News from the Amino Acid Metabolism disorder research group
For over a decade the NSW PKU Association has been generously funding PKU research at The Children’s Hospital at Westmead. The amino acid metabolism disorder research group, led by Dr Michael Nafisinia, focuses on researching potential therapies for PKU using time effective and modern technology like High Through Drug screening and clinically relevant disease models such as organoids. Two current major PKU research projects include:
1- PKU Biospecimen
Bank for drug testing and functional Genomics Research
The proximate cause of PKU is a deficiency of the enzyme phenylalanine in the liver. The genotype of a PKU patient is recognised as the primary determinant of the clinical features (mild, moderate or classic), as well as their responsiveness to treatment. Currently, the study on the pathogenesis of PKU is limited, which is partly due to the lack of appropriate disease models, and those that can mimic the pathology of the disease in vitro and in vivo. As in clinical settings obtaining patient liver cells (hepatocytes) is very difficult, the amino acid metabolism disorder group uses induced pluripotent stem cells (iPSCs) technology to reprogram back the patient’s somatic cells such as skin or blood cells into an embryonic-like pluripotent state. The embryonic-like pluripotent has identical similarities to the embryonic stem cells in terms of morphology, proliferation, gene expression pattern, epigenetics, and differentiation capacity which enables the development of an unlimited source of any type of human cell. The amino acid metabolism disorder group has already established an iPSCs library obtained from fibroblasts and lymphoblastoid cell lines (LCLs) from 7 individuals carrying:
1- compound heterozygous mutations P281L & R408Q
2- compound heterozygous mutations F39L & a splice site mutation of IVS10-11G>A
3- compound heterozygous mutations F299C & R408W
4- compound heterozygous mutations F299C & R408W
5- compound heterozygous for R252Q & IVS12+1G>A (splice site mutation) as well as homozygous for T67I
6- compound heterozygous mutations c.590_612del23; 590_612del23 (a 23-bp deletion in exon 6) & a splice site mutation in exon 8 (c.912+1G>A; IVS8+1G>A]
7- a homozygous mutation R176X
These cells have already been differentiated into hepatocytes for the purpose of high throughput drug screening. Further, as organoids are now believed to be the most clinically relevant models for medical research, the amino acid metabolism disorder group has a plan to also differentiate the iPSCs into liver organoids that resemble in vivo liver. This in turn provides an opportunity for detailed functional genomics investigations which consequently result in the identification of novel therapies for PKU.
2- High Throughput Drug Screening
With access to the patient hepatocyte and organoid library, as well as a well-established high throughput drug- screening pipeline, the amino acid metabolism disorder group aims to achieve high-throughput screening of potential therapeutic agents. As new drug discovery and development is an expensive long-drawn-out process and in order to significantly reduce time and drug development costs, in the first stage, the amino acid metabolism disorder has a plan to repurpose “old drugs” that have already been approved for use in the treatment of other diseases, especially for rare diseases.