Connective Tissue & Genes

What is connective tissue?

Connective tissue is one of the four basic tissue types. It supports, connects, or separates different types of tissues and organs of the body. In addition to providing structural support, connective tissue also determines the elasticity of the body’s organs, bones, ligaments, as well as helping to control how the body grows and develops.

Explaining genetic disorders:

Genes are stretches of DNA, most of which is located in the cell’s nucleus. Genes are coded instructions for making proteins, which are produced within the cell. When they suffer mutations, genes work abnormally, which means the protein the gene codes for is either altered or missing. As a result, genetic disorders happen.

About Marfan syndrome gene mutation:

Connective tissue is made up of proteins, one of which is a large protein called fibrillin-1, produced in cells called fibroblasts. The gene responsible with giving instructions for making fibrillin-1 is called the FBN1 gene.

There are many gene mutations that cause Marfan syndrome. Some mutations change one of the amino acids that make up the fibrillin-1 proteins, while others code abnormal fibrillin-1 proteins that don’t function properly. Mutations that cause Marfan syndrome also reduce the amount of fibrillin-1 protein produced by the cells, alter their structure and stability, or just hinder the transport of the protein out of the cell.

Fibrillin-1 and the transforming growth factor beta protein (TGF-β):

The Fibrillin-1 protein is transported out of cells into the extracellular matrix, which is a collection of extracellular molecules secreted by cells. The extracellular matrix is essential because it assures structural integrity of connective tissue. In the matrix, fibrillin-1 molecules and other proteins bind together to form fiber like strands called microfibrils.

Microfibrils form elastic fibers, which enable the skin, ligaments, and blood vessels to stretch and resume their normal shape after distortion. They also provide support to tissue such as those that support the nerves, muscles, and lenses of the eyes.

Microfibrils also store protein called transforming growth factor beta, (TGF-β) TGF-β helps control the multiplication, cellular differentiation (process by which cells specialize to carry out specific functions), cell movement, and other functions in cells. Microfibrils help regulate the availability of TGF-β, which is turned off (inactivated) when stored in microfibrils and turned on (activated) when released.

The gene mutations specific to Marfan syndrome reduce the amount of fibrillin-1 available to form microfibrils. Without enough microfibrils, excess TGF-β growth factors are activated and elasticity in many tissues is decreased, which causes the overgrowth and instability of tissues. As a result, the connective tissue in the heart, blood vessels, lungs, eyes and skeletal and nervous systems and other tissues can stretch and weaken.

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