Devo Lect 10 - Nervous system Flashcards Preview

Developmental bio > Devo Lect 10 - Nervous system > Flashcards

Flashcards in Devo Lect 10 - Nervous system Deck (24):
2

Main organs from ectoderm

Skin, pigment, brain and nerves, spinal cord

3

Main organs from mesoderm

Bones, connective tissue, muscle, heart and blood vessels

4

Main organs from endoderm

Gut epithelia, lungs, liver, pancreas

5

Hans Spemann experiment

Chimera study with two dorsal blastopores, one pigmented; formed 2nd invagination, basically formed two bodies, one not pigmented except in neural tissue; transplanted section called the organizer

6

Organizer

dorsal lip of the blastopore in amphibians; Initiates gastrulation, determines orientation; brain/neural tube forms first

7

Inductive events to form nervous system

Formation of mesoderm: endoderm induces ectoderm to become mesoderm; chordamesoderm; endoderm releases activin; form neuroectoderm

8

Chordamesoderm

Part of mesoderm which gets exposed to highest [activin], alters fate to form notochord

9

What is activin?

Growth factor that activates transduction pathway; paracrine effect from endoderm to form mesoderm by binding to receptors on ectoderm cells at specific time

10

Activin experiment

Add low concentration (.1ng/mL )forms bloodlike cells, mesenchyme; 1ng/mL forms muscle cells; 10ng/mL forms notochord; 100ng/mL forms heart muscle cells

11

What receptor type does activin bind to?

Receptor with 3 regions (binding, transmembrane, kinase)

12

Describe two engineered activin receptors

ActRIIBexd didn't have an inner or transmembrane domain, freefloating. ActRIIBdn is dominant negative without kinase domain only. These are in high concentration, so they compete for activin.

13

How did injection of ActRIIBexd affect levels of expression of Xbra? What is Xbra?

Xbra is mesodermal marker. The exd receptor blocks activin specifically, so the early expression of Xbra is delayed by about one stage, so development is abnormal (esp. anterior)

14

Rescuing activin experiment

Injected activin mRNA, activin released and acts autocrine by binding to the normal receptors after saturating the truncated ones, higher does almost completely rescues

15

Formation of neuroectoderm

Chordamesoderm induces cells of inner ectoderm to become neuroectoderm; this forms the neural plate, which folds to form neural tube

16

Cell adhesion around neural tube

Epidermis has E-cadherins; neural tube cells change adhesins to N-Cad and N-CAM to fuse; neural crest cells have no adhesins

17

Neurula embryo

An embryo that has formed the neural tube

18

What is the first organ to form

Neural tube. Not functional yet, but still organ.

19

Chordin, noggin

Molecules released from chordamesoderm which induce formation of neuroectoderm; are not GF; they alter function of growth factors by binding to them, ie growth factor antagonists (block BMP)

20

BMP

bone morphogenic proteins; important cytokines in morphogenesis (originally discovered in bone and cartilage development)

21

Chordin, noggin knockouts

If one of them knocked out: fairly normal, ears are a bit different; both knocked out: very abnormal, one eye, forebrain quite irregular; show synergy, genetic redundancy

22

Human nervous system development**

Day 19: neural plate and chordamesoderm; D 21 (stage 9): invagination, placenta functioning; D22: neural tube, somites; D23 (stage 10): neuropores; D24: Ant. neuropore closed; D26: post. closed; D27 (stage 12): 3-5mm, pharyngeal arches, limb buds, brain forming, connecting stock (umbilical cord)

23

Neuropores

Ant. and Post., openings of neural tube at stage 10. Ant. closes at D24, if not results in anencephaly; Post. closes at D26, if not results in spina bifida (need folic acid)

24

Somites

Clumps of mesoderm tissue near neural tube; form the vertebrae

25

Day of development and stages of development

Organisms develop at different rates, so we compare the stages (Carnegie stages)