PTEN deletion in spinal pathways via retrograde transduction with AAV-RG enhances forelimb motor recovery after cervical spinal cord injury; Sex differences and late-onset pathophysiologies

Spinal cord injuries (SCI) cause permanent functional impairments due to interruption of motor and sensory pathways. Regeneration of axons does not occur due to lack of intrinsic growth capacity of adult neurons and extrinsic inhibitory factors, especially at the injury site. However, some regeneration can be achieved via deletion of the phosphatase and tensin homolog (PTEN) in cells of origin of spinal pathways. Here, we deployed an AAV variant that is retrogradely transported (AAV-rg) to deliver gene modifying cargos to the cells of origin of multiple pathways interrupted by SCI, testing whether this promoted recovery of motor function. PTENf/f;RosatdTomato mice and control RosatdTomato mice received injections of different doses (number of genome copies, GCs) of AAV-rg/Cre into the cervical spinal cord at the time of a C5 dorsal hemisection injury. Forelimb grip strength was tested over time using a grip strength meter. PTENf/f;RosatdTomato mice with AAV-rg/Cre (PTEN-deleted) exhibited substantial improvements in forelimb gripping ability in comparison to controls. Of note, there were major sex differences in the extent of recovery, with male mice exhibiting greater recovery than females. However, at around 5-7 weeks post-injury/injection, many mice with SCI and AAV-rg-mediated PTEN deletion began to exhibit pathophysiologies involving excessive scratching of the ears and back of the neck and rigid forward extension of the hindlimbs. These pathophysiologies increased in incidence and severity over time. Our results reveal that although intra-spinal injections of AAV-rg/Cre in PTENf/f;RosatdTomato mice can enhance forelimb motor recovery after SCI, late-developing functional abnormalities occur with the experimental conditions used here. Mechanisms underlying late-developing pathophysiologies remain to be defined.

PTEN deletion in spinal pathways via retrograde transduction with AAV-rg enhances forelimb motor recovery after cervical spinal cord injury; sex differences and late-onset pathophysiologies

Spinal cord injuries (SCI) cause permanent functional impairments due to interruption of motor and sensory pathways. Regeneration of axons does not occur due to lack of intrinsic growth capacity of adult neurons and extrinsic inhibitory factors, especially at the injury site. However, some regeneration can be achieved via deletion of the phosphatase and tensin homolog (PTEN) in cells of origin of spinal pathways. Here, we deployed an AAV variant that is retrogradely transported (AAV-rg) to deliver gene modifying cargos to the cells of origin of multiple pathways interrupted by SCI, testing whether this promoted recovery of motor function. PTEN f/f ;Rosa tdTomato mice and control Rosa tdTomato mice received injections of different doses (number of genome copies, GCs) of AAV-rg/Cre into the cervical spinal cord at the time of a C5 dorsal hemisection injury. Forelimb grip strength was tested over time using a grip strength meter. PTEN f/f ;Rosa tdTomato mice with AAV-rg/Cre (PTEN-deleted) exhibited substantial improvements in forelimb gripping ability in comparison to controls. Of note, there were major sex differences in the extent of recovery, with male mice exhibiting greater recovery than females. However, at around 5-7 weeks post-injury/injection, many mice with SCI and AAV-rg-mediated PTEN deletion began to exhibit pathophysiologies involving excessive scratching of the ears and back of the neck and rigid forward extension of the hindlimbs. These pathophysiologies increased in incidence and severity over time. Our results reveal that although intra-spinal injections of AAV-rg/Cre in PTEN f/f ;Rosa tdTomato mice can enhance forelimb motor recovery after SCI, late-developing functional abnormalities occur with the experimental conditions used here. Mechanisms underlying late-developing pathophysiologies remain to be defined.

Harnessing rAAV-retro for gene manipulations in multiple pathways that are interrupted after spinal cord injury

This paper explores the potential of rAAV2-retro to deliver gene modifying cargoes to the cells of origin of multiple pathways that are interrupted by spinal cord injury (SCI), summarizing data from previous studies and new data from additional experiments. rAAV-retro exhibits uniquely robust and reliable long-distance retrograde transport from pre-terminal axons and synapses back to neuronal bodies. Previous studies have documented that various AAV-based genetic modifications can enable axon regeneration after SCI, but these have targeted the cells of origin of one pathway at a time. In contrast, rAAV-retro can simultaneously transduce large numbers of neurons of origin of multiple spinal pathways with single injections into the spinal cord. Our initial studies use Rosa^tdTomato and double transgenic PTEN^f/f; Rosa^tdTomato mice in which transfection with rAAV-retro/Cre deletes PTEN and activates tdT expression in the same neurons. Injections of rAAV-retro/Cre into the cervical, thoracic and lumbar spinal cord led to topographically specific retrograde transduction in cortical motoneurons and neurons in subcortical regions that give rise to different spinal pathways. Our results confirm and extend previous studies indicating selective transduction of neurons that terminate at the level of the injection with minimal retrograde transduction of axons in transit to lower levels. We document feasibility of using rAAV-retro expressing shRNA against PTEN along with a GFP reporter (rAAV-retro-shPTEN/GFP) to effectively knock down PTEN in multiple populations of neurons, which can be used in any species. Some limitations and caveats of currently available rAAV-retros are discussed. Together, our results support the potential applications of rAAV-retro for AAV-based gene-modifications for SCI.

AAV-mediated inhibition of ULK1 promotes axonal regeneration in the central nervous system in vitro and in vivo

Axonal damage is an early step in traumatic and neurodegenerative disorders of the central nervous system (CNS). Damaged axons are not able to regenerate sufficiently in the adult mammalian CNS, leading to permanent neurological deficits. Recently, we showed that inhibition of the autophagic protein ULK1 promotes neuroprotection in different models of neurodegeneration. Moreover, we demonstrated previously that axonal protection improves regeneration of lesioned axons. However, whether axonal protection mediated by ULK1 inhibition could also improve axonal regeneration is unknown. Here, we used an adeno-associated viral (AAV) vector to express a dominant-negative form of ULK1 (AAV.ULK1.DN) and investigated its effects on axonal regeneration in the CNS. We show that AAV.ULK1.DN fosters axonal regeneration and enhances neurite outgrowth in vitro. In addition, AAV.ULK1.DN increases neuronal survival and enhances axonal regeneration after optic nerve lesion, and promotes long-term axonal protection after spinal cord injury (SCI) in vivo. Interestingly, AAV.ULK1.DN also increases serotonergic and dopaminergic axon sprouting after SCI. Mechanistically, AAV.ULK1.DN leads to increased ERK1 activation and reduced expression of RhoA and ROCK2. Our findings outline ULK1 as a key regulator of axonal degeneration and regeneration, and define ULK1 as a promising target to promote neuroprotection and regeneration in the CNS.

ASF1B promotes cervical cancer progression through stabilization of CDK9

Cervical cancer (CC) is one of the most deadly cancers in women, its current treatments still result in poor outcomes and developing the novel targets and therapeutic strategies are urgently needed. Recent studies have shown that anti-silencing function 1B (ASF1B) might be used as a new proliferation marker for cancer diagnosis and prognosis. However, the expression and function of ASF1B in cervical cancer remain unclear. Here, we induced ASF1B knockdown and overexpression in cervical cancer cell lines and detected the biological behavior changes in vitro. Furthermore, we established two murine models using stable ASF1B-shRNA HeLa cells or normal HeLa cells following AAV-shRNA-ASF1B administration to evaluate how suppression of ASF1B affects tumor growth. We showed that ASF1B functions as an oncogene in cervical cancer cells. Silence of ASF1B suppressed cervical cancer cell growth in vitro and in vivo, while, ASF1B overexpression accelerated cancer cell proliferation. Furthermore, ASF1B deficiency induced cell cycle arrest and apoptosis. Mechanistically, we found that ASF1B formed stable complexes with cyclin-dependent kinase 9 (CDK9), and positively regulated CDK9 stabilization. Taken together, tumorigenic ASF1B could be targeted to suppress cervical cancer tumor growth by inducing apoptotic cell death.

Inhibition of the autophagic protein ULK1 attenuates axonal degeneration in vitro and in vivo, enhances translation, and modulates splicing

Axonal degeneration is a key and early pathological feature in traumatic and neurodegenerative disorders of the CNS. Following a focal lesion to axons, extended axonal disintegration by acute axonal degeneration (AAD) occurs within several hours. During AAD, the accumulation of autophagic proteins including Unc-51 like autophagy activating kinase 1 (ULK1) has been demonstrated, but its role is incompletely understood. Here, we study the effect of ULK1 inhibition in different models of lesion-induced axonal degeneration in vitro and in vivo. Overexpression of a dominant negative of ULK1 (ULK1.DN) in primary rat cortical neurons attenuates axotomy-induced AAD in vitro. Both ULK1.DN and the ULK1 inhibitor SBI-0206965 protect against AAD after rat optic nerve crush in vivo. ULK1.DN additionally attenuates long-term axonal degeneration after rat spinal cord injury in vivo. Mechanistically, ULK1.DN decreases autophagy and leads to an mTOR-mediated increase in translational proteins. Consistently, treatment with SBI-0206965 results in enhanced mTOR activation. ULK1.DN additionally modulates the differential splicing of the degeneration-associated genes Kif1b and Ddit3. These findings uncover ULK1 as an important mediator of axonal degeneration in vitro and in vivo, and elucidate its function in splicing, defining it as a putative therapeutic target.

The Rise of Molecules Able To Regenerate the Central Nervous System

Injury to the adult central nervous system (CNS) usually leads to permanent deficits of cognitive, sensory, and/or motor functions. The failure of axonal regeneration in the damaged CNS limits functional recovery. The lack of information concerning the biological mechanism of axonal regeneration and its complexity has delayed the process of drug discovery for many years compared to other drug classes. Starting in the early 2000s, the ability of many molecules to stimulate axonal regrowth was evaluated through automated screening techniques; many hits and some new mechanisms involved in axonal regeneration were identified. In this Perspective, we discuss the rise of the CNS regenerative drugs, the main biological techniques used to test these drug candidates, some of the most important screens performed so far, and the main challenges following the identification of a drug that is able to induce axonal regeneration in vivo.

Gene Manipulation Strategies to Identify Molecular Regulators of Axon Regeneration in the Central Nervous System

Limited axon regeneration in the injured adult mammalian central nervous system (CNS) usually results in irreversible functional deficits. Both the presence of extrinsic inhibitory molecules at the injury site and the intrinsically low capacity of adult neurons to grow axons are responsible for the diminished capacity of regeneration in the adult CNS. Conversely, in the embryonic CNS, neurons show a high regenerative capacity, mostly due to the expression of genes that positively control axon growth and downregulation of genes that inhibit axon growth. A better understanding of the role of these key genes controlling pro-regenerative mechanisms is pivotal to develop strategies to promote robust axon regeneration following adult CNS injury. Genetic manipulation techniques have been widely used to investigate the role of specific genes or a combination of different genes in axon regrowth. This review summarizes a myriad of studies that used genetic manipulations to promote axon growth in the injured CNS. We also review the roles of some of these genes during CNS development and suggest possible approaches to identify new candidate genes. Finally, we critically address the main advantages and pitfalls of gene-manipulation techniques, and discuss new strategies to promote robust axon regeneration in the mature CNS.

Breaking BAG: The Co-Chaperone BAG3 in Health and Disease

Human BAG (Bcl-2-associated athanogene) proteins form a family of antiapoptotic proteins that currently consists of six members (BAG1-6) all sharing the BAG protein domain from which the name arises. Via this domain, BAG proteins bind to the heat shock protein 70 (Hsp70), thereby acting as a co-chaperone regulating the activity of Hsp70. In addition to their antiapoptotic activity, all human BAG proteins have distinct functions in health and disease, and BAG3 in particular is the focus of many investigations. BAG3 has a modular protein domain composition offering the possibility for manifold interactions with other proteins. Various BAG3 functions are implicated in disorders including cancer, myopathies, and neurodegeneration. The discovery of its role in selective autophagy and the description of BAG3-mediated selective macroautophagy as an adaptive mechanism to maintain cellular homeostasis, under stress as well as during aging, make BAG3 a highly interesting target for future pharmacological interventions.