Talk:Bovine Development

Animation http://www.ansi.okstate.edu/resource-room/reprod/all/animations/pregnancy_cow.htm

2010

A small set of extra-embryonic genes defines a new landmark for bovine embryo staging

Reproduction. 2010 Oct 6. [Epub ahead of print]

Degrelle SA, Le Cao KA, Heyman Y, Everts RE, Campion E, Richard C, Ducroix-Crepy C, Tian C, Lewin H, Renard JP, Robert-Granié C, Hue I.

S Degrelle, UMR Biologie du Developpement et Reproduction, INRA, JOUY EN JOSAS, 78350, France. Abstract Axis specification in the mouse is determined by a sequence of reciprocal interactions between embryonic and extra-embryonic tissues so that a few extra-embryonic genes appear as 'patterning' the embryo. Considering these interactions as essential but lacking in most mammals the genetically driven approaches used in the mouse and the corresponding patterning mutants, we examined whether a molecular signature originating from extra-embryonic tissues could relate to the developmental stage of the embryo proper and predict it. To this aim we profiled bovine extra-embryonic tissues at peri-implantation stages, when gastrulation and early neurulation occur, and analysed the subsequent expression profiles through the use of predictive methods as previously reported for tumour classification. A set of 6 genes (CALM1, CPA3, CITED1, DLD, HNRNPDL, TGFB3), half of which had not been previously associated to any extra-embryonic feature, appeared significantly discriminative and mainly dependent on embryonic tissues for its faithful expression. The predictive value of this set of genes for gastrulation and early neurulation stages, as assessed on naïve samples, was remarkably high (93%). In silico connected to the bovine orthologues of the mouse patterning genes, this gene set is proposed as new trait for embryo staging. As such, this will allow saving the bovine embryo proper for molecular or cellular studies. To us, it offers as well new perspectives for developmental phenotyping and modelling of embryonic/extra-embryonic co-differentiation.

PMID: 20926692

Modulation of the maternal immune system by the pre-implantation embryo

BMC Genomics. 2010 Aug 13;11:474.

Walker CG, Meier S, Littlejohn MD, Lehnert K, Roche JR, Mitchell MD.

DairyNZ Ltd,, Hamilton, New Zealand. Caroline.Walker@dairynz.co.nz Abstract BACKGROUND: A large proportion of pregnancy losses occur during the pre-implantation period, when the developing embryo is elongating rapidly and signalling its presence to the maternal system. The molecular mechanisms that prevent luteolysis and support embryo survival within the maternal environment are not well understood. To gain a more complete picture of these molecular events, genome-wide transcriptional profiles of reproductive day 17 endometrial tissue were determined in pregnant and cyclic Holstein-Friesian dairy cattle.

RESULTS: Microarray analyses revealed 1,839 and 1,189 differentially expressed transcripts between pregnant and cyclic animals (with > or = 1.5 fold change in expression; P-value < 0.05, MTC Benjamini-Hochberg) in caruncular and intercaruncular endometrium respectively. Gene ontology and biological pathway analysis of differentially expressed genes revealed enrichment for genes involved in interferon signalling and modulation of the immune response in pregnant animals.

CONCLUSION: The maternal immune system actively surveys the uterine environment during early pregnancy. The embryo modulates this response inducing the expression of endometrial molecules that suppress the immune response and promote maternal tolerance to the embryo. During this period of local immune suppression, genes of the innate immune response (in particular, antimicrobial genes) may function to protect the uterus against infection.

PMID: 20707927

http://www.biolreprod.org/content/79/6/1219.full

"The number of morphologically healthy oocytes in the ovaries of mammals is remarkably variable at birth, ranging, for example, from 350 000 to 1 100 000 in humans [1–3] and approximately 14 000 to 250 000 in cattle [4, 5]"

2006

Dynamics of global transcriptome in bovine matured oocytes and preimplantation embryos

Proc Natl Acad Sci U S A. 2006 Dec 12;103(50):18905-10. Epub 2006 Dec 1.

Misirlioglu M, Page GP, Sagirkaya H, Kaya A, Parrish JJ, First NL, Memili E.

Department of Animal and Dairy Sciences, Mississippi State University, Mississippi State, MS 39762, USA.

Abstract Global activation of the embryonic genome is the most critical event in early mammalian development. After fertilization, a rich supply of maternal proteins and RNAs support development whereas a number of zygotic and embryonic genes are expressed in a stage-specific manner leading to embryonic genome activation (EGA). However, the identities of embryonic genes expressed and the mechanism(s) of EGA are poorly defined in the bovine. Using the Affymetrix bovine-specific DNA microarray as the biggest available array at present, we analyzed gene expression at two key stages of bovine development, matured oocytes (MII) and 8-cell-stage embryos, constituting the ultimate reservoir for life and a stage during which EGA takes place, respectively. Key genes in regulation of transcription, chromatin-structure cell adhesion, and signal transduction were up-regulated at the 8-cell stage as compared with 8-cell embryos treated with alpha-amanitin and MII. Genes controlling DNA methylation and metabolism were up-regulated in MII. These changes in gene expression, related to transcriptional machinery, chromatin structure, and the other cellular functions occurring during several cleavage stages, are expected to result in a unique chromatin structure capable of maintaining totipotency during embryogenesis and leading to differentiation during postimplantation development. Dramatic reprogramming of gene expression at the onset of development also has implications for cell plasticity in somatic cell nuclear transfer, genomic imprinting, and cancer.

PMID: 17142320

http://www.ncbi.nlm.nih.gov/pubmed/17142320

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1748150