Leucine Zipper-Bearing Kinase Is a Critical Regulator of Astrocyte Reactivity in the Adult Mammalian CNS.

Reactive astrocytes influence post-injury recovery, repair, and pathogenesis of the mammalian CNS. Much of the regulation of astrocyte reactivity, however, remains to be understood. Using genetic loss and gain-of-function analyses in vivo, we show that the conserved MAP3K13 (also known as leucine zipper-bearing kinase [LZK]) promotes astrocyte reactivity and glial scar formation after CNS injury. Inducible LZK gene deletion in astrocytes of adult mice reduced astrogliosis and impaired glial scar formation, resulting in increased lesion size after spinal cord injury. Conversely, LZK overexpression in astrocytes enhanced astrogliosis and reduced lesion size. Remarkably, in the absence of injury, LZK overexpression alone induced widespread astrogliosis in the CNS and upregulated astrogliosis activators pSTAT3 and SOX9. The identification of LZK as a critical cell-intrinsic regulator of astrocyte reactivity expands our understanding of the multicellular response to CNS injury and disease, with broad translational implications for neural repair.

OPA1 gene therapy prevents retinal ganglion cell loss in a Dominant Optic Atrophy mouse model.

Dominant optic atrophy (DOA) is a rare progressive and irreversible blinding disease which is one of the most frequent forms of hereditary optic neuropathy. DOA is mainly caused by dominant mutation in the OPA1 gene encoding a large mitochondrial GTPase with crucial roles in membrane dynamics and cell survival. Hereditary optic neuropathies are commonly characterized by the degeneration of retinal ganglion cells, leading to the optic nerve atrophy and the progressive loss of visual acuity. Up to now, despite increasing advances in the understanding of the pathological mechanisms, DOA remains intractable. Here, we tested the efficiency of gene therapy on a genetically-modified mouse model reproducing DOA vision loss. We performed intravitreal injections of an Adeno-Associated Virus carrying the human OPA1 cDNA under the control of the cytomegalovirus promotor. Our results provide the first evidence that gene therapy is efficient on a mouse model of DOA as the wild-type OPA1 expression is able to alleviate the OPA1-induced retinal ganglion cell degeneration, the hallmark of the disease. These results displayed encouraging effects of gene therapy for Dominant Optic Atrophy, fostering future investigations aiming at clinical trials in patients.

CaMKK-CaMK1a, a new post-traumatic signalling pathway induced in mouse somatosensory neurons.

Neurons innervating peripheral tissues display complex responses to peripheral nerve injury. These include the activation and suppression of a variety of signalling pathways that together influence regenerative growth and result in more or less successful functional recovery. However, these responses can be offset by pathological consequences including neuropathic pain. Calcium signalling plays a major role in the different steps occurring after nerve damage. As part of our studies to unravel the roles of injury-induced molecular changes in dorsal root ganglia (DRG) neurons during their regeneration, we show that the calcium calmodulin kinase CaMK1a is markedly induced in mouse DRG neurons in several models of mechanical peripheral nerve injury, but not by inflammation. Intrathecal injection of NRTN or GDNF significantly prevents the post-traumatic induction of CaMK1a suggesting that interruption of target derived factors might be a starter signal in this de novo induction. Inhibition of CaMK signalling in injured DRG neurons by pharmacological means or treatment with CaMK1a siRNA resulted in decreased velocity of neurite growth in vitro. Altogether, the results suggest that CaMK1a induction is part of the intrinsic regenerative response of DRG neurons to peripheral nerve injury, and is thus a potential target for therapeutic intervention to improve peripheral nerve regeneration.