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Dive into the research topics where Le Ann Blomberg is active.

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Featured researches published by Le Ann Blomberg.


Stem Cell Reviews and Reports | 2008

The Pursuit of ES Cell Lines of Domesticated Ungulates

Neil C. Talbot; Le Ann Blomberg

In contrast to differentiated cells, embryonic stem cells (ESC) maintain an undifferentiated state, have the ability to self-renew, and exhibit pluripotency, i.e., they can give rise to most if not all somatic cell types and to the germ cells, egg and sperm. These characteristics make ES cell lines important resources for the advancement of human regenerative medicine, and, if established for domesticated ungulates, would help make possible the improvement of farm animals through their contribution to genetic engineering technology. Combining other genetic engineering technologies, such as somatic cell nuclear transfer with ESC technology may result in synergistic gains in the ability to precisely make and study genetic alterations in mammals. Unfortunately, despite significant advances in our understanding of human and mouse ESC, the derivation of ES cell lines from ungulate species has been unsuccessful. This may result from a lack of understanding of species-specific mechanisms that promote or influence cell pluripotency. Thorough molecular characterizations, including the elucidation of stem cell “marker” signaling cascade hierarchy, species-appropriate pluripotency markers, and pluripotency-associated chromatin alterations in the genomes of ungulate species, should improve the chances of developing efficient, reproducible technologies for the establishment of ES cell lines of economically important species like the pig, cow, goat, sheep and horse.


BMC Genomics | 2012

Whole genome SNP discovery and analysis of genetic diversity in Turkey (Meleagris gallopavo).

Muhammad L Aslam; J.W.M. Bastiaansen; Martin G Elferink; Hendrik-Jan Megens; R.P.M.A. Crooijmans; Le Ann Blomberg; Robert C. Fleischer; Curtis P. Van Tassell; Tad S. Sonstegard; Steven G. Schroeder; M.A.M. Groenen; Julie A Long

BackgroundThe turkey (Meleagris gallopavo) is an important agricultural species and the second largest contributor to the world’s poultry meat production. Genetic improvement is attributed largely to selective breeding programs that rely on highly heritable phenotypic traits, such as body size and breast muscle development. Commercial breeding with small effective population sizes and epistasis can result in loss of genetic diversity, which in turn can lead to reduced individual fitness and reduced response to selection. The presence of genomic diversity in domestic livestock species therefore, is of great importance and a prerequisite for rapid and accurate genetic improvement of selected breeds in various environments, as well as to facilitate rapid adaptation to potential changes in breeding goals. Genomic selection requires a large number of genetic markers such as e.g. single nucleotide polymorphisms (SNPs) the most abundant source of genetic variation within the genome.ResultsAlignment of next generation sequencing data of 32 individual turkeys from different populations was used for the discovery of 5.49 million SNPs, which subsequently were used for the analysis of genetic diversity among the different populations. All of the commercial lines branched from a single node relative to the heritage varieties and the South Mexican turkey population. Heterozygosity of all individuals from the different turkey populations ranged from 0.17-2.73 SNPs/Kb, while heterozygosity of populations ranged from 0.73-1.64 SNPs/Kb. The average frequency of heterozygous SNPs in individual turkeys was 1.07 SNPs/Kb. Five genomic regions with very low nucleotide variation were identified in domestic turkeys that showed state of fixation towards alleles different than wild alleles.ConclusionThe turkey genome is much less diverse with a relatively low frequency of heterozygous SNPs as compared to other livestock species like chicken and pig. The whole genome SNP discovery study in turkey resulted in the detection of 5.49 million putative SNPs compared to the reference genome. All commercial lines appear to share a common origin. Presence of different alleles/haplotypes in the SM population highlights that specific haplotypes have been selected in the modern domesticated turkey.


In Vitro Cellular & Developmental Biology – Animal | 2005

Isolation and characterization of a bovine visceral endoderm cell line derived from a parthenogenetic blastocyst

Neil C. Talbot; Thomas J. Caperna; Anne M. Powell; Alan D. Ealy; Le Ann Blomberg; Wesley M. Garrett

SummaryA cell line, BPE-1, was derived from a parthegogenetic 8-d in vitro-produced bovine blastocyst that produced a cell outgrowth on STO feeder cells. The BPE-1 cells resembled visceral endoderm previously cultured from blastocysts produced by in vitro fertilization (IVF). Analysis of the BPE-1 cells demonstrated that they produced serum proteins and were negative for interferon-tau production (a marker of trophectoderm). Transmission electron microscopy revealed that the cells were a polarized epithelium connected by complex junctions resembling tight junctions in conjunction with desmosomes. Rough endoplasmic reticulum was prominent within the cells as were lipid vacuoles. Immunocytochemistry indicated the BPE-1 cells had robust microtubule networks. These cells have been growth for over 2 yr for multiple passages at 1∶10 or 1∶20 split ratios on STO feeder cells. The BPE-1 cell line presumably arose from embryonic cells that became diploid soon after parthenogenetic activation and development of the early embryo. However, metaphase spreads prepared at passage 41 indicated that the cell population had a hypodiploid (2n=60) unimodal chromosome content with a mode of 53 and a median and mean of 52. The cell line will be of interest for functional comparisons with bovine endoderm cell lines derived from IVF and nuclear transfer embryos.


Scientific Reports | 2017

Generation of germline ablated male pigs by CRISPR/Cas9 editing of the NANOS2 gene

Ki-Eun Park; Amy V. Kaucher; Anne M. Powell; Muhammad Waqas; Shelley E. S. Sandmaier; Melissa J. Oatley; Chi-Hun Park; Ahmed Tibary; David M. Donovan; Le Ann Blomberg; Simon G. Lillico; C. Bruce A. Whitelaw; Alan Mileham; Bhanu Prakash V.L. Telugu; Jon M. Oatley

Genome editing tools have revolutionized the generation of genetically modified animals including livestock. In particular, the domestic pig is a proven model of human physiology and an agriculturally important species. In this study, we utilized the CRISPR/Cas9 system to edit the NANOS2 gene in pig embryos to generate offspring with mono-allelic and bi-allelic mutations. We found that NANOS2 knockout pigs phenocopy knockout mice with male specific germline ablation but other aspects of testicular development are normal. Moreover, male pigs with one intact NANOS2 allele and female knockout pigs are fertile. From an agriculture perspective, NANOS2 knockout male pigs are expected to serve as an ideal surrogate for transplantation of donor spermatogonial stem cells to expand the availability of gametes from genetically desirable sires.


Reproduction, Fertility and Development | 2013

Identification of alpha-1 acid glycoprotein (AGP) as a potential marker of impaired growth in the newborn piglet

Thomas J. Caperna; Amy E. Shannon; Le Ann Blomberg; M. J. Stoll; Timothy G. Ramsay

Two studies were conducted to investigate the relationship between circulating levels of haptoglobin and α-1 acid glycoprotein (AGP) and growth in neonatal pigs. Circulating serum AGP, but not haptoglobin, was higher (P<0.001) in newborn runts than average-sized littermates. At 1 and 3 weeks, AGP and haptoglobin were similar among control and runt piglets. To determine the possible association between AGP and growth rate, blood was collected between the first and second day after birth in piglets from 10 average litters. Birthweight was positively correlated with growth rate through 21 days (linear regression correlation coefficient (CC), 0.43 (P<0.006); 0.299 (P<0.003) in males and females, respectively). Plasma AGP at birth was negatively correlated with growth (CC, -0.429 (P<0.006); -0.351 (P<0.01) in males and females, respectively). When AGP was calculated on a per kg birthweight basis, the CC with growth improved by 25 and 34% in males and females, respectively, compared with birthweight alone. Haptoglobin in blood was not correlated with growth. These data suggest that AGP at birth is reflective of growth conditions in utero or fetal maturation and may serve as an early predictive biomarker for pre-weaning growth rate.


Animal | 2016

α 1-acid glycoprotein inhibits lipogenesis in neonatal swine adipose tissue.

Timothy G. Ramsay; Le Ann Blomberg; Thomas J. Caperna

Serum α1-acid glycoprotein (AGP) is elevated during late gestation and at birth in the pig and rapidly declines postnatally. In contrast, the pig is born with minimal lipid stores in the adipose tissue, but rapidly accumulates lipid during the first week. The present study examined if AGP can affect adipose tissue metabolism in the neonatal pig. Isolated cell cultures or tissue explants were prepared from dorsal subcutaneous adipose tissue of preweaning piglets. Porcine AGP was used at concentrations of 0, 100, 1000 and 5000 ng/ml medium in 24 h incubations. AGP reduced the messenger RNA (mRNA) abundance of the lipogenic enzymes, malic enzyme (ME), fatty acid synthase and acetyl coA carboxylase by at least 40% (P<0.001). The activity of ME and citrate lyase were also reduced by AGP (P<0.05). Glucose oxidation was reduced by treatment with 5000 ng AGP/ml medium (P<0.05). The 14C-glucose incorporation into fatty acids was reduced by ~25% by AGP treatment for 24 h with 1000 ng AGP/ml medium (P<0.05). The decrease in glucose metabolism by AGP appears to function through an inhibition in insulin-mediated glucose oxidation and incorporation into fatty acids. This was supported by the analysis of the mRNA abundance for sterol regulatory element-binding protein (SREBP), carbohydrate regulatory element-binding protein (ChREBP) and insulin receptor substrate 1 (IRS1), which all demonstrated reductions of at least 23% in response to AGP treatment (P<0.05). These data demonstrate an overall suppression of lipogenesis due to AGP inhibition of lipogenic gene expression in vitro, which the metabolic data and SREBP, ChREBP and IRS1 gene expression analysis suggest is through an inhibition in insulin-mediated events. Second, these data suggest that AGP may contribute to limiting lipogenesis within adipose tissue during the perinatal period, as AGP levels are highest for any serum protein at birth.


BMC Genetics | 2014

Genome-wide candidate regions for selective sweeps revealed through massive parallel sequencing of DNA across ten turkey populations

Muhammad L Aslam; J.W.M. Bastiaansen; Hendrik-Jan Megens; R.P.M.A. Crooijmans; Fozia Nasreen; Le Ann Blomberg; Curtis P. Van Tassell; Tad S. Sonstegard; Steven G. Schroeder; M.A.M. Groenen; Julie A Long

BackgroundThe domestic turkey (Meleagris gallopavo) is an important agricultural species that is largely used as a meat-type bird. Characterizing genetic variation in populations of domesticated species and associating these variation patterns with the evolution, domestication, and selective breeding is critical for understanding the dynamics of genomic change in these species. Intense selective breeding and population bottlenecks are expected to leave signatures in the genome of domesticated species, such as unusually low nucleotide diversity or the presence of exceptionally extended haplotype homozygosity. These patterns of variation in selected populations are highly useful to not only understand the consequences of selective breeding and population dynamics, but also to provide insights into biological mechanisms that may affect physiological processes important to bring changes in phenotype of interest.ResultsWe observed 54 genomic regions in heritage and commercial turkey populations on 14 different chromosomes that showed statistically significant (P < 0.05) reduction in genomic variation indicating candidate selective sweeps. Areas with evidence of selective sweeps varied from 1.5 Mb to 13.8 Mb in length. Out of these 54 sweeps, 23 overlapped at least partially between two or more populations. Overlapping sweeps were found on 13 different chromosomes. The remaining 31 sweeps were population-specific and were observed on 12 different chromosomes, with 26 of these regions present only in commercial populations. Genes that are known to affect growth were enriched in the sweep regions.ConclusionThe turkey genome showed large sweep regions. The relatively high number of sweep regions in commercial turkey populations compared to heritage varieties and the enrichment of genes important to growth in these regions, suggest that these sweeps are the result of intense selection in these commercial lines, moving specific haplotypes towards fixation.


Molecular Reproduction and Development | 2017

Bovine trophectoderm cells induced from bovine fibroblasts with induced pluripotent stem cell reprogramming factors

Neil C. Talbot; Wendy O. Sparks; Caitlin E. Phillips; Alan D. Ealy; Anne M. Powell; Thomas J. Caperna; Wesley M. Garrett; David M. Donovan; Le Ann Blomberg

Thirteen independent induced bovine trophectroderm (iBT) cell lines were established by reprogramming bovine fetal liver‐derived fibroblasts after viral‐vector transduction with either six or eight factors, including POU5F1 (OCT4), KLF4, SOX2, MYC, NANOG, LIN28, SV40 large T antigen, and hTERT. Light‐ and electron‐microscopy analysis showed that the iBT cells had epithelial cell morphology typical of bovine trophectoderm cells. Reverse‐transcription‐PCR assays indicated that all of the cell lines expressed interferon‐tau (IFNT) at passages 1 or 2. At later passages (≥ passage 8), however, immunoblot and antiviral activity assays revealed that more than half of the iBT cell lines had stopped expressing IFNT. Messenger RNAs specific to trophectoderm differentiation and function were found in the iBT cell lines, and 2‐dimensional‐gel analysis for cellular proteins showed an expression pattern similar to that of trophectoderm cell lines derived from bovine blastocysts. Integration of some of the human reprogramming factors, including POU5F1, KLF4, SOX2, MYC, NANOG, and LIN28, were detected by PCR, but their transcription was mostly absent in the iBT cell lines. Gene expression assessment of endogenous bovine reprogramming factor orthologs revealed endogenous bLIN28 and bMYC transcripts in all; bSOX2 and bNANOG in none; and bKLF4 and bPOU5F1 in less than half of the iBT cell lines. These results demonstrate that bovine trophectoderm can be induced via reprogramming factor expression from bovine liver‐derived fibroblasts, although other fibroblast populations—e.g., derived from fetal thigh tissue—may produce similar results, albeit at lower frequencies.


Reproduction, Fertility and Development | 2017

127 ABUNDANCE OF mRNA FOR HISTONE VARIANTS, HISTONE, AND DNA MODIFICATION ENZYMES IN BOVINE IN VIVO OOCYTES AND PRE-IMPLANTATION EMBRYOS

L. Zhu; Z. Jiang; Jingyue Duan; H. Dong; X. Zheng; Le Ann Blomberg; David M. Donovan; Neil C. Talbot; J. Chen; X.C. Tian

During early embryogenesis, chromatin composition and structure undergo dramatic changes due to replacement of canonical histones by histone variants, post-translational modifications of histones, and changes in DNA methylation. These dynamics of chromatin play important roles in the regulation of gene expression and development of embryonic cells. Our goal here is to describe the above-mentioned changes using recently established transcriptome profiles of bovine in vivo-produced oocytes and pre-implantation embryos (Jiang et al. 2014 BMC Genomics, 15, 1). Ten multiparous Holstein cows were synchronized and superovulated. Artificial insemination was conducted at 12 and 24h post-standing heat using semen from bulls of proven fertility. In vivo-matured oocytes and 2- to 16-cell stage embryos were collected at 30h, and 2 to 4 days after oestrus by oviducal flushing. Early morulae, compact morulae, and blastocysts were collected by non-surgical uterine flushing on days 5, 6, and 7 after oestrus. Single-cell deep sequencing libraries were prepared from oocytes/embryos (2 samples/stage) using a SOLiDTM Total RNA-seq Kit (Thermo Fisher Scientific, Waltham, MA, USA) following the manufacturers instructions and sequenced on a 5500xl Genetic Analyzer. The reproducibility of the preparation and sequencing methods were indicated by high Pearson correlation efficiencies between the replicates. Sequencing reads were normalized to transcripts per million as final results after trimming and mapping of the reads. We found that 8, 8, 7, 13, 10, 2, and 2 out of the 14, 52, 22, 31, 23, 4, and 3 annotated histone variants, histone methyl-tranferases, histone demethylases, histone acetyl-tranferases, histone deacetylases, DNA methyl-transferases, and DNA demethylases, respectively, were highly abundant (mean transformed transcripts per kilobase million>50) in at least one of the pre-implantation development stages studied. Among histone variants with high mRNA abundance, H1FOO, H3F3A, and H3F3B were highly stored in oocytes, whereas other variants such as H2AFJ, H2AFV, H2AFX, H2AFY, H2AFZ, and CENPA were largely transcribed after the embryonic genome activation. H3F3A and H3F3B, however, were maintained at relatively high levels throughout pre-implantation development. Additionally, the mRNA for histone acetyl-transferases, TADA2A and TADA1; histone deacetylase, HDAC1 and HDAC3; histone methyl-transferases, EED and PRMT5; histone demethylase, KDM1A, were more abundant than others. It was also found that oocytes stored a large amount of DNA methyl-transferase, DNMT1, which degraded gradually after fertilization. Overall, in vivo-produced oocytes and early embryos contained more mRNA for histone-modifying enzymes than those for DNA modification. Taken together, our results suggest that although there are widely recognised and dramatic changes in embryonic DNA methylation through both active and passive mechanisms, the pre-implantation embryos may be more engaged in modifying histones than DNA.


Animal | 2012

Iron dextran treatment does not induce serum protein carbonyls in the newborn pig

Thomas J. Caperna; Amy E. Shannon; Le Ann Blomberg; Wesley M. Garrett; Timothy G. Ramsay

Oxidation of serum proteins can lead to carbonyl formation that alters their function and is often associated with stress-related diseases. As it is recommended that all pigs reared in modern production facilities be given supplemental iron at birth to prevent anemia, and metals can catalyze the carbonylation of proteins, the primary objective of this study was to determine whether standard iron dextran treatment was associated with enhanced serum protein oxidation in newborn piglets. Piglets were treated with 100 mg of iron dextran intramuscularly either on the day of birth, or on the third day after birth. Blood samples were collected from piglets 48 or 96 h after treatment and serum was harvested. For quantification, serum protein carbonyls were converted to hydrazones with dinitrophenyl hydrazine and analyzed spectrophotometrically. To identify and determine relative distribution of carbonylated proteins, serum protein carbonyls were derivatized with biotin hydrazide, separated by two-dimensional polyacrylamide gel electrophoresis, stained with avidin-fluorescein and identified by mass spectrometry. The standard iron dextran treatment was associated with no increase in total oxidized proteins if given either on the first or third day of life. In addition, with a few noted exceptions, the overall distribution and identification of oxidized proteins were similar between control and iron dextran-treated pigs. These results indicate that while iron dextran treatment is associated with a marked increase in circulating iron, it does not appear to specifically induce the oxidation of serum proteins.

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Thomas J. Caperna

United States Department of Agriculture

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Timothy G. Ramsay

United States Department of Agriculture

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Neil C. Talbot

United States Department of Agriculture

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Amy E. Shannon

United States Department of Agriculture

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Anne M. Powell

Agricultural Research Service

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David M. Donovan

United States Department of Agriculture

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Wesley M. Garrett

Agricultural Research Service

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Curtis P. Van Tassell

United States Department of Agriculture

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M. J. Stoll

United States Department of Agriculture

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Tad S. Sonstegard

Agricultural Research Service

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