Ectodermal Dysplasia Essay Research Paper The History

Ectodermal Dysplasia Essay, Research Paper

The History of the Disorder

In 1875, Charles Darwin found a new disorder that appeared in each generation of a family, affecting some of the male members and not others. This condition was more prominent in very young people. Darwin also found that the daughters were never affected although they could transmit the disease to their sons, although no males have ever transmitted the disease to their sons. Darwin started the research that led to the discovery of the gene for anhidrotic ectodermal dysplasia (EDA).10

In the early 1970’s, the EDA gene became one of the first gene linked to the X chromosome. An international team of scientists, led by Dr. Juha Kere of the University of Helsinki and Dr. Anand Srivastave from the University of Washington in St. Louis identified the location and the structure of the gene that causes the EDA disorder. The National Institute of Health, the National Institute of Dental Research, and the National Center for Human Genome Research helped sponsor this work at the National Institutes of Health. Scientists provided a molecular marker to identify female carriers of the disorder, and are a step closer to developing the therapeutic interventions to prevent or alleviate symptoms in affected individuals.2

Still, very little is known about what occurs at the molecular level to produce the features of EDA. “Dysplasia” refers to the abnormal development of the tissues, skin, hair, sweat glands, nails, and teeth. The term “anhidrotic” refers to the underdevelopment or absence of sweat glands. This could be life threatening due to the fact that it prevents the body from cooling itself down during things like fevers or hot days.

Of more than 150 different types of ectodermal dysplasia, mutations in the X chromosome account for about half of the cases. The “X linked” form of ectodermal dysplasia is associated with male children. Males have only a single X chromosome inherited from the mother, along with a Y chromosome from the father. So, males don’t have another X chromosome to cover up the infected genes. Women on the other hand, have two X chromosomes and are more likely to not show any symptoms of the abnormal gene.

Two female patients with all the symptoms of X-linked EDA led Dr. Kere, Dr. Srivastave, and other colleagues to the discovery of this gene. Earlier work by Jonathan Zonana, identified an unusual chromosomal rearrangement in one of the girls. The X chromosome had been sheared in two, with one piece sticking to the end of chromosome 9 and the remainder forming a truncated X. A similar X translocation was identified by other investigators in the second girl. Although the break points occurred in slightly different locations, both destroyed the function of the EDA gene. This indicated that the breaks occurred within the region of the chromosome that contains the gene. In other disorders where X translocations have been identified as the cause, the normal X chromosome is inactivated, leaving no functional copy of the gene. The disorder is the same as it would be in males.7

Several different studies following the inheritance pattern of the known genetic markers on the X chromosome have narrowed the position of the gene to a region called the “Xq12-q13.1” Once this region had been identified, the DNA sequences of genes needed to be studied.2

In one of the studies, scientists identified a gene in the region of the X chromosome that contained the molecular code to produce a 135-amino acid protein. This protein has a structure compatible with a transmembrane molecule, a protein that is part of the cell membrane. The protein was detected in fetal tissues and certain types of adult skin cells that are consistent with the pathology of EDA. The function of this protein still remains unknown.2

Symptoms and Progression

Before a fetus is large enough to be seen, a thin layer of cells covers the outside of the body. This layer of cells is known as the ectoderm. From this layer, skin, hair, nails, teeth nerve cells, sweat glands, parts of the eye, and parts of the ear are developed. Each of these things is then known as a ectodermal structure. There are many disorders that include one of these structures, and are not properly called ED. A combination of defects involving more than one of these structures, should be called ED.

There are many different symptoms for ED and each combination of one or more symptoms are classified in its own category. The skin is lightly pigments and appears thin, and the surface of blood vessels may be visible. The skin around the eyes is wrinkled and the skin of the palms and soles of the feet may be thick. Some other symptoms for ED may include:

. Absence of sweat glands

. Malformed finger/toe nails

. Multiple missing teeth

. Sparse hair, eyelashes and brows

. Cleft lip and palate

. Deficient tears and saliva

. Frequent respiratory infections

. Hearing or sight defects

. Missing fingers or toes

. Poorly functioning mucous membranes

. Problem with the immune system

. Other abnormalities of the ectoderm

. Prominent forehead

. Flat or depressed bridge of the nose

. Absence of mammary glands

. Peg teeth

. Foul-smelling nasal discharge

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