Lecture 12 Flashcards
What are the 4 reasons we need muscle?
1) communication= through speech, expression, writing
2) movement/posture
3) breathing= diaphragm
4) Metabolism= thermoregulation and through muscle contraction
Why do we need to study muscle formation and how?
Because of dystrophy (aging and muscle wasting), diseases and aging. Can use a paradigm= a model used to understand differentiation of muscle cells and MRF function in skeletal muscle (how they form cell shape)
What are the overall steps in producing muscle?
1) Origin= pluripotent stem cell line- cell fated to be muscle
2) specification= becomes a muscle progenitor- myoblast
3) differentiation= fuses into myotubes which requires the coordinated activation of many genes
4) maturation= refinement into slow/fast/intermediate fibres
How was MyoD isolated?
1) Used 5aza (demethylating agent) to treat cells which became muscle
2) made cDNAs from extracted mRNA and compared to untreated cells by hybridisation
3) denatured the ds to ss= those that didn’t hybridise were extracted using a filter which were assumed to be muscle genes- one of which was MyoD
How does 5aza transform cells into muscle cells?
It is a demethylating agent- methyl groups can be added to cpg or histones to epigenetically trandsform heterochromatin into euchromatin thus suppressing the genes. The genes are unrepressed when 5aza is added which are though to be muscle genes
Why is MyoD a master regulator gene?
It was inserted into a viral vector to be introduced into pigment cells- they lose differential characteristics and form myoblasts that have the capability to form myotubes. Therefore MyoD is sufficient for cells to differentiate
What are the properties of the MyoD family gene?
They are TFs that bind to the Ebox sequence CANNTG. They have a helix loop helix to bind to proteins E12 and E45 and have a DNA binding domain. Sufficient to turning any cell into a muscle. The members are Myf5, MyoD, Myogenin and MRF4
What are the origins of skeletal muscle?
Dermatome and myotome from somites