清华大学：《分子生物学》课程PPT教学课件（基因ene）第二十九章 梯度、级联和发信号的途径（Gradients, cascades, and signaling pathways）

Chapter 29 Gradients,cascades, and signaling pathways 清苇大当

Chapter 29 Gradients, cascades, and signaling pathways

29.1 Introduction 29.2 Fly development uses a cascade of transcription factors 29.3 A gradient must be converted into discrete compartments 29.4 Maternal gene products establish gradients in early embryogenesis 29.5 Anterior development uses localized gene regulators 29.6 Posterior development uses another localized regulator 29.7 How are mRNAs and proteins transported and localized? 29.8 Dorsal-ventral development uses localized receptor-ligand interactions 29.9 TGFb/BMPs are diffusible morphogens 29.10 Cell fate is determined by compartments that form by the blastoderm stage 29.11 The wingless/wnt signaling pathway 29.12 Complex loci are extremely large and involved in regulation 29.13 The homeobox is a common coding motif in homeotic genes 清苇大兰

29.1 Introduction 29.2 Fly development uses a cascade of transcription factors 29.3 A gradient must be converted into discrete compartments 29.4 Maternal gene products establish gradients in early embryogenesis 29.5 Anterior development uses localized gene regulators 29.6 Posterior development uses another localized regulator 29.7 How are mRNAs and proteins transported and localized? 29.8 Dorsal-ventral development uses localized receptor-ligand interactions 29.9 TGFb/BMPs are diffusible morphogens 29.10 Cell fate is determined by compartments that form by the blastoderm stage 29.11 The wingless/wnt signaling pathway 29.12 Complex loci are extremely large and involved in regulation 29.13 The homeobox is a common coding motif in homeotic genes

29.1 Introduction Development begins with a single fertilized egg,but gives rise to cells that have different developmental fates.The problem of early development is to understand how this asymmetry is introduced: how does a single initial cell give rise within a few cell divisions to progeny cells that have different properties from one another?The means by which asymmetry is generated varies with the type of organism.The egg itself may be homogeneous,with the acquisition of asymmetry depending on the process of the initial division cycles, as in the case of mammals.Or the egg may have an initial asymmetry in the distribution of its cytoplasmic components,which in turn gives rise to further differences as development proceeds,as in the case of Drosophila 情華大当

Development begins with a single fertilized egg, but gives rise to cells that have different developmental fates. The problem of early development is to understand how this asymmetry is introduced: how does a single initial cell give rise within a few cell divisions to progeny cells that have different properties from one another? The means by which asymmetry is generated varies with the type of organism. The egg itself may be homogeneous, with the acquisition of asymmetry depending on the process of the initial division cycles, as in the case of mammals. Or the egg may have an initial asymmetry in the distribution of its cytoplasmic components, which in turn gives rise to further differences as development proceeds, as in the case of Drosophila 29.1 Introduction

29.1 Introduction Development begins with a single fertilized egg,but gives rise to cells that have different developmental fates.The problem of early development is to understand how this asymmetry is introduced: how does a single initial cell give rise within a few cell divisions to progeny cells that have different properties from one another?The means by which asymmetry is generated varies with the type of organism.The egg itself may be homogeneous,with the acquisition of asymmetry depending on the process of the initial division cycles, as in the case of mammals.Or the egg may have an initial asymmetry in the distribution of its cytoplasmic components,which in turn gives rise to further differences as development proceeds,as in the case of Drosophila 清菜大当

Development begins with a single fertilized egg, but gives rise to cells that have different developmental fates. The problem of early development is to understand how this asymmetry is introduced: how does a single initial cell give rise within a few cell divisions to progeny cells that have different properties from one another? The means by which asymmetry is generated varies with the type of organism. The egg itself may be homogeneous, with the acquisition of asymmetry depending on the process of the initial division cycles, as in the case of mammals. Or the egg may have an initial asymmetry in the distribution of its cytoplasmic components, which in turn gives rise to further differences as development proceeds, as in the case of Drosophila 29.1 Introduction

29.2 Fly development uses a cascade of transcription factors Homeotic genes are defined by mutations that convert one body part into another;for example,an insect leg may replace an antenna. Segmentation genes are concerned with controlling the number or polarity of body segments in insects. 情菜大当

Homeotic genes are defined by mutations that convert one body part into another; for example, an insect leg may replace an antenna. Segmentation genes are concerned with controlling the number or polarity of body segments in insects. 29.2 Fly development uses a cascade of transcription factors

The egg Polarities are established along anterior- 29.3 A gradient must be posterior(head-tail)axis and dorsal-ventral (back-abdomen) Dorsal converted into discrete Anteri Posterior compartments Ventral The larva Mouth parts are at anterior,tail parts at Figure 29.1 Gradients in the posterior.Bands of denticles extend from the ventral side,and identify segmentation units along the anterior-posteror axis egg are translated into segments on the anterior- posterior axis and into Mouth Tai Denticles specialized structures on the Adult fly dorsal-ventral axis of the Segmented structure has 3 thoracic segments &8 abdominal segments larva,and then into the segmented structure of the adult fly. 清苇大当 Thorax Abdomen

Figure 29.1 Gradients in the egg are translated into segments on the anterior￾posterior axis and into specialized structures on the dorsal-ventral axis of the larva, and then into the segmented structure of the adult fly. 29.3 A gradient must be converted into discrete compartments

Fertilized egg has two nuclei 29.3 A gradient must be converted into discrete Divisions 1-8(90 min) Nuclei divide in common cytoplasm compartments (syncytium).Nuclei in polar plasm(pink) become gem cell precursors. Figure 29.2 The early Syncytial blastoderm (150 min) Nuclei migrate to periphery and divide;4 further divisions occur(in close but not development of the perfect synchrony). Drosophila egg occurs in a common cytoplasm until the ●●●●●●果●e甲色●e stage of cellular blastoderm. Cellular blastoderm (195 min) Membranes surround nuclei to form monolayer of ~6000 somatic cells. 情華大当

Figure 29.2 The early development of the Drosophila egg occurs in a common cytoplasm until the stage of cellular blastoderm. 29.3 A gradient must be converted into discrete compartments

29.4 Maternal gene products establish gradients in early embryogenesis Morphogen is a factor that induces development of particular cell types in a manner that depends on its concentration. 清菜大当

Morphogen is a factor that induces development of particular cell types in a manner that depends on its concentration. 29.4 Maternal gene products establish gradients in early embryogenesis

29.4 Maternal gene products establish gradients in early embryogenesis Follicle cells Oocyte Nurse cells Cytoplasmic bridge Figure 29.3 A Drosophila follicle contains an outer surface of follicle cells that surround nurse cells that are in close contact with the oocyte.Nurse cells are connected by cytoplasmic bridges to each other and to the anterior end of the oocyte.Follicle cells are somatic;nurse cells and the oocyte are germline in origin. 清菜大当

Figure 29.3 A Drosophila follicle contains an outer surface of follicle cells that surround nurse cells that are in close contact with the oocyte. Nurse cells are connected by cytoplasmic bridges to each other and to the anterior end of the oocyte. Follicle cells are somatic; nurse cells and the oocyte are germline in origin. 29.4 Maternal gene products establish gradients in early embryogenesis

29.4 Maternal gene products establish gradients in early embryogenesis Anterior Posterior Teminal Dorsovertral Matemal scmatic 38/ windibeute! Matemal germline exuperantie capuccino gastrlstion-defective ider mago nashi atz光 Zygotictargets 农e2en emp的y spraces Figure 29.4 Each of the four maternal systems that functions in the egg is initiated outside the egg.The pathway is carried into the egg,where each pathway has a localized product that is the morphogen.This may be a receptor or a regulator of gene expression.The final component is a transcription factor,which acts on zygotic targets that are responsible for the next stage of development. 清菜大兰

Figure 29.4 Each of the four maternal systems that functions in the egg is initiated outside the egg. The pathway is carried into the egg, where each pathway has a localized product that is the morphogen. This may be a receptor or a regulator of gene expression. The final component is a transcription factor, which acts on zygotic targets that are responsible for the next stage of development. 29.4 Maternal gene products establish gradients in early embryogenesis