Paclitaxel is a microtubule-stabilizing chemotherapeutic agent that is widely used in cancer treatment and in a number of curative and palliative regimens. Despite its beneficial effects on cancer, paclitaxel also damages healthy tissues, most prominently the peripheral sensory nervous system. The mechanisms leading to paclitaxelinduced peripheral neuropathy remain elusive, and therapies that prevent or alleviate this condition are not available. We established a zebrafish in vivo model to study the underlying mechanisms and to identify pharmacological agents that may be developed into therapeutics. Both adult and larval zebrafish displayed signs of paclitaxel neurotoxicity, including sensory axon degeneration and the loss of touch response in the distal caudal fin. Intriguingly, studies in zebrafish larvae showed that paclitaxel rapidly promotes epithelial damage and decreased mechanical stress resistance of the skin before induction of axon degeneration. Moreover, injured paclitaxel-treated zebrafish skin and scratch-wounded human keratinocytes (HEK001) display reduced healing capacity. Epithelial damage correlated with rapid accumulation of fluorescein-conjugated paclitaxel in epidermal basal keratinocytes, but not axons, and upregulation of matrix-metalloproteinase 13 (MMP-13, collagenase 3) in the skin. Pharmacological inhibition of MMP-13, in contrast, largely rescued paclitaxel-induced epithelial damage and neurotoxicity, whereas MMP-13 overexpression in zebrafish embryos rendered the skin vulnerable to injury under mechanical stress conditions. Thus, our studies provide evidence that the epidermis plays a critical role in this condition, and we provide a previously unidentified candidate for therapeutic interventions.aclitaxel is a microtubule-stabilizing chemotherapeutic agent that is widely used in the treatment of common cancers, including breast, ovarian, and lung cancer. Despite its promising anticancerous properties, paclitaxel also damages healthy tissues, most prominently peripheral axons of somatosensory neurons (reviewed in ref. 1). Paclitaxel-induced peripheral neuropathy initiates in the distal extremities and presents as neuropathic pain syndrome, temperature sensitivity, and paresthesia (tingling and numbness). Nerve biopsies from patients suggest that axon degeneration is the primary manifestation of this condition, followed by secondary demyelination and nerve fiber loss in severely affected patients (1, 2). Certain drugs have been shown in vitro and in vivo to protect against paclitaxel-induced nerve damage, including acetyl-L-carnitine, erythropoietin, alpha-lipoic acid, olesoxime, amifostine, nerve growth factor, and glutamate (reviewed in ref.3). However, so far, these agents have either not successfully passed clinical trials or merely alleviate symptoms such as pain without prevention (1). Thus, a better understanding of the underlying causes of paclitaxel-induced peripheral neuropathy is necessary and may help identify new candidate drugs with which to treat this condition.A widely...

Microarray analysis has generated a resource of target genes downstream of Sema6A/PlxnA2 signaling, which can be further investigated to elucidate the downstream effects of this well-studied neuronal and vascular guidance signaling pathway. Developmental Dynamics 246:539-549, 2017. © 2017 Wiley Periodicals, Inc.

We demonstrate that zebrafish are suitable to study glucose-induced neurotoxicity. Given the effects in zebrafish and mice, MMP-13 inhibition may be beneficial in the treatment of human diabetic neuropathy.

Histidyl-tRNA Synthetase (HARS) is a member of the aminoacyl-tRNA synthetase family, which attach amino acids to their associated tRNA molecules. This reaction is a crucial step in protein synthesis that must be carried out in every cell of an organism. However, a number of tissue-specific, human genetic disorders have been associated with mutations in the genes for aminoacyl-tRNA synthetases, including HARS. These associations indicate that, while we know a great deal about the molecular and biochemical properties of this enzyme, we still do not fully understand how these proteins function in the context of an entire organism. To this end, we set out to knock-down HARS expression in the zebrafish and characterize the developmental consequences. Through our work we show that some tissues, particularly the nervous system, are more sensitive to HARS loss than others and we reveal a link between HARS and the proliferation and survival of neuronal progenitors during development.

Histidyl tRNA Synthetase (HARS) is a member of the aminoacyl tRNA synthetase (ARS) family of enzymes. This family of 20 enzymes is responsible for attaching specific amino acids to their cognate tRNA molecules, a critical step in protein synthesis. However, recent work highlighting a growing number of associations between ARS genes and diverse human diseases raises the possibility of new and unexpected functions in this ancient enzyme family. For example, mutations in HARS have been linked to two different neurological disorders, Usher Syndrome Type IIIB and Charcot Marie Tooth peripheral neuropathy. These connections raise the possibility of previously undiscovered roles for HARS in metazoan development, with alterations in these functions leading to complex diseases. In an attempt to establish Danio rerio as a model for studying HARS functions in human disease, we characterized the Danio rerio hars gene and compared it to that of human HARS. Using a combination of bioinformatics, molecular biology, and cellular approaches, we found that while the human genome encodes separate genes for cytoplasmic and mitochondrial HARS protein, the Danio rerio genome encodes a single hars gene which undergoes alternative splicing to produce the respective cytoplasmic and mitochondrial versions of Hars. Nevertheless, while the HARS genes of humans and Danio differ significantly at the genomic level, we found that they are still highly conserved at the amino acid level, underscoring the potential utility of Danio rerio as a model organism for investigating HARS function and its link to human diseases in vivo.