1999 — 2001 |
Elefant, Felice |
F32Activity Code Description: To provide postdoctoral research training to individuals to broaden their scientific background and extend their potential for research in specified health-related areas. |
Growth Hormone Gene Expression and Histone Acetylation @ University of Pennsylvania
The human growth hormone (hGH) gene cluster encompasses pituitary and placenta specific genes that are essential for normal growth and physiology during development and in adulthood. Misregulation of the hGH gene cluster results in severe pathological consequences and illustrates the importance of the hGH genes in postnatal growth, metabolic control, and gestational physiology. A set of distal hGH regulatory elements, termed the locus control region (LCR), has been identified and shown to be essential for the appropriate expression of the hGH in the pituitary and placenta. However, the mechanism(s) underlying the functions of remote elements in general, and LCR elements in particular, are not well defined. Defining the mechanisms underlying LCR activity is of particular importance in the case of the hGH LCR as it is closely linked to other genes with at least 4 distinct tissue specificities. The various elements of the LCR involved in the appropriate tissue-specific expression of the hGH gene cluster in the pituitary and placenta were identified by their DNase I hypersensitivity (HS). In the pituitary nuclei, a subset of 4 regulatory determinants in the hGH LCR were detected in the 5'-flanking region remote from the gene cluster (designated HSI,II,III,V) and in the placenta syncytiotrophoblastic nuclei, a subset of 3 regulatory determinants were detected (designated HSIII,IV,V). The focus of this proposal will be to elucidate the mechanism(s) underlying HS activity in the pituitary and placenta by investigating the role of histone acetylation in HS function/gene activation. Aim I will test the hypothesis that histone acetylation at critical control determinants (HS) within the LCR will correlate with tissue specific gene activation from the hGH gene cluster. Aim II will test the hypothesis that the CBP/p300 histone acetylase mediates the tissue-specific and targeted hyperacetylation of histone proteins at these specific HS. The outcome of this research will provide a novel insight into the mechanism(s) underlying LCR function and how appropriate gene expression profiles are established, regulated and maintained in specific cell lineages during development.
|
0.961 |
2004 — 2005 |
Elefant, Felice |
R03Activity Code Description: To provide research support specifically limited in time and amount for studies in categorical program areas. Small grants provide flexibility for initiating studies which are generally for preliminary short-term projects and are non-renewable. |
Role of Histone Acetyltransferases During Development
DESCRIPTION (provided by applicant): Specific histone acetyltransferases (HATs) play key regulatory roles in diverse chromatin-mediated biological processes, such as gene activation, apoptosis, cell-cycle regulation, DNA replication, and repair. The importance of HATs in biological regulation is underscored by studies demonstrating their involvement in both normal cellular processes and abnormal ones, resulting in oncogenesis and developmental disorders. Despite these connections, however, little is known about the specialized roles that individual HATs play in the tissue-specific cellular processes required for proper multicellular development. The goal of this application is to further define these roles, as well as to characterize the specific developmental pathways in which individual HATs are involved. Drosophila is an ideal model organism for such studies based on its highly characterized developmental system, and the discovery that flies and humans share structurally and functionally related specific HAT genes. The principal investigator has identified and cloned three such Drosophila HATs (dHATs) that show significant homology to essential human HATs TIP60, ELP3, and HBOI. To define HAT specificity and function, Specific Aim 1 will examine the developmental and tissue-type expression patterns of each identified dHAT. Preliminary results indicate that each dHAT is differentially expressed during development. Specific Aim 2 will further investigate the roles of dTIP60 and dELP3 during development. A GAL4 targeted RNAi based system in Drosophila will be used to silence specific endogenous dHAT expression in a variety of distinct tissues and developmental stages of choice. Identifying specific tissues, cell types, and lineage marker genes affected by particular dHAT loss and making associations with well-characterized developmental pathways will allow the investigator to decipher the roles and requirement for TIP60 and ELP3 during development. As many defects in cell differentiation pathways are caused by misregulation of HATs, the goal of deciphering the basis of individual cellular HAT function will likely have far reaching implications for the understanding of human biological regulation and developmental disorders.
|
1 |
2008 — 2012 |
Elefant, Felice |
R01Activity Code Description: To support a discrete, specified, circumscribed project to be performed by the named investigator(s) in an area representing his or her specific interest and competencies. |
Tip60 and App in Neuronal Development
[unreadable] DESCRIPTION (provided by applicant): Tip60 is a key histone acetyltransferase (HAT) enzyme that plays essential roles in diverse chromatin- mediated biological processes, including gene regulation, apoptosis, cell-cycle regulation, DNA recombination and repair. Tip60 is part of a multi-protein complex that is recruited by transcription factors to the promoters of certain genes where it generally acetylates surrounding histones to activate gene expression. Thus, Tip60 recruitment is involved in epigenetic gene regulation. While it is evident that Tip60 plays a central role in transcriptional control, it remains unclear as to the tissue and cell type-specific developmental pathways and target genes that require Tip60 to function. To investigate the role of TIP60 in multicellular development, our laboratory has identified and cloned the human TIP60 homolog in Drosophila (Dmel\TIP60). We have developed a system in transgenic flies that allows for targeted and inducible overexpression of wild-type or dominant negative HAT defective Dmel\TIP60 and Dmel\TIP60 knockdown in specific tissues, cell types and developmental stages of choice. Using this system, we have determined that Dmel\TIP60 is essential for nervous system formation during early development. We show that loss of Dmel\TIP60 in the fly brain leads to substantial neuronal loss and lethality. Consistent with our finding, other groups have documented an essential role for Tip60 HAT activity in the transcriptional activation of target genes via amyloid precursor protein (APP) mediated cell signaling pathways proposed to be involved in neuronal development. Intriguingly, TIP60 levels dramatically increase in the brains of young Alzheimer's disease (AD) model mice overproducing APP long before they acquire the A2 plaques, neurotoxicity and behavioral abnormalities representative of the disease. These findings provide the basis for our central hypothesis that APP perturbation causes upregulation of endogenous TIP60, leading to misregulation of both TIP60/APP and exclusive TIP60 chromatin-mediated neuronal pathways that is relevant in both development and neurodegeneration. To test this hypothesis, the following specific aims will be carried out. Aim 1 will identify TIP60 epigenetically regulated target genes that participate in distinct neuronal developmental processes and Aim 2 will determine the extent to which TIP60 chromatin-mediated neuronal processes and target genes are affected by overexpression of APP, in vivo. Such knowledge has important implications for the development of novel chromatin-based therapeutics in TIP60 associated disorders. PUBLIC HEALTH RELEVANCE: Our goal of deciphering the role of Tip60 and APP in neuronal development should profoundly enhance our understanding of nervous system development and neurodegenerative disorders. Such knowledge has important implications for the development of novel epigenetic-based therapeutics. [unreadable] [unreadable]
|
1 |
2017 — 2021 |
Elefant, Felice |
R01Activity Code Description: To support a discrete, specified, circumscribed project to be performed by the named investigator(s) in an area representing his or her specific interest and competencies. |
Mechanisms Underlying Tip60 Hat Action in Neuroprotection of Cognitive Function
ABSTRACT Impairment of epigenetic gene control mechanisms in the brain involving reduced histone acetylation levels causes significant cognitive deficits that are a debilitating hallmark of most neurodegenerative disorders, including Alzheimer's disease (AD). Accordingly, of the neural epigenetic modifications identified to date, histone acetylation has been unequivocally linked to facilitating learning and memory by regulating cognition gene expression programs via chromatin packaging control in neurons. Nevertheless, despite the central importance of histone acetylation in higher order brain function, the specific histone acetyltransferases (HATs) that generate these neuroepigenetic marks and their mechanisms of action in neural epigenetic gene control in the brain remain largely unknown. We generated a robust Tip60;APP Drosophila model system that enables us to modulate Tip60 HAT levels in neural circuits of choice under AD associated amyloid precursor protein (APP) neurodegenerative conditions, in vivo. Its use led to our exciting discovery that Tip60 is critical for cognitive processes based on its role in neural epigenetic gene control and remarkably, promotes neuroprotection for multiple cognitive neural circuits impaired in the brain during early AD associated neurodegenerative progression. Further, our new preliminary studies indicate that Tip60 HAT function in cognitive gene control is impaired in the human AD hippocampus. Our findings have laid a solid groundwork for this proposal and our goal for this project is to identify the mechanisms underlying Tip60 HAT action in neuroprotective gene control using fly and mouse AD models, and to determine how these Tip60 epigenetic processes go awry in the brains of human AD patients. We hypothesize that Tip60 promotes neuroprotection during the AD pathological process by epigenetically reprogramming gene sets in the brain that together protect against synaptic impairment and apoptotic cell death, and thus promote cognitive function. Using a combination of molecular, cellular, biochemical and chromatin based techniques, along with behavioral assays, in Aim 1A we will use our Tip60;APP and Tip60;A?42 fly models to identify the full array of Tip60 epigenetic reprogrammed genes, and verify their mammalian Tip60 epigenetic conservation in the mouse brain. In Aim 1B we will test whether these Tip60 neuroprotective genes are epigenetically misregulated in the human AD brain, as we predict. In Aim 2A, we will dissect the transcriptional mechanisms for how Tip60 epigenetically reprograms neuroprotective genes using fly and mouse AD models. In Aim 2B we will test whether these same Tip60 transcriptional regulatory complexes are disrupted in the human AD brain, as we predict. Our studies will provide broad insights into novel Tip60 epigenetic mechanisms underlying human neurodegenerative disorders such as Alzheimer's disease, and new understanding into HAT based drug design for early therapeutic intervention of cognitive deficits.
|
1 |