes. Next, the validation of our captured genomic hits was also performed by more than one applied statistics which harbor meat production, immunity, and reproduction associated genes to strengthen our hypothesis of under-selection traits in this Pakistani goat breed. Furthermore, common candidate genes captured by more than one statistical method were subjected to gene ontology and KEGG pathway analysis to get insights of particular biological processes associated with this goat breed.

CONCLUSION

Current perception of genomic architecture of DDP goat provides a better understanding to improve its genetic potential and other economically important traits of medium to large body size, milk, and fiber production by updating the genomic insight driven breeding strategies to boost the livestock and agriculture-based economy of the country.

Genome-wide landscape of runs of homozygosity and differentiation across Egyptian goat breeds

Understanding the genomic features of livestock is essential for successful breeding programs and conservation. This information is scarce for local goat breeds in Egypt. In the current study, genomic regions with selection signatures were identified as well as runs of homozygosity (ROH), genomic inbreeding coefficients (FROH) and fixation index (FST) were detected in Egyptian Nubian, Damascus, Barki and Boer goat breeds. A total of 46,268 SNP markers and 337 animals were available for the genomic analyses. On average, 145.44, 42.02, 87.90 and 126.95 ROHs were detected per individual in the autosomal genome of the respective breeds. The mean accumulative ROH lengths ranged from 46.5 Mb in Damascus to 360 Mb in Egyptian Nubian. The short ROH segments (< 2 Mb) were most frequent in all breeds, while the longest ROH segments (> 16 Mb) were exclusively found in the Egyptian Nubian. The highest average FROH was observed in Egyptian Nubian (~ 0.12) followed by Boer (~ 0.11), while the lowest FROH was found in Damascus (~ 0.05) and Barki breed (~ 0.03). The estimated mean FST was 0.14 (Egyptian Nubian and Boer), 0.077 (Egyptian Nubian and Barki), 0.075 (Egyptian Nubian and Damascus), 0.071 (Barki and Boer), 0.064 (Damascus and Boer), and 0.015 (Damascus and Barki), for each pair of breeds. Interestingly, multiple SNPs that accounted for high FST values were observed on chromosome 6 in regions harboring ALPK1 and KCNIP4. Genomic regions overlapping both FST and ROH harbor genes related to immunity (IL4R, PHF23, GABARAP, GPS2, and CD68), reproduction (SPATA2L, TNFSF12, TMEM95, and RNF17), embryonic development (TCF25 and SOX15) and adaptation (MC1R, KDR, and KIT), suggesting potential genetic adaptations to local environmental conditions. Our results contribute to the understanding of the genetic architecture of different goat breeds and may provide valuable information for effective preservation and breeding programs of local goat breeds in Egypt.

Detection distribution of CNVs of SNX29 in three goat breeds and their associations with growth traits

As a member of the SNX family, the goat sorting nexin 29 (SNX29) is initially identified as a myogenesis gene. Therefore, this study aimed to examine the polymorphism in the SNX29 gene and its association with growth traits. In this study, we used an online platform to predict the structures of the SNX29 protein and used quantitative real-time PCR to detect potential copy number variation (CNV) in Shaanbei white cashmere (SBWC) goats (n = 541), Guizhou black (GB) goats (n = 48), and Nubian (NB) goats (n = 39). The results showed that goat SNX29 protein belonged to non-secretory protein. Then, five CNVs were detected, and their association with growth traits was analyzed. In SBWC goats, CNV1, CNV3, CNV4, and CNV5 were associated with chest width and body length (P < 0.05). Among them, the CNV1 individuals with gain and loss genotypes were superior to those individuals with a median genotype, but CNV4 and CNV5 of individuals with the median genotype were superior to those with the loss and gain genotypes. In addition, individuals with the gain genotype had superior growth traits in CNV3. In brief, this study suggests that the CNV of SNX29 can be used as a molecular marker in goat breeding.

Coat Color in Local Goats: Influence on Environmental Adaptation and Productivity, and Use as a Selection Criterion

This paper aims to review, systematically synthesize, and analyze fragmented information about the importance of coat color in local goats and its relationship with productivity and other important traits. Topics on current research on color expression are addressed, the relationship that has as a mechanism of environmental adaptation, its relationship with the production of meat, milk, and derivates, and the economic value of this characteristic. The use of this attribute as a tool to establish selection criteria in breeding programs based on results reported in the scientific literature is significant, particularly for low-income production systems, where the implementation of classic genetic improvement schemes is limited due to the lack of productive information, which is distinctive of extensive marginal or low scaled production systems around the world.

The influence of transposable elements on animal colouration

Transposable elements (TEs) are mobile genetic sequences present within host genomes. TEs can contribute to the evolution of host traits, since transposition is mutagenic and TEs often contain host regulatory and protein coding sequences. We review cases where TEs influence animal colouration, reporting major patterns and outstanding questions. TE-induced colouration phenotypes typically arise via introduction of novel regulatory sequences and splice sites, affecting pigment cell development or pigment synthesis. We discuss if particular TE types may be more frequently involved in the evolution of colour variation in animals, given that examples involving long terminal repeat (LTR) elements appear to dominate. Currently, examples of TE-induced colouration phenotypes in animals mainly concern model and domesticated insect and mammal species. However, several influential recent examples, coupled with increases in genome sequencing, suggest cases reported from wild species will increase considerably.

Genomic analysis reveals a KIT-related chromosomal translocation associated with the white coat phenotype in yak

White coat pigmentation is a striking phenotype of many domesticated species and has various genetic controls. The Tianzhu White yak, an indigenous breed with a complete white coat, has fascinated Tibetans for centuries. However, the genetic basis of this trait remains unknown. Here, we conducted population genomics analysis and genome-wide association study based on the whole-genome sequencing data of 38 white and 59 non-white-coated yak. The results revealed the presence of KIT-linked Cs alleles characterized by the translocations between chromosomes 6 and 29 in all-white yak. Furthermore, structural variations showed additional duplications of the Cs alleles in white yak compared with colour-sidedness cattle. Interestingly, the Cs alleles associated with the white coat phenotype in yak were found to have introgressed from taurine cattle. Our findings unveil the shared genetic control of the white coat phenotype and its evolution in closely related bovine species.

Selection signatures for fiber production in commercial species: A review

Natural fibers derived from diverse animal species have gained increased attention in recent years due to their favorable environmental effects, long-term sustainability benefits, and remarkable physical and mechanical properties that make them valuable raw materials used for textile and non-textile production. Domestication and selective breeding for the economically significant fiber traits play an imperative role in shaping the genomes and, thus, positively impact the overall productivity of the various fiber-producing species. These selection pressures leave unique footprints on the genome due to alteration in the allelic frequencies at specific loci, characterizing selective sweeps. Recent advances in genomics have enabled the discovery of selection signatures across the genome using a variety of methods. The increased demand for 'green products' manufactured from natural fibers necessitates a detailed investigation of the genomes of the various fiber-producing plant and animal species to identify the candidate genes associated with important fiber attributes such as fiber diameter/fineness, color, length, and strength, among others. The objective of this review is to present a comprehensive overview of the concept of selection signature and selective sweeps, discuss the main methods used for its detection, and address the selection signature studies conducted so far in the diverse fiber-producing animal species.

In it for the long run: perspectives on exploiting long-read sequencing in livestock for population scale studies of structural variants

Studies have demonstrated that structural variants (SV) play a substantial role in the evolution of species and have an impact on Mendelian traits in the genome. However, unlike small variants (< 50 bp), it has been challenging to accurately identify and genotype SV at the population scale using short-read sequencing. Long-read sequencing technologies are becoming competitively priced and can address several of the disadvantages of short-read sequencing for the discovery and genotyping of SV. In livestock species, analysis of SV at the population scale still faces challenges due to the lack of resources, high costs, technological barriers, and computational limitations. In this review, we summarize recent progress in the characterization of SV in the major livestock species, the obstacles that still need to be overcome, as well as the future directions in this growing field. It seems timely that research communities pool resources to build global population-scale long-read sequencing consortiums for the major livestock species for which the application of genomic tools has become cost-effective.

Whole-Genome Sequencing Reveals the Genomic Characteristics and Selection Signatures of Hainan Black Goat

Goats have become one of the most adaptive and important livestock species distributed in developing countries in recent years. The Hainan Black goat is a native goat breed of the Hainan region that is generally well-liked by the local population and is thus raised in large numbers. However, the genomic diversity and selective signals of the Hainan Black goat have not been clearly elucidated yet. Therefore, in this study, we performed whole-genome resequencing of 16 Hainan Black goats and compared the results with those of 71 goats of 6 other breeds from different geographic regions. Principal component analysis (PCA) and phylogenetic analysis identified seven lineages for all goats. Hainan Black goats showed the most similarity with Leizhou goats and the least similarity with Boer goats. Selective sweep analysis identified candidate genes associated with various functions, including immune resistance to disease (TNFAIP2 (TNF alpha induced protein 2) and EXOC3L4 (exocyst complex component 3 like 4)), melanin biosynthetic process (CDH15 (cadherin 15), ASIP (agouti signaling protein), and PARD3 (par-3 family cell polarity regulator)), and light sensitivity (CNGB3 (cyclic nucleotide gated channel subunit beta 3) and CNBD1 (cyclic nucleotide binding domain containing 1)), underlying strong selection signatures in Hainan Black goats. The melanin biosynthetic process, circadian entrainment, regulation of cyclic adenosine 3,5-monophosphate (cAMP)-mediated signaling, and the Rap-1 signaling pathway were significantly enriched in Hainan Black and Alashan Cashmere goats. This result may be important for understanding each trait. Selection signature analysis revealed candidate single nucleotide polymorphisms (SNPs) and genes correlated with the traits of Hainan Black goats. Collectively, our results provide valuable insights into the genetic basis of specific traits correlated with the Hainan island climate, artificial selection in certain local goat breeds, and the importance of protecting breed resources.

Roan coat color in livestock

Since domestication, a wide variety of phenotypes including coat color variation has developed in livestock. This variation is mostly based on selective breeding. During the beginning of selective breeding, potential negative consequences did not become immediately evident due to low frequencies of homozygous animals and have been occasionally neglected. However, numerous studies of coat color genetics have been carried out over more than a century and, meanwhile, pleiotropic effects for several coat color genes, including disorders of even lethal impact, were described. Similar coat color phenotypes can often be found across species, caused either by conserved genes or by different genes. Even in the same species, more than one gene could cause the same or similar coat color phenotype. The roan coat color in livestock species is characterized by a mixture of white and colored hair in cattle, pig, sheep, goat, alpaca, and horse. So far, the genetic background of this phenotype is not fully understood, but KIT and its ligand KITLG (MGF) are major candidate genes in livestock species. For some of these species, pleiotropic effects such as subfertility in homozygous roan cattle or homozygous embryonic lethality in certain horse breeds have been described. This review aims to point out the similarities and differences of the roan phenotype across the following livestock species: cattle, pig, sheep, goat, alpaca, and horse; and provides the current state of knowledge on genetic background and pleiotropic effects.

Comparative analyses of copy number variations between swamp and river buffalo

Domestic buffalo is an important livestock in the tropical and sub-tropical region, including two types: swamp and river buffalo. The swamp buffalo is mainly used as draft animal, while the river buffalo is raised for milk production. In this study, based on the new high-quality buffalo reference genome UOA_WB_1, we firstly investigated the copy number variants in buffalo using whole-genome Illumina sequencing. A total of 3,734 CNV regions (CNVRs) were detected in 106 buffalo population with a total length of 23,429,066 bp, corresponding to ∼ 0.88% of the water buffalo genome (UOA_WB_1). Our results revealed a clear population differentiation in CNV between swamp and river buffalo. In addition, a total of 667 highly differentiated CNVRs (covering 886 genes) were detected between river and swamp buffalo population. We detected a set of CNVR-overlapping genes associated with exercise, immunity, nerve, and milk trait which exhibited different copy numbers between swamp and river buffalo population. This study provides valuable genome variation resources for buffalo and would contribute to understanding the genetic differences between swamp and river buffalo.

A 13.42-kb tandem duplication at the ASIP locus is strongly associated with the depigmentation phenotype of non-classic Swiss markings in goats

BACKGROUND

The pigmentation phenotype diversity is rich in domestic goats, and identification of the genetic loci affecting coat color in goats has long been of interest. Via the detections of selection signatures, a duplication upstream ASIP was previously reported to be a variant affecting the Swiss markings depigmentation phenotype in goats.

RESULTS

We conducted a genome-wide association study using whole-genome sequencing (WGS) data to identify the genetic loci and causal variants affecting the pigmentation phenotype in 65 Jintang black (JT) goats (i.e., 48 solid black vs. 17 non-classic Swiss markings). Although a single association peak harboring the ASIP gene at 52,619,845-72,176,538 bp on chromosome 13 was obtained using a linear mixed model approach, all the SNPs and indels in this region were excluded as causal variants for the pigmentation phenotype. We then found that all 17 individuals with non-classic Swiss markings carried a 13,420-bp duplication (CHI13:63,129,198-63,142,617 bp) nearly 101 kb upstream of ASIP, and this variant was strongly associated (P = 1.48 × 10^- 12) with the coat color in the 65 JT goats. The copy numbers obtained from the WGS data also showed that the duplication was present in all 53 goats from three European breeds with Swiss markings and absent in 45 of 51 non-Swiss markings goats from four other breeds and 21 Bezoars, which was further validated in 314 samples from seven populations based on PCR amplification. The copy numbers of the duplication vary in different goat breeds with Swiss markings, indicating a threshold effect instead of a dose-response effect at the molecular level. Furthermore, breakpoint flanking repeat analysis revealed that the duplication was likely to be a result of the Bov-B-mediated nonallelic homologous recombination.

CONCLUSION

We confirmed that a genomic region harboring the ASIP gene is a major locus affecting the coat color phenotype of Swiss markings in goats. Although the molecular genetic mechanisms remain unsolved, the 13,420-bp duplication upstream of ASIP is a necessary but not sufficient condition for this phenotype in goats. Moreover, the variations in the copy number of the duplication across different goat breeds do not lead to phenotypic heterogeneity.

Genome-Wide Selective Analysis of Boer Goat to Investigate the Dynamic Heredity Evolution under Different Stages

Boer goats, as kemp in meat-type goats, are selected and bred from African indigenous goats under a long period of artificial selection. Their advantages in multiple economic traits, particularly their plump growth, have attracted worldwide attention. The current study displayed the genome-wide selection signature analyses of South African indigenous goat (AF), African Boer (BH), and Australian Boer (AS) to investigate the hereditary basis of artificial selection in different stages. Four methods (principal component analysis, nucleotide diversity, linkage disequilibrium decay, and neighbor-joining tree) implied the genomic diversity changes with different artificial selection intensities in Boer goats. In addition, the θπ, FST, and XP-CLR methods were used to search for the candidate signatures of positive selection in Boer goats. Consequently, 339 (BH vs. AF) and 295 (AS vs. BH) candidate genes were obtained from SNP data. Especially, 10 genes (e.g., BMPR1B, DNER, ITGAL, and KIT) under selection in both groups were identified. Functional annotation analysis revealed that these genes are potentially responsible for reproduction, metabolism, growth, and development. This study used genome-wide sequencing data to identify inheritance by artificial selection. The results of the current study are valuable for future molecular-assisted breeding and genetic improvement of goats.

Detection of common copy number of variation underlying selection pressure in Middle Eastern horse breeds using whole-genome sequence data

Dareshouri, Arabian, and Akhal-Teke are three Middle Eastern horse breeds that have been selected for endurance and adaptation to harsh climates. Deciphering the genetic characteristics of these horses by tracing selection footprints and copy number of variations will be helpful in improving our understanding of equine breeds' development and adaptation. For this purpose, we sequenced the whole-genome of four Dareshouri horses using Illumina Hiseq panels and compared them with publicly available whole-genome sequences of Arabian (n=3) and Akhal-Teke (n=3) horses . Three tests of FLK, hapFLK, and pooled heterozygosity were applied using a sliding window (window size=100kb, step size=50kb) approach to detect putative selection signals. Copy number variation analysis was applied to investigate copy number of variants (CNVs), and the results were used to suggest selection signatures involving CNVs. Whole-genome sequencing demonstrated 8,837,950 single nucleotide polymorphisms (SNPs) in autosomal chromosomes. We suggested 58 genes and three quantitative trait loci (QTLs), including some related to horse gait, insect bite hypersensitivity, and withers height, based on selective signals detected by adjusted p-value of Mahalanobis distance based on the rank-based P-values (Md-rank-P) method. We proposed 12 genomic regions under selection pressure involving CNVs which were previously reported to be associated with metabolism energy (SLC5A8), champagne dilution in horses (SLC36A1), and synthesis of polyunsaturated fatty acids (FAT2). Only 10 Middle Eastern horses were tested in this study; therefore, the conclusions are speculative. Our findings are useful to better understanding the evolution and adaptation of Middle Eastern horse breeds.

Selection Signature Analyses Revealed Genes Associated With Adaptation, Production, and Reproduction in Selected Goat Breeds in Kenya

Artificial and natural selection in livestock is expected to leave unique footprints on their genomes. Goat breeds in Kenya have evolved for survival, breeding, and production in various harsh ecological areas, and their genomes are likely to have acquired unique alleles for adaptation to such diverse production environments and other traits of economic importance. To investigate signals of selection for some selected goat breeds in Kenya, Alpine (n = 29), Galla (n = 12), Saanen (n = 24), and Toggenburg (n = 31) were considered. A total of 53,347 single-nucleotide polymorphisms (SNPs) generated using the Illumina GoatSNP50 BeadChip were analyzed. After quality control, 47,663 autosomal single-nucleotide polymorphisms remained for downstream analyses. Several complementary approaches were applied for the following analyses: integrated Haplotype Score (iHS), cross-population-extended haplotype homozygosity (XP-EHH), hapFLK, and FLK. A total of 404 top genomic regions were identified across all the four breeds, based on the four complementary analyses. Out of the 16 identified putative selection signature regions by the intersection of multiple-selective signal analyses, most of the putative regions were found to overlap significantly with the iHS and XP-EHH analyses on chromosomes 3, 4, 10, 15, 22, and 26. These regions were enriched with some genes involved in pathways associated directly or indirectly with environmental adaptation regulating immune responses (e.g., HYAL1 and HYAL3), milk production (e.g., LEPR and PDE4B), and adaptability (e.g., MST1 and PCK). The results revealed few intersect between breeds in genomic selection signature regions. In general, this did not present the typical classic selection signatures as predicted due to the complex nature of the traits. The results support that some various selection pressures (e.g., environmental challenges, artificial selection, and genome admixture challenges) have molded the genome of goat breeds in Kenya. Therefore, the research provides new knowledge on the conservation and utilization of these goat genetic resources in Kenya. In-depth research is needed to detect precise genes connected with adaptation and production in goat breeds in Kenya.

Selection signatures and formation of the Samosir goat breed through the cultures of the Batak Toba Tribe in Samosir Island, Indonesia

Background and Aim:

The Samosir goat has a high cultural value and is a source of germplasm in Indonesia. This study aimed to reveal the history and selection signatures of the Samosir goat.

Materials and Methods:

A total of 25 goats were divided into seven subpopulations of Indonesian goat breeds. Deoxyribonucleic acid (DNA) from blood samples was isolated with the use of the gSYNC™ DNA Mini Kit (Geneaid, Taipei, Taiwan). Cytb gene amplification was performed by the polymerase chain reaction (PCR) method, and the PCR products were sequenced. A phylogenetic tree was constructed by the neighbor-joining method using MEGA 11 software. A questionnaire was used to collect information related to the history and breeding practices of the Samosir goat on Samosir Island.

Results:

Samosir goats are divided into four groups based on their coat color: Completely white, white with brown spots, white with black spots, and white with brown and black spots. The body form of the Samosir goat is similar to that of the Kacang goat. The space below a traditional Toba Batak house is used as a goat pen. The genetic difference between the Samosir goat and the Kacang goat based on the Cytb gene was approximately 0.1%.

Conclusion:

Phylogenetic analysis between Samosir goats and other indigenous Indonesian goats revealed that Samosir goats form a single clade, with a very close genetic distance from other local goats, such as the Kacang goat. The Toba Batak culture on Samosir Island has significantly influenced the selection and formation of the Samosir goat breed.

Runs of homozygosity in Swiss goats reveal genetic changes associated with domestication and modern selection

Background

The domestication of goat (Capra hircus) started 11,000 years ago in the fertile crescent. Breed formation in the nineteenth century, establishment of herd books, and selection for specific traits resulted in 10 modern goat breeds in Switzerland. We analyzed whole-genome sequencing (WGS) data from 217 modern goats and nine wild Bezoar goats (Capra aegagrus). After quality control, 27,728,288 biallelic single nucleotide variants (SNVs) were used for the identification of runs of homozygosity (ROH) and the detection of ROH islands.

Results

Across the 226 caprine genomes from 11 populations, we detected 344 ROH islands that harbor 1220 annotated genes. We compared the ROH islands between the modern breeds and the Bezoar goats. As a proof of principle, we confirmed a signature of selection, which contains the ASIP gene that controls several breed-specific coat color patterns. In two other ROH islands, we identified two missense variants, STC1:p.Lys139Arg and TSHR:p.Ala239Thr, which might represent causative functional variants for domestication signatures.

Conclusions

We have shown that the information from ROH islands using WGS data is suitable for the analysis of signatures of selection and allowed the detection of protein coding variants that may have conferred beneficial phenotypes during goat domestication. We hypothesize that the TSHR:p.Ala239Thr variant may have played a role in changing the seasonality of reproduction in modern domesticated goats. The exact functional significance of the STC1:p.Lys139Arg variant remains unclear and requires further investigation. Nonetheless, STC1 might represent a new domestication gene affecting relevant traits such as body size and/or milk yield in goats.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12711-022-00695-w.

Detection of whole genome selection signatures of Pakistani Teddy goat

BACKGROUND

Natural and artificial selection tend to cause variability that contributes to shape the genome of livestock in a way that differentiates them among the animal kingdom. The particular aim here is to identify positive selection signatures with whole genome pooled-sequence data of Pakistani Teddy goat.

METHODS AND RESULTS

Paired-end alignment of 635,357,043 reads of Teddy goat with (ARS1) reference genome assembly was carried out. Pooled-Heterozygosity (Hp) and Tajima's D (TD) are applied for validation and getting better hits of selection signals, while pairwise F_ST statistics is conducted on Teddy vs. Bezoar (wild goat ancestor) for genomic differentiation, moreover annotation of regions under positive selection was also performed. Hp score with - ZHp > 5 detected six windows having highest hits on Chr. 29, 9, 25, 15 and 14 that harbor HRASLS5, LACE1 and AXIN1 genes which are candidate for embryonic development, lactation and body height. Secondly, - ZTD value of > 3.3 showed 4 windows with very strong hits on Chr.5 & 9 which harbor STIM1 and ADM genes related to body mass and weight. Lastly, - ZF_ST < - 5 generated four strong signals on Chr.5 & 12 harbor LOC102183233 gene. Other significant selection signatures encompass genes associated with wool production, prolificacy and coat colors traits in this breed.

CONCLUSIONS

In brief, this study identified the genes under selection in Pakistani Teddy goat that will be helpful to refining the marker-assisted breeding policies and converging required production traits within and across other goat breeds and to explore full genetic potential of this valued species of livestock.

GWAS for genetics of complex quantitative traits: Genome to pangenome and SNPs to SVs and k-mers

The development of improved methods for genome-wide association studies (GWAS) for genetics of quantitative traits has been an active area of research during the last 25 years. This activity initially started with the use of mixed linear model (MLM), which was variously modified. During the last decade, however, with the availability of high throughput next generation sequencing (NGS) technology, development and use of pangenomes and novel markers including structural variations (SVs) and k-mers for GWAS has taken over as a new thrust area of research. Pangenomes and SVs are now available in humans, livestock, and a number of plant species, so that these resources along with k-mers are being used in GWAS for exploring additional genetic variation that was hitherto not available for analysis. These developments have resulted in significant improvement in GWAS methodology for detection of marker-trait associations (MTAs) that are relevant to human healthcare and crop improvement.

Introgression of ASIP and TYRP1 Alleles Explains Coat Color Variation in Valais Goats

The Valais Blackneck goat is a Swiss goat breed with a characteristic coat color phenotype. Before the revision of the breed standard in 1938, 4 different color varieties of Valais goats were known. Besides Blackneck animals resembling the modern breed standard, the brown and white Copperneck goat, the white Capra Sempione, and the greyish Grüenochte comprised the historic Valais goats. The brown pigmentation of Copperneck goats had previously been traced back to an introgression of a mutant TYRP1 allele from Toggenburg goats. In the present study, we identified additional introgression events of distinct ASIP alleles causing the remaining 2 rare coat color patterns within the Valais Blackneck goat breed. We identified the introgression of the AWt allele from Appenzell or Saanen goats in white Capra Sempione goats. Similarly, introgression of the Apc allele from Peacock goats resulted in the greyish Grüenochte phenotype. These results demonstrate past hybridization events between breeds that are separated today. A perfect genotype-phenotype association in 393 Valais goats supported the causality of the genotyped variants for the different coat color phenotypes. Our study gives insights into the introgression of functionally relevant copy number variant (CNV) alleles controlling pigmentation between goat breeds with strikingly different coat color patterns.

Benchmarking the performance of Pool-seq SNP callers using simulated and real sequencing data

Population genomics is a fast-developing discipline with promising applications in a growing number of life sciences fields. Advances in sequencing technologies and bioinformatics tools allow population genomics to exploit genome-wide information to identify the molecular variants underlying traits of interest and the evolutionary forces that modulate these variants through space and time. However, the cost of genomic analyses of multiple populations is still too high to address them through individual genome sequencing. Pooling individuals for sequencing can be a more effective strategy in Single Nucleotide Polymorphism (SNP) detection and allele frequency estimation because of a higher total coverage. However, compared to individual sequencing, SNP calling from pools has the additional difficulty of distinguishing rare variants from sequencing errors, which is often avoided by establishing a minimum threshold allele frequency for the analysis. Finding an optimal balance between minimizing information loss and reducing sequencing costs is essential to ensure the success of population genomics studies. Here, we have benchmarked the performance of SNP callers for Pool-seq data, based on different approaches, under different conditions, and using computer simulations and real data. We found that SNP callers performance varied for allele frequencies up to 0.35. We also found that SNP callers based on Bayesian (SNAPE-pooled) or maximum likelihood (MAPGD) approaches outperform the two heuristic callers tested (VarScan and PoolSNP), in terms of the balance between sensitivity and FDR both in simulated and sequencing data. Our results will help inform the selection of the most appropriate SNP caller not only for large-scale population studies but also in cases where the Pool-seq strategy is the only option, such as in metagenomic or polyploid studies.

Variants at the ASIP locus contribute to coat color darkening in Nellore cattle

BACKGROUND

Nellore cattle (Bos indicus) are well-known for their adaptation to warm and humid environments. Hair length and coat color may impact heat tolerance. The Nellore breed has been strongly selected for white coat, but bulls generally exhibit darker hair ranging from light grey to black on the head, neck, hump, and knees. Given the potential contribution of coat color variation to the adaptation of cattle populations to tropical and sub-tropical environments, our aim was to map positional and functional candidate genetic variants associated with darkness of hair coat (DHC) in Nellore bulls.

RESULTS

We performed a genome-wide association study (GWAS) for DHC using data from 432 Nellore bulls that were genotyped for more than 777 k single nucleotide polymorphism (SNP) markers. A single major association signal was detected in the vicinity of the agouti signaling protein gene (ASIP). The analysis of whole-genome sequence (WGS) data from 21 bulls revealed functional variants that are associated with DHC, including a structural rearrangement involving ASIP (ASIP-SV1). We further characterized this structural variant using Oxford Nanopore sequencing data from 13 Australian Brahman heifers, which share ancestry with Nellore cattle; we found that this variant originates from a 1155-bp deletion followed by an insertion of a transposable element of more than 150 bp that may impact the recruitment of ASIP non-coding exons.

CONCLUSIONS

Our results indicate that the variant ASIP sequence causes darker coat pigmentation on specific parts of the body, most likely through a decreased expression of ASIP and consequently an increased production of eumelanin.

Genomic Analysis Revealed a Convergent Evolution of LINE-1 in Coat Color: A Case Study in Water Buffaloes (Bubalus bubalis)

Visible pigmentation phenotypes can be used to explore the regulation of gene expression and the evolution of coat color patterns in animals. Here, we performed whole-genome and RNA sequencing and applied genome-wide association study, comparative population genomics and biological experiments to show that the 2,809-bp-long LINE-1 insertion in the ASIP (agouti signaling protein) gene is the causative mutation for the white coat phenotype in swamp buffalo (Bubalus bubalis). This LINE-1 insertion (3' truncated and containing only 5' UTR) functions as a strong proximal promoter that leads to a 10-fold increase in the transcription of ASIP in white buffalo skin. The 165 bp of 5' UTR transcribed from the LINE-1 is spliced into the first coding exon of ASIP, resulting in a chimeric transcript. The increased expression of ASIP prevents melanocyte maturation, leading to the absence of pigment in white buffalo skin and hairs. Phylogenetic analyses indicate that the white buffalo-specific ASIP allele originated from a recent genetic transposition event in swamp buffalo. Interestingly, as a similar LINE-1 insertion has been identified in the cattle ASIP gene, we discuss the convergent mechanism of coat color evolution in the Bovini tribe.

Copy number variation: Characteristics, evolutionary and pathological aspects

Copy number variants (CNVs) were the subject of extensive research in the past years. They are common features of the human genome that play an important role in evolution, contribute to population diversity, development of certain diseases, and influence host–microbiome interactions. CNVs have found application in the molecular diagnosis of many diseases and in non-invasive prenatal care, but their full potential is only emerging. CNVs are expected to have a tremendous impact on screening, diagnosis, prognosis, and monitoring of several disorders, including cancer and cardiovascular disease. Here, we comprehensively review basic definitions of the term CNV, outline mechanisms and factors involved in CNV formation, and discuss their evolutionary and pathological aspects. We suggest a need for better defined distinguishing criteria and boundaries between known types of CNVs.

Dog colour patterns explained by modular promoters of ancient canid origin

Distinctive colour patterns in dogs are an integral component of canine diversity. Colour pattern differences are thought to have arisen from mutation and artificial selection during and after domestication from wolves but important gaps remain in understanding how these patterns evolved and are genetically controlled. In other mammals, variation at the ASIP gene controls both the temporal and spatial distribution of yellow and black pigments. Here, we identify independent regulatory modules for ventral and hair cycle ASIP expression, and we characterize their action and evolutionary origin. Structural variants define multiple alleles for each regulatory module and are combined in different ways to explain five distinctive dog colour patterns. Phylogenetic analysis reveals that the haplotype combination for one of these patterns is shared with Arctic white wolves and that its hair cycle-specific module probably originated from an extinct canid that diverged from grey wolves more than 2 million years ago. Natural selection for a lighter coat during the Pleistocene provided the genetic framework for widespread colour variation in dogs and wolves.