Associate Professor of Molecular Biology & Genetics
Publications | Research | Faculty
Background:
Jun "Kelly" Liu is an Assistant Professor of Molecular Biology and Genetics. She received a B.S. degree in Biology at Wuhan University in China and a Ph.D. in Biochemistry, Molecular and Cell Biology from Cornell University. She did her postdoctoral research at the Carnegie Institution of Washington, Department of Embryology, where she was awarded a National Institutes of Health Postdoctoral Fellowship. She joined the faculty at Cornell in 2001. She is in the graduate fields of Genetics & Development, and Biochemistry, Molecular & Cell Biology.
Courses Taught:
BioGD 385: http://instruct1.cit.cornell.edu/courses/biogd385/
BioGD 689: http://instruct1.cit.cornell.edu/courses/biogd689/
Links:
Our research interests focus on two areas of developmental biology: 1) mechanisms that determine cell fate, and 2) functions of the nuclear envelope. We have chosen the nematode Caenorhabditis elegans to explore these areas of research since C. elegans offers a number of advantages for these studies: 1) the entire cell lineage has been mapped, making possible the study of gene function at single cell resolution; 2) sophisticated genetic and molecular tools are available, including efficient transgenic techniques and a complete genome sequence.
Mesodermal cell fate specification
One of the most fascinating questions in developmental biology is how a single fertilized egg can develop into a multi-cellular organism with a complex array of tissue and cell types. We are interested in understanding mechanisms that control the specification and diversification of different cell fates during development. Specifically, we use the C. elegans post-embryonic mesoderm as a model system to study how mesodermal cell fates are specified. The C. elegans post-embryonic mesoderm is derived from a single lineage, called the M lineage. In a hermaphrodite animal, the precursor of the lineage, the M mesoblast, divides in a characteristic and reproducible pattern through larval development to generate 14 striated bodywall muscles required for locomotion, 16 non-striated sex muscles used for egg-laying, and 2 non-muscle mesodermal cells called the coelomocytes (Figure 1). None of these cells are essential for viability, making possible numerous genetic and mechanical manipulations of the lineage. We are taking a variety of molecular and genetic approaches to study how the mesodermal precursor M cell is specified, how the M lineage is diversified to generate different muscle and non-muscle cell types, and what are the similar and diverse mechanisms regulating mesodermal cell fate specification between C. elegans and vertebrates.
Nuclear envelope function during development
The nuclear envelope separates the nucleus from the cytoplasm. It is composed of the inner and outer nuclear membranes, the pore complexes, and the nuclear lamina. The nuclear lamina underlies the inner nuclear membrane, and its main components are the intermediate filament proteins lamins. Mutations in lamin and lamin-associated inner nuclear membrane proteins (emerin and LBR) cause a number of genetic diseases in humans, including muscular dystrophies, lipodystrophy, neuropathy, and pre-mature aging. The underlying molecular mechanisms are still unknown. We are interested in studying the functions of lamin and lamin-associated proteins in development by using C. elegans as a model organism. The C. elegans nuclear envelope is similar to human nuclear envelopes: it contains lamin and a number of lamin-associated proteins and it undergoes cell cycle dependent assembly/reassembly. But the C. elgans nuclear envelope has a much simpler composition than human nuclear envelopes: many proteins encoded by multiple genes in humans have a single counterpart in C. elegans. Thus functional studies of nuclear envelope proteins are much easier in C. elegans. By studying the functions of C. elegans nuclear envelope proteins, we hope to better understand the molecular mechanisms underlying nuclear envelope-associated human diseases.
For more information on our research, please visit the Liu Lab website.
Click here to view Dr. Liu's PubMed listings.
Publications
Jiang, Y., Shi, H., Amin, N. M., Sultan, I. and Liu, J. (2008) Mesodermal expression of the C. elegans HMX homolog mls-2 requires the PBC homolog CEH-20. Mech. Dev. 125: 451-461. Epub 2008 Feb 2. (Pubmed)
Foehr, M. L. and Liu, J. (2008) Dorsoventral patterning of the C. elegans postembryonic mesoderm requires both LIN-12/Notch and TGF-beta signaling. Dev. Biol. 313: 256-266. Epub 2007 Oct 25. (Pubmed)
Amin, N. M., Hu, K., Pruyne, D., Terzic, D., Bretscher, A. and Liu, J. (2007) A Zn finger/FH2 domain containing protein FOZI-1 acts redundantly with CeMyoD to specify striated body wall muscle fates in the C. elegans postembryonic mesoderm. Development 134: 19-29. Epub 2006 Nov 30. (Pubmed)
Johnston R. J. Jr., Copeland, J. W., Fasnacht, M., Etchberger, J. F., Liu, J., Honig, B. and Hobert, O. (2006) An unusual Zn-finger/FH2 domain protein controls a left/right asymmetric neuronal fate decision in C. elegans. Development 133: 3317-3328. (Pubmed)
Foehr, M. F., Lindy, A. S., Fairbank, R. C., Amin, N. M., Xu, M., Yanowitz, J., Fire, A. Z. and Liu, J. (2006) An antagonistic role for the C. elegans Schnurri homolog SMA-9 in modulating TGF-� signaling during mesodermal patterning. Development 133: 2887-2896. (Pubmed)
Haithcock, E., Dayani, Y., Neufeld, E., Zahand, A. J., Feinstein, N., Mattout, A., Gruenbaum, Y. and Liu, J. (2005) Age-related changes of nuclear architecture in C. elegans. Proc Natl Acad Sci U S A. 102: 16690-16695. (PubMed)
This article was highlighted in the same issue of PNAS 102: 16531, and featured in a commentary by Wilson, K.L. (2005) PNAS 102: 18767-18768 (Pubmed) and a News and Views article by Lans and Hoejimakers (2006) Nature 440: 32-34 (Pubmed).
Jiang, Y., Horner, V. and Liu, J. (2005) The HMX homeodomain protein MLS-2 regulates cleavage orientation, cell proliferation and cell fate specification in the C. elegans postembryonic mesoderm. Development 132: 4119-4130.(PubMed)
Margalit, A., Liu, J., Fridkin, A., Wilson, K. L. and Gruenbaum, Y. (2005) A lamin-dependent pathway that regulates nuclear organization, cell cycle progression and germ cell development. Novartis Found Symp. 264: 231-240; discussion 240-245.(PubMed)
Liang, J., Lints, R., Foehr, M. L., Tokarz, R., Yu, L., Emmons, S. W., Liu, J. and Savage-Dunn, C. (2003) The Caenorhabditis elegans schnurri homolog, sma-9, mediates stage- and cell type- specific responses to dbl-1 BMP-related signaling. Development 130: 6453-6464. (PubMed)
Liu, J., Lee, K. K., Segura-Totten, M., Neufeld E., Wilson, K. L. and Gruenbaum, Y. (2003) MAN1 and emerin have overlapping function(s) essential for chromosome segregation and cell division in Caenorhabditis elegans. Proc Natl Acad Sci U S A. 100:4598-4603. (PubMed)
Lee, K. K., Starr, D., Cohen, M., Liu, J., Han, M., Wilson, K. L. and Gruenbaum Y. (2002) Lamin-dependent localization of UNC-84, a protein required for nuclear migration in Caenorhabditis elegans. Mol. Biol. Cell 13: 892-901. (PubMed)
Gruenbaum, Y., Lee, K. K., Liu, J., Cohen, M. and Wilson, K. L. (2002) The expression, lamin-dependent localization and RNAi depletion phenotype for emerin in C. elegans. J. Cell Sci. 115: 923-929. (PubMed)
Lee, K. K., Gruenbaum, Y., Spann, P., Liu, J. and Wilson, K. L. (2000) C. elegans nuclear envelope proteins Emerin, MAN1, lamin, and nucleoporins reveal unique timing of nuclear envelope breakdown during mitosis. Mol. Biol. Cell 11: 3089-3099. (PubMed)
Liu, J., Ben-Shahar, T. R., Riemer, D., Treinin, M., Spann, P., Weber, K., Fire, A. and Gruenbaum, Y. (2000). Essential roles for Caenorhabditis elegans lamin gene in nuclear organization, cell cycle progression and spatial organization of nuclear pore complexes. Mol. Biol. Cell 11: 3937-3947. (PubMed)
Liu, J., and Fire, A. (2000). Overlapping roles of two Hox genes and the exd ortholog ceh-20 in diversification of the C. elegans postembryonic mesoderm. Development 127: 5179-5190. (PubMed)
Yu, J., Liu, J., Song, K., Turner, S. and Wolfner, M. F. (1999) Nuclear entry of the Drosophila melanogaster nuclear lamina protein YA correlates with developmentally regulated changes in its phosphorylation state. Dev. Biol. 210: 124-134. (PubMed)
Harfe, B. D., Gomes, A. Z., Kenyon, C., Liu, J., Krause, M. and Fire, A. (1998) Analysis of a Caenorhabditis elegans twist homolog identifies conserved and divergent aspects of mesodermal patterning. Genes & Dev. 12: 263-2635. (PubMed)
Liu, J. and Wolfner, M. F. (1998) Functional dissection of YA, an essential, developmentally regulated nuclear lamina protein in Drosophila melanogaster. Mol. Cell Biol. 18: 188-197. (PubMed)
Liu, J., Lopez, J. M., and Wolfner, M. F. (1997) Developmental modulations of the nuclear envelope. Curr. Topics Dev. Biol. 35: 47-70. (PubMed)
Liu, J., Lin, H., Lopez, J. M. and Wolfner, M. F. (1997) Formation of the male pronuclear lamina in Drosophila melanogaster. Dev. Biol. 184: 187-196. (PubMed)
Liu, J., Song, K. and Wolfner, M. F. (1995) Mutational analyses of fs(1)Ya, an essential, developmentally regulated, nuclear envelope protein in Drosophila. Genetics 141: 1473-1481. (PubMed)
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