High impact information on cnn

• We propose that cnn provides an example of homeotic genes directly regulating the accumulation of essential cellular proteins to carry out segment-specific morphogenetic functions [1].
• Embryos that lack maternal as well as zygotic cnn expression display defects in nuclear division, chromosome alignment, and microtubule organization, while adult flies that are mosaic for cnn-cells exhibit defects indicative of a block in cell proliferation [1].
• Here we report that CNN is an essential component of the centrosome [1].
• Centrosomin (CNN) remains in broad discrete bodies but only at the focused poles of such spindles, whereas Asp (abnormal spindle protein) is always present at the presumptive minus ends of microtubules, whether or not they are focused [2].
• The NH2-terminal half of CNN interacts with gamma-tubulin, and induces cytoplasmic foci that can initiate microtubule nucleation in vivo and in vitro in both Drosophila and mammalian cells [3].

Biological context of cnn

• The primary mutant phenotype of cnn oocytes is the failure to form a developed central microtubule organizing center (MTOC), although twin meiosis II spindles usually do form [4].
• The centrosomal localization of CNN and the involvement of microtubules in midgut morphogenesis suggest that this protein may participate in mitotic spindle assembly and the mechanics of morphogenesis through an interaction with microtubules, either directly or indirectly [5].
• We also identified the core component centrosomal protein centrosomin (CNN) at an unexpected site within the anaphase I spindle, indicating a role for CNN during the biogenesis of the female meiotic apparatus [4].
• Hemizygous cnn females produce embryos that show dramatic defects in chromosome segregation and spindle organization during the syncytial cleavage divisions [6].
• However, Numb still localizes asymmetrically in cnn mutants or after disruption of microtubules, indicating that there are two independent functions for Aurora-A in centrosome maturation and asymmetric protein localization during mitosis [7].

Anatomical context of cnn

• Immunocytochemical results demonstrate that the cnn encoded protein is localized to the centrosome and the accumulation pattern is coupled to the nuclear and centrosome duplication cycles of cleavage [5].
• The spatial and temporal expression of the cnn gene in the developing visceral mesoderm (VM) of the midgut and the central nervous system (CNS) of wild-type and homeotic mutant embryos is consistent with the idea that cnn is a homeotic target [5].
• However, there are no apparent defects in the midzone organization of cnn oocytes, whereas defects occur later when the central aster forms [4].
• There is a high occurrence of apparently linked spindles that share poles, indicating that Centrosomin is required for the proper spacing and separation of mitotic spindles within the syncytium [6].
• No molecular components of the MTOC are known except for centrosomin, which accumulates at the MTOC relatively late, at approximately stage 5 or 6 of oogenesis [8].

Associations of cnn with chemical compounds

• Characterization of a cDNA encoding CNN predicts a novel structural protein with three leucine zipper motifs and several coiled-coil domains exhibiting limited homology to the rod portion of myosin [5].

Co-localisations of cnn

• D-TACC colocalized with Cnn at these particles [9].

Other interactions of cnn

• In addition, evidence suggests that the expression of the cnn gene in the VM correlates with the morphogenetic function of Ubx in that tissue, i.e., the formation of the second midgut construction [5].
• Aurora-A and CNN are mutually dependent for localization at spindle poles, which is required for proper targeting of gamma-tubulin and other centrosomal components to the centrosome [3].

Analytical, diagnostic and therapeutic context of cnn

• Loss of zygotic cnn expression disrupts the development of the second midgut constriction, the gastric caeca, and the nervous system [1].

References