Rachael Norris

Rachael Norris

Assistant Professor (In Residence)
Phone: 860-679-3476
Email: norris@uchc.edu

My overall research interests are about the cell biology of oocyte maturation and fertilization. Currently my research is focused on membrane dynamics during fertilization in the model flowering plant, Arabidopsis thaliana, using correlative light and serial section electron microscopy.

In flowering plants, reproduction involves the fertilization of two cells within an ovule, the egg and central cells.  When a pollen grain contacts the stigma, it forms a tube that travels down the pistil to the ovules. The pollen tube contains two sperm cells: ultimately one fuses with the egg, and one fuses with the central cell (see below). While the sperm fusogen in mammals is still unknown, it has been identified in flowering plants and other organisms as Hapless2 (HAP2/GSC1), a protein that resembles a viral fusogen.  To better understand the role of HAP2 in cell-cell fusion, Iris Nakashima and I are live-imaging isolated Arabidopsis pistils with fluorescently tagged sperm nuclei and egg cells (see video and still frames below). We fix the pistils at sequential time points after sperm cell release and process them for serial section electron microscopy to visualize cell-cell fusion in plants with ultrastructural resolution.

Live imaging double fertilization by confocal microscopy

The movie above shows double fertilization in Arabidopsis, displayed at 160x time. The sperm pair movement from the outer edge of the ovule to the base of the egg indicates pollen tube rupture has occurred (1 and 2). For about 7 minutes, the sperm cells remain next to each other in a space between the egg and central cells (2). After double fertilization is complete, the sperm nuclei move apart, having fused with either the egg or central cell (3).

Electron microscopy of ovules during double fertilization

Thin sections through ovules fixed after a pollen tube burst, at different magnifications, imaged by a scanning electron microscope. We examine all sections through the female gametes to find where sperm localize around the time of fertilization.

 

Publications

Soma-to-germline BMP signal is essential for Drosophila spermiogenesis. Beard EK, Norris RP, Furusho M, Terasaki M, Inaba M. Dev Biol. 2024 Oct 2;517:140-147. doi: 10.1016/j.ydbio.2024.09.016.

The Implant-Induced Foreign Body Response Is Limited by CD13-Dependent Regulation of Ubiquitination of Fusogenic Proteins.  Ghosh M, McGurk F, Norris R, Dong A, Nair S, Jellison E, Murphy P, Verma R, Shapiro LH. J Immunol. 2024 Feb 15;212(4):663-676. doi: 10.4049/jimmunol.2300688.

Granulosa Cells Alone, Without Theca Cells, Can Mediate LH-induced Oocyte Meiotic Resumption. Norris RP, Jaffe LA. Endocrinology. 2024 Jan 16;165(3):bqad200. doi: 10.1210/endocr/bqad200.

Transfer of mitochondria and endosomes between cells by gap junction internalization. Norris RP. Traffic. 2021 Jun;22(6):174-179. doi: 10.1111/tra.12786. Epub 2021 Apr 14.

Gap junction internalization and processing in vivo: a 3D immuno-electron microscopy study. Norris RP, Terasaki M. J Cell Sci. 2021 Jan 11;134(1):jcs252726. doi: 10.1242/jcs.252726.

Anteroposterior axis patterning by early canonical Wnt signaling during hemichordate development. Darras S, Fritzenwanker JH, Uhlinger KR, Farrelly E, Pani AM, Hurley IA, Norris RP, Osovitz M, Terasaki M, Wu M, Aronowicz J, Kirschner M, Gerhart JC, Lowe CJ. PLoS Biol. 2018 Jan 16;16(1):e2003698. doi: 10.1371/journal.pbio.2003698. eCollection 2018 Jan.

Localization of phosphorylated connexin 43 using serial section immunogold electron microscopy. Norris RP, Baena V, Terasaki M. J Cell Sci. 2017 Apr 1;130(7):1333-1340. doi: 10.1242/jcs.198408. Epub 2017 Feb 15.

Redistribution of Gαs in mouse salivary glands following β-adrenergic stimulation. Hand AR, Elder KO, Norris RP. Arch Oral Biol. 2015 May;60(5):715-23. doi: 10.1016/j.archoralbio.2015.01.010. Epub 2015 Feb 25.

Intercellular signaling via cyclic GMP diffusion through gap junctions restarts meiosis in mouse ovarian follicles. Shuhaibar LC, Egbert JR, Norris RP, Lampe PD, Nikolaev VO, Thunemann M, Wen L, Feil R, Jaffe LA. Proc Natl Acad Sci U S A. 2015 Apr 28;112(17):5527-32. doi: 10.1073/pnas.1423598112. Epub 2015 Mar 16.

FGF signaling induces mesoderm in the hemichordate Saccoglossus kowalevskii. Green SA, Norris RP, Terasaki M, Lowe CJ. Development. 2013 Mar;140(5):1024-33. doi: 10.1242/dev.083790. Epub 2013 Jan 23.

Connexin43 phosphorylation in brain, cardiac, endothelial and epithelial tissues. Márquez-Rosado L, Solan JL, Dunn CA, Norris RP, Lampe PD. Biochim Biophys Acta. 2012 Aug;1818(8):1985-92. doi: 10.1016/j.bbamem.2011.07.028. Epub 2011 Jul 26. Review

Luteinizing hormone reduces the activity of the NPR2 guanylyl cyclase in mouse ovarian follicles, contributing to the cyclic GMP decrease that promotes resumption of meiosis in oocytes. Robinson JW, Zhang M, Shuhaibar LC, Norris RP, Geerts A, Wunder F, Eppig JJ, Potter LR, Jaffe LA. Dev Biol. 2012 Jun 15;366(2):308-16. doi: 10.1016/j.ydbio.2012.04.019. Epub 2012 Apr 21.

Phosphorylation of serine residues in the C-terminal cytoplasmic tail of connexin43 regulates proliferation of ovarian granulosa cells. Dyce PW, Norris RP, Lampe PD, Kidder GM. J Membr Biol. 2012 Jun;245(5-6):291-301. doi: 10.1007/s00232-012-9450-6. Epub 2012 Jun 24.

Epidermal growth factor receptor kinase activity is required for gap junction closure and for part of the decrease in ovarian follicle cGMP in response to LH. Norris RP, Freudzon M, Nikolaev VO, Jaffe LA. Reproduction. 2010 Nov;140(5):655-62. doi: 10.1530/REP-10-0288. Epub 2010 Sep 8

Cyclic GMP from the surrounding somatic cells regulates cyclic AMP and meiosis in the mouse oocyte. Norris RP, Ratzan WJ, Freudzon M, Mehlmann LM, Krall J, Movsesian MA, Wang H, Ke H, Nikolaev VO, Jaffe LA. Development. 2009 Jun;136(11):1869-78. doi: 10.1242/dev.035238.

Microinjection of follicle-enclosed mouse oocytes. Jaffe LA, Norris RP, Freudzon M, Ratzan WJ, Mehlmann LM. Methods Mol Biol. 2009;518:157-73. doi: 10.1007/978-1-59745-202-1_12.

Luteinizing hormone causes MAP kinase-dependent phosphorylation and closure of connexin 43 gap junctions in mouse ovarian follicles: one of two paths to meiotic resumption. Norris RP, Freudzon M, Mehlmann LM, Cowan AE, Simon AM, Paul DL, Lampe PD, Jaffe LA. Development. 2008 Oct;135(19):3229-38. doi: 10.1242/dev.025494.

A G(s)-linked receptor maintains meiotic arrest in mouse oocytes, but luteinizing hormone does not cause meiotic resumption by terminating receptor-G(s) signaling. Norris RP, Freudzon L, Freudzon M, Hand AR, Mehlmann LM, Jaffe LA. Dev Biol. 2007 Oct 15;310(2):240-9. Epub 2007 Jul 24.

Regulation of meiotic prophase arrest in mouse oocytes by GPR3, a constitutive activator of the Gs G protein. Freudzon L, Norris RP, Hand AR, Tanaka S, Saeki Y, Jones TL, Rasenick MM, Berlot CH, Mehlmann LM, Jaffe LA. J Cell Biol. 2005 Oct 24;171(2):255-65.