Gene replacement therapy is a single dose treatment in which a patient receives in the body a new, working copy of the missing or nonfunctional gene. The new gene is able to give the body instructions to produce a particular protein that the person is missing.
Gene therapy is delivered via vectors that carry a new, working copy of the gene into the right cells inside the body. The most commonly used vector is AAV (adeno-associated virus). Viruses are used because they are very good at transporting cargo into cells. The original, viral DNA, is replaced with DNA encoding the gene of interest, and the virus is therefore no longer considered a virus, but solely a transport vector, unable to propagate or cause disease.

The CTNNB1 gene is a very good candidate for gene replacement therapy since CTNNB1 Syndrome is caused by a loss-of-function mutation (one copy of the gene does not function properly), and also because this specific gene is small enough to fit into the vector of choice

The team at The University of Sydney, CMRI and National Institute of Chemistry Slovenia use a combination of human patient- grown stem cells and specially grown organoids (tissue cultures). Patient cell samples are obtained and reprogrammed to become pluripotent stem cells. These cells can then mature into any other type of cell or tissue found in the body, subsequently they can be used to create organoids, simplified versions of human organs. For example, pluripotent stem cells can be directed to become neurons to create brain organoids that mimic the patient’s brain responses to treatments.

Once created, gene therapy and their viral vector can be tested on human stem cells, organoids and other models. This approach leads to greater accuracy of results, as we can model how therapies could be taken up by the patient, observe short and long-term responses and predict whether the therapy would ultimately be successful.

This is a 2-year project with the objectives listed below.


  • Design a number of variants of therapeutic CTNNB1 genes and the corresponding genes that regulate their expression when inserted into a host’s DNA

  • Test these mini-gene constructs to assess their effectiveness then design a clinical AAV that contains the CTNNB1 constructs

  • Develop patient pluripotent stem cells into neurons and brain organoids

  • Conduct vector manufacturing studies, for example assessing the stability of the CTNNB1 genes in the AAV.


  • Test the new vectors in neuron and brain organoids

  • Study the expression and overexpression of the CTNNB1 gene in other models

  • Work with our research team, including clinicians, to optimise the therapeutic payload of genes that are packaged inside the viral vector

  • Work with our clinical manufacturing team towards development of bespoke protocols to enable production of clinical grade vectors for therapeutic applications.