Lab 5 - retnoic acid induced teratogenesis in zebrafish

Question 1

What are teratogens? How do they act? What are the general effects?

Answer 1

• any agent of factor that can disturb the development of the embryo
• do no act by changing the DNA sequence
• may cause congenital deformity of halt pregnancy

Question 2

What are the categories for teratogens?

Answer 2

• radiation
• maternal infection
• chemical agents
• drugs
• environment
• metabolic conditions
• infections

Question 3

What developmental deformities can teratogens mimic? What category does RA fall into?

Answer 3

• loose it
• move it
• gain it (RA)

Question 4

What category of teratogen is thalidomide, what did it cause?

Answer 4

category = drug

• caused deformities and spontaneous abortions - affects development of long bones and other things

Question 5

Name three environmental teratogenic events

Answer 5

• deepwater horizon spill
• heavy metal contamination in fresh water bodies
• BPA

Question 6

What is a poison?

Answer 6

Can negatively impact an organism at any stage of life: adults, children, newborns

Question 7

Can some teratogens be mutagens

Answer 7

yes

Question 8

What category of teratogen is zika virus, what does it cause?

Answer 8

category = infection
- causes microencephaly

Question 9

What category of teratogen is alcohol, what does it cause?

Answer 9

category = drug
- fetal alcohol spectrum disorder, most potent before women know that they are pregnant

Question 10

What are two questions we have to ask ourselves when determining the mechanism of action of a teratogen?

Answer 10

1. stage dependence
   - what stages of development are affected?
2. dose dependence
   - is the severity directly dependent on the concentration?
   - acute or chronic?

Question 11

Why do we use model organisms to screen for teratogens?

Answer 11

• Due to evolution, model organisms undergo early development using the same signaling factors as humans
• Conservation of TFs and regulatory regions

Question 12

Why use zebrafish and xenoupus as models for teratogens and not mice or flies?

Answer 12

• Vertebrates
• Easier to get eggs
• Generation time
• Visible embryos
• Develop externally

Question 13

What kind of molecule is RA, what does this mean?

Answer 13

RA is derived from vitamin A; therefore it is not a protein –> no gene for RA

Question 14

What is vitamin A required for?

Answer 14

• Embryonic development
• Normal immune system function
• Epithelial differentiation in adult
• RBC production
• Night vision

Question 15

Describe the RA gradient in the brain. How does RA treatment affect the threshold? What is the importance of a RA gradient?

Answer 15

high –> low: pr7/8 –> pr 1 in hinbrain

• RA treatment moves the threshold
• different RA concentrations turn on different Hox genes

Question 16

Describe the phenotype of Class 1 RA treatment

Answer 16

control

Question 17

Describe the phenotype of Class 2 RA treatment

Answer 17

• Thicker yolk extension
• Less circular yolk shape
• Smaller eye

Question 18

Describe the phenotype of Class 3 RA treatment

Answer 18

• Flattened head
• Underdeveloped eyes
• Thicker yolk extension
• Pointed yolk
• Shorted tail, tip deformed

Question 19

Describe the phenotype of Class 4 RA treatment

Answer 19

• Flattened head
• No eyes
• Very thick yolk extension
• Elongated yolk
• Stubby, deformed tail