LRRK2 mutations cause mitochondrial DNA damage in iPSC-derived neural cells from Parkinson's disease patients: reversal by gene correction.

Parkinson's disease associated mutations in leucine rich repeat kinase 2 (LRRK2) impair mitochondrial function and increase the vulnerability of induced pluripotent stem cell (iPSC)-derived neural cells from patients to oxidative stress. Since mitochondrial DNA (mtDNA) damage can compromise mitochondrial function, we examined whether LRRK2 mutations can induce damage to the mitochondrial genome. We found greater levels of mtDNA damage in iPSC-derived neural cells from patients carrying homozygous or heterozygous LRRK2 G2019S mutations, or at-risk individuals carrying the heterozygous LRRK2 R1441C mutation, than in cells from unrelated healthy subjects who do not carry LRRK2 mutations. After zinc finger nuclease-mediated repair of the LRRK2 G2019S mutation in iPSCs, mtDNA damage was no longer detected in differentiated neuroprogenitor and neural cells. Our results unambiguously link LRRK2 mutations to mtDNA damage and validate a new cellular phenotype that can be used for examining pathogenic mechanisms and screening therapeutic strategies.

Skin punch biopsy explant culture for derivation of primary human fibroblasts.

Tissues and cell lines derived from an individual with disease are ideal sources to study disease-related cellular phenotypes. Patient-derived fibroblasts in this protocol have been successfully used in the derivation of induced pluripotent stem cells to model disease(1). Early passages of these fibroblasts can also be used for cell-based functional assays to study specific disease pathways, mechanisms(2) and subsequent drug screening approaches. The advantage of the presented protocol over enzymatic procedures are 1) the reproducibility of the technique from small amounts of tissue derived from older patients, e.g. patients affected with Parkinson's disease, 2) the technically simple approach over more challenging methodologies using enzymatic treatments, and 3) the time consideration: this protocol takes 15-20 min and can be performed immediately after biopsy arrival. Enzymatic treatments can take up to 4 hr and have the problems of overdigestion, reduction of cell viability and subsequent attachment of cells when not handled properly. This protocol describes the dissection and preparation of a 4-mm human skin biopsy for derivation of a fibroblast culture and has a very high success rate which is important when dealing with patient-derived tissue samples. In this culture, keratinocytes migrate out of the biopsy tissue within the first week after preparation. Fibroblasts appear 7-10 days after the first outgrowth of keratinocytes. DMEM high glucose media supplemented with 20% FBS favors the growth of fibroblasts over keratinocytes and fibroblasts will overgrow the keratinocytes. After 2 passages keratinocytes have been diluted out resulting in relatively homogenous fibroblast cultures which expresses the fibroblast marker SERPINH1 (HSP-47). Using this approach, 15-20 million fibroblasts can be derived in 4-8 weeks for cell banking. The skin dissection takes about 15-20 min, cells are then monitored once a day under the microscope, and media is changed every 2-3 days after attachment and outgrowth of cells.

Small molecules greatly improve conversion of human-induced pluripotent stem cells to the neuronal lineage.

Efficient in vitro differentiation into specific cell types is more important than ever after the breakthrough in nuclear reprogramming of somatic cells and its potential for disease modeling and drug screening. Key success factors for neuronal differentiation are the yield of desired neuronal marker expression, reproducibility, length, and cost. Three main neuronal differentiation approaches are stromal-induced neuronal differentiation, embryoid body (EB) differentiation, and direct neuronal differentiation. Here, we describe our neurodifferentiation protocol using small molecules that very efficiently promote neural induction in a 5-stage EB protocol from six induced pluripotent stem cells (iPSC) lines from patients with Parkinson's disease and controls. This protocol generates neural precursors using Dorsomorphin and SB431542 and further maturation into dopaminergic neurons by replacing sonic hedgehog with purmorphamine or smoothened agonist. The advantage of this approach is that all patient-specific iPSC lines tested in this study were successfully and consistently coaxed into the neural lineage.