Biology subjects

Fransen, J. W.

Publications and source records attributed to Fransen, J. W..

3 recordsLinked to original sources

bioRxiv2025

RHO1-2 meganuclease gene editing targets human P23H rhodopsin-induced retinitis pigmentosa to rejuvenate rods and maintain cones

Autosomal dominant retinitis pigmentosa (adRP) is an inherited retinal dystrophy characterized by progressive vision loss and eventual blindness. The P23H mutation (proline to histidine substitution at codon 23) in the rhodopsin (RHO) gene represents the most common form of adRP in North Americans. Currently, there is no cure for P23H adRP. Genome editing targeting the mutant RHO allele, leaving a functional wildtype (WT) allele, is an attractive approach for P23H adRP, as only one copy of RHO is needed for normal retinal function. We re-engineered an I-Cre meganuclease, called RHO1-2, to target a 22bp recognition sequence encompassing the mutation responsible for the p.P23H RHO mutation. In vitro, RHO1-2, cuts human P23H RHO but not WT RHO. In vivo, we delivered scAAV5:GRK1:RHO1-2 via subretinal injection in early-stage degeneration using the only large animal model of human p.P23H RHO adRP (TgP23H pigs). We tested RHO1-2 efficacy and durability, on retinal function using full-field electroretinograms and on retinal structure using spectral domain optical coherence tomography and immunohistochemistry. We observe that RHO1-2 treatment: arrests rod photoreceptor degeneration, resurrects rod-driven retinal function that does not exist in untreated TgP23H pigs, restores mislocalized rhodopsin expression and rebuilds rod inner and outer segments (IS/OS). Rod rescue maintains cones. A year after RHO1-2 treatment, we show that TgP23H pigs use rod-driven vision to navigate a maze. Our results demonstrate that genome editing via RHO1-2 meganuclease is a viable treatment to cure human p.P23H RHO adRP. They also suggest that meganuclease-based editors can be effective for other IRDs. One Sentence SummaryEngineered meganuclease, RHO1-2 is a safe and promising therapeutic genome editing approach to cure human p.P23H RHO adRP.

neuroscience↗

bioRxiv2019

Genetic access to functionally distinct ganglion cell types in the Somatostatin-IRES-Cre mouse retina

Retinal ganglion cells (GCs) are a functionally diverse neuron population that encodes and transmits distinct representations of the visual image on the retina to target nuclei in the brain. Independent studies of visually-evoked responses, cell morphology, and gene expression each suggest that GCs in mouse may comprise as many as forty distinct cell types. To date, only a subset of these types have been characterized in detail, and for most genetic access is still lacking. Thus, the majority of identified GC types remains inaccessible for targeted electrophysiology and functional imaging, precluding efficient studies of their response properties, and the cell-intrinsic mechanisms and presynaptic circuits that generate these properties. Here we show that an existing mouse line that is commonly used for studies of cortical inhibitory circuits - Somatostatin-IRES-Cre (Sst-Cre), consistently labels an understudied subset of four GC types with distinct visual responses. We characterized these types both anatomically and functionally using Cre-dependent reporter mouse lines and confocal fluorescence imaging, calcium imaging, and whole-cell electrophysiology. We show that one of the labeled GC types is suppressed by luminance contrast, while another matches a recently described orientation-selective GC type. Our results give new information about these two identified GC types, and establish the utility of the Sst-Cre transgenic mouse line for studies of recently identified GC circuits in the mouse retina.

neuroscience↗

bioRxiv2018

Thy1 transgenic mice expressing the red fluorescent calcium indicator jRGECO1a for neuronal population imaging in vivo

Calcium imaging is commonly used to measure the neural activity of large groups of neurons in mice. Genetically encoded calcium indicators (GECIs) can be delivered for this purpose using non-invasive genetic methods. Compared to viral gene transfer, transgenic targeting of GECIs provides stable long-term expression and obviates the need for invasive viral injections. Transgenic mice expressing the green GECI GCaMP6 are already widely used. Here we present the generation and characterizarion of transgenic mice expressing the sensitive red GECI jRGECO1a, driven by the Thy1 promoter. Four transgenic lines with different expression patterns showed sufficiently high expression for cellular in vivo imaging. We used two-photon microscopy to characterize visual responses of individual neurons in the visual cortex in vivo. The signal-to-noise ratio in transgenic mice was comparable to, or better than, for mice transduced with adeno-associated virus. We also show that Thy1-jRGECO1a transgenic mice are useful for transcranial population imaging and functional mapping using widefield fluorescecnce microscopy. We also demonstrate imaging of visual responses in retinal ganglion cells. Thy1-jRGECO1a transgenic mice are therefore a useful addition to the toolbox for imaging activity in intact neural networks.

neuroscience↗