Mary Lou King

Professor of Cell Biology and Anatomy

Ph.D. Indiana University

Localization of RNA in Xenopus oocytes

Tel.: (305) 243-5643

email: mking@med.miami.edu

Research Interests

My laboratory studies how cell fate is determined in the early Xenopus embryo. Our work has shown that the localization of a small number of mRNAs to one pole of the future egg is critical to normal development. Proteins encoded by these localized mRNAs influence gene expression and cell fate decisions. The cells that will eventually give rise to the gametes, the primordial germ cells, comprise the first cell lineage to be specified by localized mRNAs. Only the germ cell lineage has a program of differentiation that maintains totipotency, or the ability to give rise to all other cell types. Discovering how the germline is initially specified and develops separate from the somatic cell lineages is a fundamental problem. Our long-term goals are to:

1) understand how precursors to the germ cells retain developmental totipotency

2) characterize the RNA transport systems involved in their localization.

We have isolated mRNAs localized exclusively to primordial germ cells. Remarkably, two of these RNAs, Xcat-2 (related to nanos1) and Xdazl (in DAZ family) are highly conserved and found in the germline of humans and Drosophila. Xdazl and Xcat2/nanos1 encode RNA binding proteins and likely regulate the expression of specific mRNAs. We are interested in identifying these mRNA targets and their function in germ cell development. We know that Xdazl function is essential because anti-sense depletion of Xdazl RNA results in their failure to initiate migration to the gonads. Xcat2/nanos1 is also required and can act as a potent repressor of transcription and translation. Mis-expression of Xcat2 in somatic cells leads to profound abnormal development. Our current hypothesis is that Xcat2/nanos1 is essential for the germline to retain totipotency.

How the correct mRNAs are localized to the correct locations in the egg is a fascinating problem. Germ line mRNAs localize by a diffusion/entrapment mechanism. We have identified the RNA signal required for proper localization of Xcat-2. Now we are working to isolate the proteins that bind these localization signals. Together, our studies will determine how molecular polarity is established in the oocyte and how this leads to cell fate decisions in the early embryo.

Claudia O. Rodrigues, Steve Nerlick, Elsie L. White, John L. Cleveland and Mary Lou King (2008). A Myc-Slug (Snail2)/Twist Regulatory Circuit Directs Vascular Development.  Development, in press.

Hye-Won Song, Karen Cauffman, Agnes P. Chan, Yi Zhou, Mary Lou King, Laurence D. Etkin and Malgorzata Kloc (2007). Hermes RNA binding protein targets RNAs encoding proteins involved in meiotic maturation, early cleavage, and germline development. Differentiation, 75:519-28.

King, M. L., Messitt, and Mowry, K. (2005) Putting RNAs in the Right Place at the Right Time: RNA Localization in the Frog Oocyte. Biol. Cell 97: 19-33.

Machado RJ, Moore W, Hames R, Houliston E, Chang P, King ML, Woodland HR. (2005) Xenopus Xpat protein is a major component of germ plasm and may function in its organization and positioning. Dev Biol. 287(2):289-300.

Chang, P., Torres, J., Lewis, R., Mowry, K., Houlison, E and King, M. L. (2004) Localization of RNAs to the mitochondrial cloud in Xenopus oocytes by entrapment and association with endoplasmic reticulum. Mol. Biol. Cell 15:4669-4681.

Zhou, Y., Zhang, J. and King, M.L. (2003) Xenopus ARH Couples Lipoprotein Receptors with the AP-2 Complex in Oocytes and Embryos and is Required for Vitellogenesis. J Biological Chemistry 278:44584-44592.

Bubunenko, M., Kress, T.L., Vempati, U.D., Mowry, K. King, M.L. (2002) A consensus RNA signal that directs germ layer determinants to the vegetal cortex of Xenopus oocytes. Dev. Biol. 248:82-92.

Houston, D. W. and King, M.L. (2000) A critical role for Xdazl, a germ plasm-localized RNA, in the differentiation of primordial germ cells in Xenopus. Development 127:447-456.

View published research articles by Dr. King in the National Library of Medicine

See Dr. King's homepage in her primary department!