Runs of homozygosity in European populations

Genomic characterization and insights into the belted coat pattern of a local, reconstituted pig population

The Cinghiato pig population originates from a breeding project aimed at reconstituting an extinct local swine breed, historically depicted in frescoes in Umbria, Central Italy. The selection strategy employed a reconstruction breeding program, choosing mating pairs based on the unique coat phenotype represented in these artworks. Unlike the traditional Cinta Senese breed, Cinghiato pigs exhibit a white belt encircling the trunk, while their forelimbs remain black. This study explores the genetic background of the belted coat pattern observed in the heterogeneous reconstituted population. Twenty-two pigs were genotyped using the Porcine GGP 80K SNP BeadChip. Genetic analyses were conducted to assess population structure and diversity, with comparisons made to other Italian pig breeds and wild boars. Findings reveal moderate genetic diversity within the Cinghiato population. Runs of Homozygosity patterns suggest historical inbreeding events. Moreover, several genomic regions were associated with traits relevant to niche pork production, including feed intake, leg conformation, and fat deposition. Polymorphisms were detected in 10 coat color-related genes (KIT, MC1R, ASIP, EDNRB, KITLG, MITF, OCA2, PAX3, SOX10, and TYRP1). Although some candidate variants were identified, this preliminary study highlights the need for further research to clarify the genetic mechanisms underlying the phenotypic variability of belted coat patterns.

Comparative genome analysis of international transboundary cattle breeds

Indian-origin Gir and Ongole cattle are international transboundary breeds that are reared in Brazil, The United States, Mexico, Malaysia, Panama, and other nations to provide meat and dairy products. These breeds have shown substantial genetic diversity in recent years and well suited to the ecological niche in Brazil. 90 cattle samples of Indian Gir (n = 15), Ongole (n = 17), Brazilian Gyr (n = 27), and Nellore (n = 31) breeds were genotyped using Illumina BovineHD BeadChip. Samples were analyzed to identify selection signatures using two complementing approaches: Integrated Haplotype Score (iHS) and Fixation Index (FST). Gir versus Gyr and Ongole versus Nellore revealed Pairwise FST differences of 2.85 % and 2.35 %, respectively. Using integrated haplotype score (iHS) method, 4004, 3322, 3437, and 3485 genes were found in Gir, Gyr, Ongole, and Nellore, respectively, underlying top 1 % of selected regions. Under top 1 % of selected regions, FST based method identified1897 genes for the Ongole-Nellore pair and 1966 genes for the Gir-Gyr pair. Runs of homozygosity (ROH) analysis revealed that both recent as well as ancient inbreeding in these breeds were in range of 2.6-4.5 % indicating populations to be less inbred. Numerous candidate genes, including IER5, MILR1 (immunity related traits) in Gir; and FGF12, SV2C, JMY (average daily gain, body size, reproduction related traits) in Ongole, were found under the top-selected regions. Nellore breed had carcass/growth traits (PARP2, and KCNJ11) and genes linked to mammary gland development, udder size, and carcass (MYO16, MYO1B) were found in Gyr. Present findings reveals that Brazilian cattle population (Gyr and Nellore) is more selected for carcass and growth traits along with milk production traits, whereas in Indian cattle population (Gir and Ongole) selection signature related to immunity and adaptation were more prominent. Further, sufficient genetic diversity exist within these cattle breeds for their genetic improvement.

Frailty and the Risk of Delirium: A Mendelian Randomization Study

Observational studies have explored associations between frailty and delirium, but conclusions have been controversial. We aimed to identify the potential causality effect between these 2 traits using Mendelian randomization (MR). The genetics instrument related with frailty index (FI) was taken from a summary-level genome-wide association study (GWAS), and the GWAS of delirium was obtained from the FinnGen Study. The inverse variance weighted method (IVW) was performed. MR analysis found a causal association between genetically predicted FI and an elevated risk of delirium in IVW (odds ratio [OR]: 2.85; 95% CI: 1.03-7.90; P= .04). This study encouraged early identification of the baseline frailty in intensive care units. Critical care nurses are advised to use multidimensional tools to identify frailty. Then, individualized care plans should be made according to frailty degrees, like nutrition and pre-rehabilitation for pre-frail patients. Nurses can optimize medical resources and apply cluster interventions for delirium high-risk groups.

Profiling of runs of homozygosity from whole-genome sequence data in Japanese biobank

Runs of homozygosity (ROHs) are widely observed across the genomes of various species and have been reported to be associated with many traits and common diseases, as well as rare recessive diseases, in human populations. Although single nucleotide polymorphism (SNP) array data have been used in previous studies on ROHs, recent advances in whole-genome sequencing (WGS) technologies and the development of nationwide cohorts/biobanks are making high-density genomic data increasingly available, and it is consequently becoming more feasible to detect ROHs at higher resolution. In the study, we searched for ROHs in two high-coverage WGS datasets from 3552 Japanese individuals and 192 three-generation families (consisting of 1120 family members) in prospective genomic cohorts. The results showed that a considerable number of ROHs, especially short ones that may have remained undetected in conventionally used SNP-array data, can be detected in the WGS data. By filtering out sequencing errors and leveraging pedigree information, longer ROHs are more likely to be detected in WGS data than in SNP-array data. Additionally, we identified gene families within ROH islands that are associated with enriched pathways related to sensory perception of taste and odors, suggesting potential signatures of selection in these key genomic regions.

Genome-wide scan for signatures of selection in Hanwoo and Angus cattle using whole-genome sequence data

This study used whole-genome sequence data on 406 beef cattle (203 Hanwoo and 203 Angus) to detect signatures of selection using four different methods; integrated haplotype score (iHS), Rsb, XP-EHH, and runs of homozygosity (ROH). Based on Rsb and XP-EHH analysis, 36 and 21 genomic regions differed significantly between Angus and Hanwoo breeds. Within breeds, we identified 108 regions (76 in Hanwoo and 32 in Angus) with the ROH analysis and 331 regions with the iHS method (298 in Hanwoo and 33 in Angus). The candidate genes related to meat quality, such as HSPA9 and LPL, were found within Hanwoo, while genes associated with growth and meat quantity traits, including ACTC1 and TMEM68, were identified within Angus. This study can assist in understanding the selection history of these breeds and identifying the genomic regions associated with the traits selected for in the breeding programs for these cattle breeds.

The CNV map construction and ROH analysis of Pinan cattle

Pinan cattle, as the progeny of crossbreeding improvement between Nanyang cattle and Piedmontese, have attracted attention for their excellent growth performance. In this study, we constructed a copy number variation map by whole genome resequencing of 132 Pinan cattle. In the genome of Pinan cattle, deletion-type copy number variants occupied a higher proportion and only 3.31% of CNVRs overlapped with exonic regions. It showed that Pinan cattle was clearly distinguishable from other breeds and Pinan cattle was closer to Nanyang cattle by population genetic structure analysis based on CNVRs. The degree of inbreeding in the Pinan cattle population was explored by ROH analysis, which showed that the degree of inbreeding in Pinan cattle was lower than that in European beef cattle, suggesting that the risk of inbreeding was low. Candidate genes related to muscle development (CADM3, CNTFR, DOCK3), reproductive traits (SCAPER), embryonic development (RERE) and immune traits (CD84) were identified by VST selection analysis, ROH islands and iHS selection analysis, which provided a new scientific basis for the genetic basis of the excellent traits in Pinan cattle.

Whole-Genome Sequencing Identifies Functional Genes for Environmental Adaptability in Chinese Geese

China is home to a rich diversity of goose genetic resources, with more than 30 distinct breeds. These breeds are widely distributed in various environments with high annual mean temperature differences ranging from about 3.5 °C to 23 °C and annual precipitation differences ranging from about 230 mm to 2200 mm, positioning them as excellent models for studying environmental adaptability. With three genetic-environment association methods, the LFMM, Samβada, and RDA analysis, a total of 447 genes were selected by at least two methods. These genes are significantly enriched in three pathways, including the polycomb repressive complex pathway, the alanine, aspartate, and glutamate metabolism pathway, and the GnRH signalling pathway. The scanning of all candidate single-nucleotide polymorphism variations found that only two variants located in a non-coding region (chr3:38968547, chr13:23863699) showed stronger positive selection in breeds living in a high-temperature environment. This research not only deepens our understanding of the genetic basis of goose adaptation to diverse environments but also provides a valuable resource for future selective breeding programs in the goose industry facing rapid global climate change.

A genomic tale of inbreeding in western Mediterranean human populations

Consanguineous marriages are common in many worldwide human populations, and the biological consequences for offspring can be relevant at the biomedical level. The current genomic revolution displayed through genome-wide studies is challenging the paradigm in the analysis of consanguinity. Here, we analyzed genomic inbreeding patterns in human populations located at the western edge of the Mediterranean region (Iberia and Morocco). Runs of Homozygosity (ROH) (autozygosity fragments) were identified in 139 autochthonous individuals originating from southern Iberia and Morocco via microarray data. All individuals analyzed carried at least one ROH in their genomes. The genomic inbreeding coefficient (FROH) and the presence of ROH islands (ROHi) revealed interesting patterns in the target populations as well as in the rest of the Mediterranean basin. Moroccan Berbers presented signals of recent inbreeding, relying on high coverage of long ROH (> 5 Mb) and FROH. The location and structure of ROHi among people in the western Mediterranean could be interpreted as a signature of common genetic links across the Strait of Gibraltar. We found a significant enrichment of some relevant biological functions in the estimated ROHi hotspots associated with the immune system and chemosensation. Genomic inbreeding approaches allow us to understand past population histories and can be used as a proxy to scan the genome in search of selection signals.

Genome-wide diversity and MHC characterisation in a critically endangered freshwater turtle susceptible to disease

Small, isolated populations are often vulnerable to increased inbreeding and genetic drift, both of which elevate the risk of extinction. The Bellinger River turtle (Myuchelys georgesi) is a critically endangered species endemic to a single river catchment in New South Wales, Australia. The only extant wild population, along with the breeding program, face significant threats from viral outbreaks, most notably a nidovirus outbreak in 2015 that led to a 90% population decline. To enhance our understanding of genomic characteristics in the species, including genome-wide and functional gene diversity, we re-sequenced, assembled, and analysed 31 re-sequenced genomes for pure M. georgesi (N = 31). We manually annotated the major histocompatibility complex (MHC), identifying five MHC class I and ten MHC class II genes and investigated genetic diversity across both classes in M. georgesi. Our results showed that genome-wide diversity is critically low in pure M. georgesi, contexualised through comparison with opportunistically sampled backcross animals-offspring of F1 hybrids (M. georgesi × Emydura macquarii) backcrossed to pure M. georgesi (N = 4). However, the variation observed within the core MHC region of pure M. georgesi, extending across scaffold 10, exceeded that of all other macrochromosomes. Additionally, no significant short-term changes in either genome-wide or immunogenetic diversity were detected following the 2015 nidovirus outbreak (before; N = 19, after; N = 12). Demographic history reconstructions indicated a sustained, long-term decline in effective population size since the last interglacial period, accompanied by more recent steep declines. These patterns suggested that prolonged isolation and reduced population size have significantly influenced the dynamics of genome-wide diversity. It is likely that contemporary stressors, including the recent nidovirus outbreak, are acting on an already genetically depleted population. This study offers new insights into genome-wide and immune gene diversity, including immune gene annotation data with broader implications for testudines. These findings provide crucial information to support future management strategies for the species.

Genomic Prediction of Individual Inbreeding Levels for the Management of Genetic Diversity in Populations With Small Effective Size

In populations of small effective size (Ne), such as those in conservation programmes, companion animals or livestock species, inbreeding control is essential. Homozygosity-by-descent (HBD) segments provide relevant information in that context, as they allow accurate estimation of the inbreeding coefficient, provide locus-specific information and their length is informative about the "age" of inbreeding. Our objective was to evaluate tools for predicting HBD in future offspring based on parental genotypes, a problem equivalent to identifying segments identical-by-descent (IBD) among the four parental chromosomes. In total, we reviewed and evaluated 16 approaches using simulated and real data from populations with small Ne. The methods included model-based approaches as well as more computationally efficient rule-based approaches. The accuracy of the methods was then evaluated, including with low-density marker panels, genotyping-by-sequencing data and small groups of individuals, typical features of such populations. Two model-based approaches performed consistently well, while some rule-based approaches proved accurate for genome-wide predictions. The model-based approaches were particularly efficient when genomic information was sparse or degraded. Methods using phased data proved to be more accurate, while some approaches relying on unphased genotype data were sensitive to the assumed allele frequencies. In some settings, pedigree-based predictions ranked high for recent inbreeding levels. Finally, we showed that our evaluation is also informative about the accuracy of the methods for estimating relatedness and identifying IBD segments between pairs of present-day individuals. This study shows that future inbreeding can be accurately predicted, including at specific loci, but not all methods perform equally well.

Whole Genome Insights into Genetic Diversity, Introgression, and Adaptation of Hunan Cattle

Hunan Province, located in Central-South China, has a hot and humid climate, which has shaped the unique characteristics of its cattle. In this study, we analyzed the genomic diversity of 110 indigenous Hunan cattle using whole-genome sequencing and found that they have a mixed ancestry of indicine and taurine. By grouping the cattle based on their collection regions (western, central, southeastern, and southern Hunan), we used an unsupervised three-component Gaussian model to classify the runs of homozygosity (ROH) and calculated the genomic inbreeding coefficient based on runs of homozygosity (FROH) to assess inbreeding levels. The results showed that western Hunan cattle had the highest level of hybridization, while southern Hunan cattle had the lowest. Through selective sweep analysis, we identified candidate genes and pathways related to environmental adaptation and homeostasis. Notably, the SLC5A2 gene showed strong selection signals across all four regions and exhibited a distinct haplotype compared to other referenced cattle breeds. Additionally, we detected introgression from wild species into Hunan domestic cattle and analyzed their Y-chromosome haplotypes.

Whole-genome sequencing reveals patterns of runs of homozygosity underlying genetic diversity and selection in domestic rabbits

BACKGROUND

Runs of homozygosity (ROH) are continuous segments of homozygous genotypes inherited from both parental lineages. These segments arise due to the transmission of identical haplotypes. The genome-wide patterns and hotspot regions of ROH provide valuable insights into genetic diversity, demographic history, and selection trends. In this study, we analyzed whole-genome resequencing data from 117 rabbits to identify ROH patterns and inbreeding level across eleven rabbit breeds, including seven Chinese indigenous breeds and four exotic breeds, and to uncover selective signatures based on ROH islands.

RESULTS

We detected a total of 31,429 ROHs across the autosomes of all breeds, with the number of ROHs (NROH) per breed ranging from 1316 to 7476. The mean sum of ROHs length (SROH) per individual was 493.84 Mb, covering approximately 22.79% of the rabbit autosomal genome. The majority of the detected ROHs ranged from 1 to 2 Mb in length, with an average ROH length (LROH) of 1.84 Mb. ROHs longer than 6 Mb constituted only 0.83% of the detected ROHs. The average inbreeding coefficient derived from ROHs (FROH) was 0.23, with FROH values ranging from 0.14 to 0.38 across breeds. Among Chinese indigenous breeds, the Jiuyishan rabbit exhibited the highest values of NROH, SROH, LROH, and FROH, whereas the Fujian Yellow rabbit had the lowest FROH values. In exotic rabbit breeds, the Japanese White rabbit displayed the highest values for NROH, SROH, LROH, and FROH, while the Flemish Giant rabbit had the lowest values for these metrics. Additionally, we identified 17 ROH islands in Chinese indigenous breeds and 22 ROH islands in exotic rabbit breeds, encompassing 124 and 186 genes, respectively. In Chinese indigenous breeds, we identified prominent genes associated with reproduction, including CFAP206, RNF133, CPNE4, ASTE1, and ATP2C1, as well as genes related to adaptation, namely CADPS2, FEZF1, and EPHA7. In contrast, the exotic breeds exhibited a prevalence of genes associated with fat deposition, such as ELOVL3 and NPM3, as well as growth and body weight related genes, including FAM184B, NSMCE2, and TWNK.

CONCLUSIONS

This study enhances our understanding of genetic diversity and selection pressures in domestic rabbits, offering valuable implications for breeding management and conservation strategies.

Genomic and health characteristics of crossbred dairy cattle in central Uganda

Introduction

In Africa, dairy cattle contribute significantly to the economy; however, a substantial proportion of these animals are low-yielding indigenous breeds. To increase dairy productivity, crossbreeding with exotic breeds such as European Holstein and Jersey is becoming increasingly common. Uncontrolled crossbreeding practices, however, pose a risk to the genetic integrity of local breeds, as highly productive but potentially maladapted animals may replace indigenous populations. This study aimed to characterise the genetic structure of crossbred dairy cattle in Uganda.

Methods

We used admixture analysis, while also assessing genomic diversity and inbreeding levels. Additionally, we evaluated the utility of farmer-generated phenotypic databases by integrating them with genomic data to explore the impact of exotic breed crossbreeding on disease frequency.

Results and discussion

Findings from this study show a strong influence of exotic breeds (e.g., Holstein) in Ugandan crossbred cattle, leading to lower inbreeding and observed homozygosity than those observed for indigenous breeds. Exploratory analyses of available disease records provided evidence of a strong survivor bias, likely linked to higher mortality rates from diseases such as East Coast fever. These results show the importance of investigating the genetic composition of farm animals, in order to develop informed and sustainable breeding strategies in African dairy cattle systems.

A retrospective single center analysis of fetuses with region of homozygosity detected by single nucleotide polymorphism array

We assessed the incidence and clinical significance of the fetal region of homozygosity (ROH) detected using single nucleotide polymorphism (SNP) array by analyzing clinical information and pregnancy outcomes. We collected data on 6176 mid- and late pregnancies. All fetuses were subjected to SNP array analysis. Fetuses with ROH were analyzed by karyotyping, parental SNP array verification, whole-exome sequencing, and/or placental studies. Eighty-seven ROHs met our reporting thresholds. Thirty-four fetuses were detected from noninvasive prenatal testing-positive results, with the most common detection rate (2.03%). Twenty-four cases were diagnosed using ultrasound abnormalities; fetal growth restriction was the indication with the highest diagnostic rate. Fifteen cases of uniparental disomy in mid- and late pregnancy were identified (0.24%). Nine cases were of ROH accompanied by aneuploidy or pathogenic/likely pathogenic copy number variants with an adverse pregnancy outcome rate of 88.9%. Of the remaining 78 cases, 14 carriers had adverse outcomes (including two cases of imprinting syndrome), 63 had normal development after birth, and one was lost to follow-up. ROH is relatively common in mid- and late-term pregnancies; its incidence is higher than that reported previously. SNP array is effective in assessing ROH and should be combined with multiple techniques to evaluate ROH's clinical relevance.

Uncovering genomic diversity and signatures of selection in red Angus × Chinese red steppe crossbred cattle population

Crossbreeding is a cornerstone of modern livestock improvement, combining desirable traits to enhance productivity and environmental resilience. This study conducts the first comprehensive genomic analysis of Red Angus × Chinese Red Steppe (RACS) crossbred cattle, evaluating their genetic architecture, diversity, and selection signatures relative to founder breeds (Red Angus and Chinese Red Steppe) and global populations. A total of 119 cattle, comprising 104 RACS crossbreds and 15 Chinese Red Steppes cattle, were genotyped using the GGP Bovine 100k SNP array. Additionally, the public available genotypic data generated using the BovineSNP50 chip from 550 animals across eight beef breeds (Angus, Hereford, Limousin, Charolais, Mongolian, Shorthorn, Red Angus, and Simmental) and one dairy breed (Holstein) were incorporated into the analysis. We aimed to (1) define the population structure of RACS cattle, (2) quantify their genomic diversity and inbreeding levels, and (3) pinpoint regions under selection linked to adaptive and economic traits. We employed runs of homozygosity (ROH) and population differentiation (Fst) analyses to detect selection signals. The results revealed that the crossbred (RACS), Angus, and Red Angus breeds exhibited similar clustering patterns in principal component analysis (PCA), but the crossbred population showed the highest nucleotide diversity and lowest inbreeding coefficients compared to other breeds. Notably, candidate regions associated with immune response, cold adaptation, and carcass traits were identified within the RACS population. These findings enhance our understanding of the genetic makeup of crossbred beef cattle and highlight their potential for genetic improvement, informing future selection and breeding strategies aimed at optimizing beef production in challenging environments.

Actionable genetic variants in 4,198 Scottish participants from the Orkney and Shetland founder populations and implementation of return of results

The benefits of returning clinically actionable genetic results to participants in research cohorts are accruing, yet such a genome-first approach is challenging. Here, we describe the implementation of return of such results in two founder populations from Scotland. Between 2005 and 2015, we recruited >4,000 adults with grandparents from Orkney and Shetland into the Viking Genes research cohort. The return of genetic data was not offered at baseline, but in 2023, we sent invitations to participants for consent to return of actionable genetic findings. We generated exome sequence data from 4,198 participants and used the American College of Medical Genetics and Genomics (ACMG) v.3.2 list of 81 genes, ClinVar review, and pathogenicity status, plus manual curation, to develop a pipeline to identify potentially actionable variants. We identified 104 individuals (2.5%) with 108 actionable genotypes at 39 variants in 23 genes and validated these. Working with the NHS Clinical Genetics service, which provided genetic counseling and clinical verification of the research results, and after expert clinical review, we notified 64 consenting participants (or their next of kin) of their actionable genotypes. Ten actionable variants across seven genes (BRCA1, BRCA2, ATP7B, TTN, KCNH2, MUTYH, and GAA) have risen 50- to >3,000-fold in frequency through genetic drift in ancestral island localities. Viking Genes is one of the first UK research cohorts to return actionable findings, providing an ethical and logistical exemplar of return of results. The genetic structure in the Northern Isles of Scotland with multiple founder effects provides a unique opportunity for a tailored approach to disease prevention through genetic screening.

Whole exome sequencing shows novel COL4A3 and COL4A4 variants as causes of Alport syndrome in Rio Grande do Norte, Brazil

BACKGROUND

Alport syndrome is a progressive and hereditary nephropathy characterized by hematuria and proteinuria as well as extra renal manifestations as hearing loss and eye abnormalities. The disease can be expressed as autosomal recessive or autosomal dominant at COL4A3 and COL4A4 loci, respectively, or X-linked at the COL4A5 locus. This study investigated two unrelated families with nephropathy from Brazil with the aim to identify the mutations involved with the disease.

METHODS

Whole Exome Sequencing was performed for 4 people from each pedigree (case, parents and a sibling). DNA sequences were mapped against the human genome (GRCh38/hg38 build) to identify associated mutations.

RESULTS

Two novel deleterious variants in COL4A3 and COL4A4 loci on chromosome 2 were identified. The variants were detected in the probands with mutant alleles in the homozygous state, a premature stop codon at position 481 of COL4A3 protein and a frameshift mutation leading to a stop codon at position 786 of COL4A4 protein. For both Alport cases the putative variants were surrounded by broad Runs of Homozygosity as well as genes associated with other hereditary nephropathies. Genotyping for COL4A3 validated the exome findings.

CONCLUSIONS

Two novel variants were identified in two unrelated families from northeast of Brazil. The two deleterious variants identified are located on ROH´s locus with all variants in a homozygous state.

Fine-scale spatial variation in fitness, inbreeding, and inbreeding depression in a wild ungulate

Environmental stress can exacerbate inbreeding depression by amplifying differences between inbred and outbred individuals. In wild populations, where the environment is often unpredictable and stress can be highly detrimental, the interplay between inbreeding depression and environmental variation is potentially important. Here, we investigate variation in inbreeding level, fitness and strength of inbreeding depression across a fine-scale geographic area (~12 km2) in an individually monitored population of red deer (Cervus elaphus). We show that northern regions of the study area have lower birth weights, lower juvenile survival rates, and higher inbreeding coefficients. Such fine-scale differences in inbreeding coefficients could be caused by the mating system of red deer combined with female density variation. We then tested for an inbreeding depression-by-environment interaction (ID × E) in birth weight and juvenile survival, by fitting an interaction term between the inbreeding coefficient and geographic location. We find that inbreeding depression in juvenile survival is stronger in the harsher northern regions, indicating the presence of ID × E. We also highlight that the ability to infer ID × E is affected by the variation in inbreeding within each geographic region. Therefore, for future studies on ID × E in wild populations, we recommend first assessing whether inbreeding and traits vary spatially or temporally. Overall, this is one of only a handful of studies to find evidence for ID × E in a wild population-despite its prevalence in experimental systems-likely due to intense data demands or insufficient variation in environmental stress or inbreeding coefficients.

Conservation genomics of a threatened subtropical Rhododendron species highlights the distinct conservation actions required in marginal and admixed populations

With the impact of climate change and anthropogenic activities, the underlying threats facing populations with different evolutionary histories and distributions, and the associated conservation strategies necessary to ensure their survival, may vary within a species. This is particularly true for marginal populations and/or those showing admixture. Here, we re-sequence genomes of 102 individuals from 21 locations for Rhododendron vialii, a threatened species distributed in the subtropical forests of southwestern China that has suffered from habitat fragmentation due to deforestation. Population structure results revealed that R. vialii can be divided into five genetic lineages using neutral single-nucleotide polymorphisms (SNPs), whereas selected SNPs divide the species into six lineages. This is due to the Guigu (GG) population, which is identified as admixed using neutral SNPs, but is assigned to a distinct genetic cluster using non-neutral loci. R. vialii has experienced multiple genetic bottlenecks, and different demographic histories have been suggested among populations. Ecological niche modeling combined with genomic offset analysis suggests that the marginal population (Northeast, NE) harboring the highest genetic diversity is likely to have the highest risk of maladaptation in the future. The marginal population therefore needs urgent ex situ conservation in areas where the influence of future climate change is predicted to be well buffered. Alternatively, the GG population may have the potential for local adaptation, and will need in situ conservation. The Puer population, which carries the heaviest genetic load, needs genetic rescue. Our findings highlight how population genomics, genomic offset analysis, and ecological niche modeling can be integrated to inform targeted conservation.

Purging of Highly Deleterious Mutations Through an Extreme Bottleneck

Transitions to captivity often produce population bottlenecks. On the one hand, bottlenecks increase inbreeding and decrease effective population size, thus increasing extinction risk. On the other hand, elevated homozygosity associated with inbreeding may purge deleterious mutations. Previous empirical studies of purging in captive breeding programs have focused on phenotypic measurements. We test natural selection's ability to purge deleterious mutations following an extreme population bottleneck by analyzing patterns of genetic diversity in wild and captive-bred individuals of the Lord Howe Island stick insect, Dryococelus australis. Dryococelus australis has been bred in captivity for two decades, having passed through an extreme bottleneck-only two mating pairs with few new additions since then. The magnitude of the bottleneck together with high female fecundity but low offspring recruitment set up nearly ideal conditions for the purging of deleterious mutations. As expected, captive-bred individuals had a greater number of long runs of homozygosity compared with wild individuals, implying strong inbreeding in captivity which would facilitate purging in homozygous regions. Stop-codon mutations were preferentially depleted in captivity compared with other mutations in coding and noncoding regions. The more deleterious a mutation was predicted to be, the more likely it was found outside of runs of homozygosity, implying that inbreeding facilitates the expression and thus removal of deleterious mutations, even after such an extreme bottleneck and under the benign conditions of captivity. These data implicate inbreeding and recessive deleterious mutation load in fitness variation among captive and wild D. australis.

Genome-wide detection of runs of homozygosity in Ding'an pigs revealed candidate genes relating to meat quality traits

BACKGROUND

Ding'an (DA) pig, a native Chinese breed, is renowned for its excellent meat quality, disease resistance, high reproductive performance, and adaptability. Its meat quality traits hold significant economic value. However, its conservation population has been declining due to the impact of commercialized breeds and African swine fever, which is not conducive to its development and utilization.

RESULTS

This study utilized whole-genome resequencing data from 15 DA pigs to reveal their genetic characteristics and current resource status. We analyzed the length, number, and distribution patterns of Runs of Homozygosity (ROH) in DA pigs, as well as high-frequency ROH regions. The results identified 23,208,098 single nucleotide polymorphisms (SNPs), 4,497,242 insertion and deletion (InDels), 13,622 copy number variation (CNVs), and 399,934 structure variation (SVs). Further analysis revealed relatively high genetic diversity and low inbreeding levels in DA pigs. Through functional gene enrichment analysis of high-frequency ROH regions, we identified multiple candidate genes associated with specific traits in DA pigs, including meat quality (ANKRD1, CPNE5, MYOM1), fat deposition (OBSCN, MAPK4, PNPLA1, PACSIN1, GRM4), and skeletal muscle development (LRPPRC, WNT9A).

CONCLUSIONS

This study conducted whole-genome sequencing and ROH analysis on DA pigs, revealing high genetic diversity and low inbreeding levels within the population. Through functional gene enrichment analysis of high-frequency ROH regions, we identified multiple candidate genes associated with meat quality, fat deposition, and skeletal muscle development. These findings not only enhance our understanding of the genetic mechanisms underlying the unique traits of DA pigs but also provide valuable insights for practical applications. Specifically, the identified candidate genes and genomic regions can guide conservation efforts to maintain genetic diversity and mitigate inbreeding risks. Meanwhile, these genetic insights can be integrated into breeding programs to improve meat quality and other economically important traits, thereby supporting the sustainable development and utilization of DA pigs.

Measures of Homozygosity and Relationship to Genetic Diversity in the Bearded Collie Breed

Background: Genetic diversity in closed populations, such as pedigree dogs, is of concern for maintaining the health and vitality of the population in the face of evolving challenges. Measures of genetic diversity rely upon estimates of homozygosity without consideration of whether the homozygosity is desirable or undesirable or if heterozygosity has a functional impact. Pedigree coefficients of inbreeding have been the classical approach yet they are inadequate unless based upon the entire population. Methods: Homozygosity measures based upon pedigree analyses (n = 11,898), SNP array data (n = 244), and whole genome sequencing (n = 23) were compared in the Bearded Collie, as well as a comparison of SNP array data to a pedigree cohort (n = 5042) and a mixed-breed cohort (n = 1171). Results: Molecular measures based upon DNA are more informative on an individual's homozygosity levels than pedigree analyses, although SNP coefficients of inbreeding overestimate the level of inbreeding based on the nature of SNP array methodology. Whole genome sequence (WGS) analyses revealed that the heterozygosity observed is generally in variants having neutral or low impact, which would indicate that the variability may not contribute substantially to functional diversity in the population. The majority of high-impact variants were observed in the shortest runs of homozygosity (ROH) reflecting ancestral breeding and domestication practices. As expected, mixed-breed dogs displayed higher measures of genomic diversity than either Bearded Collies or other pedigree dogs as a whole using the current paradigm algorithm models to calculate homozygosity. Conclusions: Using typical DNA-based measures reflect only a single individual and not the population thereby failing to account for regions of homozygosity that reflect ancestral breeding, domestication history, breed-defining regions, or regions positively selected for health traits. Incorporating measures of genetic diversity into dog breeding schemes is meritorious. However, until measures of diversity can distinguish between breed-defining homozygosity and homozygosity associated with positive health alleles, the measures to use as selection tools need refinement before their widespread implementation.

Genomic insights into the genetic diversity and genetic basis of body height in endangered Chinese Ningqiang ponies

BACKGROUND

Genetic diversity in livestock and poultry is critical for adapting production systems to future challenges. However, inadequate management practices, particularly in developing countries, have led to the extinction or near extinction of several species. Understanding the genetic composition and historical background of local breeds is essential for their effective conservation and sustainable use. This study compared the genomes of 30 newly sequenced Ningqiang ponies with those of 56 other ponies and 104 horses to investigate genetic diversity, genetic differentiation, and the genetic basis of body height differences.

RESULT

Population structure and genetic diversity analyses revealed that Ningqiang ponies belong to southwestern Chinese ponies. They exhibit a moderate level of inbreeding compared to other pony and horse breeds. Mitochondrial DNA analysis indicated that Ningqiang and Debao ponies share the dominant haplogroups A and C, suggesting a likely common maternal origin. Our study identified low genetic differentiation and detectable gene flow between Ningqiang ponies and Datong horses. The study also indicated the effective population size of Ningqiang ponies showed a downward trend. These findings potentially reflect the historical formation of Ningqiang ponies and population size changes. A selection signal scan (CLR and θπ) within Ningqiang ponies detected several key genes associated with bone development (ANKRD11, OSGIN2, JUNB, and RPL13) and immune response (RIPK2). The combination of genome-wide association analysis and selective signature analysis (FST) revealed significant single nucleotide polymorphisms and selective genes associated with body height, with the most prominent finding being the TBX3 gene on equine chromosome (ECA) 8. Additionally, TBX5, ASAP1, CDK12, CA10, and CSMD1 were identified as important candidate genes for body height differences between ponies and horses.

CONCLUSION

The results of this study elucidate the genetic diversity, genetic differentiation, and effective population size of Ningqiang ponies compared to other ponies and horses, further deepen the understanding of their small stature, and provide valuable insights into the conservation and breeding of local horse breeds in China.

An Analysis of the Genetic Diversity, Genetic Structure, and Selection Signal of Beagle Dogs Using SNP Chips

BACKGROUND

Beagle dogs are widely used in biomedical research, but their genetic diversity and population structure require further investigation. This study aimed to assess genetic diversity, population structure, and selection signals in a foundational Beagle breeding population using genome-wide SNP genotyping.

METHODS

A total of 459 Beagle dogs (108 males, 351 females) were genotyped using the Canine 50K SNP chip. After quality control, 456 individuals and 31,198 SNPs were retained. Genetic diversity indices, principal component analysis (PCA), identity-by-state (IBS) distance, a genomic relationship matrix (G-matrix), runs of homozygosity (ROH), and Tajima's D selection scans were analyzed.

RESULTS

The average minor allele frequency was 0.224, observed heterozygosity was 0.303, and expected heterozygosity was 0.305. A total of 2990 ROH segments were detected, with a mean inbreeding coefficient of 0.031. Phylogenetic analysis classified 106 stud dogs into 13 lineages. Selection signal analysis identified TTN (muscle function) and DLA-DRA, DLA-DOA, DLA-DMA (immune regulation) under selection.

CONCLUSIONS

The Beagle population exhibits high genetic diversity and low inbreeding. To maintain genetic stability and ensure the long-term conservation of genetic resources, structured breeding strategies should be implemented based on lineage classifications.

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.

Genomic Patterns of Homozygosity and Genetic Diversity in the Rhenish German Draught Horse

BACKGROUND/OBJECTIVES

The Rhenish German draught horse is an endangered German horse breed, originally used as working horse in agriculture. Therefore, the objective of this study was to evaluate the breed's genetic diversity using pedigree and genomic data in order to analyze classical and ancestral pedigree-based inbreeding, runs of homozygosity, ROH islands, and consensus ROH.

METHODS

We studied the genome-wide genotype data of 675 Rhenish German draught horses and collated pedigree-based inbreeding coefficients for these horses. The final dataset contained 64,737 autosomal SNPs.

RESULTS

The average number of ROH per individual was 43.17 ± 9.459 with an average ROH length of 5.087 Mb ± 1.03 Mb. The average genomic inbreeding coefficient FROH was 0.099 ± 0.03, the pedigree-based classical inbreeding coefficient FPED 0.016 ± 0.021, and ancestral inbreeding coefficients ranged from 0.03 (Fa_Kal) to 0.51 (Ahc). Most ROH (55.85%) were classified into the length category of 2-4 Mb, and the minority (0.43%) into the length category of >32 Mb. The effective population size (Ne) decreased in the last seven generations (~65 years) from 189.43 to 58.55. Consensus ROH shared by 45% of the horses were located on equine chromosomes 3 and 7, while ROH islands exceeding the 99th percentile threshold were identified on chromosomes 2, 3, 5, 7, 9, 10, and 11. These ROH islands contained genes associated with morphological development (HOXB cluster), fertility (AURKC, NLRP5, and DLX3), muscle growth, and skin physiology (ZNF gene cluster).

CONCLUSIONS

This study highlights how important it is to monitor genetic diversity in endangered populations with genomic data. The results of this study will help to develop breeding strategies to ensure the conservation of the German Rhenish draught horse population and show whether favorable alleles from the overrepresented candidate genes within ROH were transmitted to the next generation.

Genome-Wide Runs of Homozygosity Reveal Inbreeding Levels and Trait-Associated Candidate Genes in Diverse Sheep Breeds

BACKGROUND

Quantifying and controlling the inbreeding level in livestock populations is crucial for the long-term sustainability of animal husbandry. However, the extent of inbreeding has not been fully understood in sheep populations on a global scale.

METHODS

Here, we analyzed high-depth genomes of 210 sheep from 20 worldwide breeds to identify the pattern and distribution of genome-wide runs of homozygosity (ROH) and detect candidate selected genes in ROH islands for agronomic and phenotypic traits.

RESULTS

Leveraging whole-genome sequencing data, we found a large number of short ROH (e.g., <1.0 Mb) in all breeds and observed the overall higher values of ROH statistics and inbreeding coefficient in European breeds than in Asian breeds and Dorper sheep. We identified some well-known candidate genes (e.g., CAMK4, HOXA gene family, ALOX12, FGF11, and MTOR) and 40 novel genes (e.g., KLHL1, FGFRL1, WDR62, GDF6, KHDRBS2, and PAX1) that are functionally associated with fecundity, body size, and wool-related traits in sheep. Based on the candidate genes, we revealed different genetic bases for the fecundity traits of European and Asian sheep.

CONCLUSIONS

This study improves the resolution of ROH detection and provides new insights into genomic inbreeding and trait architecture in sheep as well as useful markers for future breeding practice.

PopGLen-a Snakemake pipeline for performing population genomic analyses using genotype likelihood-based methods

SUMMARY

PopGLen is a Snakemake workflow for performing population genomic analyses within a genotype-likelihood framework, integrating steps for raw sequence processing of both historical and modern DNA, quality control, multiple filtering schemes, and population genomic analysis. Currently, the population genomic analyses included allow for estimating linkage disequilibrium, kinship, genetic diversity, genetic differentiation, population structure, inbreeding, and allele frequencies. Through Snakemake, it is highly scalable, and all steps of the workflow are automated, with results compiled into an HTML report. PopGLen provides an efficient, customizable, and reproducible option for analyzing population genomic datasets across a wide variety of organisms.

AVAILABILITY AND IMPLEMENTATION

PopGLen is available under GPLv3 with code, documentation, and a tutorial at https://github.com/zjnolen/PopGLen. An example HTML report using the tutorial dataset is included in the Supplementary Material.

Genome-wide landscape of genetic diversity, runs of homozygosity, and runs of heterozygosity in five Alpine and Mediterranean goat breeds

BACKGROUND

Goat breeds in the Alpine area and Mediterranean basin exhibit a unique genetic heritage shaped by centuries of selection and adaptability to harsh environments. Understanding their adaptive traits can aid breeding programs target enhanced resilience and productivity, especially as we are facing important climate and agriculture challenges. To this aim the genomic architecture of 480 goats belonging to five breeds (i.e., Saanen [SAA], Camosciata delle Alpi [CAM], Murciano-Granadina [MUR], Maltese [MAL], Sarda [SAR]) reared in the Sardinia Island were genotyped and their genomic architecture evaluated to find molecular basis of adaptive traits. Inbreeding, runs of homozygosity (ROH) and runs of heterozygosity (ROHet) were identified. Finally, candidate genes in the ROH and ROHet regions were explored through a pathway analysis to assess their molecular role.

RESULTS

In total, we detected 10,341 ROH in the SAA genome, 11,063 ROH in the CAM genome, 12,250 ROH in the MUR genome, 8,939 ROH in the MAL genome, and 18,441 ROH in the SAR genome. Moreover, we identified 4,087 ROHet for SAA, 3,360 for CAM, 2,927 for MUR, 3,701 for MAL, and 3,576 for SAR, with SAR having the highest heterozygosity coefficient. Interestingly, when computing the inbreeding coefficient using homozygous segment (FROH), SAA showed the lowest value while MAL the highest one, suggesting the need to improve selecting strategies to preserve genetic diversity within the population. Among the most significant candidate genes, we identified several ones linked to different physiological functions, such as milk production (e.g., DGAT1, B4GALT1), immunity (GABARAP, GPS2) and adaptation to environment (e.g., GJA3, GJB2 and GJB6).

CONCLUSIONS

This study highlighted the genetic diversity within and among five goat breeds. The high levels of ROH identified in some breeds might indicate high levels of inbreeding and a lack in genetic variation, which might negatively impact the animal population. Conversely, high levels of ROHet might indicate regions of the genetic diversity, beneficial for breed health and resilience. Therefore, these findings could aid breeding programs in managing inbreeding and preserving genetic diversity.

Genomes of Galápagos Mockingbirds Reveal the Impact of Island Size and Past Demography on Inbreeding and Genetic Load in Contemporary Populations

Restricted range size brings about noteworthy genetic consequences that may affect the viability of a population and eventually its extinction. Particularly, the question if an increase in inbreeding can avert the accumulation of genetic load via purging is hotly debated in the conservation genetic field. Insular populations with limited range sizes represent an ideal setup for relating range size to these genetic factors. Leveraging a set of eight differently sized populations of Galápagos mockingbirds (Mimus), we investigated how island size shaped effective population size (Ne), inbreeding and genetic load. We assembled a genome of M. melanotis and genotyped three individuals per population by whole-genome resequencing. Demographic inference showed that the Ne of most populations remained high after the colonisation of the archipelago 1-2 Mya. Ne decline in M. parvulus happened only 10-20 Kya, whereas the critically endangered M. trifasciatus showed a longer history of reduced Ne. Despite these historical fluctuations, the current island size determines Ne in a linear fashion. In contrast, significant inbreeding coefficients, derived from runs of homozygosity, were identified only in the four smallest populations. The index of additive genetic load suggested purging in M. parvulus, where the smallest populations showed the lowest load. By contrast, M. trifasciatus carried the highest genetic load, possibly due to a recent rapid bottleneck. Overall, our study demonstrates a complex effect of demography on inbreeding and genetic load, providing implications in conservation genetics in general and in a conservation project of M. trifasciatus in particular.

Estimation of Inbreeding Depression From Overdominant Loci Using Molecular Markers

Inbreeding depression is a highly relevant universal phenomenon in population and conservation genetics since it leads to a decline in the fitness of individuals. This phenomenon is due to the homozygous expression of alleles whose effects are hidden in heterozygotes (inbreeding load). The rate of inbreeding depression for quantitative traits can be quantified if the coefficient of inbreeding (F) of individuals is known. This coefficient can be estimated from pedigrees or from the information of molecular markers, such as SNPs, using measures of homozygosity of individual markers or runs of homozygosity (ROH) across the genome. Several studies have investigated the accuracy of different F measures to estimate inbreeding depression, but always assuming that this is only due to recessive or partially recessive deleterious mutations. It is possible, though, that part of the inbreeding depression is due to variants with overdominant gene action (heterozygote advantage). In this study, we carried out computer simulations to assess the impact of overdominance on the estimation of inbreeding depression based on different measures of F. The results indicate that the estimators based on ROH provide the most robust estimates of inbreeding depression when this is due to overdominant loci. The estimators that use measures of homozygosity from individual markers may provide estimates with substantial biases, depending on whether or not low-frequency alleles are discarded in the analyses; but among these SNP-by-SNP measures, those based on the correlation between uniting gametes are generally the most reliable.

Genomic Insights Into Inbreeding and Adaptive Divergence of Trout Populations to Inform Genetic Rescue

Genetic rescue, specifically translocation to facilitate gene flow among populations and reduce the effects of inbreeding, is an increasingly used approach in conservation. However, this approach comes with trade-offs, wherein gene flow may reduce fitness when populations have adaptive differentiation (i.e., outbreeding depression). A better understanding of the interaction between isolation, inbreeding, and adaptive divergence in key traits, such as life history traits, will help to inform genetic rescue efforts. Stream-dwelling salmonids, such as the westslope cutthroat trout (Oncorhynchus lewisi; WCT), are well-suited for examining these trade-offs because they are increasingly isolated by habitat degradation, exhibit substantial variation in life history traits among populations, and include many species of conservation concern. However, few genomic studies have examined the potential trade-offs in inbreeding versus outbreeding depression in salmonids. We used > 150,000 SNPs to examine genomic variation and inbreeding coefficients in 565 individuals across 25 WCT populations that differed in their isolation status and demographic histories. Analyses of runs of homozygosity revealed that several isolated WCT populations had "flatlined" having extremely low genetic variation and high inbreeding coefficients. Additionally, we conducted genome scans to identify potential outlier loci that could explain life history differences among 10 isolated populations. Genome scans identified one candidate genomic region that influenced maximum length and age-1 to age-2 growth. However, the limited number of candidate loci suggests that the life history traits examined may be driven by many genes of small effect or phenotypic plasticity. Although adaptive differentiation should be considered, the high inbreeding coefficients in several populations suggest that genetic rescue may benefit the most genetically depauperate WCT populations.

Genome-wide insights into selection signatures for transcription factor binding sites in cattle ROH regions

Runs of Homozygosity (ROH) regions are characterized by homozygous genotypes inherited from a common ancestor, often arising from positive selection for adaptive traits. These homozygous regions may arise due to inbreeding, selective breeding, or demographic events like population bottlenecks. Transcription factor binding sites (TFBS) are short, specific DNA sequences where transcription factors bind to regulate the expression of nearby genes. These sites are essential for controlling biological processes such as development, metabolism, and immune response. TFBS act as key regulatory elements, and their variations can influence gene activity, contributing to phenotypic differences and adaptation. ROH often encompass regulatory elements, including TFBS, suggesting a functional connection between these genomic features. This study investigates TFBS within ROH regions in 297 animals of six cattle breeds: Gir (48), Tharparkar (72), Vrindavani (72), Frieswal (14), Holstein Friesian (63), and Jersey (28). Utilizing genotyped data of these animals, we identified genomic regions enriched with ROH. We focused on the central 10 kb regions of 50 ROH regions common across all breeds. Within these regions, 450 motifs were examined, identifying 168 transcription factors potentially binding to these regions. The results emphasize the role of TFBS in gene regulation and adaptive processes. By linking ROH patterns to regulatory elements, this study enhances our understanding of the genetic architecture underlying phenotypic traits and their adaptation to environmental pressures. These findings provide insights into the molecular mechanisms influencing genetic variation in cattle populations.

Identification of selection signatures and genetic diversity in the sheep

In the study, data obtained from OvineSNP50K SNP chips using the Illumina® iScan platform for Eşme sheep were used. The integrated haplotype score (iHS) and runs of homozygosity (ROH) statistical approaches were used to identify selection signatures. Using the iHS analysis, it was discovered that there are 10 genomic regions and 51 genes on ovine chromosomes 1, 9, 11, and 12 that are under selection. Three genomic regions and 97 genes on ovine chromosomes 6 and 11 were found to be under selection using the ROH analysis. Candidate genes associated with economic and ecological traits were detected using both approaches. Among the genetic diversity parameters considered in this study, the minor allele frequency (MAF), the genetic distance between individuals (D), as well as observed (Ho) and expected heterozygosities (He) values were 0.300, 0.309, 0.388, and 0.390, respectively. The obtained Ho, He and D values indicate a moderate level of genetic diversity. The ratio of polymorphic SNPs (PN) was 0.947, and the average values of FROH and FHOM were 0.030 and 0.029, respectively. Considering the PN value obtained in the study, it is evident that the SNPs in the population exhibit a high level of polymorphism at 94.7%. While the FROH value obtained indicates high genetic diversity among the individuals in the present study, the FHOM value suggests that the population is predominantly composed of heterozygous individuals. As a result, evidence indicating genetic advancements have been made for target traits in breeding programs within the population. Additionally, candidate genes suitable for future molecular marker-supported breeding programs have been identified. In addition, a better understanding of the genetic structure and production potential of the population has been achieved. Findings have shown that Eşme sheep are a breed with high meat production potential and strong adaptation abilities.

Performance of homozygosity by descent in two mice lines divergently selected for birth weight environmental variability

Inbreeding can have negative effects, such as increasing the expression of deleterious alleles or reducing fitness. A method based on Hidden Markov Models (HMM) was developed to determine the probability of an individual genome in a homozygous-by-descent state (HBD). As a result of an experiment of divergent selection for birth weight environmental variability two lines were created: high variability line (H-Line) and low variability line (L-Line). The L-Line demonstrated a better performance in traits related with robustness than the H-Line. From a selection period of 20 generations, a total of 655 individuals from the H-Line and 675 individuals from the L-Line were genotyped with a high-density SNP array. We used a predefined multiclass HMM with a total of 9 age related HBD classes and 1 non HBD class. The sum of the probabilities of each HBD class was defined as the total HBD inbreeding (FHBD). In addition, FHBD was divided into age related groups as recent and ancient. Moreover, recent pedigree inbreeding (FPEDR) was defined using different generation thresholds (4 to 14). The evolution of FHBD across generations was similar in both selected lines. However, the distribution in each age-related class was different between lines in more recent generations. The H-Line presented twice as much FHBD by ancestors from 8 generations ago than the L-Line. Moreover, the correlations between recent FHBD and FPEDR obtained with different generation thresholds were greater in the H-Line when very recent FHBD was calculated from classes related with ancestors from 1 to 8 generations ago. However, in the L-Line, considering more than 4 generations ago to define very recent inbreeding did not affect the correlations with FPEDR. The HBD was the first methodology that could detect differences in the inbreeding pattern between the selected lines that could be related with the divergent selection, despite being under the identical mating policy and similar intensity of selection.

The distribution of regions of homozygosity (ROH) among consanguineous populations-implications for a routine genetic counseling service

Regions of homozygosity (ROH) increase the risk of recessive disorders, and guidelines recommend reporting of excessive ROH in prenatal testing. However, ROH are common in populations that practice endogamy or consanguinity, and cutoffs for reporting ROH in such populations may not be evidence-based. We reviewed prenatal testing results (based on cytogenetic microarrays) from 2191 pregnancies in the Jewish and non-Jewish populations of Northern Israel and estimated the prevalence of ROH according to self-reported ethnicity and parental relationships. The proportion of the genome in ROH, ROH rate, was higher in non-Jews [Mean (SD) = 2.91% (3.92%); max = 25.54%; N = 689] than in Jews [Mean (SD) = 0.81% (0.49%); max = 3.93%; N = 1502]. In the non-Jewish populations, consanguineous marriages had the highest ROH rates [Mean (SD) = 7.14% (4.55%), N = 217], followed by endogamous [Mean (SD) = 1.13% (1.09%), N = 283] and non-endogamous [Mean (SD) = 0.69%(0. 56%), N = 189] marriages. ROH rates were greater than 5%, the ACMG-recommended cutoff, in 149/689 (21.63%) of the non-Jewish samples. Within the Jewish populations, the rates were similar between Ashkenazi, North African, and Middle Eastern Jews, but were higher for six consanguineous unions [Mean (SD) = 2.38% (1.23%)] and when spouses belonged to the same sub-population. Given the high ROH rates we observed in some subjects, we suggest that assessing the risk for recessive conditions in consanguineous/endogamous populations should be done before the first pregnancy, through genetic counseling and sequencing. Such an approach will: (1) identify couples who are at risk and counsel them on reproductive options; and (2) avoid the stress that couples who are not at risk may experience due to a prenatal ROH report.

Runs of Homozygosity and Inferences in Wild Populations

Long homozygous chromosome segments are known as runs of homozygosity (ROH); these reflect patterns of identity by descent and can be used to measure individual inbreeding, map recessive traits, and reconstruct demographic histories. Here, we review some key considerations with ROH detection and the inferences pertaining to inbreeding and demographic analyses in wild populations.

Genomic Monitoring of a Reintroduced Butterfly Uncovers Contrasting Founder Lineage Survival

Genetic factors can have a major influence on both short- and long-term success of reintroductions. Genomic monitoring can give a range of insights into the early life of a reintroduced population and ultimately can help to avoid wasting limited conservation resources. In this study, we characterise the genetic diversity of a reintroduced Carterocephalus palaemon (Chequered Skipper butterfly) population in England with respect to the spatial genetic structure and diversity of the source populations in south Belgium. We aim to evaluate the success of the reintroduction, including the effectiveness of the donor sampling strategy, and assess genetic vulnerabilities that may affect the population's future. We also use an isolation-by-distance approach to make quantitative inferences about dispersal, and we explore covariance between host mitochondrial and Wolbachia genomes. We find that, four generations following the initial release, the reintroduced population, founded by 66 wild-caught adults, has an effective size of c. 33, yet has retained similar levels of genomic heterozygosity to those in the source subpopulations in Belgium and shows low levels of inbreeding. However, the restricted number of founders and variance in reproductive success among the surviving families have resulted in a higher level of kinship, likely to result in somewhat higher rates of inbreeding in the future. Furthermore, there is a distinct split between two source landscapes in Belgium, and all genomic evidence suggests that the reintroduced population is descended from only one of these landscapes (called Fagne). We discuss potential causes behind these results, including whether Wolbachia strains are causing genetic incompatibility between clades. We conclude that a conservative strategy for any further translocations would prefer Fagne sites as sources because of the strong evidence of their ability to survive. However, our results warrant further investigation into the reasons for the divergence found in Belgium.

Comprehensive genomic analysis and selection signature detection in endangered Beigang pigs using whole-genome sequencing data

The Beigang pig was recently identified as one of the endangered breeds during a Chinese indigenous pig genetic resource survey. The Beigang breed is notable for its remarkable roughage tolerance and high reproductive capacity according to historical records. Morphologically, the Beigang pig resembles many indigenous pigs in eastern China, especially in its large ears. This makes the Beigang pig a valuable reference for studying the genetic mechanisms on large ear size in pigs. However, there is currently a lack of clear understanding regarding the genetic structure and inbreeding levels of the Beigang pig population. This study used whole-genome sequencing data from Beigang pig (N = 145 pigs) and integrated genetic information from commercial pigs and indigenous pigs in eastern China to conduct a comprehensive analysis of the Beigang pig's genetic structure. Three selection signal detection methods-runs of homozygosity, fixation index, and integrated haplotype score-were employed to explore the differences in genomic selection signatures between Beigang pig and other pig populations. Additionally, we used a public project for regulatory variants discovery and molecular phenotype prediction in farm animal species called FarmGtex to explore the expression of three genes (WIF1, LEMD3, and MSRB3) related to ear size in Beigang pig. This research identified five homozygous variant sites in the WIF1 gene as important candidate loci potentially influencing ear size in Beigang pig. The results indicate that the Beigang pig holds a unique status among Chinese indigenous pigs, characterized by high genetic diversity and low levels of inbreeding. The study also revealed that WIF1 may play a significant role in influencing ear size in this breed. These findings contribute to a deeper understanding of the population structure and genetic characteristics of Beigang pig.

Genomic scans for selection and runs of homozygosity in southern Italian turkey populations

Basilicata and Apulian (BAS-APU) turkeys, a native population in the Basilicata and Puglia regions of southern Italy, are known for their high meat quality and tolerance to local conditions. Understanding the genomic patterns of BAS-APU turkeys is critical for effective breeding and preservation strategies. In this study, we characterized runs of homozygosity (ROH), and selection signatures using the integrated haplotype score (iHS) and ROH approaches. A total of 73 BAS-APU turkeys from five populations were sequenced (12X). The inbreeding coefficients based on ROH ranged from 0.177 to 0.405. A total of 120,956 ROH were detected in BAS-APU populations. We identified 27 genomic regions that harbor 61 candidate genes in ROH islands in which single nucleotide polymorphisms (SNPs) occur in more than 90 % of individuals. In addition, we detected 608 genomic regions under positive selection using the iHS method being 104, 98, 130, 102, and 174 for BAS, APU_C, APU_M, APU_PN, and APU_PS, respectively. For both methods, most of the genes within these regions are related to production performance, reproduction, immune responses, and adaptation. This study contributes significantly to our understanding of the genetic makeup of native turkey populations in southern Italy. The identified genes under selection can aid future breeding and conservations programs for southern Italian native turkeys. The results of inbreeding levels, especially in the absence of complete pedigrees or when only a few samples are available, which is often the case for local breeds, will help to avoid genetic relatedness in the mating plan in breeding and conservation plans for BAS-APU populations. Also, the detected genes in the selective sweep regions could be used as a marker-assisted selection to improve productive traits and adaptation of BAS-APU local populations.

The Effect of Continuous Selection in KiwiCross® Composite Breed on Breed Ancestry and Productivity Performance

Composite crosses result from the mating of two or more distinct cattle breeds. Breeding performance may improve rapidly using a well-organized composite breeding system and a clear selection index. The KiwiCross® is a popular composite cross in New Zealand, combining Holstein-Friesian (high milk production) and Jersey (high milk fat). Production efficiency (PR), a key selection index, is calculated by dividing milk solids produced by mature live weight. Over decades of genetic improvement, KiwiCross® increased milk production significantly. We hypothesized that certain genomic regions from Holstein-Friesian or Jersey breeds were preserved due to artificial selection based on PR. Analysis of genomic regions using XP-EHH, hapFLK, and ROH haplotype statistics revealed selection signatures on BTA 7 and 20 in both high- and low-performance animals, with distinct regions linked to Holstein-Friesian and Jersey ancestry. Our findings suggest that selection acted on different genomic regions across generations and that preserving key ancestry-specific haplotypes is crucial for maintaining performance in composite breeds. Breeders must recognize that selection for specific traits can alter allele frequencies and lead to the loss of beneficial breed-specific haplotypes over time.

The genetic demographic history of the last hunter-gatherer population of the Himalayas

Nepal, largely covered by the Himalayan mountains, hosts indigenous populations with distinct linguistic, cultural, and genetic characteristics. Among these populations, the Raute, Nepal's last nomadic hunter-gatherers, offer a unique insight into the genetic and demographic history of Himalayan foragers. Despite strong cultural connections to other regional foragers, the genetic history of this population remains understudied. This study presents newly genotyped genome-wide SNP data of the Raute to explore their genetic isolation, their origins and potential as an older foraging lineage, and their genetic connections to other regional foragers. Our results show that high levels of inbreeding in the Raute indicate recent genetic isolation. Effective population size estimates suggest a dramatic population decline around 50 generations ago. Strong genetic similarity to Nepalese populations of various subsistence styles highlights a dynamic history of genetic interactions prior to isolation, with particular closeness to historical foragers like the Kusunda and Tharu, but excludes an ancient foraging lineage origin. The study underscores the complexity of human population dynamics in the Himalayas, suggesting a history of extensive interaction between foragers and farmers, followed by isolation and demographic decline among the Raute.

Inbreeding depression for litter size in two mice lines under divergent selection for environmental birth weight variability using genomic data

Inbreeding depression (ID) is usually observed as reduced survival and fertility and may have a variable impact in different populations. The aim of this study was to estimate ID from genomic and pedigree data in the litter size (LS) of the high variability (H-Line) and the low variability (L-Line) mice lines divergently selected for environmental birth weight variability. Of these, the L-Line performed better on traits related to robustness. A total of 1587 females from 26 selection generations were genotyped with a high-density SNP array. LS data of 732 L-Line and 648 of H-Line animals were used. The following were calculated: pedigree inbreeding coefficient (FPED), genomic inbreeding derived from different genomic matrices (FNEJ, FL&H,FVR1, FVR2, and FYAN), from runs of homozygosity (FROH) and from homozygosity by descent probabilities (FHBD). FROH were calculated in the 19 autosomes (CHR). FROH and FHBD were divided into nine lengths and age classes, respectively. All the inbreeding coefficients were standardized by the mean inbreeding coefficient of the 1st generation. Regression coefficients (m) obtained from genomic data were between -3.71 with FVR2 and -5.09 with FHBD in the H-Line, and that estimated from FPED was -5.67. In the L-Line the m obtained from genomic data were between -3.52 with FVR2 and -4.55 with FHBD, and that obtained with FPED was -4.08. Significant ID effects were detected in CHR13 in the H-Line and CHR1 and CHR9 in the L-Line. The m negative trended to be lower as the ROH length increased. The age of the homozygosity by descent segment performed differently in each line, for example FHBD raised 128 generations ago produced a significant positive effect only in the L-Line. The effect of global inbreeding coefficients on the LS was negative in both lines with a higher impact in the H-Line than in the L-Line, suggesting the L-Line having higher robustness. CHR 1, 9, and 13 were candidates for future gene search. In general, more recent FROH and FHBD presented negative effects on LS while older FROH and FHBD presented positive effects on LS in both selected lines.

Runs of homozygosity assessment using reduced representation sequencing highlight the evidence of random mating in emu (Dromaius novaehollandiae)

The domestication of emu (Dromaius novaehollandiae) began in the 1970s, but their productive characteristics have not undergone significant genetic enhancement. This study investigated the inbreeding and genetic diversity of 50 emus from various farms in Japan using Double digest restriction-site associated DNA sequencing (ddRAD-seq) markers. Single nucleotide polymorphism (SNP) calling revealed 171 975 high-quality SNPs while runs of homozygosity (ROH) analysis identified 1843 homozygous segments, with an average of 36.86 ROH per individual and a mean genome length of 27 Mb under ROH. The majority (86%) of ROH were short (0.5-1 Mb), indicating ancient or remote inbreeding. The average genomic inbreeding coefficient (FROH) was 0.0228, suggesting nearly no inbreeding. Overlapping ROH regions were identified, with top consensus regions found on chromosomes 8 and Z. Seven candidate genes related to egg production, feather development, and energy metabolism were annotated in these regions. The findings highlight the prevalence of genetic diversity and low inbreeding levels in the studied emu population. This research highlights the potentiality of random mating in genetic management and conservation of emus. Further studies should focus on enhancing productive traits through selective breeding while preserving genetic diversity to ensure the sustainable growth of the emu farming.

Inbreeding Effect on Maternal Mortality and Fertility in the Habsburg Dynasty

OBJECTIVE

We investigated inbreeding effects on longevity and fertility in the House of Habsburg, one of the principal royal dynasties of Europe.

METHODS

A total number of 124 Habsburg marriages, involving 107 men and 124 women, in the period of approximately 1450-1800 were considered for the analysis. Kinship and inbreeding coefficients were computed from genealogical information, which included more than 8000 individuals.

RESULTS

We found a significant negative association between age of death and inbreeding coefficient (F) in those women who had children (regression coefficient b = -1.06, p = 0.0008). This result led us to investigate possible inbreeding effects on maternal mortality in the period of 4 weeks after the childbirth. A strong inbreeding depression on maternal survival was detected through the Kaplan-Meier curve for groups of women with different level of inbreeding (log-rank test p = 0.0001) and the Cox proportional hazards regression analysis (hazard ratio = 2.36, p = 0.0008). Effect on fertility was also found as more inbred women had longer interbirth intervals (b = 154.66, p = 0.022). Effects of male or female inbreeding on the number of children per woman were not detected through zero-inflated regression models suggesting that reproductive compensation might be occurring among the more inbred and less-fecund women.

CONCLUSION

The effect of inbreeding in adulthood in the Habsburg lineage was at least as important as that previously reported on prereproductive survival. To our knowledge, our results are the first evidence of an inbreeding effect on maternal mortality in humans.

Comparative Analysis of Runs of Homozygosity Islands in Indigenous and Commercial Chickens Revealed Candidate Loci for Disease Resistance and Production Traits

Runs of homozygosity (ROH) are contiguous stretches of identical genomic regions inherited from both parents. Assessment of ROH in livestock species contributes significantly to our understanding of genetic health, population genetic structure, selective pressure and conservation efforts. In this study, whole genome re-sequencing data from 140 birds of 10 Iranian indigenous chicken ecotypes, 3 commercial chicken breeds and 1 red junglefowl (RJF) population were used to investigate their population genetic structure, ROH characteristics (length and frequency) and genomic inbreeding coefficients (FROH). Additionally, we examined ROH islands for selection footprints in the indigenous chicken populations. Our results revealed distinct genetic backgrounds, among which the White Leghorn breed exhibited the greatest genetic distance from other populations, while the gamecock populations formed a separate cluster. We observed significant differences in ROH characteristics, in which the commercial breeds showed a higher number of ROH compared to indigenous chickens and red junglefowls. Short ROH ranging from 0.1 to 1 Mb were dominant among the populations. The Arian line had the highest mean length of ROH, while the White Leghorn breed showed the highest number of ROH. Among indigenous chickens, the Lari-Afghani ecotype exhibited the highest FROH, but the Sari inherited the richest genetic diversity. Interestingly, GGA16 carried no ROH in the red junglefowls, whereas GGA22 had the highest FROH across all populations, except in the Isfahan ecotype. We also identified ROH islands associated with genetic adaptations in indigenous ecotypes. These islands harboured immune-related genes contributing to disease resistance (TLR2, TICAM1, IL22RA1, NOS2, CCL20 and IFNLR1), heat tolerance and oxidative stress response (NFKB1, HSF4, OSGIN1 and BDNF), and muscle development, lipid metabolism and reproduction (MEOX2, CEBPB, CDS2 and GnRH-I). Overall, this study highlights the genetic potential of indigenous chickens to survive and adapt to their respective environments.

Genome-Wide Patterns of Homozygosity and Heterozygosity and Candidate Genes in Greek Insular and Mainland Native Goats

BACKGROUND

Runs of homozygosity (ROHs) and heterozygosity (ROHets) serve for the identification of genomic regions as candidates of selection, local adaptation, and population history.

METHODS

The present study aimed to comprehensively explore the ROH and ROHet patterns and hotspots in Greek native dairy goats, Eghoria and Skopelos, genotyped with the Illumina Goat SNP50 BeadChip. SNP and functional enrichment analyses were conducted to further characterize hotspots and the candidate genes located within these genomic regions. Genetic relationships between and within breeds and inbreeding coefficients were also evaluated.

RESULTS

Clear genetic differentiation and diversified management practices were depicted between the two native populations. The ROH and ROHet average genome coverage for Skopelos (65.35 and 35 Mb) and Eghoria (47.64 and 43 Mb) indicated differences in mainland and insular goats, with Skopelos showing more long ROH fragments, reflecting its geographic isolation and small population size. An ROH hotspot (CHR12: 43.59-44.61 Mb) detected in the Skopelos population has been also reported across European goats and co-localizes with a selection signal detected in the Egyptian Barki goats and sheep adapted to hot-arid conditions. A novel ROH hotspot (CHR18: 60.12-61.81 Mb), shared among the Greek breeds, harbors candidate genes enriched in biosynthesis, metabolism, and immune response. Two well-conserved ROHet islands were detected in Greek goats on chromosomes 1 and 18, with genes participating in development and embryogenesis. The Eghoria population showed the highest number of ROHet islands, potentially reflecting its adaptability to diverse environments.

CONCLUSIONS

These findings offer new insights into the environmental adaptation and artificial selection in Greek goats and could be utilized in future breeding strategies for sustainable goat farming.

Selection signatures associated with adaptation in South African Drakensberger, Nguni, and Tuli beef breeds

In the present study 1,709 cattle, including 1,118 Drakensberger (DRB), 377 Nguni (NGI), and 214 Tuli (TUL), were genotyped using the GeneSeek® Genomic Profiler™ 150 K bovine SNP panel. A genomic data set of 122,632 quality-filtered single nucleotide polymorphisms (SNPs) were used to identify selection signatures within breeds based on conserved runs of homozygosity (ROH) and heterozygosity (ROHet) estimated with the detectRUNS R package. The mean number of ROH per animal varied across breeds ranging from 36.09 ± 12.82 (NGI) to 51.82 ± 21.01 (DRB), and the mean ROH length per breed ranged between 2.31 Mb (NGI) and 3.90 Mb (DRB). The smallest length categories i.e., ROH < 4 Mb were most frequent, indicating historic inbreeding effects for all breeds. The ROH based inbreeding coefficients (FROH) ranged between 0.033 ± 0.024 (NGI) and 0.081 ± 0.046 (DRB). Genes mapped to candidate regions were associated with immunity (ADAMTS12, LY96, WDPCP) and adaptation (FKBP4, CBFA2T3, TUBB3) in cattle and genes previously only reported for immunity in mice and human (EXOC3L1, MYO1G). The present study contributes to the understanding of the genetic mechanisms of adaptation, providing information for potential molecular application in genetic evaluation and selection programs.

Whole-Genome Resequencing to Identify Selection Signatures Associated with High Fertility in Lüliang Black Goat

Lüliang black goat (LBG) is a unique livestock genetic resource of great significance for the local agriculture and economic development of Shanxi, China. However, the kidding rate of LBG is relatively low, which limits efforts to improve the reproductive performance and economic benefits of this breed. Therefore, improving the kidding characteristics of LBG is crucial for increasing its economic benefits. In this study, 20 LBG does were selected for whole-genome resequencing and divided into two groups: 10 in the T group (does with three consecutive kiddings of twin kids) and 10 in the S group (does with three consecutive kiddings of single kids). Based on whole-genome resequencing data, this study comprehensively assessed the population structure and genetic diversity of LBG and explored the related genes that affect reproductive performance. Three selection signal analysis methods-Fst (Fixation Index), π (nucleotide diversity), and XP-CLR (Cross Population Composite Likelihood Ratio)-were applied to screen a total of 838 genes, and enrichment analysis was performed to identify genes closely related to the reproductive performance of LBG, including ENPP3, APC, and GLI2. A generalized linear model was used to conduct a correlation analysis between non-synonymous mutations in the three genes and the number of kids produced. Two loci that were significantly correlated with kidding number were identified (p < 0.05): GLI2 g.63400363 C>T and GLI2 g.63417538 C>T. In general, the LBG population has high genetic diversity and good prospects for genetic improvement. The findings revealed that mining high-fecundity selection characteristics provides a basis for research on goat reproductive mechanisms.

Genomic-Inbreeding Landscape and Selection Signatures in the Polo Argentino Horse Breed

Analyzing genetic variability and inbreeding trends is essential for effective breed management in animal populations. To this, the characterization of runs of homozygosity (ROH) provides a good genomic approach to study the phenomena. The Polo Argentino (PA) breed, globally recognized as the best adapted to playing polo, is known for its strong influence of Thoroughbreds, intense selective breeding, and extensive use of reproductive biotechnologies. This study investigates the PA's genomic variability, by characterizing the ROH landscape and identifying ROH islands (ROHi) as potential genomic footprints for the breed. PA horses (n = 506) were genotyped using EquineGGP™ array v5 (70 k). We calculated the inbreeding coefficient based on ROH (FROH-ancestral and recent) using a chromosomal approach. Finally, we identified genomic regions with increased ROH frequency (ROHi) and their associated genes. An average of 79.5 ROH per horse was detected, with a mean length of 4.6 Mb. The average FROH was 0.151, but most of them (54%) corresponded to ancestral inbreeding (ROH < 5.5 Mb). However, 4 ROHi were identified in ECA 1, 3, 7 and 17, containing 67 genes, some of which were related to behavior, neurodevelopment, and metabolic functions. This genomic analysis determined, for the first time, the length and location of homozygosity segments in the PA breed and identified ROHi associated with potential genomic regions and genes for positive selection in the breed.