A FACS-based Screen For Retroviral Silencing: A Tool For Detecting Trans-sensing In Mammalian Cells
Funder
National Health and Medical Research Council
Funding Amount
$205,010.00
Summary
Retroviruses are RNA viruses that infect cells and then become integrated into the genome of the infected cell. This property has been exploited in attempts to cure genetic diseases by replacing the defective gene: the replacement can be incorporated into the retrovirus, transported into a cell, and become part of the cell?s genetic material. However, retroviruses are frequently suppressed by the host cell some time after integration, so that their genetic information becomes silent. The factors ....Retroviruses are RNA viruses that infect cells and then become integrated into the genome of the infected cell. This property has been exploited in attempts to cure genetic diseases by replacing the defective gene: the replacement can be incorporated into the retrovirus, transported into a cell, and become part of the cell?s genetic material. However, retroviruses are frequently suppressed by the host cell some time after integration, so that their genetic information becomes silent. The factors that cause silencing of retroviruses are not well understood, but it is clear that this problem is a major impediment to retrovirus-based (and perhaps all) gene therapies. In a wide variety of organisms, including plants, flies, and yeast, it has been found that multiple copies of a gene can silence each other, a phenomenon termed cosuppression. Some reports suggest that this might happen in mammals as well. We have initiated a study of retroviral silencing, using a marker protein that produces green fluorescence as a model for the replaced gene. We find that the gene is usually silenced after integration, immediately or over time, but can be reactivated by drugs that demethylate DNA or alter chromosomal structure. We now propose to extend this work by doing a systematic analysis of the frequency of retroviral silencing in human T cells, and then to develop a system to detect and analyze cosuppression by retroviruses. This work will rely on the ability of fluorescence-activated cell sorting (FACS) to detect rare events in a large population of cells, and recover those rare cells. We will also test methods of destabilizing the silent state of a retrovirus. These experiments are likely to yield information that will benefit a broad array of gene replacement efforts. A demonstration of cosuppression would be particularly interesting because of the possibility that endogenous elements in the mammalian genome are regulated by this mechanism.Read moreRead less
The Identification Of Genes Involved In Mammalian Craniofacial Development And Disease
Funder
National Health and Medical Research Council
Funding Amount
$408,055.00
Summary
Birth defects arising from abnormal development of the embryo are a major cause of infant mortality and childhood disabilities. On average 3-4% of liveborn babies have a major congenital abnormality, and of the 15-20% of pregnancies which spontaneously abort, many are due to chromosomal or other developmental anomalies. A common feature of many developmental disorders is dysmorphology of the face, suggesting that genes important in patterning the face are also important in the development of oth ....Birth defects arising from abnormal development of the embryo are a major cause of infant mortality and childhood disabilities. On average 3-4% of liveborn babies have a major congenital abnormality, and of the 15-20% of pregnancies which spontaneously abort, many are due to chromosomal or other developmental anomalies. A common feature of many developmental disorders is dysmorphology of the face, suggesting that genes important in patterning the face are also important in the development of other organ systems. During development of the embryo many of the features of the face derive from a series of swellings termed the pharyngeal arches. The complex processes which determine how the face develops are in a large part controlled by the co-ordinated expression of a large number of genes in the first two of the five pharyngeal arch pairs. While we know some of the genes involved in these processes, the precise mechanisms of craniofacial development are relatively poorly understood. In this project we propose a large scale approach to identifying genes involved in development of the mammalian face and to further delineating their role in development and human disease. This approach takes advantage of state of the art genomic technologies available at the IMB and through existing collaborations overseas. In collaboration with Dr Bento Soares (University of Iowa) we have constructed a library containing all of the genes which are expressed in the first two pairs of pharyngeal arches in the developing mouse embryo. Using an approach designed to eliminate all those genes which are expressed in all or most tissues of the body and play a general role in the body's metabolism, we will select for those genes which play a specific and important role in embryonic development. We will then isolate the human counterparts of these genes and more thoroughly investigate their role in embryonic development and disease.Read moreRead less
The body tightly controls when and where proteins are made. Likewise once a protein has performed its function, it must be removed. Targeted proteolysis serves to reset the cell so that it can respond anew to stimuli that trigger growth and cell development. The Siah proteins are a family of proteins that control the turnover of other proteins. Siah proteins are remarkably highly conserved in evolution, and counterparts of the human proteins can be found in fruitflies, worms and plants. There ar ....The body tightly controls when and where proteins are made. Likewise once a protein has performed its function, it must be removed. Targeted proteolysis serves to reset the cell so that it can respond anew to stimuli that trigger growth and cell development. The Siah proteins are a family of proteins that control the turnover of other proteins. Siah proteins are remarkably highly conserved in evolution, and counterparts of the human proteins can be found in fruitflies, worms and plants. There are three different types of Siah protein in mice and this study investigates the function of the each protein by creating mice that lack one or more of these proteins. Our work to date has revealed that the Siah genes are involved in growth and fertility of mammals. The genes are also important for cell division, which implicates them in proliferative diseases such as cancer.Read moreRead less
Retrotransposons As Controlling Elements In Mammals: A Screen For Expression In Somatic Cells And Cancer
Funder
National Health and Medical Research Council
Funding Amount
$452,545.00
Summary
Differences between individual mammals are generally thought to be due to differences either between their genes, or between their environments. However, in many cases genetic or environmental factors cannot account for differences between individuals. We have studied mice in which dramatic differences between genetically identical individuals are due solely to the activity of a type of transposable element (transposon). There are tens of thousands of similar elements in the genomes of all mamma ....Differences between individual mammals are generally thought to be due to differences either between their genes, or between their environments. However, in many cases genetic or environmental factors cannot account for differences between individuals. We have studied mice in which dramatic differences between genetically identical individuals are due solely to the activity of a type of transposable element (transposon). There are tens of thousands of similar elements in the genomes of all mammals. A large body of evidence demonstrates that transposons can disrupt gene expression. To prevent this from occurring, most organisms have evolved mechanisms to keep transposons silent. However, fragmentary evidence indicates that transposons are at least sometimes expressed in normal and cancer cells. We hypothesize that activity of transposons in mammals alters gene expression sufficiently to cause variation between individuals, and that altered gene expression can cause disease (particularly cancer) and some manifestations of aging. As a first step toward testing this hypothesis, it is essential to acquire more complete information on the expression of transposons in normal and diseased cells. Furthermore, if transposon expression is closely linked to the development or progression of cancer or aging, then the ability to monitor such expression could have diagnostic utility. DNA array technology is coming into wide use to compare patterns of gene expression in different types of cells. We propose to adapt this method to the study of transposon expression. We will clone examples of all known classes of mouse and human transposon, and study transposon expression in: 1. Normal mice, at intervals from the earliest phase of development to old age, and 2. Human cancers of a variety of types. These studies will provide information of fundamental significance for mammalian biology, and also have the potential to lead to improved diagnosis of disease.Read moreRead less