Cyclin‐dependent kinase 5 influences Rohon‐Beard neuron survival in zebrafish

• Published in: Journal of neurochemistry Vol. 99; no. 1; pp. 251 - 259
• Main Authors: Kanungo, Jyotshnabala, Li, Bing‐Sheng, Zheng, Yali, Pant, Harish C.
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Publishing Ltd 01.10.2006; Blackwell
• Subjects: Analytical, structural and metabolic biochemistry; Animals; Apoptosis; Biological and medical sciences; Cell cycle, cell proliferation; Cell Death; Cell physiology; Cell Survival; Cyclin-Dependent Kinase 5 - genetics; Cyclin-Dependent Kinase 5 - metabolism; cyclin‐dependent kinase 5; Danio rerio; Embryo, Nonmammalian - cytology; Embryonic Development; Embryos; Enzymes and enzyme inhibitors; Freshwater; Fundamental and applied biological sciences. Psychology; Gene Expression Regulation, Developmental; Immunohistochemistry; Kinases; Molecular and cellular biology; Neurons; Neurons - cytology; Neurons - enzymology; Prenatal development; Proteins; RNA, Small Interfering - genetics; Rohon‐Beard neuron; siRNA; Transferases; Zebrafish; Zebrafish - embryology; Zebrafish Proteins - genetics; Zebrafish Proteins - metabolism; Embryo; Fertilization; Enzyme; Transferases; Central nervous system; Danio rerio; Rohon- Beard neuron; Early stage; siRNA; Survival; Cyclin-dependent kinase 5; Encephalon; Cyclin-dependent kinase; Phenotype; Protein kinase; Development; Sensory neuron; zebrafish; Apoptosis
• ISSN: 0022-3042; 1471-4159
• DOI: 10.1111/j.1471-4159.2006.04114.x

Cyclin‐dependent kinase 5 (cdk5), a member of the cyclin‐dependent kinase family, is expressed predominantly in post‐mitotic cell populations. Unlike the other cdks, cdk5 is abundant and most active in differentiated neurons. Here, we describe the function of a cdk5 ortholog in zebrafish. Cdk5 catalytic activity is meager but present in early stages of development. However, at 24 h post‐fertilization (hpf), the activity is remarkably higher and continues to be high through 48 and 72 hpf. Knocking down cdk5 by micro‐injection of a specific siRNA resulted in decreased cdk5 protein level accompanied by reduced kinase activity. In the cdk5 siRNA‐injected embryos, the number of primary sensory Rohon‐Beard (RB) neurons was significantly reduced and there were more apoptotic cells in the brain. These phenotypes were rescued by co‐injection of cdk5 mRNA. Within the first two days of development, RB neurons undergo apoptosis in zebrafish. To examine whether cdk5 has a role in RB neuron survival, cdk5 mRNA was injected into the one‐ to two‐cell embryos. In these embryos, RB neuron apoptosis was inhibited compared with the uninjected control embryos. These results suggest that in zebrafish, cdk5 influences RB neuron survival and potentially regulates early neuronal development.