RESUMO
Midkine is a 13-kDa retinoic acid-induced heparin-binding growth factor involved in various biological phenomena such as cell migration, neurogenesis, and tissue repair. We previously demonstrated that midkine-deficient (Mdk(-/-)) mice exhibited a delayed hippocampal development with impaired working memory and increased anxiety only at the age of 4 weeks. To assess whether midkine gene could play important roles in development and maintenance of central nervous system, we investigated biochemical and behavioral parameters in dopamine and glutamate neurotransmission of Mdk(-/-) mice. The Mdk(-/-) mice exhibited a hypodopaminergic state (i.e., decreased levels of dopamine and its receptors in the striatum) with no alterations of glutamatergic system (i.e., normal level of glutamate, glutamine, glycine, d-serine, l-serine, and NMDA receptors in the frontal cortex and hippocampus). We also found prepulse inhibition deficits reversed by clozapine and haloperidol in the Mdk(-/-) mice. Our results suggested that midkine deficiency may be related to neurochemical and behavioral dysfunctions in dopaminergic system.
Assuntos
Citocinas/deficiência , Dopamina/metabolismo , Inibição Neural/genética , Reflexo de Sobressalto/genética , Estimulação Acústica/métodos , Análise de Variância , Animais , Comportamento Animal/efeitos dos fármacos , Cromatografia Líquida de Alta Pressão/métodos , Antagonistas de Dopamina/metabolismo , Antagonistas de Dopamina/farmacologia , Proteínas da Membrana Plasmática de Transporte de Dopamina/metabolismo , Relação Dose-Resposta a Droga , Comportamento Exploratório/fisiologia , Relações Interpessoais , Camundongos , Camundongos Endogâmicos C57BL/metabolismo , Camundongos Endogâmicos DBA/metabolismo , Camundongos Knockout , Midkina , Atividade Motora/efeitos dos fármacos , Atividade Motora/genética , Inibição Neural/efeitos dos fármacos , Ligação Proteica/efeitos dos fármacos , Ligação Proteica/genética , Ensaio Radioligante/métodos , Receptores de Dopamina D1/metabolismo , Receptores de Dopamina D2/metabolismo , Reflexo de Sobressalto/efeitos dos fármacos , Trítio/metabolismoRESUMO
A novel 114-kDa zinc finger protein, ZEC, has been found by cDNA cloning and characterized. ZEC was strongly expressed in the testis, liver and kidney, and also in embryonic stem cells. Epitope-tagged experiments indicated nuclear localization of ZEC. ZEC contained 18 C2H2 zinc fingers which were organized in two clusters. A ZEC binding DNA sequence, C/GA/TA/TGGTTGGTTGC, which we have designated the GT box, was identified by random oligonucleotide binding selection assay. The GT box did not contain binding sites for other previously characterized transcription factors and thus represented a potentially novel DNA target sequence. Electrophoretic mobility shift assay (EMSA) showed that both clusters of zinc fingers bound to the same DNA sequence. Site-directed mutagenesis revealed that the core sequence TTGGTT within the GT box was essential to ZEC binding, while DNA sequences outside of the core sequence enhanced this interaction. Furthermore, co-transfection assays demonstrated that ZEC could activate a reporter luciferase gene driven by this DNA sequence.