Variable Expressivity And Epigenetic Inheritance At The Axin Fused Locus In The Mouse
Funder
National Health and Medical Research Council
Funding Amount
$242,545.00
Summary
Genes influence the way we look and variations in gene sequence can account for the differences between individuals. Family traits are often credited to gene variants that are passed down through generations of families. There is now intriguing evidence, some coming from our laboratory, that gene sequence is not the only thing we inherit from our parents. Modifications that alter the expression but not the sequence of a gene, known as epigenetic modifications can, it turns out, be inherited in m ....Genes influence the way we look and variations in gene sequence can account for the differences between individuals. Family traits are often credited to gene variants that are passed down through generations of families. There is now intriguing evidence, some coming from our laboratory, that gene sequence is not the only thing we inherit from our parents. Modifications that alter the expression but not the sequence of a gene, known as epigenetic modifications can, it turns out, be inherited in mammals. An epigenetic modification is a mark, present on some genes that determines whether the gene is expressed (switched on) or silent. Animals are thought to acquire this mark during development and it is retained throughout life except in germ cells where the mark is generally, but not always, erased. The establishment of the mark appears to be a stochastic event at the cellular level resulting in mosaic expression. The percentage of marked cells can differ from one individual to another . In theory, this could help to explain why individuals with identical genetic information, such as identical twins, can have different phenotypic characteristics. The fact that these modifications can be inherited implies that there is an alternative mode of inheritance of genetic traits which does not involve mutation but which can be carried from generation to generation in a semipermanent way. Understanding the mechanisms underlying these events is important if we wish to predict or modify the phenotype of an invidual or that of his or her offspring.Read moreRead less
Identification Of Variably Expressed Genes In Isogenic Mice And Humans
Funder
National Health and Medical Research Council
Funding Amount
$293,080.00
Summary
Monozygotic twins are known to have different phenotypic characteristics even though they contain identical genetic information. It is not uncommon for identical twins to have different coloured eyes and to show discordance for genetic diseases. While there is no definitive explanation for these differences they are generally thought to be caused by subtle changes in environmental conditions. We believe however, that these differences are set up during early embryonic development by the establis ....Monozygotic twins are known to have different phenotypic characteristics even though they contain identical genetic information. It is not uncommon for identical twins to have different coloured eyes and to show discordance for genetic diseases. While there is no definitive explanation for these differences they are generally thought to be caused by subtle changes in environmental conditions. We believe however, that these differences are set up during early embryonic development by the establishment of epigenetic modifications to the DNA. An epigenetic modification is a mark which determines whether a gene is expressed (switched on) or silent (switched off). The establishment of the mark appears to be a stochastic event which can result in different physical characteristics between genetically identical individuals. We would like to study this process in inbred mouse strains and in humans. Inbred mouse strains are maintained by inbreeding (brother-sister mating) to ensure that all individuals of the strain are isogenic (genetically identical) and in such a way that environmental variation is minimised. We will use established molecular techniques to find genes which are variably expressed among isogenic mice and humans. This work will enable us to discover genes which are sensitive to epigenetic modifications and whose epigenotype must be known if we are able to predict phenotype or disease state.Read moreRead less
The Establishment Of Epigenetic Marks At Metastable Epialleles In The Mouse
Funder
National Health and Medical Research Council
Funding Amount
$372,750.00
Summary
Occasionally, identical twins are found to have distinctly different characteristics, such as eye colour or severity of genetic disease, that clearly cannot be explained by their genetic makeup, and are unlikely to be the result of environmental differences. In genetically identical mice, similar cases exist, where some mice have a yellow coat and others a brown coat. In instances such as these, a growing body of evidence suggests that certain modifications to genes are responsible. These modifi ....Occasionally, identical twins are found to have distinctly different characteristics, such as eye colour or severity of genetic disease, that clearly cannot be explained by their genetic makeup, and are unlikely to be the result of environmental differences. In genetically identical mice, similar cases exist, where some mice have a yellow coat and others a brown coat. In instances such as these, a growing body of evidence suggests that certain modifications to genes are responsible. These modifications are not traditional DNA mutations, but are chemical modifications of the basic sequence. Currently, we do not know when these DNA modifications are established during foetal development. We will use the mouse coat colour gene mentioned above to investigate when the different physical characteristics are established in embryonic development. Indeed, there is increasing evidence that critical periods exist in human foetal development where minor environmental or nutritional changes can affect long-term health of the adult. Perhaps the establishment of the DNA modifications are under an environmental or nutritional influence. Further study of when and how the DNA modifications are set-up during embryonic development is necessary in order to understand these events.Read moreRead less
A Random Mutagenesis Screen To Identify Modifiers Of Epigenetic Phenomena In The Mouse.
Funder
National Health and Medical Research Council
Funding Amount
$680,750.00
Summary
In recent months, both the human and mouse genome projects have been completed. The main focus now for mammalian geneticists is to discover the function of the genes sequenced in these initiatives. One way to achieve this goal is by random mutagenesis followed by screening of mice for novel phenotypes. In the mouse, ethylnitosourea (ENU) is a chemical that can be used to perform the mutagenesis. ENU causes mutations in sperm. We are using ENU mutagenesis to search for genes that modify epigeneti ....In recent months, both the human and mouse genome projects have been completed. The main focus now for mammalian geneticists is to discover the function of the genes sequenced in these initiatives. One way to achieve this goal is by random mutagenesis followed by screening of mice for novel phenotypes. In the mouse, ethylnitosourea (ENU) is a chemical that can be used to perform the mutagenesis. ENU causes mutations in sperm. We are using ENU mutagenesis to search for genes that modify epigenetic states. Epigenetic modifications are alterations in the genome that do not change the DNA sequence, yet silence the expression of genes. Silencing occurs on a cell-by-cell basis within a tissue resulting in mosaic expression. Silencing can also occur between individuals of the same genetic makeup. For example, identical twins are occasionally found that have distinctly different characteristics, such as eye colour or severity of genetic disease. These differences may be the result of variable epigenetic modifications. However, very little is known about how these variable epigenetic modifications are controlled. We wish to find the proteins involved in establishing and maintaining epigenetic states. It is likely that these processes play a fundamental role in the determination of phenotype, both in normal development and disease.Read moreRead less
Molecular Regulation Of CRH Gene Expression In The Human Placenta
Funder
National Health and Medical Research Council
Funding Amount
$70,285.00
Summary
Approximately 70% of infant death is a result of premature birth. Preterm delivery occurs in 6-10% of pregnancies, and there has been no reduction in this rate in the last 30 years. This is largely because we remain ignorant of how normal and preterm birth is controlled. Understanding the physiology of human pregnancy is a critical step in the development of ways to detect and prevent preterm birth. Our group has demonstrated a link between production of a hormone (corticotropin releasing hormon ....Approximately 70% of infant death is a result of premature birth. Preterm delivery occurs in 6-10% of pregnancies, and there has been no reduction in this rate in the last 30 years. This is largely because we remain ignorant of how normal and preterm birth is controlled. Understanding the physiology of human pregnancy is a critical step in the development of ways to detect and prevent preterm birth. Our group has demonstrated a link between production of a hormone (corticotropin releasing hormone, CRH) in the placenta and the length of time the baby is carried in the mother. In women who will deliver prematurely the rise in CRH production occurs earlier and more rapidly, while in women who deliver late the rise occurs more slowly. This work has led to the concept of a biological clock that determines the length of time the fetus will be carried by the mother before birth, and in which production of CRH in the placenta plays a central role. We have been studying how the CRH gene is controlled in placental cells. We have discovered some regions in the DNA of the CRH gene which have important roles in controlling how much CRH is made by the placenta. The experiments described in this project will determine the molecular mechanisms that control the production of CRH in the human placenta. This will be done by examining the DNA sequences involved in controlling the CRH gene and by identifying the proteins that actually perform the regulating functions that result in either increased or decreased amounts of CRH being produced by the placenta. This important information will help us better understand how normal and preterm birth is controlled, and from that knowledge new ways to detect and prevent premature birth can be developed.Read moreRead less
In Vivo And In Vitro Studies Of The Human -308 TNF Promoter Polymorphism.
Funder
National Health and Medical Research Council
Funding Amount
$232,131.00
Summary
The identification of genetic variation in region of the DNA that controls expression of the inflammatory cytokine Tumour Necrosis Factor (TNF) and its association with a number of autoimmune and inflammatory diseases, has led to speculation that this genetic difference may play a role in predisposing some people to these diseases. We have isolated an activity, TPF1, that may regulate expression through interaction with this DNA control region. During the tenure of this grant we intend to clarif ....The identification of genetic variation in region of the DNA that controls expression of the inflammatory cytokine Tumour Necrosis Factor (TNF) and its association with a number of autoimmune and inflammatory diseases, has led to speculation that this genetic difference may play a role in predisposing some people to these diseases. We have isolated an activity, TPF1, that may regulate expression through interaction with this DNA control region. During the tenure of this grant we intend to clarify some of these questions, we will generate genetically modified mice that have either of the two genetic forms of the human TNF promoter. These mice will be compared in two models of associated disease, murine Lupus and cerebral malaria. We will also characterise the interactions of TPF1 with other components of the TNF control region. An understanding of the role of TPF1 in controlling TNF expression and an appreciation of the cell types that are able to express the phenotype, will allow the development of more subtle, cell specific strategies to modulate the activity of TNF without completely abolishing expression and may lead to better preventative and therapeutic strategies.Read moreRead less
Inherited disorders of the blood, such as sickle-cell anaemia and thalassaemia, result from mutations in the genes that produce haemoglobin. Current treatments can partially alleviate some of the debilitating symptoms of these diseases but these treatments have significant side effects, and despite the best efforts of clinicians, many patients succumb to their conditions at an early age. It has been observed that certain individuals exhibit a milder form of the disease, as a consequence of the r ....Inherited disorders of the blood, such as sickle-cell anaemia and thalassaemia, result from mutations in the genes that produce haemoglobin. Current treatments can partially alleviate some of the debilitating symptoms of these diseases but these treatments have significant side effects, and despite the best efforts of clinicians, many patients succumb to their conditions at an early age. It has been observed that certain individuals exhibit a milder form of the disease, as a consequence of the reactivation of their foetal haemoglobin genes, (a distinct set of genes that would have been active in utero but are normally silenced around the time of birth). It is widely accepted that if pharmaceutical means can be found for reactivating the foetal haemoglobin genes then many patients would benefit. The regulation of the foetal globin genes, like most human genes, is complicated and there are few obvious means of increasing their activity. Nevertheless, it is believed that by investigating the molecular mechanisms by which they are controlled it will be possible to devise therapeutic agents that mimic these mechanisms or to develop agents that prevent the shutdown of the foetal genes around birth. To this end we have been working on the molecules that regulate the activity of the haemoglobin genes. We have recently cloned a number of DNA-binding proteins, and their co-factors, that appear to be involved in silencing foetal globin gene expression. This grant proposal is concerned with learning how these new molecules operate to silence gene expression as a first step towards designing agents that will prevent the silencing.Read moreRead less
Functional Characterisation Of Regulators Of Human Globin Gene Switching
Funder
National Health and Medical Research Council
Funding Amount
$232,131.00
Summary
Red blood cells produce haemoglobin, a tetramer of two alpha globin chains and two beta-globin chains. Haemoglobin reversibly interacts with oxygen in such a way that it efficiently shuttles oxygen between the lungs and the rest of the body. Integrity of the hemoglobin molecule, and red cells which carry it, is essential for life of all organisms with blood. The alpha-globin and beta-globin chains that make up haemoglobin are prodcued by red cell precursors in the bone marrow according to the ge ....Red blood cells produce haemoglobin, a tetramer of two alpha globin chains and two beta-globin chains. Haemoglobin reversibly interacts with oxygen in such a way that it efficiently shuttles oxygen between the lungs and the rest of the body. Integrity of the hemoglobin molecule, and red cells which carry it, is essential for life of all organisms with blood. The alpha-globin and beta-globin chains that make up haemoglobin are prodcued by red cell precursors in the bone marrow according to the genetic blueprint (genes) that are inherited. Genetic disorders resulting from defects in the beta-globin gene are the most common inherited disorders of man. Children who fail to make beta-globin have a disease known as beta-thalassaemia. They are transfusion dependent from ~ 6 months of age and need intensive chelation therapy (infusions) to avoid the serious consequnces of iron overload. The average life expectancy in Western cultures is ~ 30 years. There is no cure. In third world countries where a reliable blood supply is unavailable, death occurs earlier. Patients are aften infected with blood born viruses such as hepatitis B, hepatitis C and the AIDS virus, HIV. Sickle cell anaemia is also a very common disease. It is due to a single DNA base mutation at in the beta-globin gene that results in production of normal amounts of a defective beta-globin molecule (HbS). In low oxygen, HbS molecules polymerize in red cells and irreversibly damage them. These red cells get trapped in small blood capillaries throughout the circulation causing small infarcts which results in severe pain and organ damage. The life expectancy is <2 years in the thrid world and ~20-30 years in the west. The irony of these two diseases is that there is a perfectly normal fetal globin gene that has been silenced during fetal life. This grant aims to understand the mechanism of the switch from fetal to adult globin gene usage so it can be reversed in adults with b-thalassemia and sickle cell diseaseRead moreRead less
Functional Validation Of FoxP3 Target Genes In Human Regulatory T Cells
Funder
National Health and Medical Research Council
Funding Amount
$545,341.00
Summary
Using DNA based technologies we have focused on rare white blood cells known as regulatory T cells. These cells are policeman of the immune system and are responsible for maintaining balanced immune reactions, and preventing attack against harmless substances. These cells prevent autoimmune disease in healthy individuals, and only by first understanding how they work normally can we investigate and correct the defects in autoimmune diseases such as type 1 diabetes.