Vnd and its target gene twine are required for cell cycle progression during embryonic nervous system development in Drosophila melanogaster

Abstract

Twine is a homolog of CDC25 phosphatase regulating cell cycle progression. To elucidate a possible role of twine during embryonic neurogenesis, its expression levels and patterns were determined. twine was strongly expressed in the embryonic brain, and segmentally expressed along the ventral nerve cord during stage 12–14 in which neuroblasts and ganglionic mother cells are rapidly dividing. To examine whether twine is involved in the nervous system development, immunohistochemistry using neuron-specific antibodies was performed. The results showed the reduction of dorsal clusters in the peripheral nervous system and disorganization of neurons in the central nervous system. Moreover, consistent with our microarray data, real-time PCR results show that expression level of twine is proportional to that of vnd, suggesting that Vnd functions as an activator to regulate twine expression. This relationship is also confirmed by analyzing the expression patterns of twine in vnd loss-of-function and gain-of-function mutant background. Immunostaining using anti-phospho-histone H3 and anti-BrdU antibodies revealed that Twine regulates cell cycle progression in the developing embryonic nervous system. Down-regulation of vnd also caused a significant reduction of mitotic cells in embryonic neuroblasts, suggesting a role for vnd-twine in mitosis-associated nervous system development.