2nd Year Research Reviews – 2012

2nd Year Research Reviews 2012

MPS II

Gustavo H.B. Maegawa, MD, PhD
Johns Hopkins School of Medicine, Department of Pediatrics
Baltimore, MD
“Induced-neuronal (iN) cells as told to study the pathogenesis of neurological manifestations in MPS II”

Dr. Maegawa received a one year extension. The final report will be submitted May 2015.

MPS IVA

Shunji Tomatsu, MD, PhD
Nemours Children’s Clinic – Delaware Valley of the Nemours Foundation
Wilmington, DE
“Development of Long Circulating Enzyme Replacement Therapy for MPS IVA”

Dr. Tomatsu received a one year extension. The final report will be submitted July 2015.

MPS III Grand Challenge Grant – with support from Team Sanfilippo

Dr. Brian Bigger
Stem Cell & Neurotherapies Group
Manchester, UK
”Evaluation of high dose genistein aglycone in the treatment of mucopolysaccharide diseases types IIIA, B and C”

In February of 2012, the National MPS Society announced the availability of a $235,000 Grand Challenge Grant for the treatment of MPS III. The Society and its MPS III foundation partners, including Team Sanfilippo, combined general research dollars with MPS III research dollars to create this unprecedented award amount. The purpose of the grant was to take a large step forward in finding a treatment for MPS III. Following a recommendation by the Society’s Scientific Advisory Board, the Grand Challenge Grant was awarded to Dr. Brian Bigger in June of 2012 for his project, “Evaluation of high dose genistein aglycone in the treatment of mucopolysaccharide disease types IIIA, B and C.”

The purpose of the project was to evaluate the efficacy of treating MPS III individuals with genistein using trial participants in the UK. Being a treatment trial, a significant amount of additional funds had to be raised and UK regulatory approval obtained before the trial could be started. In February of 2013, the Society’s Board became concerned about the delays in the start of the trial and whether the project was viable. A June 2013 deadline was set to begin the project or the funds would be withdrawn. Following positive movement towards starting the trial, the Society disbursed $117,500 to the project in June 2013 with the stipulation that the remaining funds would be disbursed after one year of treating trial participants if they were showing positive results.

As of May 2014, the project is not fully funded and UK regulatory approval has not been obtained. Due to the over two year intervening period since the Grand Challenge Grant was first advertised, the National MPS Society Board of Directors voted on May 3, 2014 to withdraw the undisbursed $117,500 support from the genistein project and to advertise the availability of these remaining funds to ensure they are spent on the best MPS III project at this time. The genistein project can be resubmitted for consideration along with other newer projects that may now be available.

ML II/III

Sara Cathey, MD
Greenwood Genetic Center
Greenwood, SC
PTC 124 for nonsense mutation suppression in ML II and III cultured fibroblasts

PTC124 is a compound that promotes the “read-through” of DNA nonsense mutations by inserting a random amino acid in place of the premature termination codon, allowing translation to continue until the proper termination codon is reached.  In essence, this changes the nonsense mutation, which produces no mature protein, to a missense mutation, which is typically less detrimental to the protein.  This compound is currently being investigated for the treatment of several genetic conditions, with the hope that the slight increase in protein production/activity that a missense mutation might allow could lessen the severity of disease in affected patients.

Our aim was to treat the fibroblasts of patients with mucolipidosis type II with PTC124 and then measure the activities of several lysosomal enzymes inside the cells as an indirect measurement of GlcNAc-1-phosphotransferase activity.  The initial experiment was performed in fibroblasts from an ML II patient with one nonsense mutation and one missense mutation.  Fibroblasts were handled in five different ways: either left untreated (baseline enzyme activity), or treated with four different concentrations of PTC124.  Cells were treated for approximately 24 hours.  The activity of four different lysosomal enzymes (alpha-fucosidase, beta-glucuronidase, beta-galactosidase and alpha-iduronidase) was measured in quadruplicate in the cells from each treatment condition.  PTC124-induced increased phosphotransferase activity would be expected to cause increased activity of lysosomal enzymes that rely on mannose-6-phosphate-mediated entry into the cell.  This initial experiment showed no effect on the activities of beta-galactosidase or alpha-iduronidase.  A modest but statistically significant increase in both alpha-fucosidase and beta-glucuronidase activity was observed in cells treated with 20 mM PTC124 compared to untreated cells.

Based on these preliminary results, these studies were then repeated and expanded to determine whether the results were, 1. reproducible, and,  2. due to PTC124 induced read-through of nonsense mutations.  To this aim, we used fibroblasts from an unaffected individual, from the same ML II patient described above (one nonsense mutation and one missense mutation) and from an ML III patient with no nonsense mutations.  Cells were treated with 20 mM PTC124 or left untreated.  The activities of seven different lysosomal enzymes (including the four mentioned previously) were measured in quadruplicate.  We did not observe the increase in activity for alpha-fucosidase or beta-glucuronidase that was seen in the first round of experiments in treated versus untreated cells from the ML II patient.   Furthermore, none of the seven enzymes demonstrated increased activity in treated versus untreated cells in any of the fibroblast lines.

The results obtained in the first set of experiments were not reproducible, and PTC124 does not appear to have a significant positive effect on lysosomal enzyme activity in fibroblasts harboring a nonsense mutation. It is still possible that an appreciable increase in enzyme activity would be observed following treatment with PTC124 if a patient had two nonsense mutations.  If such a sample becomes available to us, we could repeat the latter set of experiments again.