Chap 47 Animal development Preformation homunculus 1 mm

Morphogenesis is the process by which an animal takes shape Development is determined by the zygote’s genome and molecules in the egg called cytoplasmic determinants Cell differentiation is the specialization of cells in structure and function Morphogenesis is the process by which an animal takes shape FertilizationCleavageGastrulationOrganogenesis

Fig. 47-3-1 Basal body (centriole) Sperm head Acrosome Jelly coat Vitelline layer Sperm-binding receptors Egg plasma membrane

Fig. 47-3-2 Basal body (centriole) Sperm head Acrosome Hydrolytic enzymes Jelly coat Vitelline layer Sperm-binding receptors Egg plasma membrane

Acrosomal reaction Fig. 47-3-3 Sperm nucleus Acrosomal process Basal body (centriole) Actin filament Sperm head Acrosome Hydrolytic enzymes Jelly coat Vitelline layer Sperm-binding receptors Egg plasma membrane

Acrosomal reaction fast block to polyspermy Fig. 47-3-4 Sperm plasma membrane Sperm nucleus Acrosomal process Basal body (centriole) Actin filament Sperm head Fused plasma membranes Acrosome Hydrolytic enzymes Jelly coat Vitelline layer Sperm-binding receptors Egg plasma membrane

A fast block to polyspermy Cortical reaction: Fig. 47-3-5 Acrosomal reaction A fast block to polyspermy Cortical reaction: a slow block to polyspermy Sperm plasma membrane Sperm nucleus Fertilization envelope Acrosomal process Basal body (centriole) Actin filament Sperm head Cortical granule Fused plasma membranes Perivitelline space Acrosome Hydrolytic enzymes Jelly coat Vitelline layer Sperm-binding receptors Egg plasma membrane EGG CYTOPLASM

Ca2+  the formation of the fertilization envelope？ Fig. 47-4 EXPERIMENT Ca2+  the formation of the fertilization envelope？ 10 sec after fertilization 25 sec 35 sec 1 min 500 µm RESULTS 1 sec before fertilization 10 sec after fertilization 20 sec 30 sec 500 µm CONCLUSION Point of sperm nucleus entry Spreading wave of Ca2+ Fertilization envelope

10 sec after fertilization 25 sec 35 sec 1 min 500 µm Fig. 47-4a EXPERIMENT 10 sec after fertilization 25 sec 35 sec 1 min 500 µm

1 sec before fertilization 10 sec after fertilization 20 sec 30 sec Fig. 47-4b RESULTS 1 sec before fertilization 10 sec after fertilization 20 sec 30 sec 500 µm

CONCLUSION Point of sperm nucleus entry Spreading wave of Ca2+ Fig. 47-4c CONCLUSION Point of sperm nucleus entry Spreading wave of Ca2+ Fertilization envelope

Fertilization in mammals Fig. 47-5 Fertilization in mammals Zona pellucida Follicle cell Sperm nucleus Cortical granules Sperm basal body

Cleavage Holoblastic cleavage meroblastic cleavage (a) Fertilized egg Fig. 47-6 Holoblastic cleavage meroblastic cleavage Cleavage (a) Fertilized egg (b) Four-cell stage (c) Early blastula (d) Later blastula

(a) The three axes of the fully developed embryo Dorsal Right Anterior Posterior Ventral Left (b) Establishing the axes Animal pole First cleavage Pigmented cortex Animal hemisphere Point of sperm nucleus entry Future dorsal side Vegetal hemisphere Gray crescent Vegetal pole (Dorsal– ventral ) (right—left) (anterior—posterior) Fig. 47-7

(b) Establishing the axes Fig. 47-7b-1 Animal pole Animal hemisphere Vegetal hemisphere Vegetal pole (b) Establishing the axes

Blastula (cross section) Fig. 47-8-6 0.25 mm 0.25 mm Animal pole Blastocoel Vegetal pole Zygote 2-cell stage forming 4-cell stage forming 8-cell stage Blastula (cross section)

Gastrulation I (sea urchin) Future ectoderm Future mesoderm Future endoderm Animal pole Blastocoel Mesenchyme cells Vegetal plate Vegetal pole Invagination Fig. 47-9-1

Fig. 47-9-2 Future ectoderm Future mesoderm Future endoderm

Filopodia pulling archenteron tip Fig. 47-9-3 Future ectoderm Future mesoderm Future endoderm Filopodia pulling archenteron tip Archenteron

Future ectoderm Future mesoderm Future endoderm Blastocoel Archenteron Fig. 47-9-4 Future ectoderm Future mesoderm Future endoderm Blastocoel Archenteron Blastopore

Mesenchyme (mesoderm forms future skeleton) Fig. 47-9-5 Future ectoderm Future mesoderm Future endoderm Ectoderm Mouth Mesenchyme (mesoderm forms future skeleton) Digestive tube (endoderm) Anus (from blastopore)

Fig. 47-9-6 Key Future ectoderm Future mesoderm Future endoderm Archenteron Blastocoel Filopodia pulling archenteron tip Animal pole Blastocoel Archenteron Blastocoel Blastopore Mesenchyme cells Ectoderm Vegetal plate Vegetal pole Mouth Mesenchyme cells Mesenchyme (mesoderm forms future skeleton) Digestive tube (endoderm) Blastopore 50 µm Anus (from blastopore)

Gastrulation II (frog embryo) Fig. 47-10-1 Gastrulation II (frog embryo) SURFACE VIEW CROSS SECTION Animal pole Blastocoel Dorsal lip of blasto- pore Dorsal lip of blastopore Key Blastopore Future ectoderm Early gastrula Future mesoderm Vegetal pole Future endoderm Invagination and Involution

Fig. 47-10-2 SURFACE VIEW CROSS SECTION Blastocoel shrinking Archenteron Key Future ectoderm Future mesoderm Future endoderm

Fig. 47-10-3 SURFACE VIEW CROSS SECTION Ectoderm Mesoderm Blastocoel remnant Endoderm Archenteron Key Blastopore Future ectoderm Late gastrula Future mesoderm Blastopore Yolk plug Future endoderm

Fig. 47-10-4 SURFACE VIEW CROSS SECTION Animal pole Blastocoel Dorsal lip of blasto- pore Dorsal lip of blastopore Blastopore Early gastrula Vegetal pole Blastocoel shrinking Archenteron Ectoderm Mesoderm Blastocoel remnant Endoderm Archenteron Key Blastopore Future ectoderm Future mesoderm Late gastrula Blastopore Yolk plug Future endoderm

Gastrulation III (a chick embryo)

Migrating cells (mesoderm) Hypoblast Fig. 47-11 Dorsal Fertilized egg Primitive streak Anterior Embryo Left Right Yolk Posterior Ventral Primitive streak Epiblast Future ectoderm Blastocoel Endoderm Migrating cells (mesoderm) Hypoblast YOLK

Fig. 47-12 Neural folds Eye Somites Tail bud Neural fold Neural plate SEM 1 mm 1 mm Neural tube Neural crest cells Neural fold Neural plate Notochord Neural crest cells Coelom Somite Notochord Ectoderm Archenteron (digestive cavity) Mesoderm Outer layer of ectoderm Endoderm Neural crest cells (c) Somites Archenteron (a) Neural plate formation Neural tube (b) Neural tube formation

(a) Neural plate formation Fig. 47-12a Neural fold Neural plate 1 mm Neural folds Notochord Ectoderm Mesoderm Endoderm Archenteron (a) Neural plate formation

(b) Neural tube formation Fig. 47-12b-1 Neural fold Neural plate (b) Neural tube formation

(b) Neural tube formation Fig. 47-12b-2 (b) Neural tube formation

(b) Neural tube formation Fig. 47-12b-3 Neural crest cells (b) Neural tube formation

Outer layer of ectoderm Fig. 47-12b-4 Outer layer of ectoderm Neural crest cells Neural tube (b) Neural tube formation

Archenteron (digestive cavity) Fig. 47-12c Neural tube Neural crest cells Eye Somites Tail bud Notochord Coelom Somite Archenteron (digestive cavity) SEM 1 mm (c) Somites

Notochord (vertebrate) Mesenchyme cells Fig. 47-13 Notochord (vertebrate) Mesenchyme cells Eye Neural tube Notochord Forebrain Somite Coelom Heart Archenteron Endoderm Lateral fold Mesoderm Blood vessels Ectoderm Somites Yolk stalk Yolk sac These layers form extraembryonic membranes Neural tube YOLK (a) Early organogenesis (b) Late organogenesis

organogenesis ECTODERM MESODERM ENDODERM Epidermis of skin and its derivatives (including sweat glands, hair follicles) Epithelial lining of mouth and anus Cornea and lens of eye Nervous system Sensory receptors in epidermis Adrenal medulla Tooth enamel Epithelium of pineal and pituitary glands Notochord Skeletal system Muscular system Muscular layer of stomach and intestine Excretory system Circulatory and lymphatic systems Reproductive system (except germ cells) Dermis of skin Lining of body cavity Adrenal cortex Epithelial lining of digestive tract Epithelial lining of respiratory system Lining of urethra, urinary bladder, and reproductive system Liver Pancreas Thymus Thyroid and parathyroid glands Fig. 47-14

Extraembryonic membrane Amnion Allantois Embryo Amniotic cavity with amniotic fluid Albumen Shell Yolk (nutrients) Chorion Yolk sac Fig. 47-15

Mammalian development Fig. 47-16-5 Mammalian development Endometrial epithelium (uterine lining) Expanding region of trophoblast Maternal blood vessel Uterus Inner cell mass Epiblast Trophoblast Hypoblast Blastocoel Trophoblast Expanding region of trophoblast Amnion Amniotic cavity Chorion Ectoderm Epiblast Mesoderm Hypoblast Endoderm Yolk sac (from hypoblast) Yolk sac Extraembryonic mesoderm cells (from epiblast) Extraembryonic mesoderm Chorion (from trophoblast) Allantois

Cell type, position, and adhesion Morphogenesis: Cell type, position, and adhesion Ectoderm Neural plate Microtubules Actin filaments Neural tube Fig. 47-17-6

Fig. 47-18 Convergent extension Convergence Extension

CAMs(cell adhesion molecules): Cadherin RESULTS 0.25 mm 0.25 mm Control embryo Embryo without EP cadherin EP cadherin is required for proper cell organization in the blastula Fig. 47-19

An organized fibronectin matrix is required for convergent extension. Fig. 47-20 RESULTS An organized fibronectin matrix is required for convergent extension. Experiment 1 Injection the molecule to block the interaction of fibronectin and its receptor Control Matrix blocked Experiment 2 Tightly packed in a column Control Matrix blocked

Blastomeres injected with dye Fig. 47-21 The developmental fate of cells depends on their history and on inductive signals Fate map Epidermis Epidermis Central nervous system 64-cell embryos Notochord Blastomeres injected with dye Mesoderm Endoderm Blastula Neural tube stage (transverse section) Larvae (a) Fate map of a frog embryo (b) Cell lineage analysis in a tunicate

Time after fertilization (hours) Fig. 47-22 Zygote First cell division Nervous system, outer skin, muscula- ture Muscula- ture, gonads Outer skin, nervous system Germ line (future gametes) Time after fertilization (hours) Musculature 10 Hatching Intestine Intestine Mouth Anus Eggs Vulva ANTERIOR POSTERIOR 1.2 mm

Experimental egg (side view) Gray cresent affects the developmental potential of the first two daught cells EXPERIMENT Control egg (dorsal view) Experimental egg (side view) Gray crescent Gray crescent Thread Fig. 47-23a

Experimental egg (side view) Control egg (dorsal view) Experimental egg (side view) EXPERIMENT Gray crescent Gray crescent Thread RESULTS Normal Belly piece Normal Fig. 47-23b

The Organizer of Spemann and Mangold Fig. 47-24 The Organizer of Spemann and Mangold EXPERIMENT RESULTS Dorsal lip of blastopore Primary embryo Secondary (induced) embryo Pigmented gastrula (donor embryo) Nonpigmented gastrula (recipient embryo) Primary structures: Neural tube Notochord Secondary structures: Notochord (pigmented cells) Neural tube (mostly nonpigmented cells)

Dorsal lip of blastopore Fig. 47-24a EXPERIMENT Dorsal lip of blastopore Pigmented gastrula (donor embryo) Nonpigmented gastrula (recipient embryo)

RESULTS Primary embryo Secondary (induced) embryo Fig. 47-24b RESULTS Primary embryo Secondary (induced) embryo Primary structures: Neural tube Notochord Secondary structures: Notochord (pigmented cells) Neural tube (mostly nonpigmented cells)

Pattern formation Anterior Limb bud Two critical organizer regions in a limb have profound effects on the limb’s development AER (apical ectodermal ridge)---FGF ---FGF-secreting AER Removing the AER blocks outgrowth of the limb along the proximal –distal axis ZPA (zone of the polarizing activity) Cells nearest the ZPA give rise to the posterior structures (three digit) AER ZPA Limb buds Posterior 50 µm Apical ectodermal ridge (AER) (a) Organizer regions 2 Digits 3 4 Anterior Ventral Proximal Distal Dorsal Posterior (b) Wing of chick embryo Fig. 47-25

EXPERIMENT Anterior New ZPA Donor limb bud Host limb bud ZPA Posterior Fig. 47-26 EXPERIMENT Anterior New ZPA Donor limb bud Host limb bud ZPA Posterior RESULTS 4 3 2 2 3 4

HOX gene--- HoxD13 mutation  polysyndactyly Fig. 47-27 HOX gene--- HoxD13 mutation  polysyndactyly

Fertilization Cortical granule release (cortical reaction) Fig. 47-UN1 Fertilization Sperm-egg fusion and depolarization of egg membrane (fast block to polyspermy) Cortical granule release (cortical reaction) Formation of fertilization envelope (slow block to polyspermy)

2-cell stage forming Cleavage Animal pole 8-cell stage Vegetal pole Fig. 47-UN2 2-cell stage forming Cleavage Animal pole 8-cell stage Vegetal pole Blastocoel Blastula

Fig. 47-UN3 Gastrulation

Organogenesis Neural tube Neural tube Notochord Notochord Coelom Fig. 47-UN4 Organogenesis Neural tube Neural tube Notochord Notochord Coelom Coelom