Search

Purpose : Inherited retinal diseases (IRDs) are progressive neurodegenerative conditions of the retina that represent a main cause of genetic blindness in the Western world. Their high genetic heterogeneity hinders the development of effective gene-based therapies. We have recently demonstrated that the microRNA miR-204 is essential for retinal function and plays a pathogenic role in IRD in humans. Therefore, we aimed at assessing the potential therapeutic action of this microRNA in IRDs. Methods : We delivered by subretinal injection an adeno-associated viral vector carrying the miR-204 precursor to the Aipl1knockout and the P347S-RHOtransgenic mouse lines, models of autosomal recessive and dominant forms of IRDs, respectively. The impact on retinal function and degeneration was assessed by electroretinographic and immunohistological analyses. Results : We detected a notable improvement of the ERG response in the miR-204-injected eyes of P347S-RHOmice. This effect persisted for two months post-injection and was prevalent in conditions reflecting mixed cone-rod responses. We also observed a preservation of cone photoreceptors and a significant decrease in apoptotic photoreceptor cells. Photoreceptors were better preserved also in miR204-injected eyes of Aipl1 knockoutmice. Transcriptome analysis suggested that dampening of microglia activation represents one of the main mechanisms underlying the neuroprotective effect of miR-204. Conclusions : Our findings indicate that the subretinal delivery of miR-204 attenuates retinal degeneration in IRD mouse models and preserves retinal function, supporting the gene-independent therapeutic potential of this microRNA.

Gene transfer to both cone and rod photoreceptors (PRs) is essential for gene therapy of inherited retinal degenerations that are due to mutations in genes expressed in both PR types. Vectors based on the adeno-associated virus (AAV) efficiently transduce PRs of different species. However, these are predominantly rods and little is known about the ability of AAV to transducer cones in combination with rods. Here we show that AAV2/8 transduces pig cones to levels that are similar to AAV2/9, and the ONL (mainly rods) to levels that are on average, although not statistically significant, higher than both AAV2/5 and AAV2/9. We additionally found that the ubiquitous Cytomegalovirus (CMV) but not the PR-specific GRK1 promoter transduced efficiently pig cones, presumably because GRK1 is not expressed in pig cones as observed in mice and humans. Indeed, the GRK1 and CMV promoters transduce a similar percentage of murine cones with the CMV reaching the highest expression levels. Consistent with this, the AAV2/8 vectors with either the CMV or the GRK1 promoter restore cone function in a mouse model of Leber congenital amaurosis type 1 (LCA1), supporting the use of AAV2/8 for gene therapy of LCA1 as well as of other retinal diseases requiring gene transfer to both PR types.

The present work has the aim to analyze, for the first time, the physiological activity of the pig’s retina using a standardized human electoretinogram protocol approved by the International Society for Clinical Electrophysiology of Vision (ISCEV). The experiment was conducted at the Livestock and Animal Testing unit of the Physiology service of the Department of Veterinary Medical Sciences of the University of Bologna, in accordance with the national and international guidelines on animal experimentation. All procedures were examined by the Ethics Committee of the University of Bologna, authorized in derogate by the Ministry of Health and controlled by the Central Veterinary Service of the University of Bologna during the implementation phase. The subjects are 30 healthy females piglets of 3 months old and weighing 30 kg. The pre medication is performed using Azaperone (2mg/kg of Stresnil) by intramuscular injection behind the ear. Then, the Ketamine (20mg/Kg of Ketavet), Medetomidine (0,04mg/kg of Medetor) and Atropine (0.04 mg/kg of Atropine sulfate) mixture is injected intramuscularly. The subject is left alone until the loss of the righting reflex. Two drops of mydriatic (Tropicamide 1%) per eye are instilled to obtain the necessary paralysis of the pupil. The instrument used for the retinal exam, is a Ganzfeld Stimulator Model GS-MAX for use in humans. The electrical signal data is recorded, amplified and analyzed by the program EREV2000 previously set for ERG sessions running in series. The electrodes are ERG-jet metal conductor model to transfer the bioelectric signal to the amplifier and they are divided in: subcutaneous or inox needle and corneals. Four different light stimulations are sent in order to record the photoreceptors response and to compare the average amplitudes for each protocol with the human and mouse data present in literature. This study confirm that a high cone density and the particular pig’s photoreceptor topography allow this animal to be the better choice for experimental modelling of human cone diseases than mouse. Additionally, this wide data background is a good resource for researchers involved in ophthalmic studies to choose the correct animal model for their experiment and to use the smallest possible number of animals needed to obtain a scientifically valid result.

Hepatic intra-arterial chemotherapy (HIAC) leads to a higher response rate than systemic administration in untreated patients with liver metastases from colorectal cancer (CRC). The aim of this study was to evaluate the activity and safety of giving HIAC through a percutaneous catheter in pre-treated patients.Forty-five CRC patients with liver-only or liver-dominant metastases, resistant or refractory to previous systemic therapy, were treated using a temporary trans-subclavian catheter. A 3-day chemotherapy regimen of daily 5-fluorouracil (5-FU) 1000 mg/m2/day + heparin 5000 IU/day given as a 24-hour continuous infusion, and twice daily bolus injections of cisplatin (CDDP) 10 mg/m2 and mitomycin C (MMC) 2 mg/m2, was administered every six weeks.One hundred and seventeen courses were administered to 45 patients (a median of three per patient: range 1-5). Of the 44 patients evaluable for response, 16 (35%) had a partial response, 15 (33%) stable disease and 12 (26%) progressive disease. Eleven of the 16 responding patients had been refractory to a previous 5-FU-based systemic therapy. The most relevant grade 3-4 toxicities included neutropenia (22%) and thrombocytopenia (15%). Gastro-duodenal ulcers occurred in nine patients. Catheter displacement was recorded during 22 out of 117 (18%) courses.HIAC with 5-FU, CDDP and MMC given through a temporary percutaneous catheter is safe and active in pretreated patients with metastatic CRC. Iatrogenic gastroduodenal ulcers are a serious but manageable complication.

Split intein-mediated protein trans-splicing expands AAV transfer capacity, thus overcoming the limited AAV cargo. However, non-mammalian inteins persist as trans-splicing by-products, and this could raise safety concerns for AAV intein clinical applications. In this study, we tested the ability of several degrons to selectively decrease levels of inteins after protein trans-splicing and found that a version of E. coli dihydrofolate reductase, which we have shortened to better fit into the AAV vector, is the most effective. We show that subretinal administration of AAV intein armed with this short degron is both safe and effective in a mouse model of Stargardt disease (STGD1), which is the most common form of inherited macular degeneration in humans. This supports the use of optimized AAV intein for gene therapy of both STGD1 and other conditions that require transfer of large genes., Graphical abstract, Intein-mediated protein trans-splicing (PTS) expands AAV gene transfer capacity. However, non-mammalian inteins persist as trans-splicing by-products. Here, we show that ecDHFR selectively degrades inteins after PTS and that AAV intein vectors armed with this degron are both safe and effective in the retina of a mouse model of genetic blindness.

Retinal gene therapy with adeno-associated viral (AAV) vectors is safe and effective in humans. However, AAV’s limited cargo capacity prevents its application to therapies of inherited retinal diseases due to mutations of genes over 5 kb, like Stargardt’s disease (STGD) and Usher syndrome type IB (USH1B). Previous methods based on ‘forced’ packaging of large genes into AAV capsids may not be easily translated to the clinic due to the generation of genomes of heterogeneous size which raise safety concerns. Taking advantage of AAV’s ability to concatemerize, we generated dual AAV vectors which reconstitute a large gene by either splicing (trans-splicing), homologous recombination (overlapping), or a combination of the two (hybrid). We found that dual trans-splicing and hybrid vectors transduce efficiently mouse and pig photoreceptors to levels that, albeit lower than those achieved with a single AAV, resulted in significant improvement of the retinal phenotype of mouse models of STGD and USH1B. Thus, dual AAV trans-splicing or hybrid vectors are an attractive strategy for gene therapy of retinal diseases that require delivery of large genes.

Recombinant adeno-associated viral (AAV) vectors are known to safely and efficiently transduce the retina. Among the various AAV serotypes available, AAV2/5 and 2/8 are the most effective for gene transfer to photoreceptors (PR), which are the most relevant targets for gene therapy of inherited retinal degenerations. However, the search for novel AAV serotypes with improved PR transduction is ongoing. In this work we tested vectors derived from five AAV serotypes isolated from porcine tissues (referred to as porcine AAVs, four of which are newly identified) for their ability to transduce both the murine and the cone-enriched pig retina. Porcine AAV vectors expressing EGFP under the control of the CMV promoter were injected subretinally either in C57BL/6 mice or Large White pigs. The resulting retinal tropism was analyzed one month later on histological sections, while levels of PR transduction were assessed by Western blot. Our results show that all porcine AAV transduce murine and porcine retinal pigment epithelium and PR upon subretinal administration. AAV2/po1 and 2/po5 are the most efficient porcine AAVs for murine PR transduction and exhibit the strongest tropism for pig cone PR. The levels of PR transduction obtained with AAV2/po1 and 2/po5 are similar, albeit not superior, to those obtained with AAV2/5 and AAV2/8, which evinces AAV2/po1 and 2/po5 to be promising vectors for retinal gene therapy.

Background: Gene transfer using adeno-associated viral (AAV) vectors has been successfully applied in the retina for the treatment of inherited retinal dystrophies. Recently, microRNAs have been exploited to fine-tune transgene expression improving therapeutic outcomes. Here we evaluated the ability of retinal-expressed microRNAs to restrict AAV-mediated transgene expression to specific retinal cell types that represent the main targets of common inherited blinding conditions. Methodology/Principal Findings: To this end, we generated AAV2/5 vectors expressing EGFP and containing four tandem copies of miR-124 or miR-204 complementary sequences in the 3′UTR of the transgene expression cassette. These vectors were administered subretinally to adult C57BL/6 mice and Large White pigs. Our results demonstrate that miR-124 and miR-204 target sequences can efficiently restrict AAV2/5-mediated transgene expression to retinal pigment epithelium and photoreceptors, respectively, in mice and pigs. Interestingly, transgene restriction was observed at low vector doses relevant to therapy. Conclusions: We conclude that microRNA-mediated regulation of transgene expression can be applied in the retina to either restrict to a specific cell type the robust expression obtained using ubiquitous promoters or to provide an additional layer of gene expression regulation when using cell-specific promoters. © 2011 Karali et al.

Recent success in clinical trials supports the use of adeno-associated viral (AAV) vectors for gene therapy of retinal diseases caused by defects in the retinal pigment epithelium (RPE). In contrast, evidence of the efficacy of AAV-mediated gene transfer to retinal photoreceptors, the major site of inherited retinal diseases, is less robust. In addition, although AAV-mediated RPE transduction appears efficient, independently of the serotype used and species treated, AAV-mediated photoreceptor gene transfer has not been systematically investigated thus so far in large animal models, which also may allow identifying relevant species-specific differences in AAV-mediated retinal transduction. In the present study, we used the porcine retina, which has a high cone/rod ratio. This feature allows to properly evaluate both cone and rod photoreceptors transduction and compare the transduction characteristics of AAV2/5 and 2/8, the two most efficient AAV vector serotypes for photoreceptor targeting. Here we show that AAV2/5 and 2/8 transduces both RPE and photoreceptors. AAV2/8 infects and transduces photoreceptor more efficiently than AAV2/5, similarly to what we have observed in the murine retina. The use of the photoreceptor-specific rhodopsin promoter restricts transgene expression to porcine rods and cones, and results in photoreceptor transduction levels similar to those obtained with the ubiquitous promoters tested. Finally, immunological, toxicological and biodistribution studies support the safety of AAV subretinal administration to the large porcine retina. The data presented here on AAV-mediated transduction of the cone-enriched porcine retina may affect the development of gene-based therapies for rare and common severe photoreceptor diseases. © 2011 Macmillan Publishers Limited All rights reserved. Recent success in clinical trials supports the use of adeno-associated viral (AAV) vectors for gene therapy of retinal diseases caused by defects in the retinal pigment epithelium (RPE). In contrast, evidence of the efficacy of AAV-mediated gene transfer to retinal photoreceptors, the major site of inherited retinal diseases, is less robust. In addition, although AAV-mediated RPE transduction appears efficient, independently of the serotype used and species treated, AAV-mediated photoreceptor gene transfer has not been systematically investigated thus so far in large animal models, which also may allow identifying relevant species-specific differences in AAV-mediated retinal transduction. In the present study, we used the porcine retina, which has a high cone/rod ratio. This feature allows to properly evaluate both cone and rod photoreceptors transduction and compare the transduction characteristics of AAV2/5 and 2/8, the two most efficient AAV vector serotypes for photoreceptor targeting. Here we show that AAV2/5 and 2/8 transduces both RPE and photoreceptors. AAV2/8 infects and transduces photoreceptor more efficiently than AAV2/5, similarly to what we have observed in the murine retina. The use of the photoreceptor-specific rhodopsin promoter restricts transgene expression to porcine rods and cones, and results in photoreceptor transduction levels similar to those obtained with the ubiquitous promoters tested. Finally, immunological, toxicological and biodistribution studies support the safety of AAV subretinal administration to the large porcine retina. The data presented here on AAV-mediated transduction of the cone-enriched porcine retina may affect the development of gene-based therapies for rare and common severe photoreceptor diseases. Gene Therapy (2011) 18, 637-645; doi:10.1038/gt.2011.3; published online 17 March 2011

Challenges to the widespread application of gene therapy with adeno-associated viral (AAV) vectors include dominant conditions due to gain-of-function mutations which require allele-specific knockout, as well as long-term transgene expression from proliferating tissues, which is hampered by AAV DNA episomal status. To overcome these challenges, we used CRISPR/Cas9-mediated homology-independent targeted integration (HITI) in retina and liver as paradigmatic target tissues. We show that AAV-HITI targets photoreceptors of both mouse and pig retina, and this results in significant improvements to retinal morphology and function in mice with autosomal dominant retinitis pigmentosa. In addition, we show that neonatal systemic AAV-HITI delivery achieves stable liver transgene expression and phenotypic improvement in a mouse model of a severe lysosomal storage disease. We also show that HITI applications predominantly result in on-target editing. These results lay the groundwork for the application of AAV-HITI for the treatment of diseases affecting various organs.

Summary Retinitis pigmentosa (RP) is a group of progressive retinal degenerations of mostly monogenic inheritance, which cause blindness in about 1:3,500 individuals worldwide. Heterozygous variants in the rhodopsin (RHO) gene are the most common cause of autosomal dominant RP (adRP). Among these, missense variants at C-terminal proline 347, such as p.Pro347Ser, cause severe adRP recurrently in European affected individuals. Here, for the first time, we use CRISPR/Cas9 to selectively target the p.Pro347Ser variant while preserving the wild-type RHO allele in vitro and in a mouse model of adRP. Detailed in vitro, genomic, and biochemical characterization of the rhodopsin C-terminal editing demonstrates a safe downregulation of p.Pro347Ser expression leading to partial recovery of photoreceptor function in a transgenic mouse model treated with adeno-associated viral vectors. This study supports the safety and efficacy of CRISPR/Cas9-mediated allele-specific editing and paves the way for a permanent and precise correction of heterozygous variants in dominantly inherited retinal diseases.

The presence of α-synuclein aggregates in the retina of Parkinson’s disease patients has been associated with vision impairment. In this study we sought to determine the effects of α-synuclein overexpression on the survival and function of dopaminergic amacrine cells (DACs) in the retina. Adult mice were intravitreally injected with an adeno-associated viral (AAV) vector to overexpress human wild-type α-synuclein in the inner retina. Before and after systemic injections of levodopa (L-DOPA), retinal responses and visual acuity-driven behavior were measured by electroretinography (ERG) and a water maze task, respectively. Amacrine cells and ganglion cells were counted at different time points after the injection. α-synuclein overexpression led to an early loss of DACs associated with a decrease of light-adapted ERG responses and visual acuity that could be rescued by systemic injections of L-DOPA. The data show that α-synuclein overexpression affects dopamine neurons in the retina. The approach provides a novel accessible method to model the underlying mechanisms implicated in the pathogenesis of synucleinopathies and for testing novel treatments.

Inherited retinal diseases (IRDs) represent a frequent cause of genetic blindness. Their high genetic heterogeneity hinders the application of gene-specific therapies to the vast majority of patients. We recently demonstrated that the microRNA miR-204 is essential for retinal function, although the underlying molecular mechanisms remain poorly understood. Here, we investigated the therapeutic potential of miR-204 in IRDs. We subretinally delivered an adeno-associated viral (AAV) vector carrying the miR-204 precursor to two genetically different IRD mouse models. The administration of AAV-miR-204 preserved retinal function in a mouse model for a dominant form of retinitis pigmentosa (RHO-P347S). This was associated with a reduction of apoptotic photoreceptor cells and with a better preservation of photoreceptor marker expression. Transcriptome analysis showed that miR-204 shifts expression profiles of transgenic retinas toward those of healthy retinas by the downregulation of microglia activation and photoreceptor cell death. Delivery of miR-204 exerted neuroprotective effects also in a mouse model of Leber congenital amaurosis, due to mutations of the Aipl1 gene. Our study highlights the mutation-independent therapeutic potential of AAV-miR204 in slowing down retinal degeneration in IRDs and unveils the previously unreported role of this miRNA in attenuating microglia activation and photoreceptor cell death.

Retinal gene therapy with adeno-associated viral (AAV) vectors holds promises for treating inherited and noninherited diseases of the eye. Although clinical data suggest that retinal gene therapy is safe and effective, delivery of large genes is hindered by the limited AAV cargo capacity. Protein trans-splicing mediated by split inteins is used by single-cell organisms to reconstitute proteins. Here, we show that delivery of multiple AAV vectors each encoding one of the fragments of target proteins flanked by short split inteins results in protein trans-splicing and full-length protein reconstitution in the retina of mice and pigs and in human retinal organoids. The reconstitution of large therapeutic proteins using this approach improved the phenotype of two mouse models of inherited retinal diseases. Our data support the use of split intein–mediated protein trans-splicing in combination with AAV subretinal delivery for gene therapy of inherited blindness due to mutations in large genes.

Seventy-four patients who relapsed after allogeneic stem cell transplantation were enrolled in a phase IIA study and treated with the sequential infusion of donor lymphocyte infusion (DLI) followed by cytokine-induced killer (CIK) cells. Seventy-three patients were available for the intention to treat analysis. At least 1 infusion of CIK cells was given to 59 patients, whereas 43 patients received the complete cell therapy planned (58%). Overall, 12 patients (16%) developed acute graft-versus-host disease (aGVHD) of grades I to II in 7 cases and grades III to IV in 5). In 8 of 12 cases, aGVHD developed during DLI treatment, leading to interruption of the cellular program in 3 patients, whereas in the remaining 5 cases aGVHD was controlled by steroids treatment, thus allowing the subsequent planned administration of CIK cells. Chronic GVHD (cGVHD) was observed in 11 patients (15%). A complete response was observed in 19 (26%), partial response in 3 (4%), stable disease in 8 (11%), early death in 2 (3%), and disease progression in 41 (56%). At 1 and 3 years, rates of progression-free survival were 31% and 29%, whereas rates of overall survival were 51% and 40%, respectively. By multivariate analysis, the type of relapse, the presence of cGVHD, and a short (

Background. Intravenous glutamine-enriched solution seems to be effective in posttransplant period in decreasing the severity and duration of mucositis. The aim of this randomized study was to determine the benefit of glutamine supplementation both on mucosal morbidity and in posttransplant associated complications. Methods. Children undergoing allogeneic hematopoietic stem-cell transplantation (HSCT) for malignant hematological diseases were randomly assigned to standard total parenteral nutrition (S-TPN) or glutamine-enriched (GE)-TPN solution consisting of 0.4 g/kg/day of l-alanine-glutamine dipeptide. This treatment started on the day of HSCT and ended when the patients could orally cover more than 50% of their daily energy requirements. The severity and the rate of post-HSCT mucositis were based on World Health Organization criteria. All the analyses were conducted on intention-to-treat principle. Results. One hundred twenty consecutive patients (83 men; median age, 8.1 years) were enrolled. The mean duration of treatment was 23.5 and 23 days in the two treatment arms. The mean calorie intake was 1538 kcal/d in the S-TPN group and 1512 kcal/d in GE-TPN group. All patients were well nourished before and after HSCT. Mucositis occurred in 91.4% and 91.7% of patients in S-TPN and GE-TPN arm, respectively (P=0.98). Odds ratio adjusted by type of HSCT was 0.98 (95% confidence interval, 0.26-2.63). Type and duration of analgesic treatment, clinical outcome (engraftment, graft versus host disease, early morbidity, and mortality, relapse rate up to 180 days post-HSCT) were not significantly different in the two treatment arms. Conclusion. GE-TPN solution does not affect mucositis and outcome in well-nourished HSCT allogeneic patients. Copyright © 2011 by Lippincott Williams & Wilkins.

Despite the recent success of gene-based complementation approaches for genetic recessive traits, the development of therapeutic strategies for gain-of-function mutations poses great challenges. General therapeutic principles to correct these genetic defects mostly rely on post-transcriptional gene regulation (RNA silencing). Engineered zinc-finger (ZF) protein-based repression of transcription may represent a novel approach for treating gain-of-function mutations, although proof-of-concept of this use is still lacking. Here, we generated a series of transcriptional repressors to silence human rhodopsin (hRHO), the gene most abundantly expressed in retinal photoreceptors. The strategy was designed to suppress both the mutated and the wild-type hRHO allele in a mutational-independent fashion, to overcome mutational heterogeneity of autosomal dominant retinitis pigmentosa due to hRHO mutations. Here we demonstrate that ZF proteins promote a robust transcriptional repression of hRHO in a transgenic mouse model of autosomal dominant retinitis pigmentosa. Furthermore, we show that specifically decreasing the mutated human RHO transcript in conjunction with unaltered expression of the endogenous murine Rho gene results in amelioration of disease progression, as demonstrated by significant improvements in retinal morphology and function. This zinc-finger-based mutation-independent approach paves the way towards a 'repression-replacement' strategy, which is expected to facilitate widespread applications in the development of novel therapeutics for a variety of disorders that are due to gain-of-function mutations.

PURPOSE. To evaluate the suitability of gene delivery-based approaches as potential treatment of Leber Congenital Amaurosis 4 (LCA4) due to AIPL1 mutations. METHODS. Genomic DNA from patients was analyzed using a microarray chip and direct sequencing. A detailed clinical evaluation including fundus autofluorescence (FAF) and optical coherence tomography (OCT) was performed in patients with AIPL1 mutations. Aipl1 null mice and porcine eyes were subretinally injected with adeno-associated viral (AAV) vectors harboring the human AIPL1 coding sequence. RESULTS. We identified ten LCA4 patients with mutations in AIPL1. The p.W278X sequence variation was the one most frequently found. Clinical assessment revealed common features including diffuse retinal dystrophies and maculopathy. However, OCT showed partially retained photoreceptors in extra-macular regions at all ages. The FAF was elicitable at the posterior pole and absent in the fovea. AAV-mediated gene transfer in Aipl1 -/- mice was associated with restoration of AIPL1 and βPDE expression in photoreceptors and protection from degeneration. Administration of a clinically relevant dose of AAV2/8-AIPL1 to the pre-clinical large porcine retina resulted in high level of AIPL1 photoreceptor expression in the absence of toxicity. CONCLUSIONS. Using advanced imaging diagnostics we showed that maculopathy is a main feature of LCA4. We identified retinal areas at the posterior pole with surviving photoreceptors present even in adult LCA4 patients, which could be the target of gene therapy. The possible use of gene therapy for LCA4 is additionally supported by the protection from photoreceptor degeneration observed in Aipl 1-/- mice and by the high levels of photoreceptor transduction in the absence of toxicity observed following AAV2/8 delivery to the large porcine retina. PMID: 21474771 [PubMed - as supplied by publisher]

Retinal gene therapy with adeno-associated viral (AAV) vectors is safe and effective in humans. However, the limited cargo capacity of AAV prevents their use for therapy of those inherited retinopathies (IRs) due to mutations in large (>5 kb) genes. Viral vectors derived from adenovirus (Ad), lentivirus (LV) and herpes virus (HV) can package large DNA sequences, but do not target efficiently retinal photoreceptors (PRs) where the majority of genes responsible for IRs are expressed. Here, we have evaluated the mouse retinal transduction profiles of vectors derived from 16 different Ad serotypes, 7 LV pseudotypes and from a bovine HV. Most of the vectors tested transduced efficiently the retinal pigment epithelium. We found that LV-GP64 tends to transduce more PRs than the canonical LV-VSVG, albeit this was restricted to a narrow region. We observed more extensive PR transduction with HdAd1, 2 and 5/F35++ than with LV, although none of them outperformed the canonical HdAd5 or matched the extension of PR transduction achieved with AAV2/8. © 2014 Macmillan Publishers Limited All rights reserved.

Mutations in MYO7A cause autosomal recessive Usher syndrome type IB (USH1B), one of the most frequent conditions that combine severe congenital hearing impairment and retinitis pigmentosa. A promising therapeutic strategy for retinitis pigmentosa is gene therapy, however its pre-clinical development is limited by the mild retinal phenotype of the shaker1 (sh1(-/-)) murine model of USH1B which lacks both retinal functional abnormalities and degeneration. Here we report a significant, early-onset delay of sh1(-/-) photoreceptor ability to recover from light desensitization as well as a progressive reduction of both b-wave electroretinogram amplitude and light sensitivity, in the absence of significant loss of photoreceptors up to 12 months of age. We additionally show that subretinal delivery to the sh1(-/-) retina of AAV vectors encoding the large MYO7A protein results in significant improvement of sh1(-/-) photoreceptor and retinal pigment epithelium ultrastructural anomalies which is associated with improvement of recovery from light desensitization. These findings provide new tools to evaluate the efficacy of experimental therapies for USH1B. In addition, although AAV vectors expressing large genes might have limited clinical applications due to their genome heterogeneity, our data show that AAV-mediated MYO7A gene transfer to the sh1(-/-) retina is effective.

In the adult, a hypothalamic neural network acts to maintain energy balance in response to nutritional feedback from the periphery. Although there is an immediate requirement for this system to be functional at birth, it is unknown whether the components of this central neural network are expressed in the developing brain before birth. We therefore examined in the fetal sheep hypothalamus during late gestation gene expression for leptin receptor (OB-Rb) and neuropeptides that regulate energy balance in the adult. Brains were collected from fetal sheep at 110 days (n = 12) and 140 days of gestation (n = 5) (term = 150 days) and gene expression was detected in all hypothalami using in situ hybridization with radiolabelled riboprobes for OB-Rb, neuropeptide Y (NPY), agouti-related peptide, pro-opiomelanocortin and cocaine- and amphetamine-regulated transcript (CART). All mRNAs were expressed in the arcuate nucleus of fetuses at both time points. Additional sites of mRNA expression were the dorsomedial hypothalamus (DMH) for NPY, the paraventricular nucleus (PVN), ventromedial hypothalamus (VMH) and lateral hypothalamic area for CART, and the DMH, PVN and VMH for OB-Rb. We have therefore demonstrated that adult-like localization of gene expression for OB-Rb and key appetite regulatory neuropeptides is established in the ovine hypothalamus before birth. Thus, the fetus possesses a central appetite regulatory neural network with the potential to respond to changes in nutrient supply, which could impact on energy balance regulation both before and after birth.

We have investigated the factors regulating leptin synthesis, fat deposition, and circulating leptin concentrations in fetuses of well nourished ewes in late pregnancy. Vascular catheters were surgically inserted in 17 pregnant ewes and their fetuses at 103–120 d gestation (term 147 3 d). Ewes were fed a diet providing either 100% (control; n 9) or approximately 155% (well fed; n 8) of the maintenance energy requirements and fetal perirenal and interscapular fat depots were collected at 139 –141 d gestation. There was a significant relationship between the relative mass of fetal unilocular fat and fetal glucose (relative mass of unilocular fat, 1.14; fetal glucose, 0.16; r 0.50; P < 0.04; n 17), but not insulin, concentrations in the control and well-fed groups. In contrast to the controls, there was a positive relationship between the relative abundance of leptin mRNA and fetal insulin, but not glucose, concentrations in fetal perirenal adipose tissue in the well-fed group. A moderate increase in maternal nutrition also resulted in a strong reciprocal relationship between uncoupling protein 1 and leptin expression in fetal perirenal adipose tissue in late gestation (well-fed group: uncoupling protein 1 mRNA:18S rRNA,0.51; leptin mRNA:-actin mRNA, 1.53; r 0.80; P < 0.02; n 8). These studies provide evidence that fetal glucose and insulin differentially regulate fetal fat deposition and leptin mRNA expression within the fetal perirenal fat depot in the well nourished animal during late gestation. (Endocrinology 144: 4947– 4954, 2003)

Gene-expression programs modulated by transcription factors (TFs) mediate key developmental events. Here, we show that the synthetic transcriptional repressor (TR, ZF6-DB), designed to treat Rhodopsin-mediated autosomal dominant retinitis pigmentosa (RHO-adRP), does not perturb murine retinal development, while maintaining its ability to block Rho expression transcriptionally. To express ZF6-DB into the developing retina, we pursued two approaches, (i) the retinal delivery (somatic expression) of ZF6-DB by Adeno-associated virus (AAV) vector (AAV-ZF6-DB) gene transfer during retinogenesis and (ii) the generation of a transgenic mouse (germ-line transmission, TR-ZF6-DB). Somatic and transgenic expression of ZF6-DB during retinogenesis does not affect retinal function of wild-type mice. The P347S mouse model of RHO-adRP, subretinally injected with AAV-ZF6-DB, or crossed with TR-ZF6-DB or shows retinal morphological and functional recovery. We propose the use of developmental transitions as an effective mode to challenge the safety of retinal gene therapies operating at genome, transcriptional, and transcript levels.