Week 2 Flashcards
Treatment of Multiple Endocrine Neoplasia
genetic predisposition to a variety of tumors
Prophylactic thryoidectomy shows increased survival rate
Treatment of Alpha1 antitrypsin deficienty
recombinant protein replacement therapy to replace extracellular protein
Gene Therapy
introduction of DNA or RNA into human cells to treat acquired or inherited disease Ex vivo (insert outside the patient in cells/tissues which are then given to patient In vivo (DNA/RNA is injected into patient)
Retroviral Gene Therapy
RNA viruses
Integrates into the cell genome with minimal host immunge reactions.
Insert size is limited to 7-8 kn and can infect only dividing cells.
There is a risk of insertional mutagenesis
efficient in infecting dividing cells
Integrate into genomic DNA so can get passed to daughter cells
Adenoviral Gene Therapy
DNA viruses
A: wide variety of cells can be infected, insert can be 35-36kb, stable and easy to get
D: does not integrate into genome, expression can be transient
lower risk of insertional mutagenesis, Severe immune reactions
can infect non-dividing cells,
short lived effect, not passed onto daughter cells
Non-Viral Gene Therapy
liposomes, direct DNA
large insert side, could deliver multiple ch, minimal host immune response.
There is very low effiiciency and transient epression.
The safest option because it doesn’t integrate into host genome
Often degraded by cellular mechanisms and effect is hsort lived.
Safety of three different gene therapies
Retrovial: risk of insertional mutagenesis/germline integration
Adenoviral: low risk of insertional mutagenesis; severe immune response
Non-Viral: safest; no integration
Duration of Gene Therapy Approaches:
Retroviral: integrate –> passed to daughters
Adenovital: short lived–> not passed to daughters
Non-Vital: short lived -> not passed to daughters
Chromosomal Analysis Uses
aneuploidies chromosome deltions duplications insertions of moderate to large (3kb to 5kb) rearrangements
Chromosomal Analysis cannot diagnose..
single gene deletions
point mutations
small deletions, duplications, insertions, methylation, TriNT repeats
FISH can diagnose
microdeletion syndromes, recognized chromosomal rearrangements in Cancer, gene copy numbers, anueploidies in pernatal setting
Fish Cannot diagnose
deletions, rearranements that were not specifically tested for
Canot detect duplications
Expression array
tests the RNA expression of genes
tests the activity of genes rather than just the presence or absence of a gene or gene variant
Chromosomal Microarray Can diagnose
small genomic deletions/insertions >200 for deletions and >400 for duplications
aneuploidies, unbalanced chromosome rearrangements
CMA cannot diagnose
deletions and duplications below resolution of MCA, NT mutations, balanced chromosomal rearrangements
DNA sequencing can diagnose
Mutation in known genes, polymorphic variants, small 1-100 NT deletion/insertions,
ideal for looking at the sequence of a known disease gene
DNA sequencing cannot diagnose
regions that are not being tested, regions of the gene (promoters, introns) that arent sequenced,
extremely large deletions or insertions, rearrangements, chromosomal abnormalities
Allelic Heterogeneity
multiple mutations in a particular gene of loci can cause disease
Genetic Heterogeneity
multiple genes when mutated are associated with same phenotype.
Alpha Globin
Ch 16 (2 copies per cluster)
Beta - Globin
Ch 11 (1 copy per cluster)
Alpha cluster
zeta-alpha2-alpha1
beta cluster
epsilon - gammaG-gammaA-delta-beta
Pseudogene
resembles a gene but makes no protein
How does locus control region help with expression…
1) distance between LCR and gene
2) LCR makes physical contact with promoter and/or negative reglulatory regions via transcription factors
3) deletion of beta-LCR causes B0
HbA vs HbA2
HbA is major (97%) A2B2; 10-40% at birth; >95% after 2 years
HbA2 is minor (2%) A2D2;
Hb Gower I
Zeta2/E2: first Embryonic Hb
Hb Gower II
Alpha2/E2: 2nd embryonic Hb
Hb Portland
Zeta2/Gamma 2
Fetal Hb
Made in liver
A2/Y2
60-90% at birth
Globin switching during embyogenesiss
Turn off zeta and epsilon and turn on alpha and gamma
Globin switching at birth
turn off gamma and turn on beta and delta at birth
HbF and HbA
HbF has higher affinity for O2 in low O2 areas such as placenta
Genetic Disorders of Hb
1) structural variant (altered property like solubility, oxygen arrinity) - qualitative
2) Thalassemias (alter expression of alpha and beta globin) - quantitative
3) Defective globin switching
Erythroblasts
precursors to RBC made in bone marrow.
Thalassemia mechanism
when cells express abnormal Hb, proteins build up and the ones that are supposed to be going into the RBC dont’ and cell apoptosis or ineffective erythropoesis
But you still make target cells, susptible to hemolysis
Phenotype of Thalassemia
systolic murmer, lower MCV, elevated reticulocyte count
Four major mechanisms of Genetic Disease
1) loss of function or protein
2) Gain of function
3) acquisition of novel property
4) preturbed expression of gene at wrong time
Loss of function of protein
most common mutation
eliminate or reduce function of protein
examples: Duchenne MD (Xp21), Becker, Alpha-Thalassemia, Turner Syndrome, HNPP, Osteogenesiss imperfecta Type 1
PMP22 in HNPP
unequal crossing over to produce a deletion o the CMT1A protein
COL1A1 in OI Type 1
nonsense or stop mutation to produce truncated proteinll to make half amount of collagen
Gain of Fcnction proteins
Fixes or adds to protein function
Hemoglobin Kempsey
Charcot Marie Tooth Syndrome Type 1A
Charcot Marie Tooth Syndrome Type 1A
Progressive AD
duplication of PMP22 gene with unequal crossing over. that leads to demyelination of motor and sensory neurons
Acquisition of novel property
Sickle Cell anema
Osteogenesis Imperfecta Type II, III, IV
Preturbed expression of gene at wrong time
Expression at wrong time or in wrong place by ectopic expression
Hereditary Persistance of Fetal Hemoglobin
Tri/tetra nucleotide repeats
Large neurodegenerative, genetic anticipation that have unique mechanisms and distinct phenotypes
RNA splicing impaired: myotonid dystropy
loss of function: HD
Nuclear intranuclear inclusions: fragile X
loss of RNA binding: fragile X
Locus Heterogeneity
variants in different genes result in similar clinical presentation
AD
Phenocopies
environmentally caused phenotype that mimics genetic version of trait
Thalidomide
drug to treat morning sickness that mimics genetic condition of limb malformation
Heritability
proportion of total variance in a trait that is due to variation in gene.
high heritability implies differences among individual with respect to a trait.
Paternal Age Effect
Men over age of 40 have higher rate of children with deo-novo autosomal dominant conditions
Achondroplasia
Large # of cell divisions during spermatogenesis increase mutation rate and decreased ability ot make repair.
Pure Dominant
Homozygous ad heterozygotes are both equally affected
Incomplete Dominant
homozygotes are affected more severely
Anticipation
severity or onset of disease increases in next generation
Parental Transmission bias
TriNT repeat is more prone to occur in gametogenesis of male or female
X-Inactivation
Only one copy of majority of genes on X ch is necessary to function - done randomly in females
Occurs during 1st week of embryogenesis and becomes Barr body
Females are mosaic for for X-ch (half maternal and half paternal)
XIST
gene on x ch that is only expressed in inactive X.
X inactivation cannot occur in its absnce
Mechanism of X-inactivation
XIST
methylation of promoter regions in inactivated X
Non-random X Ch inactivation
preferentially turns off X due to structurally abnormal X
Skewed X inactivation
observed when female shows sign of X linked recessive conditions, such as Duchenne muscular dystrophy
more of normal X ch is turned off
Four characteristics of Epigenetic Phenomenon
1) Different gene expression pattern and phenotype arrise from identical genomes
2) inheritance through cell division but be done ins table format that is maintained through cell population expasion and fertilization
3) like a light switch on/off
4) erasable (interconvertible)
What is significant of erase-able methylation in cancer or treatment?
it is the hallmark of cancer, so it become like a stem cell
In treatment, can switch back to non-diseased setting?
