Lecture 9

2 Pages
109 Views
Unlock Document

Department
Cell and Systems Biology
Course
CSB332H1
Professor
Melanie Woodin
Semester
Winter

Description
CSB332H1S L9; Feb. 8, 2012 assembly of actin filaments (and other prots needed) on 1 side Axon Guidance of growth cone. Read: Pg. 558-562  The cascade of local clustering & consequent depletion of signaling molecs @ rest of cell o  Provide local activation & global inhibition  Required for amplification of gradient signal.   respond more effectively on upper-left side, also decreases response in regions furthest from gradient  (global inhibition on right side)  Prots get localized  growth cone turning Gradient of Ca is important  Hign Ca grad  attraction  Low Ca grad  repulsion  GCs of cultured Xenopus spinal neurons exhibit adaptation  For both attraction & during chemotactic migration, undergoing consecutive phases repulsion, Ca level above of desensitization & resensitization in presence of guidance baseline, just more so for factor netrin-1 attraction  With more time (90min) resensitizes to gradient  now   Activate cascades responsive to the chemoattractant  Adapt to envt o Ex. Phosphorylation or prot kinases – need certain levels of Ca to activate  Large grad of Ca coming from neuron but not important for act pot – important for many other things  Images of Ca-binding growth cone – been bathed in fluorescent Ca-sensitive indicator  Calcium signals induced by a netrin-1 gradient correlate w adaptation.  Fluorescence images of a GC loaded w a Ca2+-sensitive fluorescent indicator (Oregon green BAPTA-1-dextran).  Neuron was incubated w netrin-1 (5 ng ml-1) in the bath 30 min (a) or 90 min (b) before exposure to a netrin-1 gradient.  A: apply grad @ t=0 o Desensitized to netrin so growth cone not turned towards gradient, overall no global change in amt of Ca  B: resensitzation since more time passed  increase in yellow signal – indicates Ca levels increased in growth cone  so  Retina projections ganglia to optic tectum (analygous to LGN in growth cone grows towards gradient vertebrates?) in midbrain  Ca = important in signaling other molecs (ex. prots) for gene  Retina divided in nasal & temporal regions expression  Optic tectum divided btwn anterior & posterior  Nasal  innervates posterior  Temporal innverates anterior o Due to conc grads  Eph = rec  So growth growth growing from temporal region has much higher conc of Eph recs  Nasal region has lower expression of Eph recs o Ligands that activate Eph recs = Ephrins, found in optic  Black ovals = rec for chemoattractant tectum  In encountering a shallow gradient of guidance molecs (yellow  Critically important: when ephrin binds to rec  repulsive, cloud)  shallow gradient of rec activation (red oval)  inhibitory reaction  growth cone moves away from that clustering of activated recs. region o More red ovals close to gradient  Ganglion cell in temporal retina  Initial clustering  triggers recruitment & further clustering of o If grow into tectum, will choose anterior region since less cytoplasmic adaptors & effectors  eventually orientated
More Less

Related notes for CSB332H1

Log In


OR

Join OneClass

Access over 10 million pages of study
documents for 1.3 million courses.

Sign up

Join to view


OR

By registering, I agree to the Terms and Privacy Policies
Already have an account?
Just a few more details

So we can recommend you notes for your school.

Reset Password

Please enter below the email address you registered with and we will send you a link to reset your password.

Add your courses

Get notes from the top students in your class.


Submit