Can we make chicken limbs grow?

Most people only view chickens as a source of meat. A means to an end to make a nice, tasty stir fry or a heart-warming soup. However, over the past few years, I have been using them to understand more about the development of the muscles. I am interested in what controls and signals muscle development, essentially: can I grow limbs from basic tissue? If I succeed, such a technique could potentially be used in medicine to help amputees and people who suffer with muscle related diseases. What’s more, it also has potential uses in the food industry.

So why chickens? 

Much scientific research is carried out in models such as mice and rats, however for my research, this is not the case. My work uses chicken embryos. The use of chicken embryos poses fewer problems concerning animal welfare and early chick embryo development is very similar to that of other animals. They are so similar that at early stages it can be very difficult to tell the difference between chicken, human or reptile. Can you tell the difference? I use chicken eggs that are freshly laid and incubated until a certain stage of their growth. Because the embryos are sheltered in an egg, it makes them easy to handle, although if you drop one there is one big omelette on the floor…

Development of Muscles

The official term for muscle development is Myogenesis and it occurs during embryo development. Most of the muscles that form the main body and limbs originate from the mesoderm, one of the several types of tissue that can undergo differentiation. The process of differentiation is when a cell becomes defined to a particular tissue type (e.g. a muscle cell) and it beholds a specific job or function. Think of a student at university: their bachelor’s degree is very broad but is in a defined field, they then go on to do a masters learning about just one specific area. They can then go further, become more ‘defined’, and do a PhD.

Credit: Poultry CRC

Credit: Poultry CRC

During early development the mesoderm forms defined segments called somites. It is from these somites that muscle originates. Normal body (trunk) skeletal muscle forms due to various signals, however, development of the limb muscles uses a completely different set of signals. During limb development, young muscle cells (known as a myoblasts) that express a muscle marker known as Pax 3 move into the limb bud. This movement (or migration) only occurs at specific sites, just like bird migratory events only happen at certain times of the year. Once these young myoblasts have migrated they form two distinct muscle masses: the dorsal and ventral masses. Once these masses have formed, the myoblasts begin to differentiate and express specific markers of differentiated muscle, including Myf5 and MyoD. The muscles of the limb will then continue to grow and develop into the normal defined limbs that everyone recognises.

Why muscle development?

Muscle development provides an excellent model for developmental science. Up until now, research has focused on the regulation and development of somites, and the development of limbs is currently not understood. Nobody understands how limbs grow in such specific locations, therefore I aim to use muscle development in chicken embryos to shed light and understand the processes that regulate differentiation during my PhD project.

 

Helen Anderton

The University of Nottingham

@Helen_Anderton1

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