A Y CHROMOSOME MODEL FOR THE SEX DETERMINING FUNCTION OF THE HUMAN ATRX GENE
Funder
National Health and Medical Research Council
Funding Amount
$272,131.00
Summary
Human sex determination is controlled by a genetic pathway which culminates in the development of a testis or an ovary in the human embryo. At the head of this pathway is the master switch gene SRY on the Y chromosome, which controls a cascade of other genes critical for switching on testis development. Several other genes have been identified by clinical mutations which reverse sex of XY embryos. One sex reversing gene is ATRX on the human X chromosome. Mutation in ATRX causes XY embryos to dev ....Human sex determination is controlled by a genetic pathway which culminates in the development of a testis or an ovary in the human embryo. At the head of this pathway is the master switch gene SRY on the Y chromosome, which controls a cascade of other genes critical for switching on testis development. Several other genes have been identified by clinical mutations which reverse sex of XY embryos. One sex reversing gene is ATRX on the human X chromosome. Mutation in ATRX causes XY embryos to develop as females, as well as causing many unrelated disorders such as alpha-thalassemia. ATRX seems to be a transcription factor that controls the activity of other genes, but it is difficult to understand how it functions because it is active in all parts of the body and mutation has many different effects in humans. However, we recently discovered that in marsupial mammals that this gene has a copy on the Y chromosome (ATRY) as well as the X (ATRX). Remarkably, there is a division of labour between ATRY, which acts only in developing gonads, and ATRX, which is active everywhere else. This testis-specific ATRY gene may reveal how ATRX interacts with other genes to make a testis, without the complications of its action in other tissues. We will therefore clone and characterize ATRX-Y and its protein product to find out when and where it acts in the sex determining pathway. We will use very large cloned pieces of the marsupial genome to discover elements controlling the testis-specific expression, and we will identify the interactions of ATRY with other proteins. The testis determination pathway is a good model for the differentiation of other human organs. Our work on ATRY will show us how this class of transcription factors is activated in different tissues during development, and how it controls other genes. This will lead to a better understanding of the genetic control of human organogenesis and the effects of mutation on human development.Read moreRead less
ATR-X Syndrome: Role Of ATRX In Testicular Growth And Spermatogenesis
Funder
National Health and Medical Research Council
Funding Amount
$650,881.00
Summary
Infertility is surprisingly common and affects 1 in 20 Australian men. Testosterone and its receptor, the androgen receptor, are well known to be essential for spermatogenesis and fertility. We have identified an important regulator protein (ATRX) of androgen receptor activity and show that loss of function of ATRX in testes of mice leads to spermatogenesis defects. Identifying the molecular action of ATRX will lead to a better understanding of the underlying causes of infertility in men.
A New Paradigm For SWI/SNF Chromatin Function; The ATPase Dependent Remodeler Is A Component Of The MeCP2 Complex
Funder
National Health and Medical Research Council
Funding Amount
$254,250.00
Summary
DNA methylation is a major determinant in the epigenetic silencing of many genes. The mechanisms underlying that targeting of DNA methylation and the consequence, that is, transcriptional silencing are relevant to human development and disease. Examples of the significance of alterations in the controls of DNA methylation and histone deacetylation in human disease include mental retardation (fragile X syndrome, Rett syndrome) and carcinogenesis. Evidence is emerging that a family of methylation ....DNA methylation is a major determinant in the epigenetic silencing of many genes. The mechanisms underlying that targeting of DNA methylation and the consequence, that is, transcriptional silencing are relevant to human development and disease. Examples of the significance of alterations in the controls of DNA methylation and histone deacetylation in human disease include mental retardation (fragile X syndrome, Rett syndrome) and carcinogenesis. Evidence is emerging that a family of methylation specific (methyl-CpG binding domain, MBD) proteins have the capacity to bind to methylated sequences and repress transcription. The mechanisms that target CpG methylation however still remain unclear. Furthermore, it is becoming increasingly evident that methyl-CpG binding proteins are not alone in silencing transcription and other epigenetic components are thought to influence transcription (namely, SWI-SNF activation complex). This grant proposal concentrates on our most recent work which demonstrates a new molecular mechanism of transcriptional repression extending the mechanism mediated by MeCP2. Our results are the first to show that the human SWI-SNF ATPase complex is a transcriptional repressor and is identified as part of the MeCP2-histone deacetylase repressor complex. This data extends the mechanistic link between DNA methylation, chromatin remodelling and transcriptional regulation. More importantly, the experimental findings could lead to a re-examination of the mechanistic basis behind MeCP2 transcriptional repression and epigenetic modification. Our findings suggest a new paradigm for SWI-SNF as a component of the MeCP2 methylation dependent silencing complex.Read moreRead less
Characterization Of A Novel Human X-linked Gene RBMX, A Candidate For X-linked Mental Retardation
Funder
National Health and Medical Research Council
Funding Amount
$356,870.00
Summary
We recently discovered a novel gene (which we have called RBMX for RNA-binding protein, X chromosome) on the human X chromosome. Its function is quite unknown, but it is active in all tissues, and it has changed very little in evolution, so we think it must have an important function in human development. Genes with a similar sequence bind to RNA and convert it to its final active form, so RBMX may have a similar role. Other RNA-binding proteins are active in the brain, so we suspect that RBMX m ....We recently discovered a novel gene (which we have called RBMX for RNA-binding protein, X chromosome) on the human X chromosome. Its function is quite unknown, but it is active in all tissues, and it has changed very little in evolution, so we think it must have an important function in human development. Genes with a similar sequence bind to RNA and convert it to its final active form, so RBMX may have a similar role. Other RNA-binding proteins are active in the brain, so we suspect that RBMX may be involved in brain development and learning. The RBMX gene is also interesting because it has a copy called RBMY on the human Y chromosome, which is thought to have a critical (unknown) function in sperm production. Of particular note is our finding that RBMX maps to the long arm of the human X chromosome at Xq26. This is a region that contains several inherited mental retardation syndromes called X linked mental retardation (XLMR) which are carried by females and manifest in males. At least eight XLMR syndromes have been mapped to human Xq26. Several of the syndromes have characteristic skeletal and facial abnormalities, as well as a range of other anomalies.. We will completely characterise the human RBMX gene. As well as giving us fresh clues to its function, this will allow us to make a mouse strain that lacks the gene (knockout) so we can see whether it is critical for life, and if it is involved in brain development and learning. Identification of an XLMR gene coding for an RNA binding protein will shed light on the role of RNA metabolism in the brain, and the effect of disruptions of RNA processing on mental function. We will then screen the RBMX gene in families with XLMR syndromes, to look for RBMX mutations in patients which may cause XLMR. If mutations in RBMX cause one or more XMLR phenotypes, it will be possible to use this knowledge to diagnose the condition and detect carriers.Read moreRead less
Identification And Characterisation Of Novel Genes For Congenital Cataract
Funder
National Health and Medical Research Council
Funding Amount
$432,750.00
Summary
Cataracts are the leading cause of blindness worldwide. The term describes a clouding of the lens which may lead to visual impairment. Congenital cataracts (present at birth) are less common than age-related cataract but the lifelong impact on vision can be severe, with a third of patients remaining legally blind. Late complications such as aphakic glaucoma may be blinding. We have shown that congenital cataracts are often inherited and have performed a population-based study in South-Eastern Au ....Cataracts are the leading cause of blindness worldwide. The term describes a clouding of the lens which may lead to visual impairment. Congenital cataracts (present at birth) are less common than age-related cataract but the lifelong impact on vision can be severe, with a third of patients remaining legally blind. Late complications such as aphakic glaucoma may be blinding. We have shown that congenital cataracts are often inherited and have performed a population-based study in South-Eastern Australia over the past 5 years to determine the causative genes. A large number of families have been involved in the study and solid progress has been made in identifying mutations in cataract genes and understanding what effect these may have on the patient's prognosis. We have recently identified a new gene in a large Australian family with a syndrome of cataract, mental retardation and teeth problems. This syndrome, known as Nance-Horan syndrome was originally described in Australia 30 years ago and we have worked with the original family to find the exact gene responsible. We already know that this gene causes the same syndrome in other families and in this project we will examine whether it can cause cataract without the other features or mental retardation without cataract. We will perform a series of experiments to learn what this gene does and how it causes the disease. We have also selected 3 other very interesting families with congenital cataracts for further study as we either know already or strongly suspect that they will enable us to identify further new genes for cataract, and in one case mental retardation. Our work in other diseases indicates that understanding the genes in severe young onset cases can give valuable clues to the causes of age-related forms and may in the future enable new ways to prevent and treat the commonest cause of worldwide blindness.Read moreRead less
Role Of Chromatin Structure In The Regulation Of Stem Cell Function
Funder
National Health and Medical Research Council
Funding Amount
$272,036.00
Summary
The aim of this project is to understand more about the nature of stem cells. Stem cells are cells which have the capacity to proliferate indefinitely but, at the same time, retain the capacity to differentiate into one or more cell types. Lower animals, such as amphibians, have a much greater capacity than humans to regenerate body parts. For example, axolotls can regenerate an entire limb if one limb is injured. This is because they retain undifferentiated stem cells in their limbs which can b ....The aim of this project is to understand more about the nature of stem cells. Stem cells are cells which have the capacity to proliferate indefinitely but, at the same time, retain the capacity to differentiate into one or more cell types. Lower animals, such as amphibians, have a much greater capacity than humans to regenerate body parts. For example, axolotls can regenerate an entire limb if one limb is injured. This is because they retain undifferentiated stem cells in their limbs which can be reactivated in the event of injury. Interestingly the adult human brain contains a small population of stem cells. The aim of this project is to find out more about how these cells remain undifferentiated and what is it about them which allows them to form different cell types. If more is known about these cells maybe in the future it will be possible to stimulate them to repair damaged parts of the nervous system. It may also be possible to treat people suffering from diseases like Alzheimer's disease, Parkinson's disease or spinal injuries.Read moreRead less