Lecture 22 Flashcards
What type of gene is Dmef2
Transcription factor
What are the two different tissues contained within the region of the ventral lateral mesoderm that the cardiac cells originate from
Splachnic mesoderm and foregut endoderm
What is the result of a mutation in the earliest gene expressed in the vertebrate heart
No formation of the heart and no looping of the ventricles. Interestingly, upregulation of Mef2B is seen indicating a compensatory mechanism in vertebrates
The bHLH transcription factors dHand and Ehand are involved in the formation of the heart chambers. Outline their localisation
ehand and dHand show specific expression in right and left ventricules. Their restricted expression is complimentary with eHand restricted to the left ventricle and dHand restricted to the right ventricle
Lecture 22 Question 11 - See image
A – axial mesoderm, B – paraxial mesoderm, C – intermediate mesoderm, D – lateral mesoderm (splachnopleura)
What is the result of knockout of this tinman vertebrate homologue specifically expressed in the cardiac crescent
Nkx2.5 mouse mutants do form hearts but show cardiac defects at the heart looping stage.
What is the cardiac jelly
A structure that lies between the endocardial tube and the cushion cells that is rich in extracellular matrix proteins secreted by the myocardium
What is the precise role of tinman in heart development
Tinman is required to specify cells to a cardiac lineage
What is seen in the eHand conditional knockout
Only knockout eHand in the cardiac myocytes. The mice show left ventricule defects, but survive until birth
What approach can be used to stain cells for the marker of a cardiac cell fate
Immunohistochemistry
Once the cells have been specified to a cardiac lineage, what happens in the stages leading to the formation of the heart tube
These cells migrate ventrally under the influence of signals coming from the foregut endoderm and fuse in the midline to form the heart tube
What is the name of the linear structures that form from the cardiac crescent and then fuse to form the looping heart
Heart tubes
What would be used as a control in a gain or loss of function experiment that involves bead implantation into chick/mouse embryos
Implant another bead that is soaked in PBS
What process takes place during heart remodelling
Duplication of chambers
What is the result of mutation in iv
Iv mutant mice have cilia that are immotile
What domain indicative of some transcription factors do the GATA proteins contain
Zinc finger domains
What is the name of the family of tinman homologues found in vertebrates
NK-2 homeobox transcription factors
Like tinman, Dmef2 is also required to form the Drosophila heart, T or F
T
Formation of the septa in heart chamber formation involves the activity of the endocardia, T or F
T
The first stage of cardiogenesis involves the formation of a structure from a mesodermal precursor. What is the name given to this early heart structure
Cardiac crescent
A key factor in the looping of the mammalian heart is the breakage of left-right symmetry which occurs very early in embryogenesis immediately after gastrulation, T or F
T
What two diffusible molecules of the TGF-? family are specifically expressed on the left side of the embryo
Lefty and Nodal
What two processes take place in higher order animals after formation of the heart tube
Looping, chamber subdivision
What is the effects of Dmef2 mutations on cardiogenesis
In the absence of Dmef2 you can still form the precursors of cardiac myocytes. However, these cardiac myocytes are unable to differentiate to form cardiac myocytes
A gain of function experiment was carried out to investigate the role of BMP2 by implantation of a BMP2 soaked bead into the posterior of the embryo. No Nkx2.5 expression was seen. Explain these results and what this indicates about BMP2 role in cardiogenesis
BMP2 needs to be acting in an environment that is favourable for its activity. Posterior implantation of BMP2 soaked beads wouldn’t result in a cardiac specification due to high concentration of BMP antagonists (Noggin, Chordin, Follistatin) released by the notochord. There needs to be a permissive environment to control cardiac specification by BMP2 signalling
What is the role of the iv gene
Inversus viscerum encodes a dynein protein involved in the movement of the cilia