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BMS 2 > Molecular Genetics of Pattern Formation I > Flashcards

Molecular Genetics of Pattern Formation I Flashcards

1
Q

Robertsonian translocaion

A

long arms of 14 fused to 21

-leads to downs

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2
Q

Aneupolidy is typically…

A

embryonic lethal

-13 and 18 can survive post fatally

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3
Q

trisomy 13

A

midline defects, clef lip, csn malformormations, holopresencpahy-single ventricle

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4
Q

trisomy 18

A

clenched hands, low ears, rocker bottom feet

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5
Q

signle gene mutations causing genetic defects

A

especially important in SHH and HOW

-also have organ specific ones

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6
Q

Large doses of intrauterine vitamin a (vit a aka)

A

facial abnormalities, neural tube defects,

  • in acne meds
  • retinoic acid
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7
Q

when is risk of brith defects from teratogens highest

A

3-8 weeks

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8
Q

Signal transduction via receptor kinases pathway

A

ligand binds to receptor, dimerization, signalling cascade involving phosphrylation ensures, activated protein complex is a TF

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9
Q

Where does retinoic acid bind

A

to nucelar receptors always located in nuceleus

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10
Q

TGF beta signalling/SMADS pathway
draw slide 12

+main pathway for antagonism

A

TGf beta (can also be BMP4 or activin) binds to receptor

Second receptor recruited+TGF (or BMP4) binds+phosphorylates receptor

Recruits/Phosphorylates Smad 2 or 3

Smad 2/3 oligomerizes with Smad 4 and goes to nucleus where can recruit other gene proteins and activate trx of specific target gene

use something that antagonizes tgif-beta/bmp4

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11
Q

Fgf heparan sulfate

A

Fibroblast growth factors

4 receptors

used in critical early axis format and for dev of several organs (bone and cartilage)

Heparan sulfate on cell surface helps FGF present to Tyrosine kinase receptors and helps active dimeric receptor even when FGF is monomer

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12
Q

Preimplantation timeline

A

First meiosis-several divisions, morula, then blastocyst-day5

ICM embryoblast+trophoblast

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13
Q

when does implantation occur

what can icm cells become

A

day 6

ICM cells can become ecto, meso, or end

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14
Q

Two TFs i eqrly embryonic cell lineages

A

all cells express both at moral

some cell preferentatillly 1 vs other at 16 cells

the cells segregate-one forms TE other forms ICM

-happens again to form endoderm vs epiblast

eventually both cells restrict each other with reciprocal inhibition

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15
Q

2nd week germ disc’s mesoderm

A

Little embryonic mesoderm-forms connective tissue, control nervous system formation

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16
Q

what are embryonic endoderm dn mesoderm derived from

A

cell that enter primitive streak

endodermal enter first during gastrulation
-mesdermal arise from epiblast and enter, spread extensively

engrossing of epiblast cells are thought to replace hypoblast cells (become yolk sac lining)-ingressing cells fan out to form mesodermal layer

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17
Q

embryonic node

A

area of active invagination into inner embryo

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18
Q

Nodal

A

TGf-b related peptide

expressed in posterior region of embryo called “node” where mesoderm will form

when knocked out primitive streak does not form

Pattern anterior visceral endoderm-needed for anterior structure differentiation

wants more mesoderm

19
Q

Nodal expression (draw slide 19)

A

broad early, induces anterior visceral endoderm-produces new signaling molecules that establish anterior-posterior embryonic axis/promote afterior differentiation

Induced ave-produces inhibitors that suprpres nodal expression in most of embryo exposept in posterior end
-At this place, the node region, nodal expression increases to the threshold level needed for mesoderm to form a dn for primitive streak formation to begin
+flattens?

20
Q

BMP4

A

suppresses mesoderm and nervous system formation and promtes epidermis

antagonized by chordin and login
-bind to BMP4 and prevent association with receptor

opposite action of nodal
-wants less mesoderm, nodal wants more

not expressed where primitive streak formed (i am pretty sure)

21
Q

Goosecoid

A

expressed in node-TF that allows anterior structures to be induced in mesoderm-interact with cells controlling head structures

22
Q

Nodal expression in node begets

A

expression of noggin and chords

bind to BMP-4 and prevent association with BMP receptors-allows nodal expression to expand

23
Q

Brachyury

A

Knockout results in much-reduced posterior mesoderm

-tailless phenotype

24
Q

relation of mesoderm, bmp-4, chordin, noggin, brachyury, goosecoid, FA, and FGF

A

Mesoderm increase
BMP, chordin, noggin, brachury, goosecoid decrease

mesiderom decrease
RA and FGF decrrease

25
Q

proteins known for dev of anterior structures

A

chordin, noggin, brachury, goosecoid

26
Q

too much goosecoid results in

A

two heads

27
Q

Too little chords, noggin, brochure results in

A

posterior mesoderm never forming

can also be rbecuase too much runic acid/too little FGF

sironomelia-fusion of limb buds

28
Q

FGF functions + where expressed

A

expressed in primitve streak-gives rise to mesoderm

induces main second region of nodal expression-leads to left/right sidedness

FGF in mesoderm promotes continued chords and noggin expression, inhibits BMP4
-inhibiion of BMP 4 promotes more mesoderm as well as neural tissue development

29
Q

What is expressed in primitive streak

A

Nodal and FGF

30
Q

retinoic acid

A

produced and normally active in only small areas of embryo-activates nuclear RA receptors

endogenous synthetic and degradative enzymes for RA-if mutated-major abnormalities occur if too much RA
-espeically in posterior structures becoming anterior

31
Q

RA is teratogen

A

After RA exposure-RA receptors are activated on cells that do not normally see RA

Vitamin A is rpecursor to RA-high exposures are very bad

32
Q

retinoic acid interaction+what happens if 1 wins over other that isn’t supposed to

A

recipricol inhitory interactions with FGF isoform

RA produced more anteriorly, FGF more posteriorly
-RA turns off FGF8 from rostral to caudal

Maintenance of posterior FGF signaling is needed for posterior structures to develop
-too much RA-FGF turns off prematurely-problems with posterior development

33
Q

HOX expression patterns in embryo

and how relates to FGF

A

Several hox genes are linearly arranged in clusters

5’ hox genes direct development of posterior structures

more FGF exposure needed to activate 5’ HOX genes needed for posterior dev

  • too much RA-FGF turned off prematurely
  • 5’ hox gene activation doesn’t occur and there are defects in posterior structures that these genes control
34
Q

Gentic causes of birth defects

A

robertsonian translocation, error in kiosks one, isochromaseom-downs

trisomies-patau (13) edwards (18)

35
Q

Environmental causes of birth defects

A

tertogens, alocol, retinoic acid, many more

36
Q

Teratogen affecting organs one at a time during dev

A

weeks 3-8-wmveto sec

days 15-60 organ specific

days 20-36 ears, eyes, upper/loewr limbs

37
Q

Major effects of rinoic acid as teratogen

A

RA tug of war with FGF

  • RA is for anterior
  • FGF for posterior

Increase RA and decrease FGF
-defects or absence of posterior structures

38
Q

Aspects of TGF/FGF signaling cascades

A

TGF-B signalling proteins-nodal, BMP4, activin

  • nodal inhibits mesoderm formation
  • ligands bind to TGF2 receptors, recruits P, ligand binds to other half and P does too, ruer SMAD2/3, dimerizes with SMAD 4-enters nun

FGF (and TGFB) is a tyrosine kinase receprotr

  • results in axis dev, bone and cartilage dev
  • GAT heparin thing-presents FGF to receptor even if monomer-allows activity
39
Q

Changing role of TGF peptide nodal at different times in dev

A

increase nodal

  • anterior visceral endoderm (AVE)
  • inhibits nodal resision-anterior region

Nodal expression localized to small end at posterior
-node reaches threshold level-allows for mesoderm and primitive streak formation

nodal negative mice-no mesoderm or primitive streak

40
Q

mechs that lead to deficient posterior mesoderm formation

A

Ra increase and FGF decrease
-Goosecoid-TF that allows anterior structures to be induced in mesoderm moving anteriorly

Nodal+BMP-4-have opposite effects
-nodal-mesoderm increase, neural tissue formation
BMMP-4-supresses mesoderm and neural tissue formation

Node-nodal, noggin, chordin, goosecoid

BMP4-boradly experssion in epiblast

Defiecent poster mech

  • decrease chordirn, FGF, noggin
  • increase RA

Brachury decrease(TF expeeression in poseterior mesoderm)

41
Q

Retinoic acid as a teratogen in terms of FGF and homeobox

A

Increase RA, decrease FGF

more FGF needd to activte 5’ hox genes

increase RA, FGF turn off permanent (if too much)

5’ is poseterior, 3’ is anterior

42
Q

Changing role of TGF peptide nodal at different times in dev

A

increase nodal

  • anterior visceral endoderm (AVE)
  • inhibits nodal resision-anterior region

Nodal expression localized to small end at posterior
-node reaches threshold level-allows for mesoderm and primitive streak formation

nodal negative mice-no mesoderm or primitive streak

43
Q

mechs that lead to deficient posterior mesoderm formation

A

Ra increase and FGF decrease
-Goosecoid-TF that allows anterior structures to be induced in mesoderm moving anteriorly

Nodal+BMP-4-have opposite effects
-nodal-mesoderm increase, neural tissue formation
BMMP-4-supresses mesoderm and neural tissue formation

Node-nodal, noggin, chordin, goosecoid

BMP4-boradly experssion in epiblast

Defiecent poster mech

  • decrease chordirn, FGF, noggin
  • increase RA

Brachury decrease(TF expeeression in poseterior mesoderm)

44
Q

Retinoic acid as a teratogen in terms of FGF and homeobox

A

Increase RA, decrease FGF

more FGF needd to activte 5’ hox genes

increase RA, FGF turn off permanent (if too much)

5’ is poseterior, 3’ is anterior

BMS 2 (41 decks)

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