Pablo J. Ross

Pablo Ross

Position Title
Associate Professor

  • Department of Animal Science, College of Agricultural and Environmental Sciences
2239 Meyer Hall, Davis, CA 95616

Research Interests


Our laboratory specializes in animal reproduction with emphasis on gametes, early embryos and embryonic stem cells. The focus within this area is on epigenetic mechanisms that regulate the acquisition of pluripotency and the impact of assisted reproductive technologies (ART) on these mechanisms. We use a comparative approach which includes different species (cattle, sheep, pig, horses, mice, monkeys, humans), different models of ART (IVF, ICSI, SCNT) and varied models of nuclear reprogramming (early embryo development, cloning, induced pluripotency, and embryonic stem cells). Also, we make extensive use of next generation sequencing approaches to determine transcriptome and epigenetic profiles. We are currently generating epigenetic data from multiple tissues from large animals to aid in efforts to annotate the functional regions of animla genomes as part of  FAANG. For mechanistic studies we routinely microinject siRNA and CRISPR/Cas9 into oocytes and zygotes to then study consequences of gene knockdown/knockout on embryonic development. We further use these techniques to develop genetically engineered large animal models and blastocyst complementation approaches. 

Transcriptome studies in oocytes and preimplantation embryos

Transcriptome analysis of oocytes and preimplantation embryos provide important insight into the mechanisms of early development and alterations to normal development induced by Assisted Reproductive Technologies (ART), such as IVF and SCNT. We have generated important databasets on transcript expression of oocytes and embryos of different species and under different conditions. We developed state-of-the-art RNA-Seq methodologies to analyze the transcriptome of single oocytes and preimplantation embryos. The application of this methodology has provided a comprehensive insight into the gene expression program during the first differentiation event in early embryonic development, as well as clues as to the establishment and maintenance of pluripotent cells.

Pluripotent stem cells in regenerative medicine applications

Pluripotent stem cells, such as embryonic stem cells (ESC) and induced pluripotent stem cells (iPSC) represent a great promise for regenerative medicine. We work on different aspects of derivation and characterization of large animal stem cells. We are interested in developing large animal models for regenerative medicine including the possibility of using blastocyst complementation to generate human tissues/organs in animals. Along this line, we have established new ESC culture conditions that allow inter-specific chimera formation and determined the chimeric potential of different types of human iPSC in porcine and ovine embryos.

In Vitro Breeding 

Genetic improvement has contributed to a substantial progress in livestock production efficiency. However, it is limited by the generational interval, which is quite long for some mammalian species. Recent advancements such as the in vitro generation of gametes from murine embryonic stem cells[1, 2] and the derivation of embryonic stem cells (ESCs) from bovine embryos[3], allow us to propose new strategies to accelerate genetic improvement. By applying genomic selection on ESCs and subjecting them to germ cell differentiation and in vitro fertilization, the generational interval could be reduced to only a few months, thereby increasing selection intensity and accelerating genetic improvement. We are working on developing methods for the in vitro differentiation of gametes from ESCs to allow IVB approaches.

Epigenetic remodeling during preimplantation development

Embryo epigenetics research is focused on the remodeling of tri-methylation at lysine 27 of histone H3 (H3K27me3). H3K27me3 is well characterized as a negative regulator of transcription, is considered rather stable, and has significant developmental ramifications in a number of species. During our initial analysis of H3K27me3 reprogramming in preimplantation bovine embryos, we demonstrated that this epigenetic modification is dynamically remodeled, with a strong initial decrease in its abundance near the time of embryonic genome activation (8-cell stage in cattle). The decrease in H3K27me3 levels indicates a potential role for histone demethylases during the initial reprogramming of the embryonic genome. We have now established that among known H3K27me3 demethylases, only JMJD3 is expressed in oocytes and early embryos. Moreover, knockdown of JMJD3 by siRNA injection in bovine embryos resulted in abrogation of H3K27me3 reduction and impaired development to the blastocyst stage, indicating that JMJD3 has an important role during early embryonic development. Using the same siRNA knock-down model, we are expanding our research to study mechanisms of remodeling for other epigenetic marks.

Grad Group Affiliations

  • Animal Biology Graduate Group
  • Integrative Genetics and Genomics

Honors and Awards

  • 2000 Medal of honor to the best average qualification. College of Veterinary Science, La Plata National University, Argentina
  • 2000 Dr. Joaquin V. Gonzalez Distinction. La Plata National University, Argentina
  • 2007 Jacob A. Hoefer Endowed Fellowship in Animal Science, Michigan State University
  • 2016 Young Investigator Award, International Society of Transgenic Technologies
  • 2017 Early Career Achievement Award, International Embryo Transfer Society
  • 2017-2022 UC Davis Chancellor’s Fellow

    Professional Societies

    • International Embryo Transfer Society
    • American Association for the Advancement of Science
    • International Society for Transgenic Technologies
    • Society for the Study of Reproduction


    • 2007 Ph.D. Animal Science Michigan State University
    • 2002 M.Sc. Animal Science Mar del Plata National University
    • 1999 D.V.M. La Plata National University


    Bogliotti YS, Wu J, Vilarino M, Soto DA, Izpisua Belmonte JC, Ross PJ. Efficient derivation of stable primed pluripotent embryonic stem cells from bovine blastocysts. PNAS 2018

    Chung N, Bogliotti Y, Ding W, Vilarino M, Takahashi K, Chitwood J, Schultz R, Ross PJ. Active H3K27me3 demethylation by KDM6B is required for normal development of bovine preimplantation embryos. Epigenetics. 2018

    Vilarino M, Rashid ST, Suchy FP, McNabb BR, van der Meulen T, Fine EJ, Ahsan S, Mursaliyev N, Sebastiano V, Diab SS, Huising MO, Nakauchi H, Ross PJ. CRISPR/Cas9 microinjection in oocytes disables pancreas development in sheep. Sci Rep. 2017 Dec 12;7(1):17472

    Wu J, Platero-Luengo A, Sakurai M, Sugawara A, Gil MA, Yamauchi T, Suzuki K, Bogliotti YS, Cuello C, Morales Valencia M, Okumura D, Luo J, Vilariño M, Parrilla I, Soto DA, Martinez CA, Hishida T, Sánchez-Bautista S, Martinez-Martinez ML, Wang H, Nohalez A, Aizawa E, Martinez-Redondo P, Ocampo A, Reddy P, Roca J, Maga EA, Esteban CR, Berggren WT, Nuñez Delicado E, Lajara J, Guillen I, Guillen P, Campistol JM, Martinez EA, Ross PJ, Izpisua Belmonte JC. Interspecies Chimerism with Mammalian Pluripotent Stem Cells. Cell. 2017 Jan 26;168(3):473-486.

    Ferré LB, Bogliotti Y, Chitwood JL, Fresno C, Ortega HH, Kjelland ME, Ross PJ. Effect of spermatozoa motility hyperactivation factors and gamete coincubation duration on in vitro bovine embryo development using flow cytometrically sorted spermatozoa. Reproduction, fertility, and development. 2017; 29(4):805-814.

    Wu J, Vilarino M, Suzuki K, Okamura D, Bogliotti YS, Park I, Rowe J, McNabb B, Ross PJ, Belmonte JCI. CRISPR-Cas9 mediated one-step disabling of pancreatogenesis in pigs. Sci Rep. 2017 Sep 5;7(1):10487.

    Scott EY, Mansour T, Bellone RR, Brown CT, Mienaltowski MJ, Penedo MC, Ross PJ, Valberg SJ, Murray JD, Finno CJ. Identification of long non-coding RNA in the horse transcriptome. BMC genomics. 2017; 18(1):511.

    Reyes JM, Silva E, Chitwood JL, Schoolcraft WB, Krisher RL, Ross PJ. Differing molecular response of young and advanced maternal age human oocytes to IVM. Hum Reprod. 2017;32(11):2199-2208.

    Bogliotti YS, Vilarino M. and Ross PJ. Laser-assisted Cytoplasmic Microinjection in Livestock Zygotes. JoVE 2016 Issue 116; doi: 10.3791/54465

    Wu J, Okamura D, Li M, Suzuki K, Luo K, Ma L, He L, Li Z, Benner C, Tamura I, Krause MN, Nery J, Du T, Zhang Z, Hishida T, Takahashi Y, Aizawa E, Kim NY, Lajara G, Guillen P, Campistol J, Rodríguez Esteban C, Ross PJ, Saghatelian A, Ren B, Ecker J, Izpisua Belmonte JC. A spatially defined pluripotent state confers interspecies chimera competency. Nature 2015; 521: 316–321

    Reyes JM, Chitwood JL, and Ross PJ. RNA-seq profiling of bovine oocyte transcript abundance and its modulation by cytoplasmic polyadenylation. Mol Reprod Dev 2015; 82(2):103-14

    Schroeder DI, Jayashankar K, Douglas KC, Thirkill TL, York D, Dickinson PJ, Williams LE, Samollow PB, Ross PJ, Bannasch DL, Douglas GC, LaSalle JM. Early Developmental and Evolutionary Origins of Gene Body DNA Methylation Patterns in Mammalian Placentas. PLoS Genet. 2015;11(8):e1005442

    Bakhtari A and Ross PJ. DPPA3 prevents cytosine hydroxymethylation of the maternal pronucleus and is required for normal development in bovine embryos. Epigenetics 2014; 9(9):1271-9.

    Cannovas S, Cibelli J, Ross PJ. Jumonji domain-containing protein 3 regulates histone 3 lysine 27 methylation during bovine preimplantation development. Proceedings of the National Academy of Sciences of the USA (PNAS) 2012; 109(7):2400-5.

    Ross PJ and Cibelli JB. Bovine somatic cell nuclear transfer. Methods in Molecular Biology. In: Ding S (ed), Cellular Programming and Reprogramming, Methods in Molecular Biology, Humana Press, 2010; 636:155-77.

    Ross PJ, Suhr S, Rodriguez RM, Chang EA, Wang K, Siripattarapravat K, Ko T, Cibelli JB. Human Induced Pluripotent Stem Cells Produced Under Xeno-Free Conditions. Stem Cells Dev. 2009 Dec 23. 

    Suhr ST, Chang EA, Rodriguez RM, Wang K, Ross PJ, Beyhan Z, Murthy S, Cibelli JB. Telomere dynamics in human cells reprogrammed to pluripotency. PLoS One. 2009 Dec 2;4(12):e8124.

    Ross PJ, Iager AE, Rodriguez RM, Beyhan Z, Ragina NP, Fissore RA, and Cibelli JB. Activation of bovine somatic cell nuclear transfer embryos by PLCZ cRNA injection. Reproduction 2009; 137:427-37.

    Wang K, Beyhan Z, Rodriguez RM, Ross PJ, lager AE, Kaiser GG, Chen Y, and Cibelli JB. Bovine ooplasm partially remodels primate somatic nuclei following somatic cell nuclear transfer. Cloning and Stem Cells 2009; 11:187-202.

    Ross PJ, Regina NP, Rodriguez RM, Iager A, Siripattarapravat K, Lopez N, and Cibelli JB. Polycomb genes expression and histone H3 lysine 27 tri-methylation changes during bovine preimplantation development. Reproduction 2008; 136: 777- 785.

    Iager AE, Ragina NP, Ross PJ, Beyhan Z, Cunniff K, Rodriguez RM, and Cibelli JB. Trichostatin A improves histone acetylation in bovine somatic cell nuclear transfer-derived bovine early embryos. Cloning and Stem Cells 2008; 10: 371- 379.

    Ross PJ, Beyhan Z, Iager AE, Yoon SY, Malcuit C, Schellander K, Fissore RA, and Cibelli JB. Parthenogenetic activation of bovine oocytes by bovine and murine phospholipase C zeta. Comparison to chemical activation methods. BMC Developmental Biology 2008; 8:16.

    Beyhan J, Ross PJ, Iager AE, Kocabas AM, Cunniff K, Cibelli JB. Transcriptional reprogramming of somatic cell nuclei during preimplantation development of cloned bovine embryos. Developmental Biology 2007; 305: 637- 649.

    Kocabas AM, Crosby J, Ross PJ, Otu HH, Beyhan Z, Can K, Tam WL, Rosa GJM, Halgren RG, Lim B, Fernandez E, and Cibelli JB. The transcriptome of human oocytes. PNAS 2006; 103: 14027-14032.