FUNDED PROJECTS

A wide array of devastating human genetic disorders results from single gene (monogenic) loss-of-function mutations. In these disorders, both copies of the gene are affected and lead to the disease state which typically occurs early in childhood and may lead to premature death. Also classified as homozygous recessive disorders, these include dozens of illnesses like cystic fibrosis, Tay-Sachs, Niemann-Pick, Gaucher’s, Zellweger’s, and the Neuronal Ceroid Lipofuscinosis (NCL) family of neurodegenerative disorders (e.g. Batten Disease), among many others. Reintroduction of a functional copy of the defective gene (gene therapy) into the patient is considered to be the best approach to treat these illnesses and perhaps to effect a cure.

However, our ability to reintroduce the defective gene into the body using delivery vehicles such as plasmids, viruses, and nanoparticles has had little success either due to onset of the immune response or ineffective delivery.

One approach that shows real therapeutic potential is hematopoietic stem cell (HSC) transplantation (HSCT), which uses HSCs derived from healthy donors or genetically modified patient HSCs, to reintroduce the defective gene into the individual via implantation.

HSCs are immature cells found in the bone marrow and peripheral blood that can differentiate into all the blood and immune cells of the body. Importantly, HSCT has been shown to work in several published case studies of adrenoleukodystrophy and, furthermore, clinical studies for genetically modified HSCT for the treatment of X-ALD and metachromatic leukodystrophy were recently FDA- and EMA-approved, respectively. However, the mechanism by which HSCT works is not yet understood.

Several years ago, our lab discovered that cells in culture exchange the RNA messages coding for proteins (mRNAs) with each other via long thin cellular extensions, called tunneling nanotubes (TNTs). Intercellular mRNA exchange (ImAx) is gene expression-dependent, meaning the higher the amount of a given mRNA within a cell, the more likely it can undergo transfer to another cell. Importantly, our studies show that ImAx can complement genetic deficiencies which result from single gene mutations in one cell type using different types of mRNA donor cells, including HSCs. Since immune cells can migrate to nearly any place in the body and form TNT-mediated interactions between cell, we hypothesize that HSCT-mediated rescue of genetic disorders originates from the ability of differentiated HSCs (i.e. immune cells) to deliver wild-type mRNAs to the genetically deficient cells in the body by TNT-mediated ImAx.

Our MAVRI-funded study will test this hypothesis both in vitro and in vivo using mouse models for human disease (e.g. infantile NCL, Zellweger’s, and others). This work will verify whether HSCT works via RNA transfer, as expected. In parallel, our work aims to systematically explore ways to improve ImAx and increase its efficiency in the treatment of genetic disorders. If successful, HSC-mediated ImAx could prove revolutionary in treating a wide variety of human genetic disorders that have defied treatment and cure thus far.