FABRY disease is a rare genetically inherited disorder. It occurs when a specific enzyme known as alpha-galactosidase (a-gal A) is absent from human cells.
The body loses the ability to produce this enzyme when there is a mutation in the gene Galactosidase Alpha (GLA).
“Although it is a rare genetic condition, its effect is life-threatening. When the enzyme a-gal A is absent, cells accumulate a type of fat known as globotriaosylceramide(Gb3).
The excessive accumulation of Gb3 narrows the blood vessels, and leads to serious kidney and heart problems,” Associate Professor Dr Kumaran Narayanan of Monash University, Malaysia, told The Petri Dish recently.
“The cornerstone treatment for Fabry disease is Enzyme Replacement Therapy (ERT). This treatment replaces the deficient enzyme in the patient’s body via intravenous diffusion.
“However, the treatment does not cure the condition but only provides sufficient enzyme for the patient to survive from time to time,” said Kumaran.
Kumaran foresees the a-gal A, enzyme can be restored in human cells using gene therapy.
“Gene therapy introduces a healthy copy of the GLA gene to the cells to restore the normal enzyme level. Patients will be able to produce the corrected version of the enzyme once the healthy copy of the gene is injected into cells of the patients.
“For gene therapy to hail as a promising treatment, a reliable Fabry model is needed. From the model, distinct Fabry biochemical traits and the abnormal changes in the body functions caused by the disease can be determined. It ensures the enzyme is expressed accurately when the healthy copy of the gene is introduced,” he elaborated.
Thus, Kumaran and his team developed a human knockout model with a series of mutant lines. The mutant lines were developed by deleting a specific position in human cells, known as GLA exon 3, using CRISPR/Cas9 technology. Knockout is described as deleting a desired gene using gene editing.
The recent rise of the CRISPR/Cas9 gene targeting method allows researchers to readily generate mutation in any gene of interest. The model also assesses if GLA, the enzyme expressed from the vectors can clear the Gb3 deposits to the level found in a non-Fabry individual.
“Currently, we have licensed the knockout model to a Canadian biotechnology company so it can serve as a platform to facilitate studies on GLA gene expression with different mutant lines,” he added.
Parallelly, Clearance Cheong, his PhD student discovered an enzyme from a type of nematode worm, known as Caenorhabditis elegans that shares structural and functional similarities with human 𝛼-gal A. This enzyme can effectively metabolises and clears the Gb3 deposits in Fabry cells that is implicated in the condition.
“This finding holds significant promise for advancing our understanding of Fabry disease and may pave the way for potential therapeutic strategies aimed at clearing Gb3 deposits and ameliorating the condition’s symptoms,” said Kumaran.
He also noted that the treatment of Fabry disease remains financially unattainable for most patients due to its high cost. The recent initiative proposed by the Deputy Minister of Health, Datuk Dr Noor Azmi Ghazali, to create a dedicated fund for supporting the treatment of rare disease patients is a highly commendable and much-needed step.
Thus, to reduce the cost of the treatment Kumaran and his team discovered Escherichia coli (E.coli) as a potential inexpensive vector to transport GLA gene into the cells.
“Vector can be described as a vehicle that introduces healthy copy of GLA gene to the cells using a specially engineered virus. There are numerous clinical trials underway involving AAV (adeno-associated virus) as a vector but using E.coli can provide an affordable treatment for many patients,” he added.
Article originally published in: https://thepetridish.my/2023/07/03/scientist-restoring-key-enzyme-to-treat-fabry-disease/