Abnormal differentiation of dopaminergic neurons in zebrafish trpm7 mutant larvae impairs development of the motor pattern

• Published in: Developmental biology Vol. 386; no. 2; pp. 428 - 439
• Main Authors: Decker, Amanda R., McNeill, Matthew S., Lambert, Aaron M., Overton, Jeffrey D., Chen, Yu-Chia, Lorca, Ramón A., Johnson, Nicolas A., Brockerhoff, Susan E., Mohapatra, Durga P., MacArthur, Heather, Panula, Pertti, Masino, Mark A., Runnels, Loren W., Cornell, Robert A.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 15.02.2014
• Subjects: 1-Methyl-4-phenylpyridinium - toxicity; Analysis of Variance; Animals; Anura; Cell Differentiation - physiology; Cell Line; Danio rerio; Deferoxamine - pharmacology; DNA Primers - genetics; Dopamine; Dopaminergic Neurons - cytology; Electroretinography; Freshwater; Larva - growth & development; Melanocytes - metabolism; Motor Activity - drug effects; Motor Activity - genetics; Motor Activity - physiology; Mutation - genetics; Parkinson's; Patch-Clamp Techniques; Protein-Serine-Threonine Kinases - genetics; Reverse Transcriptase Polymerase Chain Reaction; TRPM Cation Channels - genetics; TRPM7; Tyrosine 3-Monooxygenase - metabolism; Zebrafish; Zebrafish - genetics; Zebrafish - growth & development; Zebrafish Proteins - genetics; Parkinson's; Zebrafish; TRPM7; Dopamine
• ISSN: 0012-1606; 1095-564X
• DOI: 10.1016/j.ydbio.2013.11.015

Transient receptor potential, melastatin-like 7 (Trpm7) is a combined ion channel and kinase implicated in the differentiation or function of many cell types. Early lethality in mice and frogs depleted of the corresponding gene impedes investigation of the functions of this protein particularly during later stages of development. By contrast, zebrafish trpm7 mutant larvae undergo early morphogenesis normally and thus do not have this limitation. The mutant larvae are characterized by multiple defects including melanocyte cell death, transient paralysis, and an ion imbalance that leads to the development of kidney stones. Here we report a requirement for Trpm7 in differentiation or function of dopaminergic neurons in vivo. First, trpm7 mutant larvae are hypomotile and fail to make a dopamine-dependent developmental transition in swim-bout length. Both of these deficits are partially rescued by the application of levodopa or dopamine. Second, histological analysis reveals that in trpm7 mutants a significant fraction of dopaminergic neurons lack expression of tyrosine hydroxylase, the rate-limiting enzyme in dopamine synthesis. Third, trpm7 mutants are unusually sensitive to the neurotoxin 1-methyl-4-phenylpyridinium, an oxidative stressor, and their motility is partially rescued by application of the iron chelator deferoxamine, an anti-oxidant. Finally, in SH-SY5Y cells, which model aspects of human dopaminergic neurons, forced expression of a channel-dead variant of TRPM7 causes cell death. In summary, a forward genetic screen in zebrafish has revealed that both melanocytes and dopaminergic neurons depend on the ion channel Trpm7. The mechanistic underpinning of this dependence requires further investigation. •Zebrafish trpm7 mutant larvae exhibit dopamine-responsive behavioral deficits.•In such larvae, dopaminergic neurons express DAT but many lack expression of TH.•trpm7 mutant larvae are hyper-sensitive to a toxin of dopaminergic neurons, MPP+.•We show that SH-SY5Y cells, which are dopaminergic, depend on TRPM7 for survival.•How Trpm7 contributes to function and viability of dopaminergic neurons is unknown.