Apolipoprotein E Polymorphism in Sheep

Using polyacrylamide gel isoelectric focusing followed by immunoblotting with anti-human apolipoprotein E (APO E) antibody, the genetic polymorphism of APO E was determined from desialylated plasma of 554 unrelated adults of four European sheep (Suffolk, Corriedale, Cheviot, and Finnish Landrace) and five Asian local sheep (Bhyanglung, Baruwal, Kagi, Lampuchhre, and Vietnamese). Twenty phenotypes consisting of the homozygous and heterozygous combinations of two APO E variants within the seven variants (E1-E7) detected were identified. Family and population data supported the hypothesis that the phenotypes are controlled by seven codominant alleles, designated APOE1 to APOE7, at a single autosomal locus. The common alleles, APOE4, APOE5, and APOE7 were observed at mean frequencies of 0.5763, 0.1471, and 0.1921 in the European sheep group and 0.4920, 0.1123, and 0.2995 in the Asian local sheep group, respectively.     

Genetic polymorphism of apolipoprotein C polypeptide in native Asian sheep

The frequency distributions of apolipoprotein C alleles in native Asian sheep (Bengal, Kagi, Lampuchhre, Vietnamese, Myanmar, Baruwal, Bhyanglung, Khalkhas, and Kuwait) were determined using a one-dimensional polyacrylamide gel isoelectric-focusing immunoblotting technique. Among these Asian sheep, the genetic locus consisted mainly of two common APOC*1 and APOC*3 alleles. The Baruwal sheep most frequently possessed APOC*1 (0.9881), showing significant differences from all other Asian sheep in allele frequency (0.7195-0.9032, P < 0.02). Compared with European sheep tested previously, these Asian sheep had significantly higher frequencies of APOC*1 (0.7828 and 0.7127 averages, P < 0.0005) and APOC*3 (0.2162 and 0.11 averages, P < 0.0001). In particular, APOC*2 was detected at an extremely low frequency (0.0025) in the Khalkhas sheep only, and was uncommon in all Asian sheep (0.001 average), in contrast with the 0.1773 average of European sheep (P < 0.00001). This finding suggests that APOC*2 is exceedingly rare in Asian sheep. With the exception of triglycerides and VLDL cholesterol in the Vietnamese sheep, no phenotypic effects on plasma lipid and lipoprotein levels in the Asian sheep tested were seen.     

Intraspecies prion transmission results in selection of sheep scrapie strains

Background

Sheep scrapie is caused by multiple prion strains, which have been classified on the basis of their biological characteristics in inbred mice. The heterogeneity of natural scrapie prions in individual sheep and in sheep flocks has not been clearly defined.

Methodology/Principal Findings

In this study, we intravenously injected 2 sheep (Suffolk and Corriedale) with material from a natural case of sheep scrapie (Suffolk breed). These 3 sheep had identical prion protein (PrP) genotypes. The protease-resistant core of PrP (PrPres) in the experimental Suffolk sheep was similar to that in the original Suffolk sheep. In contrast, PrPres in the Corriedale sheep differed from the original PrPres but resembled the unusual scrapie isolate, CH1641. This unusual PrPres was not detected in the original sheep. The PrPres distributions in the brain and peripheral tissues differed between the 2 breeds of challenged sheep. A transmission study in wild-type and TgBoPrP mice, which overexpressing bovine PrP, led to the selection of different prion strains. The pathological features of prion diseases are thought to depend on the dominantly propagated strain.

Conclusions/Significance

Our results indicate that prion strain selection occurs after both inter- and intraspecies transmission. The unusual scrapie prion was a hidden or an unexpressed component in typical sheep scrapie.     

Haplotype analysis of the apolipoprotein E and apolipoprotein C1 loci in Portugal and São Tomé e Príncipe (Gulf of Guinea): linkage disequilibrium evidence that APOE*4 is the ancestral APOE allele

The joint distributions of phenotypes from the apolipoprotein E gene (APOE) and from a closely linked restriction site polymorphism at the apolipoprotein C1 locus (APOC1) were studied in population samples from Portugal and S?o Tomé e Príncipe (Gulf of Guinea), a former Portuguese colony that was originally populated by slaves imported from the African mainland. The frequencies of the APOE alleles (*2, *3, and *4) in Portugal and S?o Tomé fitted the ranges of variation generally observed in European and African populations, respectively. Haplotype analysis showed that in both populations the strength of linkage disequilibrium was highest for the APOE*2 allele and lowest for the APOE*4 allele, suggesting that the origin of the APOE alleles followed a 4-->3-->2 pathway and thus providing independent confirmation of the results from sequence homology studies with nonhuman primates. In accordance with global trends in the distribution of human genetic variation, the European sample from Portugal presented more intense linkage disequilibrium between APOE and APOC1 than the African sample from S?o Tomé where, despite the short 4-kb distance that separates the 2 loci, the level of association between the APOC1 alleles and APOE*4 was nonsignificant.     

Ovar-MHC Polymorphism in Malpura and Avikalin Sheep Vaccinated for Peste des Petits Ruminants (PPR) Virus

India harbors a vast diversity of sheep (40 breeds). The study was carried out to assess the genetic diversity of DRB1 and DQA2 locus of the ovar-MHC and their possible association with Peste des petits ruminants (PPR) virus vaccine response in Malpura and Avikalin sheep breeds maintained at an organized institute flock in the semi-arid region of India. Genetic analysis revealed the rich diversity of DRB1 locus with 23 alleles in Malpura and 21 alleles in Avikalin sheep that included 9 new alleles. DQA2 locus also had rich diversity with 19 alleles in Malpura and 20 alleles in Avikalin sheep that included 7 new alleles. At the protein level, high variability alike at the nucleotide level was observed. A marker for footrot susceptibility, DQA2*1101 was absent in both breeds. Genotypic association of DRB1 and DQA2 with PPR vaccine response was statistically non-significant. Vaccine response being a multifactorial (polygenic and influenced by environment) variable, could not show statistically significant association with MHC genotypes in the present study. However, rich genetic diversity of DRB1 and DQA2 gene reflects the importance of this locus for future selection programs.     

Effects of sire genotype on lamb performance at weaning in extensive sheep systems

A low finishing weight and poor carcass characteristics are major causes of lower incomes in extensive sheep flocks; however, the use of terminal sire crossbreeding would improve lamb performance and carcass traits under these conditions. The aim of this study was to evaluate sire breed effects on the performance of lambs born to Corriedale ewes in extensive sheep systems in Western Patagonia. A total of 10 Corriedale, 10 Dorset, nine Suffolk and seven Texel sires, 16 of which were under a genetic recorded scheme and 20 selected from flocks not participating in genetic improvement programmes, were used across six commercial farms for 2 successive years. Data were collected from 685 lambs of the four resulting genotypes. Overall, Corriedale lambs were 0.47 kg lighter at birth than crossbred lambs (P<0.001). Suffolk and Texel sired lambs required more assistance (P<0.01) at birth than Corriedale or Dorset sired lambs, with Suffolk sired lambs requiring the most assistance (8%). Ewes sired with Suffolk rams had larger (P<0.05) litters than ewes sired with Texel or Corriedale rams. Lamb live weight gain from birth to weaning was higher (P<0.001) in crossbred lambs compared with Corriedale lambs, therefore, crossbred lambs averaged 2.9 kg heavier BW (P<0.001) than Corriedale lambs. A significant sire breed x sire source interaction was detected for lamb live weight gain (P<0.05) and lamb live weight at weaning (P<0.01), showing that the heaviest lambs were from recorded sires, except for Suffolk crossbred lambs. Mortality rate to weaning was increased (P<0.05) in Suffolk cross lambs (31%), with Corriedale lambs showing the lowest (17%) mortality. Terminal sire breeds increased (P<0.001) cold carcass weight, with 13.8, 16.0, 15.2 and 14.9 kg for the Corriedale, Dorset, Suffolk and Texel sired lambs, respectively. Carcass length, kidney knob and channel fat, fat grade, grade rule and fat depth measurements were not affected by sire breed (P>0.05). Carcass conformation was higher in Texel sired lambs compared with Corriedale lambs (P<0.05), with Dorset and Suffolk sired lambs being intermediate. Crossbred lambs showed a greater (P<0.001) eye muscle than Corriedale. Commercial cuts were affected by sire breed, as a result of the Corriedale lambs being smaller and having lighter carcass than crossbred lambs. Significant improvement in lamb weights at weaning and carcass traits could be expected when using a terminal sire on Corriedale ewes in Western Patagonia. However, no advantages were detected with the use of recorded sires under these production systems.     

Comparative Susceptibility of Sheep of Different Origins,Breeds and PRNP Genotypes to Challenge with Bovine Spongiform Encephalopathy and Scrapie

Sheep are natural hosts of the prion disease, scrapie. They are also susceptible to experimental challenge with various scrapie strains and with bovine spongiform encephalopathy (BSE), which affects cattle and has been accidentally transmitted to a range of other species, including man. Incidence and incubation period of clinical disease in sheep following inoculation is controlled by the PRNP gene, which has different alleles defined on the basis of polymorphisms, particularly at codons 136, 154 and 171, although other codons are associated with survival time, and the exact responses of the sheep may be influenced by other breed-related differences. Here we report the results of a long term single study of experimental scrapie and BSE susceptibility of sheep of Cheviot, Poll Dorset and Suffolk breeds, originating from New Zealand and of a wide range of susceptible and resistant PRNP genotypes. Responses were compared with those of sheep from a closed Cheviot flock of UK origin (Roslin Cheviot flock). The unusually long observation period (6–8 years for most, but up to 12 years for others) allows us to draw robust conclusions about rates of survival of animals previously regarded as resistant to infection, particularly PRNP heterozygotes, and is the most comprehensive such study reported to date. BSE inoculation by an intracerebral route produced disease in all genotype groups with differing incubation periods, although M112T and L141F polymorphisms seemed to give some protection. Scrapie isolate SSBP/1, which has the shortest incubation period in sheep with at least one VRQ PRNP allele, also produced disease following sub-cutaneous inoculation in ARQ/ARQ animals of New Zealand origin, but ARQ/ARQ sheep from the Roslin flock survived the challenge. Our results demonstrate that the links between PRNP genotype and clinical prion disease in sheep are much less secure than previously thought, and may break down when, for example, a different breed of sheep is moved into a new flock.     

Linkage relationships of the apolipoprotein C1 gene and a cytochrome P450 gene (CYP2A) to myotonic dystrophy

Summary We have studied the genetic linkage of two markers, the apolipoprotein C1 (APOC1) gene and a cytochrome P450 (CYP2A) gene, in relation to the gene for myotonic dystrophy (DM). A peak lod score of 9.29 at 2 cM was observed for APOC1-DM, with a lod score of 8.55 at 4cM for CYP2A-DM. These two markers also show close linkage to each other ( _max = 0.05, Z _max = 9.09). From examination of the genotypes of the recombinant individuals, CYP2A appears to map proximal to DM because in one recombinant individual CYP2A, APOC2 and CKMM had all recombined with DM. Evidence from another CYP2A-DM recombinant individual places CYP2A proximal to APOC2 and CKMM. Localisation of CYP2A on a panel of somatic cell hybrids also suggests that it is proximal to DM and APOC2/C1/E gene cluster.     

Genetic structure and admixture in sheep from terminal breeds in the United States

Selection for performance in diverse production settings has resulted in variation across sheep breeds worldwide. Although sheep are an important species to the United States, the current genetic relationship among many terminal sire breeds is not well characterized. Suffolk, Hampshire, Shropshire and Oxford (terminal) and Rambouillet (dual purpose) sheep (n = 248) sampled from different flocks were genotyped using the Applied Biosystems Axiom Ovine Genotyping Array (50K), and additional Shropshire sheep (n = 26) using the Illumina Ovine SNP50 BeadChip. Relationships were investigated by calculating observed heterozygosity, inbreeding coefficients, eigenvalues, pairwise Wright’s F_ST estimates and an identity by state matrix. The mean observed heterozygosity for each breed ranged from 0.30 to 0.35 and was consistent with data reported in other US and Australian sheep. Suffolk from two different regions of the United States (Midwest and West) clustered separately in eigenvalue plots and the rectangular cladogram. Further, divergence was detected between Suffolk from different regions with Wright’s F_ST estimate. Shropshire animals showed the greatest divergence from other terminal breeds in this study. Admixture between breeds was examined using admixture , and based on cross-validation estimates, the best fit number of populations (clusters) was K = 6. The greatest admixture was observed within Hampshire, Suffolk, and Shropshire breeds. When plotting eigenvalues, US terminal breeds clustered separately in comparison with sheep from other locations of the world. Understanding the genetic relationships between terminal sire breeds in sheep will inform us about the potential applicability of markers derived in one breed to other breeds based on relatedness.     

Looking for prognosticators in ovine anaplasmosis: discriminant analysis of clinical and haematological parameters in lambs belonging to differently susceptible breeds experimentally infected with <Emphasis Type="Italic">Anaplasma ovis</Emphasis>

Background

A study was carried out to evaluate the response of different native sheep breeds to experimental infection with Anaplasma ovis, the most prevalent sheep tick-borne pathogen in Apulia (Southern Italy). Thirty-four lambs belonging to a Northern European breed (Suffolk) and two Southern Italian breeds (Comisana and Altamurana) were infected. Eleven clinical as well as haematological parameters were monitored at different temporal resolutions on the same subjects before and after the infection, resulting in a data set of 435 observations. The present work, aiming to further the research, presents the results of a multivariate analysis carried out to identify which parameters out of the eleven considered are the most reliable parameters to be considered as markers of the disease phenotype as well as prognosticators of practical clinical importance.

Results

Data were analysed by discriminant analysis. Out of the eleven considered variables (red blood cells, packed cell volume, mean corpuscular volume, mean corpuscular haemoglobin, mean corpuscular haemoglobin content, haemoglobin concentration, white blood cells, neutrophils, leukocytes, platelets, rectal temperature), only seven were included in the step-wise model since significantly increasing the Mahlanobis distance between the two closest groups. Both discriminant functions resulted to be highly significant (P?<?0.0001) and the percentage of variation accounted for by the first discriminant function was 63.6% of the variance in the grouping variable.

Conclusions

Taken together, the observed results stress the marked differentiation among the three breeds in terms of physio-pathological phenotypes indicating packed cell volume and red blood cell count as the most informative parameters in the routine clinical practice for A. ovis infection in sheep.

     

Accuracy of pedigree and genomic predictions of carcass and novel meat quality traits in multi-breed sheep data assessed by cross-validation

Background

Genomic predictions can be applied early in life without impacting selection candidates. This is especially useful for meat quality traits in sheep. Carcass and novel meat quality traits were predicted in a multi-breed sheep population that included Merino, Border Leicester, Polled Dorset and White Suffolk sheep and their crosses.

Methods

Prediction of breeding values by best linear unbiased prediction (BLUP) based on pedigree information was compared to prediction based on genomic BLUP (GBLUP) and a Bayesian prediction method (BayesR). Cross-validation of predictions across sire families was used to evaluate the accuracy of predictions based on the correlation of predicted and observed values and the regression of observed on predicted values was used to evaluate bias of methods. Accuracies and regression coefficients were calculated using either phenotypes or adjusted phenotypes as observed variables.

Results and conclusions

Genomic methods increased the accuracy of predicted breeding values to on average 0.2 across traits (range 0.07 to 0.31), compared to an average accuracy of 0.09 for pedigree-based BLUP. However, for some traits with smaller reference population size, there was no increase in accuracy or it was small. No clear differences in accuracy were observed between GBLUP and BayesR. The regression of phenotypes on breeding values was close to 1 for all methods, indicating little bias, except for GBLUP and adjusted phenotypes (regression = 0.78). Accuracies calculated with adjusted (for fixed effects) phenotypes were less variable than accuracies based on unadjusted phenotypes, indicating that fixed effects influence the latter. Increasing the reference population size increased accuracy, indicating that adding more records will be beneficial. For the Merino, Polled Dorset and White Suffolk breeds, accuracies were greater than for the Border Leicester breed due to the smaller sample size and limited across-breed prediction. BayesR detected only a few large marker effects but one region on chromosome 6 was associated with large effects for several traits. Cross-validation produced very similar variability of accuracy and regression coefficients for BLUP, GBLUP and BayesR, showing that this variability is not a property of genomic methods alone. Our results show that genomic selection for novel difficult-to-measure traits is a feasible strategy to achieve increased genetic gain.     

Genetic influences on Alzheimer's disease: evidence of interactions between the genes APOE, APOC1 and ACE in a sample population from the South of Brazil

Alzheimer’s disease is a complex neurodegenerative disorder. Several genes have been suggested as Alzheimer’s susceptibility factors, the apolipoprotein E (APOE) gene being an established susceptibility gene and the genes coding angiotensin-converting enzyme (ACE) and apolipoprotein C1 (APOC1) being considered possible candidate genes for the disease. The objective of this study was to investigate the association of ACE and APOC1 gene polymorphisms with susceptibility to Alzheimer’s disease and dementia in general, both alone and combined with the APOE gene. Forty-seven patients with dementia in general (35 of them with Alzheimer’s disease) and 85 controls were investigated. The haplotypes E*3/−317*ins and E*4/−317*ins of APOE/APOC1 genes were significantly more frequent in the groups with Alzheimer′s disease and dementia in general (P < 0.001). The frequency of the ACE*ins allele was also greater in the groups with Alzheimer’s disease and dementia in general (P = 0.022; P = 0.045), but genotype frequencies were only different in groups without the E*4/−317*ins haplotype (P = 0.012 for Alzheimer’s disease; P = 0.04 for dementia). Our data point to important genetic interactions involved in these diseases.     

Apolipoprotein E phenotypes and hyperlipidemia in patients under maintenance hemodialysis

Summary Apolipoprotein E phenotypes and gene frequencies were determined in 560 patients receiving long-term hemodialysis. In addition, fasting plasma lipid- and apolipoprotein-concentrations were evaluated in 245 of these individuals. The distribution of the three major apolipoprotein E alleles (4, 3, and 2) and that of the six common apolipoprotein E phenotypes (E4/4, E3/3, E2/2, E4/2, E4/3, and E3/2) in the dialysis group was nearly identical to that of healthy controls. Patients with the apolipoprotein E phenotypes E2/2, E4/4 and E4/3 (comprising 24% of the whole group) had higher mean plasma cholesterol- and triglyceride-concentrations than those with the apolipoprotein E phenotypes E3/3 and E3/2 (72% of the whole group). Thus, the genetic polymorphism of apolipoprotein E may contribute to the individual risk of accelerated atherosclerosis in patients under maintenance hemodialysis.     

Genetic diversity of three Chinese native sheep breeds

The sheep (Ovis aries L.) has been an important farm animal species since its domestication. A wide array of indigenous sheep breeds with abundant phenotypic diversity exists for domestication and selection. Therefore, assessing the genetic diversity of a local sheep resource using a multi-molecular system is helpful for maintaining and conserving those breeds. This study aimed to investigate the genetic diversity of three native Chinese sheep breeds (Tibetan sheep, Sishui Fur sheep, and Small-tailed Han sheep) using 15 microsatellite markers and the second exon of the DRA gene. In regards to the microsatellites, on average, 19 alleles per loci were observed among all individuals. Across loci, the HO within the population was 0.652 ± 0.022 in Tibetan sheep, 0.603 ± 0.023 in Small-tailed Han sheep and 0.635 ± 0.022 in SFS, and for most populations, the H _E and H _O were inconsistent. In addition, affluent private alleles within the breed indicated that the breeds have different domestication histories or sites. In regards to the 2 exon of the DRA gene, three haplotypes were constructed by seven single-nucleotide polymorphisms (SNPs), which were identified in the second DRA exon and inferred the potential for phenotypic variety in these Chinese native sheep. In summary, the current study reveals the importance of implementing effective conservation strategies for these three native Chinese sheep.     

Genome-wide analysis reveals population structure and selection in Chinese indigenous sheep breeds

Background

Traditionally, Chinese indigenous sheep were classified geographically and morphologically into three groups: Mongolian, Kazakh and Tibetan. Herein, we aimed to evaluate the population structure and genome selection among 140 individuals from ten representative Chinese indigenous sheep breeds: Ujimqin, Hu, Tong, Large-Tailed Han and Lop breed (Mongolian group); Duolang and Kazakh (Kazakh group); and Diqing, Plateau-type Tibetan, and Valley-type Tibetan breed (Tibetan group).

Results

We analyzed the population using principal component analysis (PCA), STRUCTURE and a Neighbor-Joining (NJ)-tree. In PCA plot, the Tibetan and Mongolian groups were clustered as expected; however, Duolang and Kazakh (Kazakh group) were segregated. STRUCTURE analyses suggested two subpopulations: one from North China (Kazakh and Mongolian groups) and the other from the Southwest (Tibetan group). In the NJ-tree, the Tibetan group formed an independent branch and the Kazakh and Mongolian groups were mixed. We then used the d_i statistic approach to reveal selection in Chinese indigenous sheep breeds. Among the 599 genome sequence windows analyzed, sixteen (2.7%) exhibited signatures of selection in four or more breeds. We detected three strong selection windows involving three functional genes: RXFP2, PPP1CC and PDGFD. PDGFD, one of the four subfamilies of PDGF, which promotes proliferation and inhibits differentiation of preadipocytes, was significantly selected in fat type breeds by the Rsb (across pairs of populations) approach. Two consecutive selection regions in Duolang sheep were obviously different to other breeds. One region was in OAR2 including three genes (NPR2, SPAG8 and HINT2) the influence growth traits. The other region was in OAR 6 including four genes (PKD2, SPP1, MEPE, and IBSP) associated with a milk production quantitative trait locus. We also identified known candidate genes such as BMPR1B, MSRB3, and three genes (KIT, MC1R, and FRY) that influence lambing percentage, ear size and coat phenotypes, respectively.

Conclusions

Based on the results presented here, we propose that Chinese native sheep can be divided into two genetic groups: the thin type (Tibetan group), and the fat type (Mongolian and Kazakh group). We also identified important genes that drive valuable phenotypes in Chinese indigenous sheep, especially PDGFD, which may influence fat deposition in fat type sheep.

Electronic supplementary material

The online version of this article (doi:10.1186/s12864-015-1384-9) contains supplementary material, which is available to authorized users.     

Comparing genomic prediction accuracy from purebred,crossbred and combined purebred and crossbred reference populations in sheep

Background

The accuracy of genomic prediction depends largely on the number of animals with phenotypes and genotypes. In some industries, such as sheep and beef cattle, data are often available from a mixture of breeds, multiple strains within a breed or from crossbred animals. The objective of this study was to compare the accuracy of genomic prediction for several economically important traits in sheep when using data from purebreds, crossbreds or a combination of those in a reference population.

Methods

The reference populations were purebred Merinos, crossbreds of Border Leicester (BL), Poll Dorset (PD) or White Suffolk (WS) with Merinos and combinations of purebred and crossbred animals. Genomic breeding values (GBV) were calculated based on genomic best linear unbiased prediction (GBLUP), using a genomic relationship matrix calculated based on 48 599 Ovine SNP (single nucleotide polymorphisms) genotypes. The accuracy of GBV was assessed in a group of purebred industry sires based on the correlation coefficient between GBV and accurate estimated breeding values based on progeny records.

Results

The accuracy of GBV for Merino sires increased with a larger purebred Merino reference population, but decreased when a large purebred Merino reference population was augmented with records from crossbred animals. The GBV accuracy for BL, PD and WS breeds based on crossbred data was the same or tended to decrease when more purebred Merinos were added to the crossbred reference population. The prediction accuracy for a particular breed was close to zero when the reference population did not contain any haplotypes of the target breed, except for some low accuracies that were obtained when predicting PD from WS and vice versa.

Conclusions

This study demonstrates that crossbred animals can be used for genomic prediction of purebred animals using 50 k SNP marker density and GBLUP, but crossbred data provided lower accuracy than purebred data. Including data from distant breeds in a reference population had a neutral to slightly negative effect on the accuracy of genomic prediction. Accounting for differences in marker allele frequencies between breeds had only a small effect on the accuracy of genomic prediction from crossbred or combined crossbred and purebred reference populations.     

Genetic Mechanisms of Resistance and Susceptibility to Leukemia in Ayrshire and Black Pied Cattle Breeds Determined by Allelic Distribution of Gene BoLA-DRB3

In the herds of Ayrshire and Black Pied cattle breeds of Russian selection, comparative analysis of allelic distribution of BoLA-DRB3 was performed in animal groups with different status of persistent lymphocytosis (PL) caused by the bovine leukemia virus (BLV). Alleles were typed by PCR–RFLP. Different spectra of BoLA-DRB3 alleles mediating susceptibility and resistance to leukemia were detected in the studied breeds. The role of amino acid motives in 1 domain of BoLA-DRB3 antigens was confirmed: ER (in positions 70–71), in resistance to leukemia and VDTY and VDTV (75–78), in susceptibility to leukemia. The nucleotide sequence of allele BoLA-DRB3.2*7with deletion of codon 65, which resulted in the changed conformation of the corresponding antigen molecule, was associated with resistance to PL. Cows of Black Pied and Ayrshire breeds with genotypes coding VDTY/VDTV (RR = 11.67, P = 0,014) and VDTY/VDTY (RR = 4.71, P = 0.022), respectively, were shown to be susceptible to PL. The role of heterozygosity level was demonstrated (estimated by BoLA-DRB3 alleles and by amino acid motives in positions 75–78 of the antigen) as an unspecific factor of resistance to PL. The lowest heterozygosity level by amino acid motives (75–78) was revealed in PL animals, for which sample inbreeding coefficients were detected: F = 0.324 and 0.084 in Ayrshire and Black Pied breeds, respectively.     

Predictive potential of microsatellite markers on heterosis of fecundity in crossbred sheep

Small Tail Han (STH) sheep is a famous Chinese local breed and has perfect prolificacy performance, but it is inferior to imported mutton sheep breeds on meat production. In this study, six imported male sheep populations (White Suffolk, Black Suffolk, Texel, Dorper, South African Mutton Merino and East Friesian) were crossbred with STH female sheep respectively. The heterosis values of litter size, average daily gain (ADG) and feed conversion ratio (FCR) of crossbred sheep were analyzed for seeking the optimal cross. Meanwhile 28 microsatellite markers were used to measure the genetic distance between imported populations and STH population. Regression between the genetic distance and heterosis was analyzed for evaluating potential of microsatellite on predicting heterosis. Results showed a significant positive linear correlation (r = 0.892, P < 0.05) between heterosis of litter size and genetic distance D _A of six crosses. This implied that these microsatellite markers had moderate potential to forecast heterosis of litter size in sheep. Results of this study also indicated that South African Mutton Merino and East Friesian sheep would be the optimal sire breeds for the litter size and might bring the greatest economic benefit in six imported populations; Suffolk sheep could be prior consideration as sire breeds when breeding objective focused on ADG. Finally these results provided valuable information for Chinese sheep industry.     

Genetic variations in the myostatin gene (MSTN) in New Zealand sheep breeds

Myostatin, which is also known as growth and differentiation factor 8 (GDF8), acts as a negative regulator of skeletal muscle growth. Variation in the myostatin gene (MSTN) has been associated with variation in muscularity in many animals including sheep. Polymerase chain reaction-single strand conformational polymorphism (PCR-SSCP) analysis was used to investigate MSTN in a diverse range of sheep breeds including the New Zealand (NZ) Romney, Coopworth, Corriedale, Dorper, Perendale, Suffolk, Merino, Dorset Down, Poll Dorset, Texel and other NZ cross-bred sheep. A total of 28 nucleotide substitutions were identified from nucleotide c.-1199 in the promoter region to c.*1813 (based on NCBI GenBank accession number DQ530260) and including the well-described substitution c.*1232G>A (MSTN g+6223G>A). Of these 28 substitutions, 3 were located in the promoter region, 3 in the 5′UTR, 11 in intron 1, 5 in intron 2 and 5 in the 3′UTR. One substitution in exon 1 (c.101G>A) potentially results in an amino acid substitution of glutamic acid (Glu) with glycine (Gly) at codon 34. Ten of these substitutions have not been reported previously. The genetic variation revealed in this study suggests this gene is more variable than hitherto reported and provides a foundation for future research into how this variation affects muscle and growth traits.     

The plasminogen polymorphism in South African Negro populations: genetics and anthropogenetics

Summary Genetic polymorphism of human plasminogen (PLG) was investigated in 1252 unrelated individuals from eight South African Bantu-speaking Negro tribes. PLG phenotypes were determined by isoelectric focusing (pH 3.5–9.5 and 5–8 gradients) of neuraminidase-treated samples and subsequent detection by caseinolytic overlay or immunoblotting with specific antibody. No significant difference in the distribution of PLG alleles among the eight ethnic groups was observed. The combined allele frequencies of the common alleles in South African Negroes were 0.6977 for PLG*A, 0.2736 for PLG*B. In addition, six rare alleles were seen: PLG*A3, *A1, *M2, *B1, *B2, *B3. The rare variant PLG*B2 was proven to segregate by autosomal Mendelian inheritance in a family. The combined frequency for the rare alleles was 0.0287. The distribution of phenotypes in the total population sample was found to be in Hardy-Weinberg equilibrium. A striking difference in PLG allele distribution between Negroes from South Africa and published Negroid frequencies from North America could be observed. This difference was also seen in comparison with Mongoloid populations; in contrast, PLG frequencies for South African Negroes were similar or almost identical to known Caucasoid distributions.