Genome-wide scan for signatures of selection in the Brangus cattle genome.

Brangus is a composite cattle breed developed with the objective of combining the advantages of Angus and Zebuine breeds (Brahman, mainly) in tropical climates. The aim of this work was to estimate breed composition both genome-wide and locally, at the chromosome level, and to uncover genomic regions evidencing positive selection in the Argentinean Brangus population/nucleus. To do so, we analysed marker data from 478 animals, including Brangus, Angus and Brahman. Average breed composition was 35.0% ± 9.6% of Brahman, lower than expected according to the theoretical fractions deduced by the usual cross-breeding practice in this breed. Local ancestry analysis evidenced that breed composition varies between chromosomes, ranging from 19.6% for BTA26 to 56.1% for BTA5. Using approaches based on allelic frequencies and linkage disequilibrium, genomic regions with putative selection signatures were identified in several chromosomes (BTA1, BTA5, BTA6 and BTA14). These regions harbour genes involved in horn development, growth, lipid metabolism, reproduction and immune response. We argue that the overlapping of a chromosome segment originated in one of the parental breeds and over-represented in the sample with the location of a signature of selection constitutes evidence of a selection process that has occurred in the breed since its take off in the 1950s. In this regard, our results could contribute to the understanding of the genetic mechanisms involved in cross-bred cattle adaptation and productivity in tropical environments.

Naturally monozygotic quadruplets in a Braford cow confirmed by DNA analysis: A case report.

Cattle are a monotocous species, despite naturally conceived multiple births are sometimes observed. Although the number of twins has consistently increased, triplet and quadruplet pregnancies represent 0.015% and 0.004% of the total births, respectively. Multiple births are the result of multiple ovulation and/or the spontaneous cleavage of one fertilized oocyte, which is known as monozygotic (MZ) twinning. In cattle, approximately 5% to 14% of all twin births are MZ, and births with more than two MZ calves are extremely rare. Monozygotic animals are genetically identical, and those derived from two or more zygotes are genetically different. Furthermore, the presence of placental vascular anastomosis can result in foetal chimerism. Notwithstanding, animals born as single calves can be chimeras when one of the foetal twins dies undetected in utero. Here, we used DNA testing to study the zygotic condition of an unusual female quadruplet born from a Braford cow bred in a multi-sire natural mating system without hormone stimulation. Two tissues with different embryological origin were sampled to test zygosity and possible chimerism. The results showed an identical genotype, confirming they all originated in an MZ pregnancy and suggesting the lack of chimerism in all animals. The use of MZ twins in breeding and selection systems provides an alternative to the conventional progeny testing. Some works have suggested a genetic background of MZ twins in humans. This female and her daughters could be the founders of a lineage to study the possible inheritance of MZ multiple births in cattle.

The importance of manganese in the cytoplasmic maturation of cattle oocytes: blastocyst production improvement regardless of cumulus cells presence during in vitro maturation.

Adequate dietary intake of manganese (Mn) is required for normal reproductive performance in cattle. This study was carried out to investigate the effect of Mn during in vitro maturation of bovine cumulus-oocyte complexes (COC) on apoptosis of cumulus cells, cumulus expansion, and superoxide dismutase (SOD) activity in the COC. The role of cumulus cells on Mn transport and subsequent embryo development was also evaluated. Early apoptosis decreased in cumulus cells matured with Mn compared with medium alone. Cumulus expansion did not show differences in COC matured with or without Mn supplementation. SOD activity was higher in COC matured with 6 ng/ml Mn than with 0 ng/ml Mn. Cleavage rates were higher in COC and denuded oocytes co-cultured with cumulus cells, either with or without Mn added to in vitro maturation (IVM) medium. Regardless of the presence of cumulus cells during IVM, the blastocyst rates were higher when 6 ng/ml Mn was supplemented into IVM medium compared with growth in medium alone. Blastocyst quality was enhanced when COC were matured in medium with Mn supplementation. The results of the present study indicated that Mn supplementation to IVM medium enhanced the 'health' of COC, and improved subsequent embryo development and embryo quality.

Association of a region of bovine chromosome 1 (BTA1) with age at puberty in Angus bulls.

Age at puberty is an important component of reproductive performance in cattle, so it is important to identify genes that contribute to the regulation of the onset of puberty and polymorphisms that explain differences between bulls. In a previous study, we found putative associations between age at puberty in Angus bulls and single-nucleotide polymorphisms (SNPs) in Chromosomes 1 and X. In the present work we aimed to confirm these findings in a larger sample of Angus bulls (n = 276). Four SNPs located in these regions were genotyped using SEQUENOM technology and the genotypes obtained were tested for association with age at puberty. The results showed that SNPs rs135953349 and rs110604205 on BTA1 were still significantly associated with age of puberty estimated at progressive sperm motility of 10% (P < 0.05). The association previously found on Chromosome X could not be confirmed. Analysis of the bovine genome revealed that the associated region (99.17-99.99 Mb) contained four predicted loci: myelodysplasia syndrome 1 (MDS1) and ecotropic virus integration site 1 (EVI1) complex locus (MECOM), eGF-like and EMI domain-containing 1 pseudogene-like (LOC100337483), microRNA mir-551b (MIR551B) and mCG140927-like (LOC100139843). The results obtained could contribute to the understanding of puberty regulation and could be useful for further identification and annotation of gene function in the context of reproduction.

Comparison of the effectiveness of microsatellites and SNP panels for genetic identification, traceability and assessment of parentage in an inbred Angus herd.

During the last decade, microsatellites (short tandem repeats or STRs) have been successfully used for animal genetic identification, traceability and paternity, although in recent year single nucleotide polymorphisms (SNPs) have been increasingly used for this purpose. An efficient SNP identification system requires a marker set with enough power to identify individuals and their parents. Genetic diagnostics generally include the analysis of related animals. In this work, the degree of information provided by SNPs for a consanguineous herd of cattle was compared with that provided by STRs. Thirty-six closely related Angus cattle were genotyped for 18 STRs and 116 SNPs. Cumulative SNPs exclusion power values (Q) for paternity and sample matching probability (MP) yielded values greater than 0.9998 and 4.32E(-42), respectively. Generally 2-3 SNPs per STR were needed to obtain an equivalent Q value. The MP showed that 24 SNPs were equivalent to the ISAG (International Society for Animal Genetics) minimal recommended set of 12 STRs (MP ∼ 10(-11)). These results provide valuable genetic data that support the consensus SNP panel for bovine genetic identification developed by the Parentage Recording Working Group of ICAR (International Committee for Animal Recording).

Association between GNRHR, LHR and IGF1 polymorphisms and timing of puberty in male Angus cattle.

BACKGROUND: In bovines, there are significant differences within and among beef breeds in the time when bulls reach puberty. Although the timing of puberty is likely to be a multigenic trait, previous studies indicate that there may also be single genes that exert major effects on the timing of puberty within the general population. Despite its economic importance, there are not many SNPs or genetic markers associated with the age of puberty in male cattle. In the present work, we selected three candidate genes, GNRHR, LHR and IGF1, and associated their polymorphisms with the age of puberty in Angus male cattle. RESULTS: After weaning, 276 Angus males were measured every month for weight (W), scrotal circumference (SC), sperm concentration (C) and percentage of motility (M). A total of 4 SNPs, two within GNRHR, one in LHR and one in IGF1 were genotyped using the pyrosequencing technique. IGF1-SnaBI SNP was significant associated (P < 0.01) with age at SC 28 cm, but it were not associated with age at M 10% and C 50 million. Genotype CC exhibited an average age at SC 28 cm of 7 and 11 days higher than CT (p = 0.037) and TT (p = 0.012), respectively. This SNP explained 1.5% of the genetic variance of age of puberty at SC28. LHR-I499L, GNRHR-SNP5 and GNRHR-SNP6 were not associated with any of the measurements. However, GNRHR haplotypes showed a suggestive association with age at SC 28 cm. CONCLUSIONS: The findings presented here could support the hypothesis that IGF1 is a regulator of the arrival to puberty in male calves and is involved in the events that precede and initiate puberty in bull calves. Given that most studies in cattle, as well as in other mammals, were done in female, the present results are the first evidence of markers associated with age at puberty in male cattle.

Analysis of apoptosis and DNA damage in bovine cumulus cells after exposure in vitro to different zinc concentrations.

The purpose of this study was to investigate the effect of Zn (zinc) concentration on CCs (cumulus cells) during in vitro maturation. For this purpose, DNA integrity of CCs by addition of different Zn concentrations [0 (control); 0.7 µg/ml (Zn1); 1.1 µg/ml (Zn2) and 1.5 µg/ml (Zn3)] to the culture medium was evaluated by comet assay. In addition, early apoptosis was analysed by annexin staining assay. CCs treated with Zn showed a significant decrease in the DNA damage in a dose-dependent manner. Comet assay analysed for TM (tail moment) was significantly higher in cells cultured without Zn (control, P<0.01) with respect to cells treated with Zn (control: 5.24±16.05; Zn1: 1.13±5.31; Zn2: 0.10±0.36; Zn3: 0.017±0.06). All treatments were statistically different from the control (P = 0.014 for Zn1; P<0.01 for Zn2 and Zn3). The frequency of apoptotic cells was higher in the control group (control: 0.142±0.07; Zn1: 0.109±0.0328; Zn2:0.102±0.013; Zn3: 0.0577±0.019). Statistical differences were found between control and Zn1 (P = 0.0308), control and Zn2 (P = 0.0077), control and Zn3 (P<0.0001), Zn1 and Zn3 (P<0.001) and Zn2 and Zn3 (P = 0.0004). No differences were found between Zn1 and Zn2. In conclusion, low Zn concentrations increase DNA damage and apoptosis in CCs cultured in vitro. However, adequate Zn concentrations 'protect' the integrity of DNA molecule and diminish the percentage of apoptotic CC.

Epidemiology of Cranial Cruciate Ligament Rupture and Patellar Luxation in Dogs from the Province of Buenos Aires, Argentina.

OBJECTIVE: The aim of this study was to investigate the prevalence of cranial cruciate ligament rupture and patellar luxation and the associated risk factors in dogs. MATERIALS AND METHODS: A total of 13,072 clinical records of dogs were reviewed from School Hospital (Faculty of Veterinary Sciences, National University of La Plata). Data of age, breed, sex, body weight, patellar luxation and cranial cruciate ligament rupture condition were registered. Chi-squared and Fisher's exact tests were used to compare the prevalence of cranial cruciate ligament rupture and patellar luxation with the variables and then univariable logistic regression was used to evaluate the risk of having cranial cruciate ligament rupture and patellar luxation. Multivariable logistic regression was used including all variables to assess the odds of having patellar luxation and cranial cruciate ligament rupture. RESULTS: Of 13,072 patients treated, 72 and 51 had cranial cruciate ligament rupture and patellar luxation respectively. Sex was not a major risk factor for either condition. Adult (odds ratio [OR] = 8.2) and senior (OR = 4.3) patients had increased risk of having cranial cruciate ligament rupture, while for patellar luxation age was not a risk factor. Groups 2, 3 and 8 were more likely to have cranial cruciate ligament rupture (OR = 5.5, OR = 9.1 and OR = 2.6), and group 11 had lower risk of having patellar luxation (OR = 0.08). Maxi (OR = 2.4) and giant (OR = 6.0) breeds had higher risk of having cranial cruciate ligament rupture, and medium and maxi breeds had higher risk of patellar luxation (OR = 0.05 and OR = 0.3). Multivariate OR test confirmed that age (adult), body size (giant and maxi) and breed group (Group 3) were significantly associated with having cranial cruciate ligament rupture, and age was associated with having patellar luxation. CLINICAL SIGNIFICANCE: This is the first epidemiological study of cranial cruciate ligament rupture and patellar luxation in dogs from School Hospital (Faculty of Veterinary Sciences, National University of La Plata). Giant and large adult dogs from the Molossoid and Terrier breeds were more likely to have cranial cruciate ligament rupture, while mixed and large dog breeds showed the lowest risk of having patellar luxation.

Low-dose radiation employed in diagnostic imaging causes genetic effects in cultured cells.

BACKGROUND: Exposure to environmental, diagnostic, and occupational sources of radiation frequently involves low doses. Although these doses have no immediately noticeable impact on human health there is great interest in their long-term biological effects. PURPOSE: To assess immediate and time-delayed DNA damage in two cell lines exposed to low doses of ionizing radiation by using the comet assay and micronucleus test, and to compare these two techniques in the analysis of low-dose induced genotoxicity. MATERIAL AND METHODS: CHO and MRC-5 cells were exposed to 50 milliSievert (mSv) of ionizing radiation and assayed immediately after irradiation and at 16 or 12 passages post-irradiation, respectively. Comet assay and micronucleus test were employed. RESULTS: The comet assay values observed in 50 mSv-treated cells were significantly higher than in the control group for both sample times and cell lines (P < 0.001). Micronuclei frequencies were higher in treated cells than in the control group (P < 0.01, CHO cells passage 16; P < 0.05, MRC-5 cells immediately after exposure; P < 0.01 MRC-5 cells passage 12). Correlation analysis between the two techniques was statistically significant (correlation coefficient 0.82, P < 0.05 and correlation coefficient 0.86, P < 0.05 for CHO and MRC-5 cells, respectively). Cells scored at passages 12 or 16 showed more damage than those scored immediately after exposure in both cell lines (no statistically significant differences). CONCLUSION: Cytomolecular and cytogenetic damage was observed in cells exposed to very low doses of X-rays and their progeny. A single low dose of ionizing radiation was sufficient to induce such response, indicating that mammalian cells are exquisitely sensitive to it. Comet and micronucleus assays are sensitive enough to assess this damage, although the former seems to be more efficient.

Genomic structural diversity in Criollo Argentino horses: Analysis of copy number variations.

Copy number variation (CNV) has been proved to be widespread in human, animal and plant genomes. Together with single nucleotide polymorphisms (SNPs), CVNs play a key role in genetic diversity. In this study, genome-wide detection of CNVs was performed based on SNP data from 24 Criollo Argentino horses genotyped with the GGP Equine70k array. Overall, 165 CNVs meeting stringent quality control criteria were identified and then aggregated into 87 CNV regions (CNVRs), representing a horse genome coverage of 13.69 Mb. Functional analysis of CNVRs allowed the identification of 337 genes implicated in a wide range of biological functions such as signal transducer activity (olfactory receptors), receptor activities and binding. Furthermore, enrichment analysis showed that the most represented protein classes (over 25%) were immunoglobulin receptor subfamily, immunoglobulins and major histocompatibility complex antigen (beta-2-microglobulin). To the best of our knowledge, this is the first report of CNV in Criollo Argentino horses.