Chromosome X News and Research

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The X chromosome is one of the two sex chromosomes in humans (the other is the Y chromosome). The sex chromosomes form one of the 23 pairs of human chromosomes in each cell. The X chromosome spans about 155 million base pairs (the building blocks of DNA) and represents approximately 5 percent of the total DNA in cells.

Each person normally has one pair of sex chromosomes in each cell. Females have two X chromosomes, while males have one X and one Y chromosome. Early in embryonic development in females, one of the two X chromosomes is randomly and permanently inactivated in somatic cells (cells other than egg and sperm cells). This phenomenon is called X-inactivation or Lyonization. X-inactivation ensures that females, like males, have one functional copy of the X chromosome in each body cell. Because X-inactivation is random, in normal females the X chromosome inherited from the mother is active in some cells, and the X chromosome inherited from the father is active in other cells.

Some genes on the X chromosome escape X-inactivation. These genes are located at the tip of the short (p) arm of the X chromosome in an area known as the pseudoautosomal region. Although many genes are unique to the X or Y chromosome, genes in the pseudoautosomal region are present on both chromosomes. As a result, men and women each have two functional copies of these genes. Many genes in the pseudoautosomal region are essential for normal development.

Identifying genes on each chromosome is an active area of genetic research. Because researchers use different approaches to predict the number of genes on each chromosome, the estimated number of genes varies. The X chromosome likely contains between 900 and 1,400 genes.

Genes on the X chromosome are among the estimated 20,000 to 25,000 total genes in the human genome.

Two specific genes, Wnt4 and Fgf9 fight to determine sexual differentiation

Whether or not a fertilized mammalian egg ultimately develops into a male or female is determined by the winner of a tug of war between two different genes encoding signaling proteins and the divergent pathways they control.

1 Jun 2006

Potential novel treatment strategy for Ewing's sarcoma

Using molecular and cell-based models, researchers at Georgetown University Medical Center have refined the picture of how a cancer-promoting protein associated with Ewing's sarcoma functions.

1 Jun 2006

Sperm donor passes rare dangerous disease on to four children

According to a new report in the U.S., a sperm donor may have unwittingly passed an extremely rare and dangerous genetic ailment to five children born to four couples.

22 May 2006

Telomere erosion may lead to shorter life expectancy in men

This new study published in the journal "Cytogenetic and Genome Research" shows significantly shorter telomeres and higher erosion rates in men than in women, which likely causes a shorter life expectancy of male cells and tissues.

17 May 2006

Genetic cause of hearing loss in aging

Researchers at Indiana University School of Medicine have taken a step toward understanding the genetics that make people more susceptible to the loss of hearing as they age.

17 May 2006

Researchers link novel mutated gene to mental retardation and imbalance syndrome

Researchers at the University of California, San Diego School of Medicine have identified a genetic cause for a form of pediatric brain malformation involving the cerebellum.

11 May 2006

New understanding of chromosomal glue

Researchers have a new understanding of the process cells use to ensure that sperm and eggs begin life with exactly one copy of each chromosome - a process that must be exquisitely regulated to prevent problems such as miscarriages and mental retardation.

8 May 2006

New approaches to genetic disease, based on cells' own ability to correct themselves

New approaches to genetic disease, based on cells' own ability to correct themselves, will be outlined today at the annual conference of the European Society of Human Genetics in Amsterdam, The Netherlands.

8 May 2006

Mutated gene leads to JSRD

The research team, directed by Joseph Gleeson, M.D., Director of the Neurogenetics Laboratory at the UCSD School of Medicine and associate professor in the Department of Neurosciences, have identified a new gene that, when mutated, leads to JSRD. Their findings will be published on-line in advance of publication in the journal Nature Genetics.

8 May 2006

Environmentally damaged DNA may contribute to human genetic diversity

In this month's issue of the leading scientific journal Genome Research, scientists from Kyushu University report how environmentally damaged DNA may contribute to human genetic diversity.

2 May 2006

Finding indicate why some kinds of Leukemia are more aggressive than others

New clues to why some kinds of leukemia are more aggressive and deadly than others are coming from research examining the types of genetic damage that allow some blood cells to grow out of control, scientists report.

28 Apr 2006

Blood cancers may be caused by inactivation of a "tumor suppressor" gene

The discovery of a gene, called PRDM1, as a tumor suppressor sheds new light on the cause - and possible treatment - of diffuse large B-cell lymphomas (DLBCLs), a cancer of the blood's B-lymphocytes. DLBCLs comprise about 30 percent of non-Hodgkin's lymphomas.

25 Apr 2006

Cancer found grow by switching off DNA - may lead to new generation treatments

Cancer researchers have formulated a new concept for how cancer cells can escape normal growth controls by turning off DNA. These findings may have far-reaching implications for the new generation of cancer therapies.

25 Apr 2006

Arf gene loss enhances oncogenicity and limits imatinib response in mouse models of Bcr-Abl-induced acute lymphoblastic leukemia

23 Apr 2006

New method designed to analyze the genes that regulate the immune system

Seattle scientists have developed a new method for analyzing the Major Histocompatibility Complex (MHC) of the human genome.

20 Apr 2006

Promising treatment for Huntington's disease soon to be tested clinically

At the Institut Curie, CNRS and Inserm researchers have shown that cysteamine, which is already used to treat a rare disease called cystinosis, prevents the death of neurons in Huntington's disease. Like Alzheimer's and Parkinson's, Huntington's disease, is characterized by the abnormal death of neurons.

19 Apr 2006

Researchers develop system for observing nuclear motion

The cell is understood to be highly organized, with specialized areas for different functions and molecular motors shuttling components around.

18 Apr 2006

First gene therapy human trial in the United States for a form of muscular dystrophy under way

The clinical trial for Duchenne muscular dystrophy (DMD) tests the safety and effectiveness of a therapy that was developed over two decades by scientists at the University of North Carolina Chapel Hill's School of Medicine and the University of Pittsburgh.

16 Apr 2006

Dasatinib provides significant benefit in chronic myeloid leukemia patients resistant to Gleevec

A study led by researchers from the Howard Hughes Medical Institute has found that dasatinib provides significant benefit in chronic myeloid leukemia (CML) patients resistant to Gleevec. (imatinib), according to a study presented during the 97th Annual Meeting of the American Association for Cancer Research.

11 Apr 2006

Researchers identify the role of a protein in hemoglobin gene silencing

Virginia Commonwealth University Massey Cancer Center researchers have identified the role of a protein in hemoglobin gene silencing that may one day be a potential target for the treatment of genetic blood disorders like sickle-cell anemia and beta-thalassemia on the molecular level.

11 Apr 2006