Chromosome 22
22q11.2 deletion syndrome is a disorder that involves heart defects, an opening in the palate (cleft palate), distinctive facial features, low calcium levels and an increased risk of behavioral problems and mental illnesses such as schizophrenia. Most people with 22q11.2 deletion syndrome are missing approximately 3 million base pairs in a copy of chromosome 22 in each cell. Elimination occurs near the middle of the chromosome at a location designated as q11.2. This region contains 30 to 40 genes, but many of these genes have not been fully studied. It is believed that the loss of a particular gene, TBX1, is responsible for many of the characteristics of the syndrome.
Duplication of 22q11.2 is caused by an additional copy of some genetic material at position q11.2 on chromosome 22. In most cases, this additional genetic material consists of a sequence of approximately 3 million base pairs ( 3 Mb) This sequence is the same that is missing in the 22q11.2 deletion syndrome. A small percentage of affected individuals have a shorter doubling in the same region. Duplication affects one of two copies of chromosome 22 in each cell.
22q13.3 deletion syndrome, also called Phelan-McDermid syndrome, is caused by a deletion near the end of the long arm (q) of chromosome 22. A ring chromosome 22 can also cause the syndrome. Researchers believe that several critical genes near the end of the q arm of chromosome 22 are lost when the chromosome 22 ring is formed. If the breaking point in the long arm is at the position of chromosome 22q13.3, people with the Ring chromosome 22 will experience signs and symptoms similar to those of a simple deletion. It is believed that the loss of a particular gene, SHANK3, is responsible for many of the characteristic features such as developmental delay, intellectual disability and absent or very delayed speech; They may also suffer from certain autism traits, episodes of nausea and vomiting and in fewer cases may suffer seizures.
Chronic myeloid leukemia is due to a reorganization (translocation) of genetic material between chromosome 9 and 22. This slow-growing cancer leads to an overproduction of abnormal white blood cells. The excess of white blood cells results in detriment of the production of red blood cells and platelets. Common characteristics of the condition include excessive tiredness (fatigue), fever, weight loss and enlargement of the spleen.
The translocation involved in this condition, written as t (9; 22), fuses part of the ABL1 gene on chromosome 9 with part of the BCR gene on chromosome 22, creating an abnormal fusion gene called BCR-ABL1, resulting from this fusion. He is known as the Philadelphia chromosome. It is a somatic mutation. The protein produced by the BCR-ABL1 gene tells cancer cells to continue dividing abnormally and prevents them from self-destruct, leading to the overproduction of abnormal cells and the shortage of normal blood cells.
The Philadelphia chromosome has also been found in some cases of rapid progression blood cancers known as Acute leukemia.
Dermatofibrosarcoma protuberans. it is due to a translocation of genetic material between chromosomes 17 and 22, written as t (17; 22), causes a rare type of skin cancer (see chromosome 17)
Emanuel syndrome. it is due to the presence of additional material on chromosomes 11 and 22, a condition also known as derivation of chromosome 22 der (22), which happens when the translocation of genetic material between the chromosomes involved is not done in a balanced way, that is that genes are lost or gained. In this particular case, individuals have 3 copies of some genes, which alter their functions resulting in intellectual disability and birth defects. (see chromosome 11)
Ewing's sarcoma is a type of cancerous tumor caused by translocations of chromosome 22. These types of tumors develop in the bones (the common month) or soft tissues, such as cartilage and nerves. It occurs more frequently in children and young people, it can cause fever and broken bones. The most common translocation, t (11; 22), fuses part of the EWSR1 gene on chromosome 22 with part of the FLI1 gene on chromosome 11, creating the fusion gene EWSR1 / FLI1. These types of mutations are somatic. This gene is involved in the transcription of a series of proteins. Deregulation of transcription leads to uncontrolled growth and division (proliferation) and abnormal maturation and survival of cells, which causes the development of tumors.
Opitz G / BBB Syndrome. it is caused by a deletion on a copy of chromosome 22. This condition causes several abnormalities along the midline of the body, including widely separated eyes (ocular hypertelorism), difficulty breathing or swallowing (trachea and esophageal malformation), malformations brain, (delayed motor skills, disability in social skills), absent or underdeveloped corpus callosum, distinct facial features and genital abnormalities (undescended testicles, exit from the urethra under the penis) in men. The deletion that causes the Opitz G / BBB syndrome is in the same area as the deletion that causes the 22q11.2 deletion syndrome, so it is often considered part of that syndrome.
A small percentage of individuals with schizophrenia have a small deletion in a region of chromosome 22 called 22q11. The 22q11 region contains several genes that are believed to affect the risk of schizophrenia. In addition to schizophrenia, some people with this deletion have additional signs and symptoms that include a condition called 22q11.2 deletion syndrome (described above).
Cat's eye syndrome is a rare disorder most often caused by a chromosomal change called inverted duplicate 22. In people with this condition, each cell has at least one additional small chromosome composed of genetic material from chromosome 22 that has doubled abnormally The additional genetic material causes the characteristic signs and symptoms of cat's eye syndrome, including an abnormality in the eye called iris coloboma (a gap or division in the colored part of the eye), small skin marks or pits in front of the ear, abnormal ear formation, heart defects, kidney problems, malformations of the anus and, in some cases, developmental delay.
Other changes in the number or structure of chromosome 22 can have a variety of effects such as intellectual disability, delayed development, language problems, distinctive facial features and behavioral problems. Frequent changes in chromosome 22 include an extra piece of chromosome in each cell (partial trisomy), a missing segment of the chromosome in each cell (partial monosomy) and a ring chromosome 22. Translocations of genetic material between chromosomes can also lead to additional or missing material from chromosome 22. The most common of these translocations involves chromosomes 11 and 22.
