Mutations in the rhodopsin gene cause retinal degeneration and clinical phenotypes including retinitis pigmentosa (RP) and congenital stationary night blindness. Effective gene therapies have been difficult to develop, however, because generating precise levels of rhodopsin expression is critical; overexpression causes toxicity, and underexpression would result in incomplete rescue. Current gene delivery strategies routinely use cDNA-based vectors for gene targeting; however, inclusion of noncoding components of genomic DNA (gDNA) such as introns may help promote more endogenous regulation of gene expression. Here we test the hypothesis that inclusion of genomic sequences from the rhodopsin gene can improve the efficacy of rhodopsin gene therapy in the rhodopsin knockout (RKO) mouse model of RP. We utilize our compacted DNA nanoparticles (NPs), which have the ability to transfer larger and more complex genetic constructs, to deliver murine rhodopsin cDNA or gDNA. We show functional and structural improvements in RKO eyes for up to 8 months after NP-mediated gDNA but not cDNA delivery. Importantly, in addition to improvements in rod function, we observe significant preservation of cone function at time points when cones in the RKO model are degenerated. These results suggest that inclusion of native expression elements, such as introns, can significantly enhance gene expression and therapeutic efficacy and may become an essential option in the array of available gene delivery tools.

Rab GTPases are important regulators of intracellular membrane trafficking in eukaryotes. Both activating and inactivating mutations in Rab genes have been identified and implicated in human diseases ranging from neurological disorders to cancer. In addition, altered Rab expression is often associated with disease prognosis. As such, the study of diseases associated with Rabs or Rab-interacting proteins has shed light on the important role of intracellular membrane trafficking in disease etiology. In this review, we cover recent advances in the field with an emphasis on cellular mechanisms.

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