Probes for INS

Chronic stress is a well-known risk factor for the development of hypertension. However, the underlying mechanisms remain unclear. Corticotropin-releasing hormone (CRH) neurons in the central nucleus of the amygdala (CeA) are involved in the autonomic responses to chronic stress. Here, we determined the role of CeA-CRH neurons in chronic stress-induced hypertension.Borderline hypertensive rats (BHRs) and Wistar-Kyoto (WKY) rats were subjected to chronic unpredictable stress (CUS). Firing activity and M-currents of CeA-CRH neurons were assessed, and a CRH-Cre-directed chemogenetic approach was used to suppress CeA-CRH neurons. CUS induced a sustained elevation of arterial blood pressure (ABP) and heart rate (HR) in BHRs, while in WKY rats, CUS-induced increases in ABP and HR quickly returned to baseline levels after CUS ended. CeA-CRH neurons displayed significantly higher firing activities in CUS-treated BHRs than unstressed BHRs. Selectively suppressing CeA-CRH neurons by chemogenetic approach attenuated CUS-induced hypertension and decreased elevated sympathetic outflow in CUS-treated BHRs. Also, CUS significantly decreased protein and mRNA levels of Kv7.2 and Kv7.3 channels in the CeA of BHRs. M-currents in CeA-CRH neurons were significantly decreased in CUS-treated BHRs compared with unstressed BHRs. Blocking Kv7 channel with its blocker XE-991 increased the excitability of CeA-CRH neurons in unstressed BHRs but not in CUS-treated BHRs. Microinjection of XE-991 into the CeA increased sympathetic outflow and ABP in unstressed BHRs but not in CUS-treated BHRs.CeA-CRH neurons are required for chronic stress-induced sustained hypertension. The hyperactivity of CeA-CRH neurons may be due to impaired Kv7 channel activity, which represents a new mechanism involved in chronic stress-induced hypertension.We found that hyperactivity of CRH neurons in the CeA, likely due to diminished Kv7 channel activity, play a major role in the development of chronic stress-induced hypertension. Our study suggests that CRH neurons in the brain may be targeted for treating chronic stress-induced hypertension. Thus, increasing Kv7 channel activity or overexpressing Kv7 channels in the CeA may reduce stress-induced hypertension. Further studies are needed to delineate how chronic stress diminishes Kv7 channel activity in the brain.

The lateral septum (LS) is a basal forebrain GABAergic region that is implicated in social novelty. However, the neural circuits and cell signaling pathways that converge on the LS to mediate social behaviors aren't well understood. Multiple lines of evidence suggest that signaling of brain-derived neurotrophic factor (BDNF) through its receptor TrkB plays important roles in social behavior. BDNF is not locally produced in LS, but we demonstrate that nearly all LS GABAergic neurons express TrkB. Local TrkB knock-down in LS neurons decreased social novelty recognition and reduced recruitment of neural activity in LS neurons in response to social novelty. Since BDNF is not synthesized in LS, we investigated which inputs to LS could serve as potential BDNF sources for controlling social novelty recognition. We demonstrate that selectively ablating inputs to LS from the basolateral amygdala (BLA), but not from ventral CA1 (vCA1), impairs social novelty recognition. Moreover, depleting BDNF selectively in BLA-LS projection neurons phenocopied the decrease in social novelty recognition caused by either local LS TrkB knockdown or ablation of BLA-LS inputs. These data support the hypothesis that BLA-LS projection neurons serve as a critical source of BDNF for activating TrkB signaling in LS neurons to control social novelty recognition.

Facioscapulohumeral muscular dystrophy (FSHD) is among the most prevalent muscular dystrophies, ranging from 1 in 8,333 to 1 in 20,000. Currently no treatment exists that alters the course of FSHD, and therapy development remains an unmet need in the field. Abnormal reactivation of the DUX4 gene in skeletal muscle has emerged as an underlying cause of muscle weakness and wasting in FSHD. We propose that DUX4 silencing is the most direct route to FSHD therapy. Toward this goal, we developed an AAV6-CRISPR-Cas13 strategy to silence DUX4 mRNA. Cas13 targets and cleaves RNA instead of DNA, and avoids potential risks of permanent off-target genome editing that could arise with DNA-targeting systems. Intramuscular delivery of an AAV6 vector encoding a PspCas13b enzyme and DUX4-targeting guide RNAs reduced DUX4 mRNA by >50% and improved histopathological outcomes in FSHD mice. To investigate possible off-target effects, we performed RNA-seq of treated versus control or untreated human myoblasts and also examined potential collateral RNA cleavage activity using a dual reporter system. Although we did not detect collateral cleavage, our RNA-sequencing results suggested some guide RNAs could induce potential off-target gene expression changes. We are currently exploring mechanisms to explain these differential off-target effects. To address whether PspCas13b can activate a mammalian host immune response, we injected wild-type mice with AAV-Cas13b and investigated immune cell infiltration and pro-inflammatory cytokine profiles. We find evidence of an immune response against PspCas13b in injected mouse muscles. Importantly, transient immunosuppression reduced immune responses to Cas13b in treated animals. In conclusion, our data support that Cas13b can target and reduce DUX4 expression in FSHD muscles, but minimizing cellular immune response may be necessary to translate AAV-Cas13b therapy.

The development of new genetic tools has revolutionized our ability to study the functional role of specific neuronal populations and circuits generating behavior. Although this revolution has already taken place in small animal models such as mice, adoption of these techniques has been relatively slow for animals more closely related to humans, such as nonhuman primates. Current challenges include effective delivery to much larger structural targets in the primate brain, cell-type specific transduction, and immunological responses. In this chapter, we will review some of the challenges and considerations that are specific to using these viral technologies in the nonhuman primate brain. Ultimately, these challenges can be met with new advances in surgical technique and gene therapy that will spin out new viral vectors with enhanced features able to compensate for the limitations of current vectors. As the existing challenges are circumvented, this will lead to a revolution in primate neuroscientific research and a greater understanding of the functional role circuits play in complex behaviors relevant to human neurological and psychiatric diseases.

Of the adeno-associated viruses (AAVs), AAV9 is known for its capability to cross the blood-brain barrier (BBB) and can, therefore, be used as a noninvasive method to target the central nervous system. Furthermore, the addition of the peptide PhP.B to AAV9 increases its transduction across the BBB by 40-fold. Another neurotropic serotype, AAV5, has been shown as a gene therapeutic delivery vehicle to ameliorate several neurodegenerative diseases in preclinical models, but its administration requires invasive surgery. In this study, AAV9-PhP.B and AAV5-PhP.B were designed and produced in an insect cell-based system. To AAV9, the PhP.B peptide TLAVPFK was added, whereas in AAV5-PhP.B (AQTLAVPFKAQAQ), with AQ-AQAQ sequences used to swap with the corresponding sequence of AAV5. The addition of PhP.B to AAV5 did not affect its capacity to cross the mouse BBB, while increased transduction of liver tissue was observed. Then, intravenous (IV) and intrastriatal (IStr) delivery of AAV9-PhP.B and AAV5 were compared. For AAV9-PhP.B, similar transduction and expression levels were achieved in the striatum and cortex, irrespective of the delivery method used. IStr administration of AAV5 resulted in significantly higher amounts of vector DNA and therapeutic miRNA in the target regions such as striatum and cortex when compared with an IV administration of AAV9-PhP.B. These results illustrate the challenge in developing a vector that can be delivered noninvasively while achieving a transduction level similar to that of direct administration of AAV5. Thus, for therapeutic miRNA delivery with high local expression requirements, intraparenchymal delivery of AAV5 is preferred, whereas a humanized AAV9-PhP.B may be useful when widespread brain (and peripheral) transduction is needed.

Rett syndrome is a neurological disease due to loss-of-function mutations in the transcription factor, Methyl CpG binding protein 2 (MECP2). Because overexpression of endogenous MECP2 also causes disease, we have exploited a targeted RNA-editing approach to repair patient mutations where levels of MECP2 protein will never exceed endogenous levels. Here, we have constructed adeno-associated viruses coexpressing a bioengineered wild-type ADAR2 catalytic domain (Editasewt) and either Mecp2-targeting or nontargeting gfp RNA guides. The viruses are introduced systemically into male mice containing a guanosine to adenosine mutation that eliminates MeCP2 protein and causes classic Rett syndrome in humans. We find that in the mutant mice injected with the Mecp2-targeting virus, the brainstem exhibits the highest RNA-editing frequency compared to other brain regions. The efficiency is sufficient to rescue MeCP2 expression and function in the brainstem of mice expressing the Mecp2-targeting virus. Correspondingly, we find that abnormal Rett-like respiratory patterns are alleviated, and survival is prolonged, compared to mice injected with the control gfp guide virus. The levels of RNA editing among most brain regions corresponds to the distribution of guide RNA rather than Editasewt. Our results provide evidence that a targeted RNA-editing approach can alleviate a hallmark symptom in a mouse model of human disease.

The efficiency of recombinant Adeno-associated virus vectors (AAV) transducing host cells is very low, limiting their therapeutic potential in patients. There are several cellular pathways interacting and interfering with the journey of the AAV from the cell surface to the nucleus, opening the possibility to enhance AAV transduction by modifying these interactions. In this study, we explored the results of AAV hepatic transduction when different mTOR inhibitors.- rapamycin, MLN0128, RapaLink-1 -were used in preconditioned juvenile and adult mice. We confirmed rapamycin as an AAV hepatic transduction enhancer in juvenile and adult mice; however, RapaLink-1, a stronger mTOR inhibitor and a clear hepatic autophagy inducer, had no positive effect. Moreover, MLN0128 reduced AAV hepatic transduction. Therefore, our results show a complex interaction between the mTOR pathway and AAV-mediated hepatic transduction and indicate that mTOR inhibition is not a straightforward strategy for improving AAV transduction. More studies are necessary to elucidate the molecular mechanisms involve in the positive and negative effects of mTOR inhibitors on AAV transduction efficiency.

Duchenne muscular dystrophy (DMD) is a fatal muscle disease caused by dystrophin deficiency. Dystrophin consists of the amino terminus, central rod domain with 24 spectrin-like repeats and four hinges (H), cysteine-rich domain, and carboxyl terminus. Several highly abbreviated micro-dystrophins are currently in clinical trials. They all carry H1 and H4. Here we investigated whether these two hinges are essential for micro-dystrophin function in murine DMD models. Three otherwise identical micro-dystrophins were engineered to contain H1 and/or H4 and were named H1/H4 (with both H1 and H4), ∆H1 (without H1), and ∆H4 (without H4). These constructs were packaged in adeno-associated virus serotype-9 and delivered to the tibialis anterior muscle of 3-month-old male mdx4cv mice (1E12 vector genome particles/muscle). Three months later, we detected equivalent micro-dystrophin expression in total muscle lysate. However, only H1/H4 and ∆H1 showed correct sarcolemmal localization. ∆H4 mainly existed as subsarcolemmal aggregates. H1/H4 and ∆H1, but not ∆H4, fully restored the dystrophin-associated protein complex and significantly improved the specific muscle force. Eccentric contraction-induced force decline was best protected by H1/H4, followed by ∆H1, but not by ∆H4. Next, we compared H1/H4 and ∆H1 in 6-week-old male mdx mice by intravenous injection (1E13 vector genome particles/mouse). Four months post-injection, H1/H4 significantly outperformed ∆H1 in extensor digitorum longus muscle force measurements but two constructs yielded comparable ECG improvements. We conclude that H4 is essential for micro-dystrophin function and H1 facilitates force production. Our findings will help develop next-generation micro-dystrophin gene therapy.

Research on adeno-associated virus (AAV) and its recombinant vectors as well as on fluorescence microscopy imaging is rapidly progressing driven by clinical applications and new technologies, respectively. The topics converge, since high and super-resolution microscopes facilitate the study of spatial and temporal aspects of cellular virus biology. Labeling methods also evolve and diversify. We review these interdisciplinary developments and provide information on the technologies used and the biological knowledge gained. The emphasis lies on the visualization of AAV proteins by chemical fluorophores, protein fusions and antibodies as well as on methods for the detection of adeno-associated viral DNA. We add a short overview of fluorescent microscope techniques and their advantages and challenges in detecting AAV.