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Peter J. Hansen - One of the best experts on this subject based on the ideXlab platform.
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146 CONSEQUENCES OF Embryonic EXPOSURE TO COLONY-STIMULATING FACTOR 2 ON TROPHOBLAST ELONGATION, INTERFERON TAU SECRETION, AND GENE EXPRESSION IN THE Embryonic Disc AND TROPHECTODERM
Reproduction Fertility and Development, 2011Co-Authors: B. Loureiro, M. G. Favoreto, Jeremy Block, Silvia F. Carambula, Kathleen A. Pennington, Alan D. Ealy, Peter J. HansenAbstract:This study was designed to evaluate possible mechanisms by which colony-stimulating factor 2 (CSF2) acts during Day 5 to 7 of development to improve Embryonic and fetal survival and decrease fetal losses. One hypothesis was that CSF2 causes increased secretion of interferon-τ (IFNT) by the trophoblast of elongated conceptuses. Colony-stimulating factor 2 might also affect elongation of the trophoblast and improve survival of the Embryonic Disc (ED) because of evidence that treatment of embryo with CSF2 caused differential regulation of a large number of genes involved in developmental processes and a decrease in apoptosis. Bovine embryos were produced in vitro in the presence or absence of 10 ng mL–1 of CSF2 beginning at Day 5 after fertilization. Embryos were transferred at Day 7 to lactating dairy cows using a timed embryo transfer protocol (n = 20 and 15 for control and CSF2, respectively). At Day 15, embryos were recovered and assessed for length, stage, and presence of an ED. The flushings recovered from the first 60 mL were stored for antiviral activity analysis. A total of 4 filamentous conceptuses were divided into 1) the ED and a small amount of adjacent trophoblast and 2) tissue containing trophoblast only. These tissues were analysed for gene expression using the Bos taurus Two Colour Microarray Chip from Agilent (Palo Alto, CA). Quantitative real time PCR analysis of 11 differentially expressed genes and 1 housekeeping gene (GAPDH) was performed to confirm the microarray results. In addition, quantitative real-time PCR of IFNT was performed in all recovered embryos (7 and 10 for control and CSF2, respectively). Results suggest that higher pregnancy rates at Day 30 represents increased Embryonic survival at Day 15 (35% for controls v. 66% for CSF2; P
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146 consequences of Embryonic exposure to colony stimulating factor 2 on trophoblast elongation interferon tau secretion and gene expression in the Embryonic Disc and trophectoderm
Reproduction Fertility and Development, 2011Co-Authors: B. Loureiro, M. G. Favoreto, Jeremy Block, Silvia F. Carambula, Kathleen A. Pennington, Alan D. Ealy, Peter J. HansenAbstract:This study was designed to evaluate possible mechanisms by which colony-stimulating factor 2 (CSF2) acts during Day 5 to 7 of development to improve Embryonic and fetal survival and decrease fetal losses. One hypothesis was that CSF2 causes increased secretion of interferon-τ (IFNT) by the trophoblast of elongated conceptuses. Colony-stimulating factor 2 might also affect elongation of the trophoblast and improve survival of the Embryonic Disc (ED) because of evidence that treatment of embryo with CSF2 caused differential regulation of a large number of genes involved in developmental processes and a decrease in apoptosis. Bovine embryos were produced in vitro in the presence or absence of 10 ng mL–1 of CSF2 beginning at Day 5 after fertilization. Embryos were transferred at Day 7 to lactating dairy cows using a timed embryo transfer protocol (n = 20 and 15 for control and CSF2, respectively). At Day 15, embryos were recovered and assessed for length, stage, and presence of an ED. The flushings recovered from the first 60 mL were stored for antiviral activity analysis. A total of 4 filamentous conceptuses were divided into 1) the ED and a small amount of adjacent trophoblast and 2) tissue containing trophoblast only. These tissues were analysed for gene expression using the Bos taurus Two Colour Microarray Chip from Agilent (Palo Alto, CA). Quantitative real time PCR analysis of 11 differentially expressed genes and 1 housekeeping gene (GAPDH) was performed to confirm the microarray results. In addition, quantitative real-time PCR of IFNT was performed in all recovered embryos (7 and 10 for control and CSF2, respectively). Results suggest that higher pregnancy rates at Day 30 represents increased Embryonic survival at Day 15 (35% for controls v. 66% for CSF2; P < 0.07), a greater capacity of the embryo to elongate (39 mm for controls v. 62 mm for CSF2) and secrete IFNT (mean IFNT IU = 349 074 for control and 1 883 060 for CSF2; P < 0.07) at Day 15. In addition, the amount of IFNT mRNA was 22 times higher (P = 0.06) in the CSF2-treated embryos. There was no difference in the presence of an ED between groups. Analysis of gene expression between the ED and trophoblast in filamentous embryos indicated no difference in transcription among this subset of embryos. However, more than 500 genes were identified as being preferentially expressed in the ED. These genes represent candidate markers for ED that should prove useful for studying the differentiation of the bovine conceptus through the periattachment period. In conclusion, results support the idea that the increased survival of embryos exposed to CSF2 from Day 5 to 7 of development is the result of increased Embryonic survival before Day 15 and a greater capacity of the embryo to elongate and secrete IFNT at Day 15. The reduction in Embryonic and fetal loss after Day 30 caused by CSF2 is probably not a direct reflection of altered gene expression at Day 15. USDA Grant 2009-65203-05732 and the Southeast Milk Dairy Checkoff Program. BL was supported by a CAPES/Fulbright fellowship.
Christoph Viebahn - One of the best experts on this subject based on the ideXlab platform.
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pitx2 and nodal as conserved early markers of the anterior posterior axis in the rabbit embryo
Annals of Anatomy-anatomischer Anzeiger, 2018Co-Authors: Ruben Ploger, Christoph ViebahnAbstract:Abstract Attaining molecular and morphological axial polarity during gastrulation is a fundamental early requirement for normal development of the embryo. In mammals, the first morphological sign of the anterior–posterior axis appears anteriorly in the form of the anterior marginal crescent (or anterior visceral endoderm) while in the avian the first such sign is the Koller’s sickle at the posterior pole of the Embryonic Disc. Despite this inverse mode of axis formation many genes and molecular pathways involved in various steps of this process seem to be evolutionarily conserved amongst amniotes, the nodal gene being a well-known example with its functional involvement prior and during gastrulation. The pitx2 gene, however, is a new candidate described in the chick as an early marker for anterior–posterior polarity and as a regulator of axis formation including twinning. To find out whether pitx2 has retained its inductive and early marker function during the evolution of mammals this study analyses pitx2 and nodal expression at parallel stages during formation of the anterior–posterior polarity in the early rabbit embryo using whole-mount in situ hybridization and serial light-microscopical sections. At a late pre-gastrulation stage a localized reduction of nodal expression presages the position of the anterior pole of the Embryonic Disc and thus serves as the earliest molecular marker of anterior–posterior polarity known so far. Pitx2 is expressed in a polarized manner in the anterior marginal crescent and in the posterior half of the Embryonic Disc during further development. In the anterior segment of the posterior pitx2 expression domain, the anterior streak domain (ASD) is defined by nodal expression as a hypothetical progenitor region of the anterior half of the primitive streak. The expression patterns of both genes thus serve as signs of a conserved involvement in early axis formation in amniotes and, possibly, in twinning in mammals as well.
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SEM reveals filopodia-like protrusions in the early Embryonic Disc of the chick
2017Co-Authors: L. Surchev, Christoph Viebahn, Hans-georg Sydow, Nikoloz TsikoliaAbstract:Embryonic development depends on an enormous amount of signaling events between a continuously growing number of cells. According to the classical view, signal transduction is based on either simple diffusion, transcytosis or migrating cells. Very recently the existence of filopodia-like protrusions has been proposed as a novel mechanism of long-range intercellular signaling during chick somite and limb development. Analogous thinner structures called cytonemes play a role in the development of Drosophila melanogaster , as well. The present study gives new insight into this problem by adding important information using scanning electron microscopy (SEM). Early chick embryos between stages 4 and 5 (representing late gastrulation and early neurulation) were dissected, fixed and critical-point dried and were then fractured in several steps, each step followed by platinum/palladium coating and analysis by SEM. Fracturing was carried out sequentially in the same specimens at different anterior-posterior levels anterior to the primitive node and the ultrastructure of the Embryonic Disc was analysed with special emphasis on cellular processes. We found cell protrusions of different shape and size in all three layers (mesoderm, epiblast, and hypoblast) of the early Embryonic Discs. They were most abundant and prominent between the mesodermal cells but also seen in other layers as well as between layers. These protrusions can be roughly classified into cytoplasmic bridges with mid-bodies, cilia-like protrusions, as well as filopodia-like protrusions. As previously shown, cilia of different length are present on the apical surface of epiblast and hypoblast cells. Similarly a plethora of variable protrusions with or without mid-bodies are seen between neighbouring cells within Embryonic layers. Unexpectedly, we found that cells of the mesodermal layer form a dense net of filopodia-like contacts with the epithelial cells of the epiblast. Our data prove that filopodia-like protrusions are present at earlier developmental stages than previously shown. Their abundance indicates a major role in the intercellular communication during early chick Embryonic development and may provide a structural basis of cell-to-cell communication during gastrulation and early neurulation in the chick.
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rho kinase activity controls directional cell movements during primitive streak formation in the rabbit embryo
Development, 2015Co-Authors: Viktoria Stankova, Nikoloz Tsikolia, Christoph ViebahnAbstract:During animal gastrulation, the specification of the Embryonic axes is accompanied by epithelio-mesenchymal transition (EMT), the first major change in cell shape after fertilization. EMT takes place in disparate topographical arrangements, such as the circular blastopore of amphibians, the straight primitive streak of birds and mammals or in intermediate gastrulation forms of other amniotes such as reptiles. Planar cell movements are prime candidates to arrange specific modes of gastrulation but there is no consensus view on their role in different vertebrate classes. Here, we test the impact of interfering with Rho kinase-mediated cell movements on gastrulation topography in blastocysts of the rabbit, which has a flat Embryonic Disc typical for most mammals. Time-lapse video microscopy, electron microscopy, gene expression and morphometric analyses of the effect of inhibiting ROCK activity showed – besides normal specification of the organizer region – a dose-dependent disruption of primitive streak formation; this disruption resulted in circular, arc-shaped or intermediate forms, reminiscent of those found in amphibians, fishes and reptiles. Our results reveal a crucial role of ROCK-controlled directional cell movements during rabbit primitive streak formation and highlight the possibility that temporal and spatial modulation of cell movements were instrumental for the evolution of gastrulation forms.
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BMP signals and the transcriptional repressor BLIMP1 during germline segregation in the mammalian embryo
Development Genes and Evolution, 2011Co-Authors: Clas Hopf, Christoph Viebahn, Bernd PüschelAbstract:Molecular factors and tissue compartments involved in the foundation of the mammalian germline have been mainly described in the mouse so far. To find mechanisms applicable to mammals in general, we analyzed temporal and spatial expression patterns of the transcriptional repressor BLIMP1 (also known as PRDM1 ) and the signaling molecules BMP2 and BMP4 in perigastrulation and early neurulation embryos of the rabbit using whole-mount in situ hybridization and high-resolution light microscopy. Both BMP2 and BMP4 are expressed in annular domains at the boundary of the Embryonic Disc, which—in contrast to the situation in the mouse—partly belong to intraEmbryonic tissues. While BMP2 expression begins at (pregastrulation) stage 1 in the hypoblast, BMP4 expression commences—distinctly delayed compared to the mouse—diffusely at (pregastrulation) stage 2; from stage 3 onwards, BMP4 is expressed peripherally in hypoblast and epiblast and in the mesoderm at the posterior pole of the Embryonic Disc. BLIMP1 expression begins throughout the hypoblast at stage 1 and emerges in single primordial germ cell (PGC) precursors in the posterior epiblast at stage 2 and then in single mesoderm cells at positions identical to those identified by PGC-specific antibodies. These expression patterns suggest that function and chronology of factors involved in germline segregation are similar in mouse and rabbit, but higher temporal and spatial resolution offered by the rabbit demonstrates a variable role of bone morphogenetic proteins and makes “blimping” a candidate case for lateral inhibition without the need for an allantoic germ cell niche.
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germ layer differentiation during early hindgut and cloaca formation in rabbit and pig embryos
Journal of Anatomy, 2010Co-Authors: Romia Hassoun, Christoph Viebahn, P Schwartz, Detlef Rath, Jorg MannerAbstract:Relative to recent advances in understanding molecular requirements for endoderm differentiation, the dynamics of germ layer morphology and the topographical distribution of molecular factors involved in endoderm formation at the caudal pole of the Embryonic Disc are still poorly defined. To Discover common principles of mammalian germ layer development, pig and rabbit embryos at late gastrulation and early neurulation stages were analysed as species with a human-like Embryonic Disc morphology, using correlative light and electron microscopy. Close intercellular contact but no direct structural evidence of endoderm formation such as mesenchymal–epithelial transition between posterior primitive streak mesoderm and the emerging posterior endoderm were found. However, a two-step process closely related to posterior germ layer differentiation emerged for the formation of the cloacal membrane: (i) a continuous mesoderm layer and numerous patches of electron-dense flocculent extracellular matrix mark the prospective region of cloacal membrane formation; and (ii) mesoderm cells and all extracellular matrix including the basement membrane are lost locally and close intercellular contact between the endoderm and ectoderm is established. The latter process involves single cells at first and then gradually spreads to form a longitudinally oriented seam-like cloacal membrane. These gradual changes were found from gastrulation to early somite stages in the pig, whereas they were found from early somite to mid-somite stages in the rabbit; in both species cloacal membrane formation is complete prior to secondary neurulation. The results highlight the structural requirements for endoderm formation during development of the hindgut and suggest new mechanisms for the pathogenesis of common urogenital and anorectal malformations.
Randall S. Prather - One of the best experts on this subject based on the ideXlab platform.
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transcriptional profiling of day 12 porcine Embryonic Disc and trophectoderm samples using ultra deep sequencing technologies
Molecular Reproduction and Development, 2010Co-Authors: Clay S Isom, William G. Spollen, Sean M. Blake, Bethany K. Bauer, Gordon K. Springer, Randall S. PratherAbstract:cDNA derived from trophectoderm (TE) and Embryonic Disc (ED) of a single day 12 porcine embryo was subjected to next-generation sequencing using the Illumina platform. The short sequencing reads from triplicate sequencing runs were aligned to a custom database designed to represent the known porcine transcriptome. As expected, genes involved in epithelial cell function and steroid biosynthesis were more abundant in cells from the TE; genes involved in maintenance of pluripotency and chromatin remodeling were more highly expressed in cells from the ED. Quantitative real-time PCR was used to confirm the validity of the approach. We conclude that gene expression profiles of even extremely small samples (
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Transcriptional profiling of day 12 porcine Embryonic Disc and trophectoderm samples using ultra-deep sequencing technologies.
Molecular reproduction and development, 2010Co-Authors: S. Clay Isom, William G. Spollen, Sean M. Blake, Bethany K. Bauer, Gordon K. Springer, Randall S. PratherAbstract:cDNA derived from trophectoderm (TE) and Embryonic Disc (ED) of a single day 12 porcine embryo was subjected to next-generation sequencing using the Illumina platform. The short sequencing reads from triplicate sequencing runs were aligned to a custom database designed to represent the known porcine transcriptome. As expected, genes involved in epithelial cell function and steroid biosynthesis were more abundant in cells from the TE; genes involved in maintenance of pluripotency and chromatin remodeling were more highly expressed in cells from the ED. Quantitative real-time PCR was used to confirm the validity of the approach. We conclude that gene expression profiles of even extremely small samples (
Poul Hyttel - One of the best experts on this subject based on the ideXlab platform.
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Breaking down pluripotency in the porcine embryo reveals both a premature and reticent stem cell state in the inner cell mass and unique expression profiles of the naive and primed stem cell states.
Stem cells and development, 2014Co-Authors: Vanessa J. Hall, Poul HyttelAbstract:To date, it has been difficult to establish bona fide porcine Embryonic stem cells (pESC) and stable induced pluripotent stem cells. Reasons for this remain unclear, but they may depend on inappropriate culture conditions. This study reports the most insights to date on genes expressed in the pluripotent cells of the porcine embryo, namely the inner cell mass (ICM), the trophectoderm-covered epiblast (EPI), and the Embryonic Disc epiblast (ED). Specifically, we reveal that the early porcine ICM represents a premature state of pluripotency due to lack of translation of key pluripotent proteins, and the late ICM enters a transient, reticent pluripotent state which lacks expression of most genes associated with pluripotency. We describe a unique expression profile of the porcine EPI, reflecting the naive stem cell state, including expression of OCT4, NANOG, CRIPTO, and SSEA-1; weak expression of NrOB1 and REX1; but very limited expression of genes in classical pathways involved in regulating pluripotency. Th...
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From zygote to implantation: morphological and molecular dynamics during embryo development in the pig.
Reproduction in Domestic Animals, 2009Co-Authors: O Oestrup, Vanessa J. Hall, Stoyan Petkov, Xa Wolf, S Hyldig, Poul HyttelAbstract:The increasing focus on the pig as a biomedical model calls for studies which investigate morphological and molecular mechanisms during initial Embryonic development in this species. In the pig, the paternal genome is actively demethylated in the zygote, whereas the maternal genome remains methylated. The major genome activation occurs at the four-cell stage, when prominent ribosome-synthesizing nucleoli develop in the blastomeres, allowing for trophectoderm and inner cell mass (ICM) differentiation. Unlike in mice, the pluripotency gene OCT4 is initially expressed in both compartments. The ICM differentiates into epiblast and hypoblast approximately at the time of hatching from the zona pellucida, and subsequently the loss of the Rauber's layer results in an uncovered epiblast establishing the Embryonic Disc again in contrast to mice. This particular and protracted ICM/epiblast biology may contribute to the lack of success in culturing porcine Embryonic stem cells. The Embryonic Disc subsequently becomes polarized by a posterior thickening, which includes ingression of the first extra-Embryonic mesoderm. Thereafter, the primitive streak forms and gastrulation results in formation of the somatic germ layers and germline, i.e. the primordial germ cells. The latter remain pluripotent for a period and may be isolated and cultured as Embryonic germ cells in vitro.
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Bovine embryos contain a higher proportion of polyploid cells in the trophectoderm than in the Embryonic Disc.
Molecular reproduction and development, 2002Co-Authors: D. Viuff, Anne Palsgaard, Lee F. Rickords, Lartey G. Lawson, Torben Greve, Mette Schmidt, Birthe Avery, Poul Hyttel, Preben D. ThomsenAbstract:The frequency of polyploid cells in the Embryonic Disc (ED) and in the trophectoderm (TE) was assessed in 50 in vitro produced bovine embryos fixed at days 7–8 post insemination (pi) and in 20 in vitro produced embryos that were transferred to uteri of recipients at day 7 and then recovered and fixed at day 12 pi. Separation of TE and ED cells was obtained by microdissection and the frequency of polyploid cells was determined by interphase cytogenetic analysis using fluorescence in situ hybridization (FISH) with chromosome 6- and chromosome 7-specific probes. The results show that 96% of day 7 embryos contain polyploid cells in the TE, whereas only 58% contain polyploid cells in the ED. In day 12 embryos 85% of TE and 40% of ED preparations contain polyploid cells. Statistical analysis revealed that the frequency of polyploid cells was significantly higher in the TE than in the ED in embryos containing less than 25% polyploid cells (n = 65). The few embryos (n = 5), which contained more than 25% polyploid cells, did not show this difference. Further, it was revealed that the level of polyploidy on day 7–8 was significantly higher than on day 12, both in the TE (two-fold) and in the ED (seven-fold). Mol. Reprod. Dev. 62:483–488, 2002. © 2002 Wiley-Liss, Inc.
B. Loureiro - One of the best experts on this subject based on the ideXlab platform.
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146 CONSEQUENCES OF Embryonic EXPOSURE TO COLONY-STIMULATING FACTOR 2 ON TROPHOBLAST ELONGATION, INTERFERON TAU SECRETION, AND GENE EXPRESSION IN THE Embryonic Disc AND TROPHECTODERM
Reproduction Fertility and Development, 2011Co-Authors: B. Loureiro, M. G. Favoreto, Jeremy Block, Silvia F. Carambula, Kathleen A. Pennington, Alan D. Ealy, Peter J. HansenAbstract:This study was designed to evaluate possible mechanisms by which colony-stimulating factor 2 (CSF2) acts during Day 5 to 7 of development to improve Embryonic and fetal survival and decrease fetal losses. One hypothesis was that CSF2 causes increased secretion of interferon-τ (IFNT) by the trophoblast of elongated conceptuses. Colony-stimulating factor 2 might also affect elongation of the trophoblast and improve survival of the Embryonic Disc (ED) because of evidence that treatment of embryo with CSF2 caused differential regulation of a large number of genes involved in developmental processes and a decrease in apoptosis. Bovine embryos were produced in vitro in the presence or absence of 10 ng mL–1 of CSF2 beginning at Day 5 after fertilization. Embryos were transferred at Day 7 to lactating dairy cows using a timed embryo transfer protocol (n = 20 and 15 for control and CSF2, respectively). At Day 15, embryos were recovered and assessed for length, stage, and presence of an ED. The flushings recovered from the first 60 mL were stored for antiviral activity analysis. A total of 4 filamentous conceptuses were divided into 1) the ED and a small amount of adjacent trophoblast and 2) tissue containing trophoblast only. These tissues were analysed for gene expression using the Bos taurus Two Colour Microarray Chip from Agilent (Palo Alto, CA). Quantitative real time PCR analysis of 11 differentially expressed genes and 1 housekeeping gene (GAPDH) was performed to confirm the microarray results. In addition, quantitative real-time PCR of IFNT was performed in all recovered embryos (7 and 10 for control and CSF2, respectively). Results suggest that higher pregnancy rates at Day 30 represents increased Embryonic survival at Day 15 (35% for controls v. 66% for CSF2; P
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146 consequences of Embryonic exposure to colony stimulating factor 2 on trophoblast elongation interferon tau secretion and gene expression in the Embryonic Disc and trophectoderm
Reproduction Fertility and Development, 2011Co-Authors: B. Loureiro, M. G. Favoreto, Jeremy Block, Silvia F. Carambula, Kathleen A. Pennington, Alan D. Ealy, Peter J. HansenAbstract:This study was designed to evaluate possible mechanisms by which colony-stimulating factor 2 (CSF2) acts during Day 5 to 7 of development to improve Embryonic and fetal survival and decrease fetal losses. One hypothesis was that CSF2 causes increased secretion of interferon-τ (IFNT) by the trophoblast of elongated conceptuses. Colony-stimulating factor 2 might also affect elongation of the trophoblast and improve survival of the Embryonic Disc (ED) because of evidence that treatment of embryo with CSF2 caused differential regulation of a large number of genes involved in developmental processes and a decrease in apoptosis. Bovine embryos were produced in vitro in the presence or absence of 10 ng mL–1 of CSF2 beginning at Day 5 after fertilization. Embryos were transferred at Day 7 to lactating dairy cows using a timed embryo transfer protocol (n = 20 and 15 for control and CSF2, respectively). At Day 15, embryos were recovered and assessed for length, stage, and presence of an ED. The flushings recovered from the first 60 mL were stored for antiviral activity analysis. A total of 4 filamentous conceptuses were divided into 1) the ED and a small amount of adjacent trophoblast and 2) tissue containing trophoblast only. These tissues were analysed for gene expression using the Bos taurus Two Colour Microarray Chip from Agilent (Palo Alto, CA). Quantitative real time PCR analysis of 11 differentially expressed genes and 1 housekeeping gene (GAPDH) was performed to confirm the microarray results. In addition, quantitative real-time PCR of IFNT was performed in all recovered embryos (7 and 10 for control and CSF2, respectively). Results suggest that higher pregnancy rates at Day 30 represents increased Embryonic survival at Day 15 (35% for controls v. 66% for CSF2; P < 0.07), a greater capacity of the embryo to elongate (39 mm for controls v. 62 mm for CSF2) and secrete IFNT (mean IFNT IU = 349 074 for control and 1 883 060 for CSF2; P < 0.07) at Day 15. In addition, the amount of IFNT mRNA was 22 times higher (P = 0.06) in the CSF2-treated embryos. There was no difference in the presence of an ED between groups. Analysis of gene expression between the ED and trophoblast in filamentous embryos indicated no difference in transcription among this subset of embryos. However, more than 500 genes were identified as being preferentially expressed in the ED. These genes represent candidate markers for ED that should prove useful for studying the differentiation of the bovine conceptus through the periattachment period. In conclusion, results support the idea that the increased survival of embryos exposed to CSF2 from Day 5 to 7 of development is the result of increased Embryonic survival before Day 15 and a greater capacity of the embryo to elongate and secrete IFNT at Day 15. The reduction in Embryonic and fetal loss after Day 30 caused by CSF2 is probably not a direct reflection of altered gene expression at Day 15. USDA Grant 2009-65203-05732 and the Southeast Milk Dairy Checkoff Program. BL was supported by a CAPES/Fulbright fellowship.