Midterm 1 - Notes 4 (Part 2) Flashcards
What is the most common severe musculoskeletal birth defect?
Club foot disease
Club foot disease
Is a disease (normally presented at birth) that has the foot pointing down and inwards and the soles of the feet are facing each other
What are the odds of a child getting club foot?
1 in 1,000
What kind of component does clubfoot have?
A genetic component
- 25% of cases are familia
- inherited throughout generations
What kind of condition is club foot disease?
Clubfoot segregates as an autosomal dominant condition
What does an autosomal dominant condition mean?
It means you only need one mutation to cause the disease (instead of 2)
What is LOD?
It is the probability of linkage over the probability of no linkage
What does it mean when the Max LOD score of the club foot disease was 3.31?
Since it is over 3 that means it is 1000x more likely that there is a linkage
What can they conclude from the 3.31 LOD score?
That there might be multiple locations that contribute to the disease, but there is a region that effects more common
What probably doesnt happen in the club foot study because of the small sample size?
Co-segregation
Pitx1
Is a transcription master regulator
- important in hind limb development
What is the benefit of having so many markers?
We are able to actually trace the break points of the haplotype blocks
In the club foot study what was the SNP allele found in all healthy individuals?
The G allele
In the club foot study what was the SNP allele found in all affected individuals?
The A allele
Where were the SNPs located?
On the coding region
- nonsynonymous
What did Glu change to?
Lys (E130K)
Pitx1 protein
is a transcription factor that binds to the cis regulatory element and have other target genes regulating the activation of transcription
Why did they expand there sample range to 500 healthy humans in the club foot study?
To see if the SNP was present in those individuals who did not have a club foot
- that way we can tell if this change is a potential cause for the club foot
Were is the Pitx1 gene located?
In the DNA binding domain
- homeodomain
Homeodomain
Is a special class of helix-turn-helix DNA binding domain - helices 2 and 3 make this up
Is Glu high conserved among Pitx1 families?
Yes
What did the mutations replace Glu acidic amino acid with?
A basic one –> Lys, K
What could happen if you change the charge from positive to negative?
It could effect the interaction of the targets
What does the cross section perform?
Immediate DNA interaction in the transcriptional genes
What was the hypothesis of the Glu to Ly(E130K) mutation?
E130K mutation affects DNA binding specificity of Pitx1
- affects transcriptional activation of target genes
- -> affects normal leg development
- this is what causes the disease phenotype
What happens if you reduce binding to core binding site in the Pitx1 E130K mutant?
It reduces the activation of targets in E130K Pitx1
What is the result when Pitx1 is KO of mice? (3)
- Lethal
- Reduces hind limbs
- Loss of all function
What is the result when cis-element is deleted? (2)
- Loss of expression only in pelvis
- coding region was fine - Pelvic spine reduction
What is the result when there is a point mutation in the homeodomain? (2)
- Reduced protein (TF) activity
- Hind limb malfunctions
- still works but not as efficient as the wild type
