Transgenic zebrafish model of neurodegeneration

Abstract

In Alzheimer's disease (AD), the microtubule-associated protein, tau, is compromised in its normal association with microtubules and forms into paired helical filaments (PHF) that are the hallmark cytoskeletal pathology of the disease. Several posttranslational modifications of tau including phosphorylation have been implicated in AD pathogenesis. In addition, and importantly, mutations in the genes encoding human tau have recently been implicated in a variety of hereditary dementias, collectively termed frontotemporal dementia with parkinsonism linked to chromosome 17 (FTDP-17). This has rekindled interest in the importance of tau in neurodegenerative diseases (cf. Vogel [1998] Science 280:1524-1525; Goedert et al. [1998] Neuron 21:955-958; D'Souza et al. [1999] PNAS 96:5598-5603). Despite significant progress in the field of tau biology and neurodegenerative diseases, several important issues remain unresolved. The early functional consequences of tau alterations in living neurons is incompletely understood, and it is not clear how tau in neurodegenerative diseases becomes redistributed from its normal concentration in neuronal axons to pathological inclusions in neuronal soma known as neurofibrillary tangles (NFT). One of the reasons for these gaps in knowledge is the relative paucity of model systems to study these processes. We have developed a transgenic model system to study the functional consequences and trafficking patterns in zebrafish neurons of human tau either mutated on sites associated with hereditary dementias or altered at select posttranslational modification sites. The overall guiding hypothesis is that the model allows dissection of a hierarchy of events relevant to potential mechanisms of neurodegenerative diseases related to critical early stages in development of disease. We showed that a FTDP-17 mutant form of human tau expressed in zebrafish neurons produced a cytoskeletal disruption that closely resembled the NFT in human disease. This model system will prove useful in the study of other mutant taus in vertebrate neurons in vivo, and the approaches developed here will have broad usefulness in the study of functional consequences and potential genetic analyses of introducing into living vertebrate neurons other molecules involved in the pathogenesis of neurodegenerative diseases.

A zebrafish model of tauopathy allows in vivo imaging of neuronal cell death and drug evaluation

“…We have overcome these limitations with the efficient Tol2 transposon and Gal4/UASbased expression of human TAU-P301L in transgenic zebrafish. In contrast to previous studies (11,12), we could monitor early pathology, including disease-specific hyperphosphorylation and conformational changes of TAU as well as neuronal and behavioral abnormalities within the first 2 days of embryonic development in stable transgenic zebrafish. Furthermore, the larvae developed substantial neurodegeneration after a few days.…”

“…We have further advanced the system to allow introduction of various other genes and promoters to facilitate the generation of different zebrafish disease models. In contrast to previous studies (11,12), we were able to monitor early pathology, including disease-specific hyperphosphorylation and conformational changes of TAU, neuronal and behavioral abnormalities as well as increased neuronal cell death within the first days of embryonic development in stable transgenic zebrafish. The rapid appearance of a pathologic phenotype allows one not only to use the embryos to study disease progression in a transparent vertebrate but also to validate and even screen on a relatively large scale for compounds that modify early phenotypes, such as TAU hyperphosphorylation, in vivo.…”

Generation and characterization of transgenic zebrafish lines using different ubiquitous promoters

“…In addition, zebrafish have also become an attractive model for studying neurodegeneration (Grunwald et al 1988;Furutani-Seiki et al 1996;Tomasiewicz et al 2002;Vihtelic et al 2005), regeneration of various tissues and organs (Vihtelic and Hyde 2000;Poss et al 2002;Bai et al2005;Iovine et al 2005; Lee et al 2005;Whitehead et al 2005;Thummel et al 2006a;Nakatani et al 2007), adult behaviors (Orger et al 2004;Muto et al2005;Ninkovic and Bally-Cuif 2006;Bretaud et al 2007;Yu et al 2007) and aging (Gerhard 2007). To fully exploit zebrafish in these studies, great emphasis is being placed on generating fish that express desired transgenes in either specific subsets of cells or a wide range of tissues and cells.…”

Mitophagy and neurodegeneration

“…20 Several neurodegenerative diseases have been modeled in zebrafish by expressing mutant forms of the human disease gene under the control of a zebrafish promoter. Examples of these genes include MAPT, 21,22 SOD1, 23 and HTT. 24 Fusion of green fluorescent protein (GFP) to the disease-causing transgene can be used to monitor the clearance of protein aggregates, 24 and a similar approach of fluorescently tagging mitochondrial proteins can be used to monitor mitophagy in an intact organism under a variety of conditions.…”