ScienceWeek
DEVELOPMENTAL BIOLOGY: ON GENE REGULATION IN CHORDATES (động vật có dây sống)
The following points are made by Patrick Lemaire (Science 2006 312:1145):
1) Ascidians ?(lớp Hải tiêu) are invertebrate chordates (động vật có dây sống không xương sống) that belong to the tunicates (có vỏ bao), the closest living sister group of vertebrates (động vật có xương sống) [1], from which they diverged (phân ly/phân ký/phân tách ) more than 500 million years ago. New work [2] reports an analysis of the ascidian Ciona intestinalis (sea squirt) to generate the first metazoan whole-embryo gene regulatory network (hệ thống điều hòa gene toàn bộ phôi ở động vật đa bào). It appears (cho thấy rằng/xuất hiện) quite different from vertebrate networks despite (bất chấp) ?the conservation (sự bảo thủ) of a common, tadpole-like larval body plan (cách thức định hình cơ thể ấu trùng dạng nòng nọc).
2) Gene regulatory networks consist of functional linkages (liên kết về mặt chức năng) between transcription factors (yếu tố phiên mã), cell signaling components (các thàng phần tham gia chuyển hóa dấu hiệu tế bào), and the cis-regulatory modules (mô-đun điều hòa dạng cis) that control their expression at the transcriptional level [3]. The action of such networks is a major force driving animal development, from a simple egg to a complex larva. These networks are proposed to be free standing (tồn tại tự do, một mình/đơn độc)-- that is, the regulation of each network component can be accounted for ?(bị ngăn chặn) by the presence of other components. Ultimately, the networks control the precise (chính xác) expression of differentiation genes that confer specific attributes to each embryonic cell. The identification of networks in echinoderms (động vật da gai) (sea urchins) [4] and vertebrates [5] has illuminated the developmental logic underlying animal embryogenesis (quá trình phát sinh/hình thành phôi). In addition, comparing gene-regulatory networks (hệ thống điều hòa gene) that give rise to homologous anatomical structures (cấu trúc hình thái giải phẫu ?có tính tương đồng) across taxa or phyla have helped to elucidate (làm sáng tỏ) the evolutionary origin of these structures [3].
3) Like lower vertebrates, developing Ciona make tadpole larvae (số nhiều của larva). But these tadpoles have only 2600 cells, and the size of the Ciona genome is only 1/20 that of the mouse. In addition, ascidian genomes have not undergone the vertebrate-specific duplication events (những sự kiên/những lần tự sao lục ). The extreme genetic and cellular simplicity (sự đơn giản) of Ciona is a boon ?(điểm thuận lợi) to biologists attempting to reconstruct gene regulatory networks (xây dựng lại hệ thống điều hòa gene). It is, however, unlikely to reflect (phản ánh) the condition of the ancestral chordate. Rather, most of it probably results from secondary simplification (có kết quả từ sự đơn giản hóa thứ cấp) ?that has occurred since the tunicate and vertebrate lineages separated.
4) Thus, despite a shared larval body plan, the extent of conservation between ascidian and vertebrate gene regulatory networks has been uncertain. For instance, unlike in vertebrates, most ascidian tail muscle cells (tế bào cơ ở đuôi) form autonomously, following the inheritance of the localized maternal Zic-family transcription factor Macho-1. Notochord formation in ascidians and vertebrates involves the induced expression of the T-box transcription factor Brachyury by signals elicited by fibroblast growth factor. On the other hand, signals from bone morphogenetic protein play opposite roles in the formation of this tissue in ascidians and vertebrates.
References (abridged):
1. F. Delsuc, H. Brinkmann, D. Chourrout, H. Philippe, Nature 439, 965 (2006)
2. K. S. Imai, M. Levine, N. Satoh, Y. Satou, Science 312, 1183 (2006)
3. E. H. Davidson, D. H. Erwin, Science 311, [796] (2006)
4. E. H. Davidson et al., Science 295, [1669] (2002)
5. M. Loose, R. Patient, Dev Biol. 271, 467 (2004)
Science http://www.sciencemag.org
ScienceWeek http://scienceweek.com
DEVELOPMENTAL BIOLOGY: ON GENE REGULATION IN CHORDATES (động vật có dây sống)
The following points are made by Patrick Lemaire (Science 2006 312:1145):
1) Ascidians ?(lớp Hải tiêu) are invertebrate chordates (động vật có dây sống không xương sống) that belong to the tunicates (có vỏ bao), the closest living sister group of vertebrates (động vật có xương sống) [1], from which they diverged (phân ly/phân ký/phân tách ) more than 500 million years ago. New work [2] reports an analysis of the ascidian Ciona intestinalis (sea squirt) to generate the first metazoan whole-embryo gene regulatory network (hệ thống điều hòa gene toàn bộ phôi ở động vật đa bào). It appears (cho thấy rằng/xuất hiện) quite different from vertebrate networks despite (bất chấp) ?the conservation (sự bảo thủ) of a common, tadpole-like larval body plan (cách thức định hình cơ thể ấu trùng dạng nòng nọc).
2) Gene regulatory networks consist of functional linkages (liên kết về mặt chức năng) between transcription factors (yếu tố phiên mã), cell signaling components (các thàng phần tham gia chuyển hóa dấu hiệu tế bào), and the cis-regulatory modules (mô-đun điều hòa dạng cis) that control their expression at the transcriptional level [3]. The action of such networks is a major force driving animal development, from a simple egg to a complex larva. These networks are proposed to be free standing (tồn tại tự do, một mình/đơn độc)-- that is, the regulation of each network component can be accounted for ?(bị ngăn chặn) by the presence of other components. Ultimately, the networks control the precise (chính xác) expression of differentiation genes that confer specific attributes to each embryonic cell. The identification of networks in echinoderms (động vật da gai) (sea urchins) [4] and vertebrates [5] has illuminated the developmental logic underlying animal embryogenesis (quá trình phát sinh/hình thành phôi). In addition, comparing gene-regulatory networks (hệ thống điều hòa gene) that give rise to homologous anatomical structures (cấu trúc hình thái giải phẫu ?có tính tương đồng) across taxa or phyla have helped to elucidate (làm sáng tỏ) the evolutionary origin of these structures [3].
3) Like lower vertebrates, developing Ciona make tadpole larvae (số nhiều của larva). But these tadpoles have only 2600 cells, and the size of the Ciona genome is only 1/20 that of the mouse. In addition, ascidian genomes have not undergone the vertebrate-specific duplication events (những sự kiên/những lần tự sao lục ). The extreme genetic and cellular simplicity (sự đơn giản) of Ciona is a boon ?(điểm thuận lợi) to biologists attempting to reconstruct gene regulatory networks (xây dựng lại hệ thống điều hòa gene). It is, however, unlikely to reflect (phản ánh) the condition of the ancestral chordate. Rather, most of it probably results from secondary simplification (có kết quả từ sự đơn giản hóa thứ cấp) ?that has occurred since the tunicate and vertebrate lineages separated.
4) Thus, despite a shared larval body plan, the extent of conservation between ascidian and vertebrate gene regulatory networks has been uncertain. For instance, unlike in vertebrates, most ascidian tail muscle cells (tế bào cơ ở đuôi) form autonomously, following the inheritance of the localized maternal Zic-family transcription factor Macho-1. Notochord formation in ascidians and vertebrates involves the induced expression of the T-box transcription factor Brachyury by signals elicited by fibroblast growth factor. On the other hand, signals from bone morphogenetic protein play opposite roles in the formation of this tissue in ascidians and vertebrates.
References (abridged):
1. F. Delsuc, H. Brinkmann, D. Chourrout, H. Philippe, Nature 439, 965 (2006)
2. K. S. Imai, M. Levine, N. Satoh, Y. Satou, Science 312, 1183 (2006)
3. E. H. Davidson, D. H. Erwin, Science 311, [796] (2006)
4. E. H. Davidson et al., Science 295, [1669] (2002)
5. M. Loose, R. Patient, Dev Biol. 271, 467 (2004)
Science http://www.sciencemag.org
ScienceWeek http://scienceweek.com
