ABSTRACT
BACKGROUND: We recently identified a novel oncogene, Cancer-upregulated gene 2 (CUG2), which is essential for kinetochore formation and promotes tumorigenesis in mammalian cells. However, the in vivo function of CUG2 has not been studied in animal models. RESULTS: To study the function of CUG2 in vivo, we isolated a zebrafish homologue that is expressed specifically in the proliferating cells of the central nervous system (CNS). Morpholino-mediated knockdown of cug2 resulted in apoptosis throughout the CNS and the development of neurodegenerative phenotypes. In addition, cug2-deficient embryos contained mitotically arrested cells displaying abnormal spindle formation and chromosome misalignment in the neural plate. CONCLUSIONS: Therefore, our findings suggest that Cug2 is required for normal mitosis during early neurogenesis and has functions in neuronal cell maintenance, thus demonstrating that the cug2 deficient embryos may provide a model system for human neurodegenerative disorders.
Subject(s)
Central Nervous System/embryology , Central Nervous System/metabolism , Gene Expression Regulation, Developmental , Mitosis/physiology , Nuclear Proteins/metabolism , Zebrafish Proteins/metabolism , Zebrafish/embryology , Zebrafish/metabolism , Amino Acid Sequence , Animals , Apoptosis/genetics , Cell Transformation, Neoplastic/metabolism , Chromosome Aberrations/embryology , Chromosomes/genetics , Kinetochores/metabolism , Morpholinos/genetics , Neurodegenerative Diseases/genetics , Neurogenesis/genetics , Nuclear Proteins/genetics , RNA Interference , RNA, Small Interfering , Sequence Alignment , Spindle Apparatus/genetics , Spindle Apparatus/pathology , Zebrafish/genetics , Zebrafish Proteins/geneticsABSTRACT
MCPH is a neurodevelopmental disorder characterized by a global reduction in cerebral cortical volume. Homozygous mutation of the MCPH5 gene, also known as ASPM, is the most common cause of the MCPH phenotype. To elucidate the roles of ASPM during embryonic development, the zebrafish aspm was identified, which is specifically expressed in proliferating cells in the CNS. Morpholino-mediated knock-down of aspm resulted in a significant reduction in head size. Furthermore, aspm-deficient embryos exhibited a mitotic arrest during early development. These findings suggest that the reduction in brain size in MCPH might be caused by lack of aspm function in the mitotic cell cycle and demonstrate that the zebrafish can provide a model system for congenital diseases of the human nervous system.
Subject(s)
Brain/embryology , Cell Cycle Proteins/genetics , Microcephaly/genetics , Zebrafish Proteins/genetics , Zebrafish/embryology , Amino Acid Sequence , Animals , Cell Cycle , Gene Knockdown Techniques , Humans , Mitosis/genetics , Molecular Sequence Data , Organ Size/genetics , Zebrafish/geneticsABSTRACT
The van gogh (vgo) mutant in zebrafish is characterized by defects in the ear, pharyngeal arches and associated structures such as the thymus. We show that vgo is caused by a mutation in tbx1, a member of the large family of T-box genes. tbx1 has been recently suggested to be a major contributor to the cardiovascular defects in DiGeorge deletion syndrome (DGS) in humans, a syndrome in which several neural crest derivatives are affected in the pharyngeal arches. Using cell transplantation studies, we demonstrate that vgo/tbx1 acts cell autonomously in the pharyngeal mesendoderm and influences the development of neural crest-derived cartilages secondarily. Furthermore, we provide evidence for regulatory interactions between vgo/tbx1 and edn1 and hand2, genes that are implicated in the control of pharyngeal arch development and in the etiology of DGS.
Subject(s)
DiGeorge Syndrome/genetics , T-Box Domain Proteins/genetics , Zebrafish/metabolism , Amino Acid Sequence , Animals , Branchial Region/metabolism , Ear/embryology , Endoderm/metabolism , Humans , Mesoderm/metabolism , Molecular Sequence Data , Mutation , Sequence Deletion , T-Box Domain Proteins/metabolismABSTRACT
The T-box genes Tbx4 and Tbx5 have been shown to have key functions in the specification of the identity of the vertebrate forelimb (Tbx5) and hindlimb (Tbx4). Here we show that in zebrafish, Tbx5 has an additional early function that precedes the formation of the limb bud itself. Functional knockdown of zebrafish tbx5 through the use of an antisense oligonucleotide resulted in a failure to initiate fin bud formation, leading to the complete loss of pectoral fins. The function of the tbx5 gene in the development of zebrafish forelimbs seems to involve the directed migration of individual lateral-plate mesodermal cells into the future limb-bud-producing region. The primary defect seen in the tbx5-knockdown phenotype is similar to the primary defects described in known T-box-gene mutants such as the spadetail mutant of zebrafish and the Brachyury mutant of the mouse, which both similarly exhibit an altered migration of mesodermal cells. A common function for many of the T-box genes might therefore be in mediating the proper migration and/or changes in adhesive properties of early embryonic cells.
