Pharangeal patterning

jambomber's version from 2015-05-21 13:43

Section 1

Question Answer
what did Noden show?Transposition of presumptive mandibular and hyoid arch neural crest results in ectopic mandibular arch skeleton
What does Nodens experiments discover“Ectopic beaks” originate from the hyoid arch-derived region of hosts
What did Noden conclude?resides within the neural crest population prior to its emigration from the neural epithelium
What is the conseqynece of Hox2 -Hyoid transformed to mandibular. What does this demo- HOX patterns in arches are important to patterning
How were heterotypic grafts used to show plasticity?Loss of Hoxb1 expression in dispersed cells upon transposition from r4 to r2
How was the Idea of community effects being important supportedTransplantation of single cells in the zebrafish hindbrain revealed plasticity in Hox gene expression
What changes were observed in zebrafish transplanted NCCsLoss of Hoxb3 expression upon transplantation from r6 to r1-r3 2) xr6/r7 cells ; upregulate Hoxa2 when contributing to hyoid arch (pa2) crest, but not when contributing to mandibular arch (pa1) crest
How is Hox gene plasticity relevant o devoAlterations in cell fate 1) Cells transplanted from r6 to r2 alter their neural fate, and contribute to the trigeminal ganglion (V) 2) Cells transplanted from r6 to r3 contribute to hyoid arch cartilages
Which proteins are important for which stages of Hox2 expression Point mutations in Krox20 binding sites within Hoxa2 r3/r5 enhancer abolish r3/5 expression, Deletion or point mutations in AP-2 binding sites within Hoxa2 NC enhancer
How do we know Hox2 contributes to the selection of hyoid fate in arches1) mandibular-to-hyoid homeotic transformation on injected side (DEX treatment at St. 28) 2) Cre-lox floxing of Hox2 in developing jaw results in the ectopic formation of Meck cart in hyoid arch
Where is the Isthmic organiser? What does it produce@ Midbrain hindbrain boundry ie b/w 1 and 2 - Fgf8 production
What did Trainor show?Fgf8 bead is sufficinet to prevent Hox2 in hyoid arch- as is a graft of R1+ Organiser to r4 position Transposition of r1- isthmus to r4 results in normal hyoid arch skeleton

Section 2

Question Answer
How do we know Hox negatives = facial skeleton1) Bilateral extirpation of neural crest results in complete loss of the facial skeleton 2) Orthotopic quail-chick grafts contribute to facial skeletal elements, but heterotopic grafts (e.g. from r4-r6) do not
What regions of crainofacial skeleton are lost when foregut endoderm extripated1) Nasal 2) Meckels 3) Quadrate and Articular
What did Couly show by grafting?That supernumary cartiliges can be unduced by diff regions f foregut ednoderm 1-- position 2= Extra beak+ Meckels cartalige
how do we know only Only Hox-negative neural crest cells can give rise to facial skeletal elements in response to signalling from foregut endodermGrafts of foregut endoderm to the level of r7 induc only small cartilaginous nodules. Grafts of mesencephalic (1-3) neural crest and foregut endoderm to the level of r7 however induce supernumerary Meckel’s cartilage/articular
How is Shh pattern of expression changed trhrough devoShh is expressed initially in foregut endoderm to the level of the forebrain midbrain boundary (until 6ss), then expands beyon this boundary (by 8ss)
What did forehead removal show6ss removal of Shh-expressing tissue results in loss of the lower jaw; 8ss removal of Shh-expressing tissue (or 6ss removal + SHH bead) rescues lower jaw development
How do we know SHh importantTransplantion of quail SHH fibroblats at the level of the foregut induces supernumerary, mirror-image Meckel’s cartilage
What is the consequence of Dlx5/6 Cre k/oLower upper transformation Homeotic transformation of lower jaw dermal skeleton (dentary) into upper jaw dermal skeleton (maxilla)
Where does endothilin signalling function in relation to DlxS? Where are endothilin components expressedUpstream 2) Endothelin-1 is expressed in ventral mandibular arch epithelium; Endothelin receptor A is expressed in mandibular arch neural crest-derived mesenchyme
What is the phenotype of endothilin -/- miceAnalogous to Dlx5-/-
What can cause upper to lower jaw transformationConstitutive activation of EDNRA results in upper-to-lower jaw homeotic transformation
What is the transformation syndrome called in humans- what genes involvedauriculocondylar syndrome Endothelin-1, PLCB4, GNAI3
Summarise HOx2 controlHoxa2 regulated independently in hindbrain and neural crest; functions in post-migratory neural crest cells to select for hyoid arch identity
What direction of transplation Triton vs bombinatorBomb to triton orthotopic grafts
What intrinsic differcne between duck and quail nerual crestDuck possess a greater number of migratory neural crest cells, Duck exhibit enhanced response to proliferative signals, Duck NC mesenchyme proliferates relatively faster than quail NC mesenchyme 4) Neural crest mesenchyme regulates timing of osteogenesis in a cell-autonomous manner