Posts Tagged ‘genetics’

Alzheimer’s Disease

May 11, 2010

Alzheimer’s disease is the most common form of dementia. Common symptoms include memory loss, confusion, irritability and aggression, mood swings and language breakdown. It is often misdiagnosed as senility. Progression of the disease varies widely. About 26.6 million people were diagnosed with Alzheimer’s in 2006.

There are two types of Alzheimer’s. Late-onset, or sporadic, Alzheimer’s is more common and is diagnosed in people 65 years of age or older. Early-onset, or familial Alzheimer’s disease (FAD), usually develops in adults in their 30’s and 40’s. This type only occurs in about 1 out of every 1000 Alzheimer’s cases. These individuals have a family history of FAD. Genetics has been linked to Alzheimer’s.

Genetics of Alzheimer’s

Genetics and Alzheimer’s are linked but the relationship is not completely understood. If a parent has been diagnosed with FAD, 50% of his offspring will develop it. It is due to autosomal dominant mutations. Therefore, even if a person has only one copy of the gene, he will develop that type. A person who has not developed the disease can not pass it on. Late-onset Alzheimer’s, on the other hand, is not inherited. There are, however, families in which clusters of cases exist.

Three genes have been discovered that influence a person’s risk of getting FAD. These include an amyloid precursor protein (APP) gene and two presenilin genes (PSEN-1 and PSEN-2). These genes exist on chromosomes 1, 14 and 21. A mutation on chromosome 21 causes a build-up in the amount of amyloid protein in the brain. An increase in the amount of amyloid protein has been linked to FAD. Mutations in all of these genes cause senile plaques.

Many genes affect a person’s chances of getting late-onset Alzheimer’s. Some genes are thought to have protective influence. A combination of multiple genes increases the risk of developing it. Only one gene has been identified so far. Apolipoprotein E (APOE) mutations are the cause of about 50% of all late-onset Alzheimer’s. It is found in three forms:

  • APOE2 gives a person some protection against getting Alzheimer’s.
  • APOE3 gives an individual an “average risk” of developing Alzheimer’s.
  • APOE4 increases a person’s risk of getting Alzheimer’s. People with one copy are four times more likely and those with two copies are ten times more likely to develop the disease. Having two copies, however, does not mean that a person will definitely get the disease.

Recent research has, however, made it possible to determine which genes have an influence on developing this disorder. It will only take time to identify these genes. The role of each gene will then be determined. It may then be possible to treat and prevent the disease.

Treatment of Alzheimer’s

Treatment is targeted at alleviating the symptoms of Alzheimer’s. Research has not yet discovered a way to prevent or delay the onset or progression of this condition. Clinical trials are ongoing. Some lifestyle changes that may help include exercise, mental stimulation and a healthy diet. Cardiovascular health and pharmaceutical products may also have an influence on one’s risk.

Cystic Fibrosis: Signs and Symptoms, Causes, Treatment

May 11, 2010

Cystic fibrosis (CF) is a genetic disease affecting the mucus glands of the lungs, pancreas, liver, sinuses, intestines and sex organs. Mucus, which is normally thin and watery, usually keeps tissues moist. Those who develop CF, however, have very thick mucus which results in frequent lung infections. This mucus can block ducts leading to the pancreas as well. Sweat glands are also affected.

Signs and Symptoms of Cystic Fibrosis

Genetic tests can identify individuals with a mutated gene even before they are born. Newborn genetic screening tests can detect the disease as well. Sweat tests must be performed after birth, however, to determine if the individual is a carrier or has the disease. 

Symptoms and severity differ from person to person. One individual may have terrible lung and digestive disorders. Others may not have any symptoms until later in life. Some symptoms include:

  • bloated feeling
  • deficiency in the fat-soluble vitamins A, D, E and K
  • greasy and/or bulky stools
  • intestinal gas
  • malnourished
  • poor growth
  • shortness of breath
  • stomach pain or discomfort.

In advanced cases lung and pancreatic disorders cause many problems. Mucus in the lungs harbors bacteria which cause lung infections and blocks airways making it difficult to breathe. Respiratory failure is a major problem.

Ducts in the pancreas are blocked by mucus as well. The pancreas normally produces digestive enzymes that break down food in the intestines. If the ducts are blocked, proteins and fats will not be metabolized correctly. When this happens, the person suffers from stomach and intestinal disquietude, malnutrition and abnormal stools.

People who have CF have sweat which is five times as salty as a healthy individual’s sweat. Their mineral balance can be upset if they perspire and lose large quantities of sodium, which is very important in the body’s normal functions. This loss can also result in a heat emergency or abnormal heart rhythms.

What Causes Cystic Fibrosis

Medical research has established a genetic link to cystic fibrosis. A single gene on chromosome 7 makes a protein called the cystic fibrosis transmembrane conductance regulator (CFTR). This gene is responsible for making sweat, mucus and digestive juices. This protein controls chloride ions going in and out of cells.

People who have cystic fibrosis have a mutation in the CFTR gene. This means that chloride ions are not capable of getting through the membrane of the cells. In most cases, however, the CFTR protein is missing. The shortened version is identified by the body and destroyed.

CF is inherited and is not contagious. It is a recessive disorder, meaning people with one normal gene and one mutated gene are carriers of the disease. Offspring must inherit the mutated gene from each parent to have symptoms. Offspring of two parents who are carriers have a 25% chance of developing the disease.

Treatment for Cystic Fibrosis

Treatment involves the use of antibiotics and clearing the mucus out of the lungs. They are prescribed enzymes to help them digest their food and obtain nutrients. Surgery is sometimes necessary to clear obstructions. Lung transplants may be required if tissue damage is too severe.

Progress toward a Cure

There is no cure for CF. Cystic fibrosis prognosis is not good. But research gives hope that there is an increasing life expectancy of people with CF. Recent developments in treating and curing the disease are under development. Gene therapy is in the future. This involves placing a normal CFTR gene in the infected cells.

Some other developments toward a cure target the metabolic pathways involved in the disease. These include:

  • Correcting the problems with the lining of the lungs to prevent infections
  • Improving the mucus so it is not so thick
  • New antibiotics
  • New medications to reduce the toxic effects of the inflammatory immune response.

Breast Cancer: Symptoms, Causes, Genetics and Genetic Testing

May 11, 2010

Breast cancer is defined as cancer that originates in the breast cells. Women are 100 times more likely to develop it than men. It is the second most common form of cancer after lung cancer. Every year about 200,000 American women are diagnosed with breast cancer. It killed half a million people in 2005.

Breast cancer can spread through the lymphatic system or blood vessels to other parts of the body. This spread is referred to as metastasizing. It can metastasize to the lungs, brain, liver or bones.

There are non-specific and specific symptoms. Non-specific means that they could be symptoms for some other condition. Some non-specific symptoms include:

  • bone and joint pain
  • chills
  • discharge from one nipple
  • fever
  • jaundice.

Some specific symptoms include change in the size or shape of the breast or nipple and a lump in the breast or the lymph nodes in the armpit and/or collarbone

Inflammatory breast cancer occurs when breast cancer cells enter the small lymph vessels next to the skin. Symptoms include:

  • orange peel texture of the skin
  • pain
  • redness
  • swelling
  • warmth.

Paget’s disease of the breast also manifests itself in the skin and resembles eczema. Symptoms may include:

  • discharge
  • itching
  • lump
  • mild flaking of the skin around the nipple
  • redness
  • sensitivity
  • tingling.

Causes of Breast Cancer

Breast cancer stems from a combination of hereditary and environmental influences. People who have a family history with multiple cases of breast or ovarian cancer are at higher risk of getting breast cancer. Breast cancer is more common if one has an Ashkenazi (Eastern European) Jewish background. It usually occurs sporadically and is not inherited. Some risk factors include:

  • age
  • alcohol intake
  • childbearing
  • environmental factors like radiation and tobacco use
  • high fat intake
  • hormones
  • obesity
  • sex.

Genetics of Breast Cancer

About 5-10% of those diagnosed have a hereditary form of breast cancer. If a person inherits a mutation in the breast cancer 1 (BRCA1) or breast cancer 2 (BRCA2) genes, she is at higher risk of developing breast cancer. It is rare to inherit a mutation. Only one in 1000 has a mutation in one of these genes.

People who have the mutation may get cancer or may lead a long healthy life. Having a mutation does not guarantee the individual will develop cancer. About 13% of the population develops breast cancer. Those with a mutation in either of these genes are three to seven times more likely to get it.

How Genetic Testing Is Done for Breast Cancer Patients

Genetic testing looks at sequences of DNA to identify changes. The sequence of DNA has been determined for healthy people. If there is a mutation in a gene, it can make a person more susceptible to certain diseases. Certain inherited conditions have been linked to mutations in certain genes. Genetic testing is the comparison of the sequence of sample DNA to the agreed upon sequence for a normal gene to identify these risks.

Genetic testing for breast cancer is only performed on people who are at high risk of getting cancer. This blood test identifies the presence of mutations in the BRCA genes. A breast cancer genetic testing lab determines the patient’s risk of getting cancer. Genetic counseling is included in this test to make sure people are informed of their risk and options for the future.

Progress toward a Cure

Treatment for breast cancer today relies heavily on surgery, chemotherapy and radiation. Gene therapy is one option of curing breast cancer. It is not yet possible, but eventually doctors will be able to fix the mutations in the genes. Research continues to search for more genes that influence a person’s risk of developing breast cancer.

Some ways to prevent breast cancer include:

  • Chemoprevention – Some medications, such as tamoxifen, decrease one’s chance of developing cancer.
  • Mastectomy – Preventative removal of breast tissue reduces the risk of cancer by 90%.
  • Surveillance – More frequent self-exams, clinical exams, MRI’s and mammograms discover cancer earlier.

Prostate Cancer: Biology, Genetics, Prevalence

May 11, 2010

Prostate cancer can only occur in men because the prostate is a gland which exists in the male reproductive system. Prostate cancer detection begins with screening for prostate specific antigen (PSA). Detection occurs less often when symptoms develop or by physical examination. Prostate cancer diagnosis is confirmed by biopsy. Risk factors include age, ethnicity, family history and diet.

Prostate cancer is the most common cancer in American men. It can be painful, make urinating difficult and cause erectile dysfunction. Men who are at average risk of prostate cancer have a 14% chance of developing prostate cancer by the time they are 80 years of age. Prostate cancer is the second leading cause of cancer death in men. Many men develop prostate cancer, do not have any symptoms and die of other causes related to old age.

Biology of Cancer

Cancer occurs when genes mutate and do not produce the correct regulatory proteins which normally control cell functions. Cells then multiply out of control. Cancer can spread to other parts of the body, such as bones and lymph nodes. Genes can mutate before a person is born. This is considered to be hereditary. This type of cancer can be inherited by offspring in future generations. Genes can also mutate during a person’s lifetime. The cells derived from this line would then be immortal.

Prostate Cancer Genetics

Most prostate cancer is sporadic, so 75% of individuals with prostate cancer mutated genes after birth. Only 5% of men inherit prostate cancer. The remaining 20% develop familial prostate cancer, which means that a combination of environmental and shared genes resulted in cancer.

Genetics has been implicated in the development of prostate cancer. Every cell contains two copies of each gene; one copy originates from the mother and one from the father. When prostate cancer is inherited, it follows an autosomal dominant inheritance. This means that the mutation only has to occur in one copy of the gene for the individual to be at higher risk of developing cancer. Each child has 50% chance of inheriting the mutation causing prostate cancer from a parent who has the mutation.

The only way a person can know if they are at high risk of having a genetic mutation is genetic testing. Since there is no genetic test for prostate cancer, one must rely on family history. If a man has a strong family history of prostate cancer, he can participate in prostate cancer research to determine what the genes are that are correlated with it.

Prostate cancer risk factors include mutations in several genes. A gene on chromosome 17 is associated with increased risk of prostate cancer.  Research must be continued to verify these findings to determine if they can be used for genetic testing in the future. Several other mutated genes have been identified as being responsible for increased likelihood of developing prostate cancer.

Prevalence of Prostate Cancer

Rates of prostate cancer vary widely throughout the world. It is least prominent in South and East Asia, more common in Europe and most common in the United States. In 2008, about 186,000 men in the US will be diagnosed with prostate cancer. It normally develops in men over 50 years old. An estimated 28,000 deaths will occur from prostate cancer. Although the incidence of prostate cancer is decreasing overall, black men are twice as likely to develop this cancer as white men.

Progress toward a Cure

Prostate cancer prevention may be in the near future. Men can determine their risk factor through their family history and attempt to control certain environmental and lifestyle factors. These factors include a balanced diet, healthy weight, exercising, limiting alcoholic beverages and avoiding tobacco products. Eventually research will determine which genetic mutations are correlated with prostate cancer.