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ICB- developmental biology > left/right assymetry > Flashcards

left/right assymetry Flashcards

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1
Q

give some examples of organs that display left/right asymmetry

A

heart, spleen, liver, gut, lung lobes, brain

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2
Q

when left/right asymmetry is correct what is this called

A

situs solitus

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3
Q

what is the inverse of situs solitus and how many people are affected?

A

situs invertus

1/10,000

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4
Q

which organ develops in the midline and then moves to the left side and loops to the right?

A

the heart

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5
Q

what does tbx5 mutation cause?

A

stronger limb malformation on the left hand side

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6
Q

name a ventricle signal in the developing embryo

A

Shh

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7
Q

name three genes that are expressed only in L or R side of embryo?

A

Shh
FGF
nodal

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8
Q

how is L/R asymmetry made in organogenesis?

A
  • directional looping
  • increased proliferation
  • regulated branching
  • cell death
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9
Q

describe two past theories of what causes L/R assymetry

A
  • electric/magnetic fields

- chiral molecules

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10
Q

what causes Kartagener syndrome?

A

immotile cilia

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11
Q

name 3 symptoms of Kartagener syndrome

A
  • chronic respiratory infection
  • male infertility
  • situs invertus in 50% of cases
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12
Q

what was suggested about L/R asymmetry from the finding of Kartagener syndrome

A

that cilia are involved in the development of L/R asymmetry

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13
Q

what was observed in some situs invertus mice?

A

dynein motor protein defects (involved in cilia movement)

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14
Q

why does a combination of situs solitus and situs invertus lead to problem?

A

organs do not fit together well and can crush each other

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15
Q

what is the node called in chicks (where it was discovered)

A

Hensen’s node

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16
Q

what is the node

A

a major conserved signalling centre essential for gastrulation

17
Q

what does each cell of the node have?

A

a single cilia of the 9+0 class

18
Q

what is the 9+0 class cilia made up of?

A

dynein arms on 9 microtubule doublets

19
Q

are cilia chiral?

A

yes

20
Q

what does KIF stand for?

A

kinesin like protein

21
Q

what was observed in KIF3-A and KIF3-B knock out mice? and what was different about their nodes?

A

randomised organ L/R asymmetry

nodes displayed no cilia

22
Q

are nodal cilia motile?

A

yes, they create a nodal flow towards the left

23
Q

where are the cilia located and what signalling causes this?

A

cilia are on the posterior end of the node cell

Wnt planar cell polarity signalling causes this

24
Q

what is special about the cilia positioning?

A

they don’t interfere with each other or produce turbulence

25
Q

what was observed when cilia removed from nodes and artificial rightward flow induced?

A

situs invertus

26
Q

what causes polycystic kidney disease?

A

mutation in Pkd2 (polycystin 2), a calcium channel associated with mechanosensing cilia

27
Q

what is are the symptoms of polycystic kidney disease?

A

enlarged kidneys full of cysts

28
Q

does the node also have mechanosensing cilia?

A

yes, located on specific regions of node

29
Q

what are mechanosensing cilia?

A

cilia that respond to bending with a calcium influx through Pkd2

30
Q

what do Pkd2 mutants show?

A

L/R asymmetry defects

31
Q

how does nodal flow affect L/R asymmetry?

A

bending of mechanosensing cilia leads to influx in calcium on the left hand side
this leads to activation of left handed genes

32
Q

name three left bias genes in the nodal area? what happens to these if mutated in mice?

A

Nodal, lefty and PitX

mid-gestational death

33
Q

how many people are left handed?

A

1/9

34
Q

what occurs in Kartagener syndrome and what does it suggest?

A

situs invertus in all organs than the brain

suggests an independent mechanism for brain asymmetry

35
Q

how is L/R asymmetry achieved in chicks? and what happens if this is disrupted?

A

only R eye see light

if chicks develop in dark then there is no asymmetry

36
Q

why is the brain asymmetrical?

A

to allow us to parallel process/multi-task

ICB- developmental biology (5 decks)

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