Turner Syndrome

NewsRx Bundle A quick and inexpensive way to view the most recent articles for a one-time project. Custom Reports on Turner Syndrome Tired of prepackaged reports that just don't meet your needs? Target your needs!

What is Turner syndrome?

Turner syndrome is a chromosomal condition that affects development in females. Women with this condition tend to be shorter than average and are usually unable to conceive a child (infertile) because of an absence of ovarian function. Other features of Turner syndrome can include extra skin on the neck (webbed neck), puffiness or swelling (lymphedema) of the hands and feet, skeletal abnormalities, heart defects, and kidney problems. Developmental delays, learning disabilities, and behavioral problems are also possible, although these characteristics vary among affected females.

How common is Turner syndrome?

This condition occurs in about 1 in 2,500 female births worldwide, but is much more common among pregnancies that do not survive to term (miscarriages and stillbirths). Prenatal testing has probably decreased the number of diagnosed cases of this disorder.

What are the genetic changes related to Turner syndrome?

Turner syndrome is a chromosomal condition related to the X chromosome.

The SHOX gene is associated with Turner syndrome.

People typically have two sex chromosomes in each cell; females have two X chromosomes, while males have one X chromosome and one Y chromosome. Turner syndrome results when a female's cells have one normal X chromosome and the other sex chromosome is missing or altered. The missing genetic material affects development and causes the characteristic features of the condition.

About half of individuals with Turner syndrome have monosomy X, which means each cell in the individual's body has only one copy of the X chromosome instead of the usual two sex chromosomes. Turner syndrome can also occur if one of the sex chromosomes is partially missing or rearranged rather than completely missing. Some women with Turner syndrome have a chromosomal change in only some of their cells, which is known as X-chromosome mosaicism.

Researchers have not yet determined which genes on the X chromosome are responsible for most signs and symptoms of Turner syndrome. They have, however, identified one gene called SHOX that is important for bone development and growth. Missing one copy of this gene likely causes short stature and skeletal abnormalities in women with Turner syndrome.

Can Turner syndrome be inherited?

Most cases of this condition are not inherited, but occur as random events during the formation of reproductive cells (eggs and sperm). An error in cell division called nondisjunction can result in reproductive cells with an abnormal number of chromosomes. For example, an egg or sperm cell may lose a sex chromosome as a result of nondisjunction. If one of these atypical reproductive cells contributes to the genetic makeup of a child, the child will have a single X chromosome in each cell and will be missing the other sex chromosome.

X-chromosome mosaicism is also not inherited. It occurs as a random error during cell division in early fetal development. As a result, some of an affected person's cells have the usual two sex chromosomes (either two X chromosomes or one X chromosome and one Y chromosome), and other cells have only one copy of the X chromosome.

Source: National Institutes of Health

Scientists at Babraham Institute target attention deficit hyperactivity disorder genetics

"Under attentionally demanding conditions 39,XO mice displayed impaired discriminative response accuracy and slowed correct reaction times relative to 40,XX mice; these deficits were alleviated in a version of the task with reduced attentional demands. Parental origin of the X did not affect performance of the 5-CSRTT. In contrast, the attentional phenotype was rescued in 40,XY*X mice possessing a single maternally inherited X chromosome and a small Y*X chromosome that comprises a complete pseudoautosomal region (PAR), and a small X-specific segment. Our findings are consistent with an X-monosomy effect on attention and suggest the existence of X-linked gene(s) that escape X-inactivation, are present on the small Y*X chromosome and impact on attentional functioning; the strongest candidate gene is Sts, encoding steroid sulfatase," wrote W. Davies and colleagues, Babraham Institute.

The researchers concluded: "The data inform the TS literature and indicate novel genetic mechanisms that may be of general significance to the neurobiology of attention."

Davies and colleagues published the results of their research in Biological Psychiatry (X-monosomy effects on visuospatial attention in mice: a candidate gene and implications for Turner syndrome and attention deficit hyperactivity disorder. Biological Psychiatry, 2007;61(12):1351-60).

For additional information, contact W. Davies, Laboratories of Cognitive and Behavioral Neuroscience and Developmental Genetics and Imprinting, The Babraham Institute, Babraham Research Campus, Babraham, UK.

The publisher of the journal Biological Psychiatry can be contacted at: Elsevier Science Inc., 360 Park Avenue South, New York, NY 10010-1710, USA.

Keywords: United Kingdom, Babraham, Attention Deficit Hyperactivity Disorder Genetics, ADHD, Attention Deficit Hyperactivity Disorder, Developmental Disabilities, Endocrinology, Genetics, Mental Health, Psychiatry, Turner Syndrome.

This article was prepared by Mental Health Weekly Digest editors from staff and other reports. Copyright 2007, Mental Health Weekly Digest via NewsRx.com.