in
herman is dependent
recessive gene
Jurneile muscular destropp
on sen linked
intesive
33 cases were found in pop of some
800.000 people. Early age of disease
expressed is only male most
of
those who had it died
upon
early age m.none upon 21 age
Answers
Answer:
DMD is an X-linked recessive progressive myopathy, with an
incidence of about 1 in 3500 male live births [2] was first described by
French neurologist Guillaume Benjamin Amand Duchenne in 1860s.
DMD is described as progressive myopathy leading to muscle
weakness and eventually its degradation. Muscle weakness progresses
from hip girdle muscles and neck flexors, the shoulder girdle and distal
limb and trunk muscles. Usually boys are affected at the age of 3 to 5
years, present due to difficulty in climbing stairs or rising from sitting
position, most patients using Gowers maneuvers, and enlarged calf
muscles are present classically, due to replacement of muscles by fats
by the age of 12 years. Patients can survive beyond 20 years of age in
areas with advanced medicine but usually die due to respiratory failure
or cardiac failure as about 95% patients with DMD develop cardiac
abnormalities or both [2] in absence of advanced support. Serum
creatine kinase levels are grossly elevated above normal limit. DMD
patient have on average IQ approximately 1 standard deviation below
the mean.
Discussion
Dystrophin is a structural protein in skeletal muscle, cardiac muscle
and brain. It interacts with multimeric protein complex associated
with sarcolemma proteins which plays an important role to maintain
integrity of muscle membrane [2].
Molecular genetic studies indicate that dystrophin is a huge gene
located on the short (p) arm of the X chromosome at position 21.2.and
about two thirds of mutations in this gene lead to DMD but no clear
correlation found between the extent of deletion and severity of
disorder. The protein product of the human and mouse DMD loci by
using polyclonal antibodies directed against fusion proteins reflecting
2 distinct regions of the mouse cDNA. The protein, called dystrophin,
is about 400 kD in size and represents about 0.002% of total striated
muscle protein [3].
The finding of dystrophin mRNA in brain may explain mental
retardation in DMD patients [4]. Dystrophin in brain is transcribed
from a different promoter from that used in muscle. The brain-type
promoter of the dystrophin gene is highly specific to neurons. By
contrast, the muscle-type promoter is active in a wider range of cell
types, including not only striated and smooth muscle, but also glial
cells to a lesser extent, and probably neurons [5].
The replacement of the missing protein, dystrophin, using myoblast
transfer in humans or viral/liposomal delivery in the mouse DMD
model is insufficient and short-lived. An alternative approach to
treatment would be to upregulate the closely related protein, utrophin,
which might be able to compensate for the dystrophin deficiency in all
relevant muscles [6].
Acknowledgement
Mr. Ateeq Ur Rehman, Institute of Physical Medicine and
Rehabilitation (IPM&R)
References
1. Richard A, Thompson MD, Paul JV Jr, Cleveland MD (1959) Serum
aldolase in muscle disease. AMA Arch Intern Med. 103 (4): 551-564.
2. Nussbaum R, McInnes RR, Willard HF (2007) Thompson & Thompson
genetics in medicine. Elsevier Health Sciences.
3. Hoffman EP, Brown RH Jr, Kunkel LM (1987) Dystrophin: The protein
product of the Duchenne muscular dystrophy locus. Cell 51: 919-928.
4. Chamberlain JS, Pearlman JA, Muzny DM, Gibbs RA, Ranier JE, et al.
(1988) Expression of the murine duchenne muscular dystrophy gene in
muscle and brain. Science 239: 1416-1418.
5. Chelly J, Kaplan JC, Maire P, Gautron S, Kahn A (1988) Transcription of
the dystrophin gene in human muscle and non-muscle tissues. Nature
333: 858-860.
6. Tinsley JM, Potter AC, Phelps SR, Fisher R, Trickett JI, et al. (1996)
Amelioration of the dystrophic phenotype of mdx mice using a truncated
utrophin transgene. Nature 384: 349-353.
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