What is the cause of muscular dystrophy?

Answer 1

Duchenne muscular dystrophy is caused by a nonsence mutation in the dystrophin gene on the x-chromosome, this type mutation that occuurs in duchenne is what sets it apart from beckers or any other dystrophy. a nonsence mutation is a point mutation(additon or sutraction of a nucleotide in an exon) which causes the gene for dystrophin to be read half way which in turn causes muscle wasting.

Answer 2

The muscular dystrophies are a group of muscle wastage diseases with many different causes. Excuse me for focusing on one type.

Duchenne muscular dystrophy (DMD) is the most common and, unfortunately, also one of the most severe muscular dystrophies. It is caused by one or more genetic mutations on the X chromosome (within the DMD gene), causing the subsequent 'loss' of a very important protein, dystrophin, nearly always in males. Humans have two copies of every gene in every cell of their body* (one from the mother and one from the father). In cases where one copy of a gene is faulty, it is often the case that the healthy gene can compensate. Human males have only one X chromosome, so if they are given a faulty version of the DMD gene by their mother (they have to get a complementary Y chromosome from their father) they will have DMD. Because females can carry a faulty DMD gene without presenting any symptoms of the disease, the condition can lie hidden within a family until a male is born with the condition. It should also be noted that the DMD gene is the largest in the human genome (the entire catalogue of approx 20,000 genes in humans), making it more susceptible to random mutation than most other genes and allowing the possibility that the disease can arise in a family without maternal carriers. NOTE every time a cell divides (happens to most cells a lot) there is a chance that mutations are adopted into the genome without repair, but for this to become part of a whole body this mutation must happen in a parent's sperm or egg when it is created or in a 'stem' cell at a very early stage of human development (this mutation may then be passed down to every further cell derived from this mutant).

The genetic cause of DMD has been known since the 1980s but the cellular changes that happen as a result of the loss of the dystrophin and that cause the symptoms of DMD, are still being defined. Dystrophin is predominantly a structural protein. Within muscle, dystrophin is located on the inside of the cell at the membrane border where it has an integral role coupling the molecular skeleton of the cell to the scaffolding matrix on the outside of the cell (via a large protein complex actually spanning the muscle cell membrane). In this model, dystrophin helps to stabalise the muscle membrane during muscle contraction and stretch. When dystrophin is absent in DMD, the muscle membrane is fragile. When the muscle memebrane is torn, the chemical composition of the muscle cell is changed and danger signals are released to the outside of the cell. If compromised too much, individual muscle cells can die. The danger signals that are released from dying cells can cause chronic inflammation. In a healthy muscle cell, temporary inflammation following stress (exercise or damage) can premote muscle regrowth, but in DMD, perpetual inflammation and regrowth ultimately leads to compromised and exhausted muscle, that becomes progressively less able to regenerate. Muscle cells are also normally arranged in structured functional arrays so as best to work together when needed (a single muscle like biceps brachii is made up of thousands of individual muscle fibres/cells). In DMD muscle these arrays become progressively more disarrayed upon cycle and cycle of cell death, repair, and replacement, also contributing to loss of voluntary muscle force. Eventually in humans, DMD muscle fibres lose their ability to regenerate and are heterogeneously replaced with fat.

Muscle is repaired in humans by satellite cells, a special population of stem-cell-like cells that normally reside on the outside of muscle fibres until recruited to repair damaged muscle or to coalesce to form new fibres. There is some evidence that these cells specifically exhaust through repeated cycles of division necessary to maintain working numbers.

The dystrophin protein, in one form or another, is also normally found in the brain, including at the blood brain barrier, the cerebellum, and the hippocampus. Versions are also found in the retina and the kidney. In DMD, dystrophin expression may also be lost at these sites contributing to the complicated pathology.

Finally, certain genetic mutations cause shorter but semi-functional versions of the dystrophin protein to be maintained in muscle or in any of the above sites. Due to many versions of these shorter dystrophin proteins being semi-functional, a less severe form of muscular dystrophy than DMD can arise, termed Becker muscular dystrophy (BMD).

*not including the gametes (sperm and eggs) that are made and stored for sexual reproduction

Answer 3

DMD, BMD, CMD, and most forms of LGMD, are due to defects in the genes for a complex of muscle proteins. This complex spans the muscle cell membrane to unite a fibrous network on the interior of the cell with a fibrous network on the outside

Answer 4

Muscular dystrophy, just like cystic fibrosis, is due to a severe selenium deficiency. Selenium is one of the essential minerals needed to sustain life. Most persons are also very low in the mineral zinc, as well. Most authorities will tell you that both diseases are hereditary diseases which means the information to have the disease is coded in your DNA and therefore can not be fixed... You inherited the disease. In the case of both Muscular Dystrophy and Cystic Fibrosis, the condition is due to mineral deficiency. Linus Pauling, winner of the Noble peace prize for his studies with vitamin C, proved that ALL diseases are due to mineral deficiencies, and if person is given the missing minerals in their diet their condition will reverse itself.