Gregory Johnson

Pregnancy

Implantation

Placentation

Uterine Biology

Gene Regulation and Expression

Research from my laboratory has exploited the prolonged peri-implantation period of pregnancy in pigs and sheep. At this time elongating conceptuses remain free-floating within the uterine lumen for an extended period, requiring extensive paracrine signaling between conceptus and endometrium. This is followed by an extended and incrementally advancing period of conceptus attachment to the uterine wall that allows for examination of the molecules that are physically involved in this attachment process. My laboratory has established that osteopontin (OPN; secreted phosphoprotein 1, SPP1) is upregulated in the uterine environment by steroid hormones, estrogen in pigs and progesterone in sheep, to interact with apically expressed integrin receptors on the uterine luminal epithelium and conceptus trophectoderm to attach the conceptus to the uterus for implantation in pigs and sheep. This knowledge has been effectively transferred to understanding of the attachment phase of implantation in humans through in vitro experiments performed by the highly respected laboratory of John Aplin in Manchester, England. My laboratory has also worked to unravel uterine responses to paracrine factors secreted by the conceptuses of ruminants, interferon tau (IFNT), and pigs (estrogens and INFs gamma and delta (IFNG and IFND). Through our research we have established that estrogens and IFNs induce expression of largely non-overlapping sets of genes. Evidence suggests that pig conceptuses orchestrate essential events of early pregnancy including pregnancy recognition signaling, implantation and secretion of histotroph by precisely controlling temporal and spatial, cell-specific, changes in uterine gene expression through initial secretion of estrogens, followed by cytokines including IFNG and IFND. We have established that IFNG induces a limited inflammatory response in the uterine stroma that involves the active recruitment of T cells to the endometrium that may be essential for remodeling of the uterine storma for implantation. New studies suggest that knockdown of IFNG in porcine conceptuses by CRISPR/Cas9 technology compromises pregnancy. Further, my laboratory has been instrumental in the establishment and utilization of cell lines from the uterus and placenta of sheep and pigs, including uterine luminal and glandular epithelial and stromal cell lines, as well as conceptus trophectoderm cell lines. These cell lines have been utilized by many laboratories, and have provided the opportunity to mechanistically address functions of prominent proteins that are hypothesized to be active within the uterine environment of pregnancy in mammals, including livestock and women. I am a proud member of the Uterine Biology and Pregnancy group at TAMU, which is one of the more productive reproductive biology research programs in the United States.

VIBS 343/602 Histology

VMID 686 Scientific Ethics

VTMI Advanced Immunological Conceptus, Reproductive Immunology

ANSC 631 Advanced Reproductive Biology

VIBS 609 Anatomy of Reproductive Systems

Current

Dr. Thaina Manilla, Postdoctoral Fellow

Mr. Darshil Shah, Ph.D. Student

Selected from a total of 181:

1) Johnson GA, Burghardt RC, Bazer FW and Spencer TE. Minireview: Osteopontin: roles in implantation and placentation.  Biol Reprod 2003; 69:1458-1471. (cited 352 times)

2) Johnson GA, Burghardt RC and Bazer FW.  Osteopontin: A leading candidate adhesion molecule for implantation in pigs and sheep.  J Anim Sci & Biotechnol. 2014; 5:56-70. (cited 57 times)

These two reviews have served to establish osteopontin and its integrin receptors as key molecules involved in the attachment of the conceptus to the uterus during implantation. Osteopontin now rivals fibronectin for acceptance by the scientific community for this function.

3) Johnson GA, Bazer FW, Jaeger LA, Ka H, Garlow JE, Pfarrer C, Spencer TE and Burghardt RC.  Muc-1, integrin and osteopontin expression during the implantation cascade in sheep.  Biol Reprod 2001; 65:820-828. (cites 233 times)

4) Johnson GA, Burghardt RC, Spencer TE, Newton GR, Ott TL and Bazer FW. Ovine Osteopontin: II. Osteopontin and αv,β3 integrin expression in the uterus and conceptus during the peri-implantation period. Biol Reprod 1999; 61:892-899. (cited 192 times)

5) Johnson GA, Spencer TE, Burghardt RC and Bazer FW. Ovine Osteopontin: I. Cloning and expression of mRNA in the uterus during the peri-implantation period. Biol Reprod 1999; 61:884-891. (cited 128 times)

These three manuscripts were the first to introduce osteopontin as an adhesion protein during implantation in any species. Osteopontin is now proposed to serve this role in multiple other species including rodents and humans.

6) Garlow JE, Ka H, Johnson GA, Burghardt RC, Jaeger LA and Bazer FW. Analysis of osteopontin at the maternal-placental interface in pigs.  Biol Reprod 2002; 66: 718-725. (cited 159 times)

7) Erikson DW, Burghardt RC, Bayless KJ and Johnson GA.  Secreted phosphoprotein 1 (SPP1, osteopontin) binds to integrin alphavbeta6 on porcine trophectoderm cells and integrin alphavbeta3 on uterine luminal epithelial cells, and promotes trophectoderm cell adhesion and migration.  Biol Reprod 2009; 81:814-825. (cited 106 times)

8) Frank JW, Seo H, Burghardt RC, Bayless KJ and Johnson GA. ITGAV (Alpha V Integrins) Bind SPP1 (Osteopontin) to Support Trophoblast Cell Adhesion. Reproduction 2017; 153:695-706.

The first manuscript was the first to establish osteopontin as an adhesion molecule for implantation in pigs . Although I am listed as a middle author, I directed the research and wrote the manuscript. The second manuscript for the first time identifies integrins on conceptus trophectoderm and uterine luminal epithelium that potentially bind to osteopontin during implantation. The third manuscript demonstrates a functional role for osteopontin and an integrin to support conceptus trophectoderm adhesion.

9) Johnson GA, Spencer TE, Burghardt RC, Taylor KM, Gray CA and Bazer FW. Progesterone modulation of osteopontin gene expression in the ovine uterus. Biol Reprod 2000; 62:1315-1321. (cited 128 times)

10) White FJ, Ross JW, Joyce MM, Geisert RD, Burghardt RC and Johnson GA.  Steroid regulation of cell specific secreted phosphoprotein 1 (osteopontin) expression in the pregnant porcine uterus.  Biol Reprod 2005; 73:1294-1301. (cite 100 times)

These manuscripts are the first to establish that steroid hormones regulate the temporal and spatial expression of osteopontin at the uterine-placental interface of any species.In the case of the sheep, progesterone from the CL induces osteopontin expression by the uterus. In the case of the pig, estrogen from the conceptus trophectoderm induces osteopontin expression by the uterus.

11) Johnson GA, Burghardt RC, Newton GR, Bazer FW and Spencer TE. Development and characterization of immortalized ovine endometrial cell lines. Biol Reprod 1999; 61:1324-1330. (cited 107 times

12) Wang G, Johnson GA, Spencer TE and Bazer FW. Isolation, immortalization and initial characterization of uterine cell lines: an in vitro model system for the porcine uterus. In Vitro Cell Dev Biol Anim 2000; 36:650-656. (cited 40 times)

13) Kim J, Erikson DW, Burghardt RC, Spencer TE, Wu G, Bayless KJ, Johnson GAt and Bazer FWt.  Secreted phosphoprotein 1 binds integrins to initiate multiple cell signaling pathways, including FRAP1/mTOR, to support attachment and force-generated migration of trophectoderm cells.  Matrix Biol 2010; 29:369-382. tCo-Corresponding Authors (cited 68 times)

The first manuscript describes the development of immortalized uterine cell lines in the sheep that have been distributed to laboratories around the world. The second manuscript describes the development of immortalized uterine cell lines in the pig that have been distributed around the world. Although I am listed as a middle author, I directed the studies and wrote the manuscript. The third describes the use of an immortalized porcine trophectoderm cell line that has been distributed around the world.

14) Joyce MM, Burghardt RC, Geisert RD, Burghardt JR, Hooper RN, Ross JW, Ashworth MD and Johnson GA.  Pig conceptuses secrete estrogen and interferons to differentially regulate uterine STAT1 in a temporal and cell-type specific manner.  Endocrinology 2007; 148:4420-4431. (cited 86 times)

15) Johnson GA, Bazer FW, Burghardt RC, Spencer TE, Wu G and Bayless KJ.  Conceptus-uterus interactions in pigs:  endometrial gene expression in response to estrogens and interferons from conceptuses.  Soc Reprod Fertil Suppl 2009; 66:321-332. (cited 84 times)

16) McLendon BA, Seo H, Kramer AC, Burghardt RC, Bazer FW and Johnson GA. Pig conceptuses secrete ingerferon gamma to recruit T cells to the endometrium during the peri-implantation period. Biol Reprod, 2020, https://doi.org/10.1093/biolre/ioaa132.

The fist manuscript is the one of the first (the other two firsts were also published by my laboratory) to establish that conceputus interferons (IFNs) induce gene expression in the porcine uterus. The second manuscript reviews the regulation of gene expression in the porcine uterus by Conceptus produced estrogens and IFNs. The third manuscript establishes a role for IFN gamma to regulate the endometrial immune response during implantation in pigs

17) Joyce MM, Burghardt JR, Burghardt RC, Hooper RN, Bazer FW and Johnson GA.  Uterine major histocompatibility class I molecules and beta 2 microglobulin are regulated by progesterone and conceptus interferons during pig pregnancy.  J Immunol 2008; 181:2494-2505. (cited 55 times)

This manuscript establishes the regulation of type I major histocompatibility molecules at the uterine-placental interface of pigs and provides comparative insight into how different species, in this case a species with epitheliochorial placentation, regulate the immune system for acceptance of the fetal-placental semi-allograft.

18) Seo H, Bazer FW, Burghardt RC and Johnson GA. Immunohistochemical examination of trophoblast syncytialization during early placentation in sheep. Int J Mol Sci, 2019; 20:4530-4543. (cited 5 times)

This manuscript challenges the dogma of how syncytialization develops during synepitheliochorial placental development in the sheep. This manuscript has the potential to change how week envision placentation in sheep.

19) Burghardt RC, Burghardt JR, Taylor II JD, Reeder AT, Nguyen BT, Spencer TE and Johnson GA.  Enhanced focal adhesion assembly reflects increased mechanosensation and mechanotransduction  along the maternal/conceptus interface during pregnancy in sheep.  Reproduction 2009; 137:583-593. (cited 57 times)

20) Seo H, Li X, Wu G, Bazer FW, Burghardt RC, Bayless KJ and Johnson GA.  Mechanotransduction drives morphogenesis to develop folding at the uterine-placental interface of pigs.  Placenta, 2020; 90:62-70. (cited 4 times)

21) Seo H, Frank JW, Burghardt RC, Bazer FW and Johnson GA. Integrins and OPN localize to adhesion complexes during placentation in sheep. Reproduction, 2020, accepted.

These manuscripts are some of the only reports of in vivo adhesion complex assembly in response to integrin activation at the uterine-placental interface of any species. They establish that matrix proteins interact with integrins to induce the formation of adhesion complexes which then profoundly influence changes in uterine and placental morphology during pregnancy.

22) Steinhauser CB, Landers M, Myatt L, Burghardt RC, Vallet JL, Bazer FB and Johnson GA.

Fructose Synthesis and Transport at the Uterine-Placental Interface of Pigs: Cell-Specific Localization of SLC2A5, SLC2A8, and Components of the Polyol Pathway.  Biol Reprod 2016; 95:108-121. (cited 20 times)

23) Kramer AC, Steinhauser CB, Gao H, Seo H, McLendon BA, Burghardt RC, Wu G, Bazer FW and Johnson GA. Steroids Regulate Expression of SLC2A1 and SLC2A3 to Deliver Glucose into Trophectoderm for Metabolism via glycolysis. Endocrinology, 2020; DOI: 10.1210/endocr/bqaa098.

The first manuscript establishes a potential role for fructose to support the elongation and implantation of conceptus trophectoderm in pigs.  The second is the first to demonstrate the porcine conceptuses directly utilize both glucose and fructose to support conceptus trphectoderm elongation during the periimplantation period.

24) Wing TT, Erikson DW, Burghardt RC, Bazer FW, Bayless KJ and Johnson GA.  OPN binds alpha v integrin to promote endothelial progenitor cell incorporation into vasculature.  Reproduction, 2020; 159:465-478.

25) Johnson GA, Burghardt RC, Joyce MM, Spencer TE, Bazer FW, Pfarrer C and Gray CA.  Osteopontin expression in uterine stroma indicates a decidualization-like differentiation during ovine pregnancy.  Biol Reprod 2003; 68:1951-1958. (cited 104 times)