Developmental Biology

1. An Understanding of Everything Developmental Biology

2. Stages & Events of Chordate Embryogenesis Developmental Process Embryonic Stage Zygote Morula Blastula Gastrula Neurulation Neurula Pharyngula Fetus

3. Gametogenesis • Process of producing gametes • Spermatogenesis • Oogenesis • Meiotic cell division • Packaging of material into oocytes • Removal of cytoplasm from sperm

4. Accumulation of Vitellogenin during Oogenesis in Xenopus

5. Localization of Developmental Regulatory Factors • Dsh, Xcat-2, Xlsirt, Vg-1 mRNAs localized to vegetal pole of vertebrate eggs Xlsirt mRNA

6. Bicoid Gradient in Drosophila Egg & Embryo

7. Fertilization - Sperm and Egg Fusion

8. Fertilization Induces a Rearrangement of Cytoplasmic, Localized Factors • Initial localization of material in eggs is radially symmetrical • Fertilization creates a point of asymmetry and causes rotational reorganization of cytoskeleton to generate bilateral symmetry Gray crescent

9. Reorganization ofCytoplasmic Maternal Factors Set Up Signaling Cascades

10. Figure 20.12 Molecular Mechanisms of the Primary Embryonic Organizer

11. Cleavage Distributes Maternal Components to Blastomeres

12. Figure 19.7 Asymmetry in the Early Embryo (Part 1)

13. Figure 19.7 Asymmetry in the Early Embryo (Part 2)

14. Autonomous Development of Separated Tunicate Blastomeres

15. Figure 19.8 The Principle of Cytoplasmic Segregation

16. Figure 20.10 HansSpemann’s Early Experiments

17. Figure 20.11 The Dorsal Lip Induces Embryonic Organization

18. Fate Map of a Frog Blastula

19. Figure 20.9 Gastrulation in the Frog Embryo (Part 1)

20. Figure 20.9 Gastrulation in the Frog Embryo (Part 2)

21. Figure 20.9 Gastrulation in the Frog Embryo (Part 3)

22. Figure 20.15 Neurulation in the Frog Embryo (Part 1)

23. Figure 20.15 Neurulation in the Frog Embryo (Part 2)

24. Figure 20.13 Gastrulation in Amniotes (Part 1)

25. Figure 20.13 Gastrulation in Amniotes (Part 2)

26. Figure 20.16 The Development of Body Segmentation Mouse embryo

27. Drosophila Homeotic and Vertebrate Hox Genes Control A-P Patterning

28. Hox Genes Pattern A-P Axis

29. Concepts in Developmental Biology • Polarity • Established by localization of maternal gene products • Established by inductive signaling events • Morphogenesis • Cellular movements and embryonic structure formation • Regulated by cell-signaling & cell adhesion mechanisms • Differentiation • Specialization of cells to a particular fate • Growth • Increase in cell number • Increase in cell size

30. Cell Specification • Differentiation • The process and the processes associated with a cell becoming specialized • Occurs in multiple steps

31. Cell Specification • Autonomous • All differentiation information is contained within the cell • Conditional • Differentiation information supplied through interactions with other cells

32. Cell Specification - Steps • Commitment • Specification • Determination • Terminal differentiation

33. Cell Specification - Commitment • Specification • A cell is said to be specified when: • Cells differentiate autonomously when removed from normal environment (embryo) and placed in a neutral environment (culture medium) • Placing cells into a non-neutral environment (a different place in the embryo) causes the cells to follow the fate of other cells the new location rather than their original fate

34. Cell Specification - Committment • Determination • A cell is said to be determined when: • Cells differentiate autonomously even when placed in a non-neutral environment • When moved to a different location within the embryo, the transplanted cells differentiate according to their original fate

35. Cell Specification - Terminal Differentiation • When a cell can no longer change or be changed into anything other than the cell type it is • Can be associated with permanent changes in DNA • DNA Methylation is a prominent factor • B-cells (plasma cells) rearrange the immunoglobulin (Ig) genes so that they can now only form a single type of Ig

36. Spemann’s Specification Experiments Inductive signals trigger conditional specification, determination and differentiation Presumptive neural plate ectoderm in the early gastrula was uncommitted. Later gastrula neuroectoderm was committed to a neural fate.

37. Dorsal Lip Transplantation

38. Reversal of Terminal Differentiation • Embryonic Stem cells • Totipotent or pluripotent cells • Dedifferentiated stem cells • Pluripotent • Derived from previously differentiated cells • Cloning proves nuclear equivalence

39. Figure 19.3 Cloning a Plant (Part 1)

40. Cloning by Nuclear Transplantation • Nuclear transplant experiments have shown that somatic cells contain the entire genome. • Nucleus of an unfertilized egg is replaced with the nucleus of a somatic cell • These experiments led to two important conclusions: • No information is lost in the early stages of embryonic development (a principle known as genomic equivalence). • The cytoplasmic environment around a nucleus can modify its fate.

41. The First Cloning Experiment – Nuclear Transplantation in Xenopus laevis Cloning of the frog Xenopus laevis by nuclear transplantation of albino gut cell nuclei into enucleated, wt oocytes. All progeny are albino & female tadpole oocyte nucleus

42. First Mammalian Clone

43. Dolly & Bonnie

44. Figure 19.10 Induction during Vulval Development in C. elegans (Part 1)

45. Figure 19.10 Induction during Vulval Development in C. elegans (Part 2)

46. A Gene Cascade Controls Pattern Formation in the Drosophila Embryo Maternal effect genes Gap genes Pair rule genes Segment polarity genes Homeotic genes

47. Bicoid and Nanos Protein Gradients Provide Positional Information (Part 1)

48. Figure 19.14 Bicoid and Nanos Protein Gradients Provide Positional Information (Part 2)

49. Figure 19.16 A Homeotic Mutation in Drosophila Antennapedia

50. Figure 19.12 Organ Identity Genes in Arabidopsis Flowers (Part 1)