1. Early Vertebrate Development Early Development of Mammals Early Development of Birds…if we have time.

2. Long and Winding Road… Both Egg and Sperm have to overcome physical barriers. Ampulla- site of fertilization.

3. Cleavage in Mammals Rotational cleavage – 1 st Meriodionally – 2 nd one divides meriodionally, one divides equatorially Asynchrony No real Mid-Blastula Transition.

4. Compaction Division of early embryo up to 8 cell stage is loosely arranged. At 8 cell stage, cells form tight interactions and divide into 16 cell morula. Internal Cells= Internal Cell mass (ICM) Most external cells become trophoblast.

5. Early Cells in Mammalian Embryo Totipotent Pluripotent

6. Cavitation. Trophoblast cells secrete fluid into Morula: blastocoel Trophoblast Na + pumps are activated by oviduct cells.

7. Hatching of Mammalian Blastula Zona pellucida prevents embryo from attaching to oviduct wall. Trypsin like protease: releases embryo from ZP.

8. Mammalian Gastrulation Mother provides nutrients The reliance of embryo on Mother has resulted in fetal organs – Chorion – Hypoblast/epiblast – Germ disc – Amniotic cavity

9. Mammalian Gastrulation: Primative Groove

10. Extraembryonic Membranes Trophoblast cells make up cytotrophoblast and syncytiotrophoblast. Trophoblasts and Uterine tissue: Placenta

11. Axis specification in Mammals Two signaling centers – Node – Anterior Visceral Endoderm(AVE) Work together to form anterior region. Notochord: dorsal infolding of small ciliated cells AVE: visceral endoderm migrates forward. Antagonists of Nodal – Lefty-1; Cerberus – Nodal activates expression of posterior genes; Lefty-1 and Cerberus blocks this activity

12. Axis Specification: Anterior-Posterior positioning FGF and Retinoic acid gradients. Ultimately leads to differential expression of Hox genes

13. Anterior-Posterior Axis: Hox Code

14. Retinoic Acid and Hox Gene Expression

15. Dorsal-Ventral and Left-Right Axes DV axis formation: Poorly characterized. Left-right axis formation: Nodal and Pitx2

16. Early Development of Birds: Cleavage

17. Gastrulation: Birds The Hypoblast The primative streak

18. The Primitive Streak

19. Primitive Streak: Molecular mechanisms of migration

20. Regression of Primitive streak

21. Axis specification in Birds Gravity and PMZ

22. Left Right Axis