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BMS249 DEVELOPMENTAL NEUROBIOLOGY > MECHANISMS OF AXON GUIDANCE 2 AND 3 > Flashcards

MECHANISMS OF AXON GUIDANCE 2 AND 3 Flashcards

1
Q

POLARITY IS ESTABLISHED AS NEURONS ARE …….

A

BORN

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2
Q

……… IN ENVIRONMENT INFLUENCE NEURITE SLECTION

A

CUES

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3
Q

WHAT REGIONS MAKE UP THE ANATOMY OF A GROWTH CONE

A

CENTRAL
TRANS
PERIPHERAL

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4
Q

THE CENTRAL REGION OF A GROWTH CONE IS MADE UP OF

A

MICROTUBULES

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5
Q

THE TRANS AND PERIPHERAL REGIONS ARE MADE UP OF

A

F ACTIN

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6
Q

WHAT IS A FILOPODIA

A

MEMBRANE PROJECTIONS THAT EXTEND OUTWARDS FROM THE GROWTH CONE

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7
Q

WHAT IS A LAMELLOPODIA

A

AN ACTIN MESH BETWEEN THE FILOPODIA

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8
Q

IN FILOPODIA THE ACTIN BUNDLES ARE ………………………… TO FORM LARGER ……………….OF NARROW EXTENSIONS

A

POLARISED

BUNDLES

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9
Q

IN LAMELLA THE ……………. BUNDLES ARE ……………. LINKED INTO A NET.

A

ACTIN

CROSS

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10
Q

F ACTIN…………………….. IN A RESTING GROWTH CONE

A

TREADMILLS

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11
Q

WHAT IS TREADMILLING

A

F ACTIN MOVES FROM THE PERIPHERY TO CENTRE WHERE IT BREAKS DOWN TO REJOIN THE TIP

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12
Q

IN THE RESTING GROWTH CONE, TUBULIN IS DRAGGED SPORADICALLY INTO THE ……………………… - WHEN THE …………………. CONE COMES INTO CONTACT WITH AN ATTRACTIVE ………….., THIS BECOMES MORE ………………

A

FILOPODIA
GROWTH
CUE

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13
Q

THE GROWTH CONE ……………….. IN THE PRESENCE OF A CUE

A

REORGANISES

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14
Q

HOW DOES THE GROWTH CONE REORGANISE IN THE PRESENCE OF A CUE

A
  1. F ACTIN TREADMILLING SLOWS AND ACCUMULATES

2. ACCUMULATION STABILISES THE FILOPODIUM AND DRAGS MICROTUBULES INTO THE BACK OF THE FILOPODIUM

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15
Q

WHAT CAN AN ATTRACTIVE CUE BE COMPARED TO

A

ACTS AS A MOLECULAR CLUTCH IN ORDER TO PROPEL THE GROWTH CONE FORWARD

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16
Q

AN …………-TUBULIN LINK PULLS MICROTUBULES IN THE WAKE OF THE EXTENDING FILOPODIA

A

ACTIN

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17
Q

GROWTH CONES CAN BE ……………………… AND ……………………. BY CUES

A

REPELLED

ATTRACTED

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18
Q

WHAT STRUCTURALLY HAPPENS TO THE GROWTH CONE UPON REPULSION BY A CUE

A

THE GROWTH CONE COLLAPSES

THERE IS A DECREASE IN F ACTIN

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19
Q

WHEN MIXTURES OF DIFFERENT NEURONAL TYPES ARE IN CULTURE, WITH WHAT NEURONAL TYPES THEY SEEM TO FASCICULATE WITH

A

THEIR OWN KIND

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20
Q

WHAT ARE SEMAPHORINS

A

A FAMILY OF INHIBITORY GUIDANCE CUES

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21
Q

WHAT ARE THE MAIN TYPES OF SEMAPHORINS FOUND IN THE GRASSHOPPER EMBRYO LIMB

A

MEMBRANE BOUND

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22
Q

WHAT HAPPENS TO THE AXONS OF MICE THAT LACK SEMA3

A

AXONS STRAY INTO THE WRONG TERRITORIES

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23
Q

WHAT IS THE FUNCTION OF SEMAPHORINS

A

CAN CHANNEL AXON GROWTH

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24
Q

ALTHOUGH SEMAPHORINS CHANNEL AXON GROWTH WHAT IS STILL ALSO NEEDED FOR AXONAL GROWTH

A

PERMISSIVE FACTORS

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25
Q

AXON CANNOT ……………… WHERE THEY CANNOT ……………………
BUT THERE IS NO LINK BETWEEN STRENGTH OF ………………………. AND AMOUNT OF AXON GROWTH

A

GROW
ATTACH
ADHESION

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26
Q

HOW CAN YOU MEASURE ADHESION

A

WHAT SPEED OF CENTRIFUGE IT WITH DETACH

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27
Q

THERE IS NO LINK BETWEEN STRENGTH OF ADHESION AND AMOUNT OF AXON GROWTH - GIVE AN EXAMPLE

A

COLLAGEN HAS HIGHER ADHESION BUT LAMININ HAS HIGHER OUTGROWTH

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28
Q

‘COLLAGEN HAS HIGHER ADHESION BUT LAMININ HAS HIGHER OUTGROWTH’
WHAT CAN YOU CONCLUDE FROM THIS

A

GROWTH CONES NEED SUBSTRATES PERMISSIVE FOR GROWTH, ATTACHMENT IS NOT ENOUGH

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29
Q

EVEN IF A GROWTH CONE IS ………………., IT STILL ATTACHES TO A REPELLANT AXON

30
Q

PERMISSIVE FACTORS CAN ………………. SUBSTRATE PATHS IN THE EMBRYO. LAMININ PROMOTES GROWTH IN THE OPTIC NERVE BUT IT DOES NOT …………………. THE …………………….. OF GROWTH, ONLY THAT IS CAN ………………. THERE

A

DEFINE
DICTATE
DIRECTION
GROW

31
Q

WHAT EFFECT DOES BLOCKAGE OF A LAMININ RECEPTOR DO

A

SLOWS GROWTH BUT DOES NOT CHANGE THE DIRECTION

32
Q

………………. OF LAMININ ALSO DO NOT DIRECT AXON GROWTH. IN THIS WAY LAMININ IS ……………………. BUT NOT …………………………

A

GRADIENTS
PERMISSIVE
INSTRUCTIVE

33
Q

AXON GROWTH IS A BALANCE BETWEEN PERMISSIVE (CONTACT …………..) AND ……… …………………….(CONTACT REPELLANTS) HOWEVER DIRECTION IS SIGNALLED BY ………………….. ATTRACTION/REPULSION

A

ATTRACTION
NON PERMISSIVE
CHEMO

34
Q

WHAT ARE EPHRINS

A

NON PERMISSIVE FACTORS USED IN EARLY PATTERNING AND TO GUIDE AXONS

35
Q

EPHRINS ARE CELL …………………. MOLECULES DETECTED BY ……………
THESE CAUSE …………………. BETWEEN CELLS WHICH HELPS TO ……………………………. DISCRETE DOMAINS. LATER IN DEVELOPMENT THEY ARE USE TO KEEP …………….. OUT OF SPECIFIC AREAS.

A 
SUFACE
EPHS
REPULSION
COMPARTMENTALISE
AXONA
36
Q

KEY PATTERNING …………………. SECRETE LONG DISTANCE ………………… MOLECULES CHEMO ATTRACTANTS AND REPELLANTS

A

ORGANISERS

GUIDING

37
Q

IF YOU TAKE A DORSAL SPINAL CORD (FLOOR PLATE) EXPLANT AND PLACE IT ECTOPICALLY, AXONS MOVE TOWARDS THE FLOOR PLATE
WHAT DOES THIS SUGGEST

A

SUGGESTS THERE IS A CHEMOATTRACTANT IN THE FLOOR PLATE

38
Q

CELL (SUCH AS THE FLOOR PLATE) EXPRESSING THE ……………….. GENE CAN TUEN COMMISSURAL AXONS

39
Q

WHAT PROTEINS IN THE FLOOR PLATE CAN REPEL COMMISSURAL AXONS

40
Q

LONG AND …………… RANGE CUES WORK …………………. TO GUIDE AXONS TO THEIR TARGETS
EG GRASSHOPPER …………
SUGGESTS A GRADIENT OF SEMA2 DIRECTS TI1 TOWARDS THE BODY WHILE SEMA 1 STOP AXONS FROM STRAYING

A

SHORT

TOGETHER

41
Q

COMMISSURAL AXONS ARE GUIDED BY ……………………….. FACTORS IN THE ROOF PLATE AND ……………….. PLATE, BMP7 AND ……………….. RESPECTIVELY.

A

CHEMOTROPIC
FLOOR
NETRIN

42
Q

BMP7 IS EARLIER USED TO …………………… THE CELL TYPES OF THE ……………… CORD, ANTAGONISING …………..
THIS SUGGESTS FACTORS MAY BE RE USED FOR ………………. GUIDANCE

A

PATTERN
SPINAL
SONIC HEADGEHOG
AXON

43
Q

WHAT HAPPENS WHEN NETRIN IS KNOCKED OUT

A

AXON GUIDANCE IS DISRUPTED BUT SOME C AXONS STILL MAKE IT TO THEIR DESTINATION

44
Q

WHY DO SOME AXONS STILL REACH THEIR TARGET IS NETRIN HAS BEEN KNOCKED OUT

A

BECAUSE SONIC HEDGEHOG ALSO GUIDES AXONS

45
Q

WHAT WILL A SMOOTHENED KNOCK OUT HAVE AFFECT ON

A

SMOOTHENED IS PART OF THE SHH PATHWAY

THEREFORE THIS WILL DISRUPT AXON GUIDANCE

46
Q

HOW CAN YOU GET TISSUE SPECIFIC DELETION OF A GENE

A

USE OF CRE RECOMBINASE AND LOX P

47
Q

EXPLAIN METHODOLOGY OF TISSUE SPECIFIC DELETION OF A GENE

A
  1. BACTERIOPHAGE P1 ENCODES CRE RECOMBINASE THAT CAN BE INSERTED INTO HOST GENOME
  2. CRE RECOMBINASE BINDS TO LOXP (A SPECIFIC 34 BASE SEQUENCE) WHICH IS CAN CUT AND BIND TO ANOTHER LOXP
  3. WE CAN SPECIFICALLY DELETE DNA BETWEEN THESE SEQUENCES - FLOXING
  4. HOMOLOGOUS RECOMBINATION - CROSSING A MOUSE WITH A FLOXED ALLEL AND A MOUSE WITH A CRE UNDER A TISSUE SPECIFIC PROMOTER WILL GIVE A MOUSE WITH NORMAL EXPRESSION EXCEPT FOR IN THE TARGET TISSUE
48
Q

AXONS REPROGRAM WHEN ………………… POINTS ARE ENCOUNTERED. AFTER TRANSIT OF THE MIDLINE, C AXONS LOSE ……………………………. TO ……………………..

A

CHOICE
RESPONSIVENESS
NETRINS

49
Q

POST CROSSING, AXONS BECOME SENSITIVE TO SOMETHING …………………… IN THE FLOOR PLATE. THERE IS ………………….. OF NETRIN SENSITIVITY AND SENSITIVITY NOW TO ……………………………….. AND SLITS. THESE ARE EXPRESSED IN THE …………………….. PLATE AND ……………….. SPINAL CORD CREATING A CHANNEL THROUGH WHICH C ………………. CAN GROW. THE FLOOR PLATE HAS ………………………………. THE AXONS.

A 
INHIBITORY
LOSS
SEMAPHORINS
FLOOR 
VENTRAL
AXONS
REPROGRAMMED
50
Q

WHAT DETERMINES WHETHER C AXONS CROSS OR NOT AND WHAT PREVENTS RECROSSING

A

ROBO (ROUNDABOUT)

COMM (COMMISSURELESS)

51
Q

WHAT IS ROBO

A

RECEPTOR FOR SLIT

52
Q

WHAT IS THE ACTION OF ROBO

A

WHERE ROBO IS EXPRESSED AT HIGH LEVELS ON AXONS THAT DO NOT CROSS THE MIDLINE

53
Q

WHAT OCCURS IN ROBO MUTANTS

A

ROBO MUTANTS CANNOT DETECT SLIT AND THEREFORE KEEP CROSSING THE MIDLINE

54
Q

WHAT IS COMM

A

COMM IS EXPRESSED ONLY IN AXONS THAT NORMALLY CROSS THE MIDLINE

55
Q

WHAT HAPPENS TO A COMM MUTANT

A

AXONS DO NOT CROSS THE MIDLINE AND ARE LONGITUDINAL ONLY

56
Q

FORCED COMM EXPRESSION RESULTS IN WHAT

A

A PHENOTYPE THAT MATCHES THE ROBO MUTANT

57
Q

WHAT CAN BE SAID ABOUT FORCED COMM EXPRESSION IN CONCLUSION

A

COMM CONTROLS ROBO

58
Q

HOW DOES COMM CONTROL ROBO

A

COMM CONTROLS A TRAFFICKING PROTEIN REACHING THE CELL SURGACE TO THAT THE GROWTH CONE CANNOT RECEIVE SLIT INHIBITORY SIGNALS BEFORE CROSSING

59
Q

COMM AND ROBO ARE NOT FOUND IN VERTEBRATES, WHAT OCCURS IN VERTEBRATES INSTEAD

A

IN VERTEBRATES ROBO=ROBO1 BUT IT IS EXPRESSED BEFORE AND AFTER CROSSING
THERE IS NO COMM, ONLY ANOTHER ROBO LIKE PROTEIN, RIG 1 THAT APPEARS TO BLOCK ROBO1 UNTIL THE MIDLINE IS CROSSED

60
Q

FOLLOWER AXONS USE THE ………………….. SCAFFOLD. THEY MUST STAY ON AND GET OFF AT THE RIGHT PLACE. THIS IS DONE BY …………………. BINDING BY CELL ………………….. MOLECULES.
FASCICULATION AND DEFASCICULATION IN FLIES IS CONTROLLED BY ……………………..2. BEAT PROTEIN CAN ALSO CAUSE ……………………..

A 
PIONEER
HOMOPHILIC
ADHESION
FASCICULIN
DEFASCICULATION
61
Q

OVEREXPRESSION OF FASCICULIN 2 CAUSES WHAT

A

AXONS TO MISS THEIR TARGETS

62
Q

WHAT ARE THE TWO TYPES OF TARGET SELECTION

A

DISCRETE (CELLULAR)

TOPOGRAPHIC (MULTICELLULAR)

63
Q

IN DISCRETE TARGETS, ABLATION OF THE TARGET MUSCLES LEADS TO WHAT

A

FAILURE OF THE MOTOR AXON TO LEAVE THE TRUNK

64
Q

THE TARGETS SECRETE CUES THAT PROMPT THE AXONS TO LEAVE THE TRUNK AND DEFASCICULATE TO THEIR TARGET. WHAT ARE EXAMPLES OF THE CUES.

A

NETRIN

FASCICULIN 3

65
Q

IN TOPOGRAPHIC MAPS, …………………………… NEURONS SEND ……………… TO NEIGHBOURING SITES TO MAINTAIN ORDER.

A

NEIGHBOURING

AXONS

66
Q

THERE ARE TWO THEORIES FOR TARGETS BY SPERRY WHAT ARE THEY

A
  1. EACH AXON HAS A SPECIFIC LABEL FOR EACH TARGET

2. A COORDINATE SYSTEM OF GRADIENTS OF SIGNALLING MOLCEULES OF LONGITUDE/LATITUDE READ BY RECEPTORS OF TARGET

67
Q

WHICH OF SPERRY’S TWO TARGET THEORIES WAS CORRECT

68
Q

HOW CAN WE SHOW MODEL 2 TARGET SELECTION THEORY WAS CORRECT

A

THE STRIPE ASSAY

69
Q

WHAT IS THE STRIPE ASSAY

A

CELLS FROM THE POSTERIOR TECTUM MAKE A NON PERMISSIVE FACTOR THAT REPELS TEMPORAL RETINAL AXONS
TEMPORAL AXONS AVOID STRIPES OF THE POSTERIOR TECTUM

70
Q

WHAT IS THE INHIBITORY FACTOR CAUSING STRIPES IN THE POSTERIOR TECTUM

A

EPHRINS A2/A5 TO RECEPTOR EPH A3

71
Q

WHAT CAN WE CONCLUDE ABOUT THE STRIPE ASSAY

A

NON PERMISSIVE REPELLANT FACTORS CAN BE INSTRUCTIVE TO FORM TOPOGRAPHIC MAPS

BMS249 DEVELOPMENTAL NEUROBIOLOGY (14 decks)

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