Ariel B. Abraham
B.S. University of Maryland, 2001

4th Year Graduate Student

Advisor: Styliani-Anna Tsirka, Ph.D.

Department: Pharmacological Sciences

Graduate Program: Molecular Cellular & Pharmacology



Abstract:

Title: Examining The Role of High Mobility Group proteins in Embryonic Neural Stem Cell Maintenance, Differentiation, and Survival

Neural Stem Cells (NSCs) are a group of primitive cells that reside in the developing embryonic and mature adult mammalian central nervous system. In vitro clonal and population analysis studies of NSCs have identified the putative NSC of embryonic and adult CNS as a proliferating epidermal growth factor-responsive cell whose progeny differentiate into astrocytes, oligodendrocytes, and neurons. Subsequent studies demonstrated that the rate of NSC proliferation and the frequency of NSC differentiation into different neural cell lineages is distinct in different regions of embryonic rodent brain and change over time, indicating that NSCs are both regionally and temporally specified. Despite this knowledge, the molecular mechanisms by which NSCs regulate their maintenance, including the ability to proliferate and self-renew, are not fully understood. In an effort to identify new molecular determinants of NSC maintenance, including molecules that play a regulatory role in NSC proliferation and self renewal, NSCs were isolated from the whole brains of embryonic E12.5 C57 Bl6/wild type mice and grown as neurospheres. Shotgun proteomics of proteins isolated from bulk neurosphere lysates from different passages in vitro was used to identify changes in the NSC proteome which may play a regulatory role in stem cell maintenance. Using this approach, 219 proteins were identified in early passage NSCs, while 249 proteins were identified in late passage NSCs. Proteins identified include members of the High Mobility Group (HMG) family in both early and late passage NSCs. HMG proteins are non-histone proteins found in the nuclei of mammalian cells that alter chromatin structure by binding to nucleosomes and the minor groove of DNA in a sequence independent manner. The expression of several proteins identified by shotgun proteomics in early and late passage NSCs, including members of the HMG family, was confirmed. Western blot data of lysates from neuronal, astrocyte, and oligodendroycte cultures indicate that HMG protein expression is different in differentiated neural cells compared to proliferating NSCs. Current work is focused on validating data on HMG expression differences, and future work will determine what role (if any) certain HMGs play in regulation of NSC proliferation, self-renewal, differentiation, and survival, as well as the molecular mechanisms by which HMGs exert their effects.

Publication:

Characterization of Gene and Protein Expression Patterns of Chromatin Structural Proteins HMGB1, 2, 3, and 4 in Proliferating and Differentiating Forebrain Neural Stem Cells. In preparation.