Theme 5: Neoplasia - Part 1 Flashcards
What is Huntington’s disease?
progressive neurogenerative disorder with motor, cognitive and psychiatric disturbance
-mode of inheritance is autosomal dominant
What effect does Huntington’s have on your movement, memory and mood?
Movement:
- chorea (involuntary motor movement)
- dystonia (prolonged contraction in abnormal position)
- bradykineasia (slowing of movement)
- swallowing/choking
- dysarthria (difficulty speaking)
Mood:
- depression
- euphoria
- apathy
- anxiety
- aggression
- psychotic symptoms
Cognition:
- loss of executive functioning
- rigidity of thought
- memory loss
- dementia
What is the mean age of onset and the mean survival time?
Mean age of onset: 35 to 44 years
Mean survival time: 15 to 20 years after onset
Huntington’s has complete penetrance. What does this mean?
all individuals with the disease causing mutation will have clinical symptoms of the disease
Which gene is affected in Huntington’s?
HTT gene at 4q16.3
What is the HD mutation?
an expansion of CAG repeats with >40 triplet repeats
- few people will develop HD with 36-39 repeats = reduced penetrance alleles
- 27-35 repeats = will not develop HD but next generation might
What amino acid does CAG code for?
glutamine
what is the relationship between the HD triplet repeat size and age of onset?
as the size of the repeat increases, the age of onset gets younger
What is anticipation?
- the onset of a disorder occurs at an earlier age as it is passed from one generation to the next
- often associated with an increase in severity of symptoms
- phenomenon associated with triplet repeat disorders
Anticipation is often linked to a specific parental gender. Which parent provides a high anticipation risk with HD?
Paternal inheritance
-if HD is passed by the father, there is much higher chance of the triplet expanding than if it were passed on by mother
what are two other examples of triplet repeat disorders?
- myotonic dystrophy
- fragile X syndrome
high anticipation risk is associated to maternal inheritance (opposite of HD)
What is Juvenile HD?
- onset under 20 years
- rare
- usually paternally inherited (and repeats have expanded)
What is predictive testing?
The use of a genetic test in an asymptomatic, at risk person to predict the future of a disease
What are the reasons to undertake predictive testing?
- screening to detect early disease - cancer, arrhythmia
- initiate treatments early
- take prophylactic measures
- may offer prenatal testing options
- inform other relatives
- plan future care, careers
What are three other conditions where predictive gene testing is possible?
- BRCA (familial breast cancer genes)
- HNPCC (hereditary non-polyposis colon cancer)
- Myotonic dystrophy
What are the treatments for HD?
- symptomatic treatment only at present
- no prevention or cure
What is exclusion testing?
For parents who do not want predictive testing but want to ensure their children are not at risk - predicts whether the foetus is at risk
What is bioinformatics?
A combination of principles from computer science and IT, used to handle and interpret the large datasets generated by genomic analysis
What are the limitations of bioinformatics?
- computers simply follow a set of rules, they are not aware of what they’re doing
- variants are missed
Stats about rare diseases:
- What % of the population will be affected by a rare disease?
- What % of rare diseases have a genetic component?
- What % of rare diseases affect children?
- 7%
- 80%
- 75%
What is Cockayne Syndrome?
- A rare and fatal autosomal recessive neurodegenerative disorder charachterized by growth failure (dwarfism), impaired development of the nervous system, photosensitivity, eye disorders and premature ageing
- Most children with severe CS do not survive to 7
- no cure
- treatment of symptoms: hearing acids, protection of skin and eyes from sun, dental hygiene
What is FTT?
Failure to thrive - insufficient weight gain or inappropriate weight loss
Explain the genome analysis pipeline
- Collect DNA
- genomic DNA (e.g blood)
- tissue DNA (e.g tumour) - Capture DNA of interest
- clinical exome/ exome/ whole genome - Sequence captured DNA
- short/long read
- single-end/paired-end - Analyse sequence
- align data to human genome and call variants, SNVs, CNVs etc - Variant interpretation
- does the variant cause disease?
In what ways can cells adapt?
- increase in size of cells (hypertrophy)
- increase in number of cells (hyperplasia)
- decrease in size and metabolic activity of cells (atrophy)
- increase in functional activity of cells
- change in the phenotype of cells (metaplasia)
Can fibroblasts adapt to environmental change?
they can survive severe metabolic stress without harm e.g absence of oxygen
-don’t need to adapt
Can epithelial cells adapt to environmental change?
- labile (flexible) cell population
- active stem cell compartment
- highly adaptive in number and function
- adapt easily
What are the 3 types of adaptive response?
- Increased cellular activity - increased size or number of cells
- Decreased cellular activity - decreased size or number of cells
- Change in cell function and/or morphology
What does hypertrophy result in? Examples
- increase in size of existing cells - resulting in increase in size of organ
- increase in function capacity
- seen in permanent cell populations e.g cardiac and skeletal muscle
- increased synthesis of structural components (explains why organ gets larger)
- increased metabolism
- growth of the uterus in pregnancy results from the hypertrophy of muscle fibres
Why does left ventricular hypertrophy occur?
- systemic hypertension is caused by increased peripheral vascular resistance
- so will increase the work required of the left ventricle
- hypertrophy will compensate for some time, but if hypertension is untreated, left ventricle will fail
What is sub cellular hyperplasia and hypertrophy?
-increase in size and number of sub cellular organelles
What is an example of hormone-driven hyperplasia?
proliferation of the glandular epithelium of the female breast at puberty and during pregnancy