BIO 302 Lecture Notes - Lecture 6: Axon Guidance, Superior Colliculus, Housekeeping Gene
Axon guidance - how do nerves know where to grow/
• Nerves end out “processes” ( projection ) that “ explore’ their environment for clues
where to go
• Controlled by cytoskeletal
o Microtubules
▪ Colchicine
o Microfilaments
▪ Cytochalasin
Models for axon guidance
• Chemotaxis- attraction or repulsion by different chemical signals
o Cells omit netrin I (attachment )
▪ Cells move towards higher concentration
o Cells omit semaphorin III (repellent )
Lumsden Exp:
• Axos grows towards specific tissues and not others
Consistent with hypothesis that neurons are getting an attractive signal from tissue
What would happen if you rotated the eyeball upside down?
Images would be seen upside down
Neurons map to reverse location in optic tectum in relation to where they are in the retina.
How do neurons know where to stop in the optic tectum?
• Neurons have EPH A4/15 receptors
Rules:
• Xos with EPH A4/6 receptors permitted to grow through ephrin A2 cells
• EPHA4/5 cells not permitted to grow through ephrin A5 cells.
• EPh A3 cells not permitted to grow through ephrin A2 cells
• Cell behavior depends on what receptors are on the axon and what signals are in a
particular cell/area in the brain
What would transcriptional regulation mean?
- regulating mRNA synthesis
Gene Regulation-
Transcriptional regulation
• All cells have same DNA/Genes
• Cells
o Neurons: ---A----B---C----D---
o Muscle: ---A----B---C----D---
• Promoter: place on DNA that RNA polymerase binds to and transcribes the gene
• “Housekeeping” gene - metabolic etc. all cells need
Trx. Regulation: determines what genes are transcribed -> mRNA in which cells
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Axon guidance - how do nerves know where to grow: nerves end out processes ( projection ) that explore" their environment for clues where to go, controlled by cytoskeletal, microtubules, colchicine, microfilaments, cytochalasin. Models for axon guidance: chemotaxis- attraction or repulsion by different chemical signals, cells omit netrin i (attachment , cells move towards higher concentration, cells omit semaphorin iii (repellent ) Lumsden exp: axos grows towards specific tissues and not others. Consistent with hypothesis that neurons are getting an attractive signal from tissue. Neurons map to reverse location in optic tectum in relation to where they are in the retina. How do neurons know where to stop in the optic tectum: neurons have eph a4/15 receptors. Transcriptional regulation: all cells have same dna/genes, cells, neurons: ---a----b---c----d--, muscle: ---a----b---c----d--, promoter: place on dna that rna polymerase binds to and transcribes the gene. Housekeeping gene - metabolic etc. all cells need.
