Mapping of an immotile short tail sperm defect in the Finnish Yorkshire on porcine Chromosome 16

Genomic structure analysis and construction of DNA fingerprint for four sheep populations

The Yongdeng Qishan sheep (QS) is a sheep population found locally in China. To gain in-depth knowledge of its population characteristics, three control groups were chosen, comprising the Lanzhou fat-tailed sheep (LFT), TAN sheep (TAN), and Minxian black fur sheep (MBF), inhabiting the nearby environments. This study genotyped a total of 120 individuals from four sheep populations: QS, LFT, TAN, and MBF. Using Specific-Locus Amplified Fragment Sequencing, we conducted genetic diversity, population structure, and selective sweep analysis, and constructed the fingerprint of each population. In total, there were 782 535 single nucleotide polymorphism (SNP) variations identified, with most being situated within regions that are intergenic or intronic. The genetic diversity analysis revealed that the QS population exhibited lower genetic diversity compared to the other three populations. Consistent results were obtained from the principal component, phylogenetic tree, and population structure analysis, indicating significant genetic differences between QS and the other three populations. However, a certain degree of differentiation was observed within the QS population. The linkage disequilibrium (LD) patterns among the four populations showed clear distinctions, with the QS group demonstrating the most rapid LD decline. Kinship analysis supported the findings of population structure, dividing the 90 QS individuals into two subgroups consisting of 23 and 67 individuals. Selective sweep analysis identified a range of genes associated with reproduction, immunity, and adaptation to high-altitude hypoxia. These genes hold potential as candidate genes for marker-assisted selection breeding. Additionally, a total of 86 523 runs of homozygosity (ROHs) were detected, showing non-uniform distribution across chromosomes, with chromosome 1 having the highest coverage percentage and chromosome 26 the lowest. In the high-frequency ROH islands, 79 candidate genes were associated with biological processes such as reproduction and fat digestion and absorption. Furthermore, a DNA fingerprint was constructed for the four populations using 349 highly polymorphic SNPs. In summary, our research delves into the genetic diversity and population structure of QS population. The construction of DNA fingerprint profiles for each population can provide valuable references for the identification of sheep breeds both domestically and internationally.

Phenotypic varieties of sperm pathology: Genetic abnormalities or environmental influences can result in different patterns of abnormal spermatozoa

The present paper reviews in detail ultrastructural and molecular studies addressed to characterize different phenotypes of sperm pathology in sterile men. In each case ultrastructural, immunocytochemical, molecular and genetic information is provided to differentiate two main kinds of sperm pathologies: systematic phenotypes with known or suspected genetic origin and non-systematic ones, usually secondary to different pathologies of the male reproductive system. Special attention is paid to detailed ultrastructural features profusely illustrated with electron micrographs. Diagnostic and fertility prognostic values of these phenotypes are also discussed and, when possible, comparison with similar pathologies in mammals and birds are discussed.

Boar management and semen handling factors affect the quality of boar extended semen

Artificial insemination (AI) is the preferred method for reproduction in the majority of the intensive pig production systems Worldwide. To this end, fresh extended ready-to-use semen doses are either purchased from AI-centres or produced by boars kept on-farm. For profitable semen production, it is necessary to obtain a maximum amount of high quality semen from each boar. This paper reviews current knowledge on factors that may affect semen quality by influencing the boar or the semen during processing. Genetic markers could be used for early detection of boars with the highest fertility potential. Genetic selection for fast growth might jeopardize semen quality. Early detection of boars no longer fit for semen production might be possible by ultrasonography of the testes. Seasonal variation in sperm quality could be associated with changes in photoperiod and heat stress during summer. Comfortable housing, with appropiate bedding material to avoid locomotion problems is essential. In some areas, cooling systems may be necessary to avoid heat stress. The sperm quality can be manipulated by feeding strategies aiming, for instance, to increase sperm resistance to oxidative stress and extend storage duration. High collection frequency will negatively influence sperm quality. Also, if collection is not hygienically performed it will result in bacterial contamination of the semen doses. The concern over bacterial contamination has risen not only because of its negative effect on semen quality but also due to the detection of antimicrobial resistance in isolates from extended semen. Moreover, bacterial and viral pathogens must be monitored because they affect semen production and quality and constitute a risk of herd infection. During processing, boar sperm are submitted to many stress factors that can cause oxidative stress and capacitation-like changes potentially reducing their fertility potential. Dilution rate or dilution temperature affects the quality of the semen doses. Some packaging might preserve semen better than others and some plastic components might be toxic for sperm. Standard operation procedures and quality assurance systems in AI centres are needed.

SPEF2 functions in microtubule-mediated transport in elongating spermatids to ensure proper male germ cell differentiation

Sperm differentiation requires specific protein transport for correct sperm tail formation and head shaping. A transient microtubular structure, the manchette, appears around the differentiating spermatid head and serves as a platform for protein transport to the growing tail. Sperm flagellar 2 (SPEF2) is known to be essential for sperm tail development. In this study we investigated the function of SPEF2 during spermatogenesis using a male germ cell-specific Spef2 knockout mouse model. In addition to defects in sperm tail development, we observed a duplication of the basal body and failure in manchette migration resulting in an abnormal head shape. We identified cytoplasmic dynein 1 and GOLGA3 as novel interaction partners for SPEF2. SPEF2 and dynein 1 colocalize in the manchette and the inhibition of dynein 1 disrupts the localization of SPEF2 to the manchette. Furthermore, the transport of a known SPEF2-binding protein, IFT20, from the Golgi complex to the manchette was delayed in the absence of SPEF2. These data indicate a possible novel role of SPEF2 as a linker protein for dynein 1-mediated cargo transport along microtubules.

Hereditary Sterilizing Short-Tail Sperm Defect in Finnish Yorkshire Boars

A new infertility syndrome has recently been described in Finnish Yorkshire boars. Typical for the syndrome is total akinesia and severe tail malformation of the spermatozoa. Morphometric analysis was performed on semen smears from 20 affected and 18 control boars and on testicular tissue sections from 5 affected and 4 control boars. Semen morphometry revealed that, in affected boars, the length of the sperm tails was only 33% of that of the controls (15.4 μm vs. 47.0 μm, P < 0.0001). Typical for the spermatozoa of affected boars was also an abundant frequency of proximal cytoplasmic droplets (72.4% vs. 6.9%, P < 0.0001), whereas no major sperm-head abnormalities were recorded. In the testicular tissue samples, viewed at light microscopic level, the volume densities of seminiferous tubules or interstitium did not differ. The most characteristic change in the seminiferous epithelium of the affected boars was a reduced number of elongated spermatids. Densities of Sertoli cells and Leydig cells between affected and control boars did not differ. The ultrastructure of testicular tissue from affected boars showed severe alterations in the assembly of the midpiece and tail of the spermatozoa. As well, a typical finding in the seminiferous epithelium of affected boars was conspicuous deposition of lipid droplets. The pathogenesis of this syndrome severely affects spermiogenesis and motility. Spermatozoa have malformed, short tails, which never become motile. This syndrome is not manifested in the structure or function of other ciliated cells in the affected animals.

Detection of one large insertion/deletion (indel) and two novel SNPs within the <i>SPEF2</i> gene and their associations with male piglet reproduction traits

Abstract. The sperm flagella 2 (SPEF2) gene is essential for normal sperm tail development and male fertility. To fully characterize the structure of the mutation and to further study the function of the pig SPEF2 gene, we explored the insertion/deletion (indel) and novel single-nucleotide polymorphisms (SNPs) within the pig SPEF2 gene, and tested their associations with the testicular sizes in male Large White (LW) and Landrace (LD) pigs from China. Herein, a large insertion located at the SPEF2 gene in chromosome 16 was found, and two alleles of "I" (insertion) and "D" (deletion) were designated. Allele "D" was dominant in all analyzed pigs. Two novel SNPs (namely (NC_010458) g.19642G > A, resulting in AfaI aCRS PCR–PFLP, and g.19886C > G, resulting in EcoRI aCRS PCR–PFLP) were found in LW and LD pigs. Association testing revealed that g.19886C > G was significantly associated with the testis long circumference (TLC) in LW pigs (P < 0.05), suggesting that this SNP would be the DNA marker for the marker-assisted selection (MAS) in reproduction traits. This preliminary result indicates that the pig SPEF2 gene had significant effects on male reproduction traits. These findings could not only extend the spectrum of genetic variations in the pig SPEF2 gene but also contribute to implementing MAS in genetics and breeding in pigs.

L1 insertion within SPEF2 gene is associated with increased litter size in the Finnish Yorkshire population

Immotile, short-tail sperm defect (ISTS) expanded in the Finnish Yorkshire population in the end of 1990s. The causal mutation for this defect is a recent L1 insertion within the SPEF2 gene in chromosome 16. Even though all homozygous boars are eliminated from the population because of infertility, the amount of affected boars increased rapidly until marker-assisted selection against the defect was established. To elucidate the associated effects of the ISTS defect on production traits, we have investigated the association of the L1 insertion and PRLR haplotype with reproduction traits in the Finnish Yorkshire population. Two data sets including 357 sows and 491 AI-boars were genotyped for the presence of the L1 insertion and analysed for association with reproduction traits. A Proc Mixed procedure (SAS Inc) and a software package for analysing multivariate mixed models (DMU) were used to study the effect of polymorphisms on reproduction traits. The L1-insertion within SPEF2 gene was associated with litter size in the first parity. The SPEF2 gene is located adjacent to a candidate gene for litter size in the pig, PRLR. Haplotypes within PRLR exon 10 were analysed in data set of 93 AI-boars for the association with reproduction traits. However, no associations were detected within the analysed data set indicating that PRLR sequence variants are not the causal cause for the identified effect on litter size.

Immotile short-tail sperm defect in Nelore (Bos taurus indicus) breed bulls

This case study reported the presence of short tail sperm defect in the semen of three Nelore breed bulls. The sperm presented 0% of motility in the three animals evaluated and a total of 70%, 61% and 34% of pathologies of the intermediate piece of the tail respectively for animals 1, 2 and 3. It was identified that animals 2 and 3 had high degree of inbreeding, although no relationship was found with animal 1. Animal 2 was the only one that presented inbreeding coefficient (6.25%). His half-sib (animal 3) and animal 1, from the same herd, had shown no inbreeding, showing that inheritance is not the only determinant factor for its incidence on Nelore males.

Ultrastructure of sperm 'tail stump' defect in wild boar

Sperm 'tail stump' defect was found in ejaculates of a wild boar maintained in captivity. It was in good physical condition, the testes and genital tract were found to be of normal size and consistency. There was no evidence of macroscopic abnormalities at the clinical analysis and at necropsy. The volume and concentration of the semen samples obtained by electroejaculation were lower than normal. The slides examined contained a high level of abnormal spermatozoa (52.7%). The most frequent morphological finding was a droplet-like form attached to the base of the head or a very short stump. The non-stumped spermatozoa had no normal tail but a shortened one. Analysing the histological structure with light microscopy, no ring of spermatozoa was observed lining the lumen of the seminiferous tubules and the characteristically cellular structure was not conserved. The ultrastructural examination evidenced a disorganisation of the normal tubular structure of the flagellum, with lost of regular pattern of the axial bundle of fibrils and the mitochondrial helix. The origin of this abnormality is unknown.

Infertile Finnish Yorkshire boars carry a full-length LINE-1 retrotransposon within the KPL2 gene

The KPL2 gene is expressed predominantly in cells with cilia or flagella. We have previously demonstrated that a large intronic insertion in KPL2 is associated with immotile sperm cells and infertility in the domesticated pig (Sus scrofa). To fully characterize the structure of the mutation, we have now cloned and sequenced the insertion. The data identified the presence of a long interspersed nuclear element-1 (LINE-1) encoding all activities required for retrotransposition, including a 5'-untranslated region (UTR) with an internal RNA polymerase II promoter, two open reading frames (ORF1 and ORF2) separated by an intergenic region and a 3' UTR containing a polyadenylation signal. Characterization of the junctions between the LINE-1 and the genomic target revealed the presence of direct repeats of 14 bp at both ends, showing that integration occurred by target-primed reverse transcription. Furthermore, sequence analysis suggested that the aberrant splicing pattern of KPL2 transcripts induced by the LINE-1 element is caused by interference with putative intronic splice signals and activation of a cryptic splice site. These data demonstrate that integration of a transposition-competent L1 element into KPL2 is responsible for the defective spermatozoa, which accentuates the role of mobile DNA elements as insertional mutagens in mammalian genomes.

Multinuclear-multiflagellar sperm defect in a bull--a new sterilizing sperm defect

The development and use of modern techniques, such as intracytoplasmic sperm injection (ICSI), gene knockout and sperm fluorescence in situ hybridization with chromosome- specific probes, have significantly increased our knowledge about sperm defects. We describe a new oligoasthenoteratozoospermic defect in a bull. Because of its morphological characteristics the defect was named the multinuclear-multiflagellar sperm defect. All spermatozoa in the ejaculate were abnormal. Many of the spermatozoa had multiple nuclei and multiple sperm tails. All spermatozoa lacked an acrosome, and only seldom did spermatozoa have a mitochondrial helix in the midpiece area. Meiosis and spermiogenesis were severely affected in this otherwise phenotypically normal bull. The sperm defects resembled the phenotype of a targeted gene knockout Hrb(-/-) (HIV-1 Rev-binding/interacting protein) mutant mouse strain, which is expressed as sterility in males, while females remain fertile. Since the father of this bull has been extensively used in at least three countries the defective gene has possibly become widespread in the red and white breeds (Ayrshire, Swedish Red and White, Norwegian Red) in the Nordic countries. However, it is not proved that the father of this bull is a carrier of this defect.

Transplantation of normal boar testicular cells resulted in complete focal spermatogenesis in a boar affected by the immotile short-tail sperm defect

Transplantation of testicular cells, also known as spermatogonial stem cell transplantation, is a relatively new approach in the field of male infertility. We used this technique to determine whether donor-derived sperm production in unrelated porcine recipients is possible following ultrasound-guided transfer of testicular cells. This study was undertaken because we had a strain of Finnish Yorkshire boars with a hereditary recessive gene defect rendering all spermatozoa immotile and anatomically abnormal in homozygous boars. Thus, monitoring of the focal success of colonization of donor spermatogonia with subsequent production of progressively motile spermatozoa was extremely sensitive. Testicular cells from young normal crossbred boars were transplanted into the testes of two boars affected with the immotile short-tail sperm (ISTS) defect. Prior to the transplantations, busulfan was used to suppress recipients' endogenous spermatogenesis. The ejaculates were collected and analysed for the presence of motile spermatozoa. In one of the two recipient boars transplanted with testicular cells from normal donors, motile spermatozoa appeared in the ejaculates 12 weeks after the transplantation. Spermatozoa manually selected under a microscope from a frozen aliquot of ejaculate collected 27 weeks after transplantation were genotyped. In two of the 20 vials the donor-derived genotype was visible. The genotyping results substantiated the success - as indicated by the appearance of motile spermatozoa after the spermatogonial transfer. Thus, donor-derived sperm production in unrelated recipients is possible. In addition, the production after transplantation of progressively motile spermatozoa with normal tail lengths shows that the ISTS defect in Finnish Yorkshire boars apparently results from defective transcription of an essential gene for sperm motility in germline cells. To conclude, the transplantation of donor testicular cells can, at least in boars with the ISTS defect, result in complete focal spermatogenesis.

An intronic insertion in KPL2 results in aberrant splicing and causes the immotile short-tail sperm defect in the pig

The immotile short-tail sperm defect is an autosomal recessive disease within the Finnish Yorkshire pig population. This disease specifically affects the axoneme structure of sperm flagella, whereas cilia in other tissues appear unaffected. Recently, the disease locus was mapped to a 3-cM region on porcine chromosome 16. To facilitate identification of candidate genes, we constructed a porcine-human comparative map, which anchored the disease locus to a region on human chromosome 5p13.2 containing eight annotated genes. Sequence analysis of a candidate gene KPL2 revealed the presence of an inserted retrotransposon within an intron. The insertion affects splicing of the KPL2 transcript in two ways; it either causes skipping of the upstream exon, or causes the inclusion of an intronic sequence as well as part of the insertion in the transcript. Both changes alter the reading frame leading to premature termination of translation. Further work revealed that the aberrantly spliced exon is expressed predominantly in testicular tissue, which explains the tissue-specificity of the immotile short-tail sperm defect. These findings show that the KPL2 gene is important for correct axoneme development and provide insight into abnormal sperm development and infertility disorders.

A Monte Carlo Approach for Estimation of Haplotype Probabilities in Half-Sib Families

The objective of this work was to propose an algorithm (HAPROB) to estimate haplotype probabilities for genotyped members of half-sib families for which parents lacked genotypic information. The algorithm had 2 basic steps. First, a Monte Carlo-based approach was used to estimate haplotype probabilities for sires conditional upon offspring genotypes and population allelic frequencies, and then offspring-haplotype probabilities were estimated conditional upon sire probabilities and population frequencies. The 2 steps were alternated iteratively until estimates of population frequencies were essentially unchanged. Simulation was used to evaluate effects of the number of Monte Carlo cycles on the accuracy of the reconstructed haplotypes. Fifty thousand cycles was found to be sufficient for the haplotype configurations considered. Accuracy of the algorithm was compared with that obtained by the public domain SIMWALK2 software. Predictions of the most likely haplotype configurations are produced by SIM-WALK2, but no estimates of probability are given. The accuracy of the current approach was comparable to that obtained from SIMWALK2. The proportions of times that haplotypes were reconstructed correctly were 87.0 and 92.4% (sires and offspring) for HAPROB vs. 87.5 and 91.5% for SIMWALK2. Effects of family size on accuracy of reconstruction were examined. Accuracy of reconstruction was only about 4% for sires with 2 offspring, but accuracy among the offspring themselves was 65%. Accuracy increased quickly as family size increased and reached 100% for sires with 30 offspring. Maximum accuracy for offspring was about 96%. Estimates of haplotype probabilities produced can be used in regression analyses to estimate effects of haplotypes on quantitative phenotypes.