Related Genetic Counseling Issues
Use of APOE genotyping for predictive testing
In contrast to the use of APOE testing as an adjunct diagnostic test in individuals with dementia, there is general agreement that APOE testing has limited value used for predictive testing for AD in asymptomatic persons. Data suggest that a young asymptomatic person with the APOE e4/e4 genotype may have an approximately 30% lifetime risk of developing AD. Further refinement of this risk reveals that women with an APOE e4/e4 genotype have a 45% probability of developing AD by age 73 years, whereas men have a 25% risk. These risks are lowerand the likely age of onset laterfor persons with only one APOE e4 allele or no APOE e4 allele . These estimates are not generally considered clinically useful however, a research study to assess the potential use of APOE testing in relatives of individuals with late-onset AD is under way.,
Down syndrome
Family members of persons with DS are not at increased risk for AD.
Do Genes Cause Diseases
Genetic mutations can cause diseases. If a person inherits a genetic mutation that causes a certain disease, then he or she will usually get the disease. Sickle cell anemia, cystic fibrosis, and some cases of early-onset Alzheimer’s disease are examples of inherited genetic disorders.
Other changes or differences in genes, called genetic variants, may increase or decrease a person’s risk of developing a particular disease. When a genetic variant increases disease risk but does not directly cause a disease, it is called a genetic risk factor.
Identifying genetic variants may help researchers find the most effective ways to treat or prevent diseases such as Alzheimer’s in an individual. This approach, called precision medicine, takes into account individual variability in genes, environment, and lifestyle for each person.
The expression of geneswhen they are switched on or offcan be affected, positively and negatively, by environmental and lifestyle factors, such as exercise, diet, chemicals, or smoking. The field of epigenetics is studying how such factors can alter a cell’s DNA in ways that affect gene activity.
Health Environmental And Lifestyle Factors
Research suggests that a host of factors beyond genetics may play a role in the development and course of Alzheimers. There is a great deal of interest, for example, in the relationship between cognitive decline and vascular conditions such as heart disease, stroke, and high blood pressure, as well as conditions such as diabetes and obesity. Ongoing research will help us understand whether and how reducing risk factors for these conditions may also reduce the risk of Alzheimers.
A nutritious diet, physical activity, social engagement, and mentally stimulating pursuits have all been associated with helping people stay healthy as they age. These factors might also help reduce the risk of cognitive decline and Alzheimers. Researchers are testing some of these possibilities in clinical trials.
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Causes Of Alzheimers: Is It Hereditary
Increasing cases of Alzheimers disease
The Alzheimers Association states that Alzheimers disease is the sixth leading cause of death in the United States, and that more than 5 million Americans are affected by the condition. Additionally, one out of three seniors dies of Alzheimers or some other type of dementia. That number will likely increase as the aging population increases.
Scientists have been researching Alzheimers for decades, but still there is no cure. Learn more about how genes are related to the development of Alzheimers, as well as other potential causes of the condition.
Genetic And Hereditary Risk Factors For Alzheimer’s Disease
Alzheimers disease is an incurable condition, involving the loss of memory and cognitive skills. As the incidence of Alzheimers continues to rise, so too does the push for medical science to discover the cause of the disease. Is it genetic? If so, what are the hereditary risk factors of Alzheimers disease?
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Nebula Genomics Dna Report For Alzheimers Diseases
Is Alzheimers disease genetic? We created a DNA report based on a study that attempted to answer this question. Below you can see a SAMPLE DNA report. To get your personalized DNA report, purchase our Whole Genome Sequencing!
To learn more about how Nebula Genomics reports genetic variants in the table above, check out the Nebula Research Library Tutorial.
How Genes Influence Alzheimers
Genes literally control every function in each of the human bodys cells. Some genes determine the characteristics of the body, such as a persons eye or hair color. Others make a person more likely to get a disease.
Several genes have been identified that are linked to Alzheimer’s disease. Some of these genes can increase the risk of getting Alzheimers . Other genes, most of which are rare, guarantee that a person will develop a disease. These are called deterministic genes.
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More Alzheimers Research Is Needed
Experts continue to research the complex biological and environmental factors that influence Alzheimers disease, but, if you are concerned about your risks, talk to your doctor about your family history and other health concerns that you may have.
Early detection is crucial to getting the maximum benefits of treatment, and it can give you more time and more say in planning for your future.
Has heredity been a factor in your loved ones Alzheimers diagnosis? Please share your story in the comments below.
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Symptoms And Symptoms Of Alzheimer ‘s Disease
about different diseases and genetic disorders. One genetic disorder that has affected the lives of many is, Alzheimers Disease. Alzheimers is the most common type of dementia that affects and causes problems with thinking, behavior and memory. Most of the time, symptoms of Alzheimers develop slowly and progress and worsen over time. Eventually the symptoms become severe enough that they begin to interfere with normal and daily tasks. It was originally thought that Alzheimers was a result
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Effect Of Genes In Other Types Of Dementia
Some types of dementia have links to other genetic malformations.
Huntingtons disease, for example, alters chromosome 4, which can lead to progressive dementia. Huntingtons disease is a dominant genetic condition. This means that if either parent has the condition, they can pass on the gene to their offspring and they will develop the disease.
Symptoms of Huntingtons disease do not usually become evident until a person reaches 3050 years of age. This can make it difficult for doctors to predict or diagnose before a person has children and passes on the gene.
Researchers think that dementia with Lewy bodies or Parkinsons dementia may also have a genetic component. However, they also believe that other factors outside of genetics might play a role in the development of these conditions.
Researchers have identified several risk factors for Alzheimers disease.
These include:
- difficulty recognizing people
- frequently misplacing objects and belongings
The aging process might naturally impair a persons memory, but Alzheimers disease leads to more consistent periods of forgetfulness.
Over time, a person with Alzheimers may need an increasing amount of assistance with daily living, such as brushing teeth, getting dressed, and cutting food.
They may also experience agitation, restlessness, personality withdrawals, and speech problems.
The Genetics Of Alzheimers Disease
Robert C. Barber
1Department of Pharmacology and Neuroscience, University of North Texas Health Science Center, 3500 Camp Bowie Boulevard, Fort Worth, TX 76107, USA
Abstract
Alzheimers disease is a progressive, neurodegenerative disease that represents a growing global health crisis. Two major forms of the disease exist: early onset and late onset . Early onset Alzheimers is rare, accounting for less than 5% of disease burden. It is inherited in Mendelian dominant fashion and is caused by mutations in three genes . Late onset Alzheimers is common among individuals over 65 years of age. Heritability of this form of the disease is high , but the etiology is driven by a combination of genetic and environmental factors. A large number of genes have been implicated in the development of late onset Alzheimers. Examples that have been confirmed by multiple studies include ABCA7, APOE, BIN1, CD2AP, CD33, CLU, CR1, EPHA1, MS4A4A/MS4A4E/MS4A6E, PICALM, and SORL1. Despite tremendous progress over the past three decades, roughly half of the heritability for the late onset of the disease remains unidentified. Finding the remaining genetic factors that contribute to the development of late onset Alzheimers disease holds the potential to provide novel targets for treatment and prevention, leading to the development of effective strategies to combat this devastating disease.
1. Introduction
2. Familial Alzheimers Disease
2.1. Amyloid Precursor Protein
2.2. Presenilins 1 and 2
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What Part Do Genes Play In Dementia
Genes can play a role in the development of dementia. However, their effects are complicated and how and whether dementia is passed down the ‘patterns of inheritance’ vary considerably.
The importance of genes in different dementias varies considerably. For example, the role of genes in frontotemporal dementia seems to be much greater than in vascular dementia.
We all know how children often take after their parents or grandparents. This is in part because some things physical characteristics, for example are passed down to us from our parents in the form of about 20,000 different genes.
It is important to understand that genes are only part of the picture. Whatever genes you may have inherited, most people can significantly reduce their chances of getting dementia through simple lifestyle choices.
How to reduce your risk of dementia
Learn about lifestyle changes that can help to minimise the risk of developing dementia.
There are two types of differences that can occur in genes: variants and mutations.
Eugenics And The Eugenics Movement
in the heritability of social behaviors, implementing enforcement mechanisms such as military force, law, and forced medical procedures in order to maintain the well being of societies future generations. Although society today frowns upon many instances of eugenics in our history, it is still being practiced in the 21st century. Contemporary eugenics has become much more technologically advanced and individually focused through the means of prenatal diagnosis and preimplantation genetic diagnosis
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People Affected By Dementia Are Often Concerned About Whether The Condition Can Be Passed Along In Families
Here we discuss the role of heredity in Alzheimers disease and other forms of dementia.
Dementia is the term used to describe the symptoms of a large group of illnesses which cause a progressive decline in a persons functioning. It is a broad term to describe a loss of memory, intellect, rationality, social skills and what would be considered normal emotional reactions. Alzheimers disease is the most common form of dementia, accounting for 50% to 70% of all cases of dementia. It occurs relatively frequently in older people, regardless of family history. For females aged 65 to 69 years dementia affects 1 person in 80 compared to 1 person in 60 for males. For both males and females aged 85 and over the rate is approximately 1 person in 4.
Genes Associated With Autosomal Dominant Ad
Although several hundred families carry one of the following mutations, they account for less than 1% of cases.
AD1: Amyloid precursor protein
Inheritance and clinical features
In the 1980s, Kang and colleagues purified both plaque and vascular amyloid deposits and isolated their 40-residue constituent peptide , which subsequently led to the cloning of the APP type I integral membrane glycoprotein from which A is proteolytically derived. The APP gene was then mapped to chromosome 21q, which accounted for the observation that patients with Down syndrome develop amyloid deposits and the neuropathological features of AD when in their 40s.,
Since then, over 32 different APP missense mutations have been identified in 85 families. Interestingly, most of these mutations are located at the secretase cleavage sites or the APP transmembrane domain on exons 16 and 17 . Information regarding APP mutations are available in the NCBI database and the Alzheimer Disease Mutation Database . Mutations within APP account for 10% to15% of early-onset familial AD ,, appear to be family specific, and do not occur within the majority of sporadic cases with AD. The majority of these EOFAD mutations are in or adjacent to the A peptide sequence , the major component of amyloid plaques , Most cases containing APP mutations have an age of onset in the mid-40s and -50s.
Gene location and structure
Gene function and expression
Genetic variation
AD3: Presenilin 1
Inheritance and clinical features
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Cell Adhesion And Endocytosis
Endocytosis is central to AD because APP, A, and APOE are all internalized through the endolysosomal trafficking pathway, and alterations in APP trafficking through intracellular compartments can directly influence APP proteolytical cleavage . Several genes identified in GWAS-LOAD studies are associated with cell adhesion and endocytosis, including BIN1, CD2AP, EPHA1, PICALM, and SORL1 .
Genes: A Blueprint For Health And Disease
The genes encoded in our DNA are profoundly involved in many aspects of our health. They act as a sort of blueprint for the construction, operation, and repair of our bodies throughout life. Genes provide instructions for the creation and regulation of our bodys building blocks. We inherit one copy of each gene from each of our parents, which is one reason why every person has a unique appearance and metabolism.
The effects of a gene can be dramatically changed by mutation of even one pair of its molecules. Specific versions of genes, called alleles, are passed down through a familys lineage, potentially creating an entire population of people who share a healthy characteristic such as resistance to cancer a more neutral characteristic such as eye color or a heightened risk for a specific disease such as Alzheimers disease .
Many of us have learned about Mendel, who was an Austrian monk, and the pea plants he bred as he discovered basic principles of genetic inheritance. Just as with Mendels plants, some physical characteristics can be transmitted to our offspring through inheritance of even one version of a gene. Many diseases are inherited this way, too.
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Genes And Dementia With Lewy Bodies
Dementia with Lewy bodies is caused by a build-up of abnormal proteins in the brain and may have symptoms similar to those seen in Parkinsons disease. Age is currently the biggest known risk factor for dementia with Lewy bodies, although research is underway to find out whether genes may also play a role.
The Latest In Alzheimers And Dementia Testing
There are many tests today that can help determine whether you are at risk for Alzheimers or dementia. These include:
- Cognitive assessments. Medical professionals continue to refine their ability to evaluate and assess a persons cognitive health with motor skill and mental tests.
- Brain scans. Brain imaging can also shed light on alterations in the brain that may lead to or be causing dementia.
- Blood tests. Tests can detect a protein in the blood called NfL . It has proven to be an early biological marker for Alzheimers. Other tests can evaluate the level of amyloid and tau proteins in the blood.
- DNA testing. There are many tests available today that can detect the ApoE gene which has been associated with late-onset Alzheimers. Even genealogy companies like 23andMe can test for variants of the ApoE gene.
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Managing Alzheimer’s Disease Behavior
Common behavioral symptoms of Alzheimers include sleeplessness, wandering, agitation, anxiety, and aggression. Scientists are learning why these symptoms occur and are studying new treatments drug and nondrug to manage them. Research has shown that treating behavioral symptoms can make people with Alzheimers more comfortable and makes things easier for caregivers.
The Basics Of Alzheimers Disease
Scientists are conducting studies to learn more about plaques, tangles, and other biological features of Alzheimers disease. Advances in brain imaging techniques allow researchers to see the development and spread of abnormal amyloid and tau proteins in the living brain, as well as changes in brain structure and function. Scientists are also exploring the very earliest steps in the disease process by studying changes in the brain and body fluids that can be detected years before Alzheimers symptoms appear. Findings from these studies will help in understanding the causes of Alzheimers and make diagnosis easier.
One of the great mysteries of Alzheimers disease is why it largely affects older adults. Research on normal brain aging is exploring this question. For example, scientists are learning how age-related changes in the brain may harm neurons and affect other types of brain cells to contribute to Alzheimers damage. These age-related changes include atrophy of certain parts of the brain, inflammation, blood vessel damage, production of unstable molecules called free radicals, and mitochondrial dysfunction .
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Genetic Testing And Counseling
In contrast, EOFAD, with an age at onset before 60 to 65 years old, has an autosomal dominant mode of inheritance in which 20% to 70% of cases are estimated to have a PSEN1 mutation, 10% to 15% of cases are estimated to have an APP mutation, and PSEN2 mutations are rare., Indeed, approximately 60% of patients with EOAD have another known affected family member. The remaining 40% of patients with EOAD may lack a family history because of an early death of a parent, failure to recognize the disorder in family members, or, very rarely, a de novo mutation. If the parent of a patient with EOAD has a mutant allele, then the risk to the patients sibling of inheriting the mutant allele is 50%. The child of a patient with EOAD who carries a mutation has a 50% chance of transmitting the mutant allele to each of their children.
In this article, we have reviewed the genetics of AD. Further molecular genetic investigations should clarify the roles of additional known genes in the pathogenesis of both common sporadic as well as rare familial forms of AD. Already, investigations of the normal and aberrant functions of A protein and ApoE has provided insight into the underlying mechanisms for AD. Such research will continue to provide new strategies for therapeutic interventions.