The Embryological And Molecular Basis Of Zic2 Involvement In Holoprosencephaly
Funder
National Health and Medical Research Council
Funding Amount
$624,145.00
Summary
The brain is the most complex organ in the human body and diseases or disorders of the brain can become evident at any stage of life. Generally such problems have profound consequnces for the affected individuals and their families. One of the most common problems of brain development that is evident either at birth or within the first years of life is called holoprosencephaly (HPE). This condition affects the midline of the brain and the face and can lead to delay in mental, motor and language ....The brain is the most complex organ in the human body and diseases or disorders of the brain can become evident at any stage of life. Generally such problems have profound consequnces for the affected individuals and their families. One of the most common problems of brain development that is evident either at birth or within the first years of life is called holoprosencephaly (HPE). This condition affects the midline of the brain and the face and can lead to delay in mental, motor and language development, seizures, and obvious facial abnormalities. In its most severe form only one eye develops in the middle of the face, a condition known as cyclopia and a large majority of the severely affected children will die late in gestation or at birth. This condition can be inherited, but because the genetic lesions that cause this problem affect different people differently, people can carry the causative genetic change(s) without knowing it. We need to identify and study the genetic lesions that contribute to this condition in order to begin to understand how we can stop these mutations affecting the developing foetus. Because it is difficult to study embryonic development in humans we have generated a mouse model of this condition. In the mouse model just one gene (called Zic2) is altered and embryos that have two copies of this alteration develop the most severe form of cyclopia and die in the second half of gestation. This means that the normal role of this gene is to stop us developing HPE. We will use this mouse model to see just when and how the Zic2 gene prevents HPE. In addition, we will look to see what other genes Zic2 interacts with by breeding mice that carry the mutation in Zic2 with mice that carry a mutation in a second gene that can also cause HPE. These experiments are very important because if we understand how Zic2 and other genes protect us from HPE we can begin to design strategies to decrease the risk of a child developing this condition.Read moreRead less
The Role Of Cholesterol In Patched/hedgehog Signalling During Mammalian Development.
Funder
National Health and Medical Research Council
Funding Amount
$198,660.00
Summary
Fluctuations in levels of cholesterol during development of the mammalian embryo have been shown to have catastrophic affects leading to gross deformities particularly in terms of brain and facial development. The requirement of the developing embryo for cholesterol has been linked to the patched-hedgehog signalling pathway which we have previously shown to be central to mammalian development as well as tumour formation. In particular, the patched protein which is responsible for regulating sign ....Fluctuations in levels of cholesterol during development of the mammalian embryo have been shown to have catastrophic affects leading to gross deformities particularly in terms of brain and facial development. The requirement of the developing embryo for cholesterol has been linked to the patched-hedgehog signalling pathway which we have previously shown to be central to mammalian development as well as tumour formation. In particular, the patched protein which is responsible for regulating signalling through this complex cascade of protein interactions has a domain similar to that which in other proteins has been shown to detect and respond to intracellular levels of cholesterol. The patched protein binds to hedgehog at the surface of the cell and mediates the transduction of the the hedgehog signal into the cell. By analogy to the role of sterol sensing domains in other proteins, we hypothesise that this domain in patched detects fluctuations in intracellular cholesterol levels which in turn alter trafficking of patched to the cell surface where it can participate in the hedgehog receptor complex. This hypothesis is supported by our preliminary data which suggests that patched is normally localised both at the cell surface and intracellularly. We are proposing a series of experiments to test our hypothesis, most of which deal with determing the localisation of patched in a cell culure system exposed to agents aimed at varying the intracellular levels of cholesterol. Subcellular localisation of patched will be analysed by immunofluorescence, electron microscopy and immunoblotting analysis. We will also test the ability of patched to aggregate at the cell surface with other molecules important in receiving and sending the hedgehog signal. The experiments in this proposal are likely to give the first clues as to the function of the sterol sensing domain in patched and its role in mediating the vital link between cholesterol and embryonic development.Read moreRead less