1. Structural Genomics and Human Health
Lei Xie, PhD

2. Enter the Genome & IT Era

3. Background –
Proteins are the worker molecules that make possible every activity in your body

4. Background – Generic Codes

5. Background – From DNA to Protein
DNA carries the genetic information of a cell and consists of thousands of genes
genes are transcribed into RNA (transcription)
proteins are built based upon the code in the RNA (translation).

6. Background -
3D shape enables proteins to accomplish their function in your body
Proteins are made of amino acids like beads on a necklace.
To become active, proteins must fold into their final shape

7. Genes and Disease

8. The Human Genome Project has a Broad Impact

9. Personalized Medicine

10. Background - SNPs Definition – must occur in > 1% of population
Accounts for > 90% of all genetic variation
Est. 1.4M in initial map of the genome
60,000 in coding regions
A synonymous SNP does not change the protein; non-synonymous does
Synonymous still important in regulation eg transcription factor binding etc.
See

11. Genetic Variation and its Relationship to Disease has Been Known for Some Time..

12. Example: Sickle cell anemia
Sickle cell anemia (SCA) is an autosomal recessive disease caused by a point mutation (SNP) in the hemoglobin beta gene (HBB) found in region 15.5 on the short arm (p) of chromosome 11
The hemoglobin protein (HBB) is 146 aa long and has a molecular weight of ~15,867 Da

13. Example: Sickle cell anemia
Hemoglobin (HBB), found in red blood cells, is responsible for carrying oxygen around the body
It is made up of two different types of protein chains: alpha and beta
Normal adult HBB is a tetrameric protein consisting of two alpha chains and two beta chains (see PDB structure)
The hemoglobin beta gene (HBB) codes for the beta chain found in hemoglobin (often called ‘beta globin’)
A point mutation (SNP) in beta globin is responsible for the sickling of red blood cells seen in SCA

14. Example: Sickle cell anemia
In SCA the hydrophobic aa valine takes the place of hydrophilic glutamic acid at the 6th aa position of the HBB beta polypeptide chain
This is caused by a SNP in which a T is substituted for an A in the middle position of codon 6
The SNP converts the GAG codon (encoding Glu) to a GTG codon (encoding Val)

15. Example: Sickle cell anemia
Normal deoxy hemoglobin:
4 grey clusters are non-covalently bonded heme groups which bind oxygen
Gold spheres are phosphate groups
Green and blue chains are alpha, gold and turquoise chains are beta.
Red box highlights the region in which the sixth glutamic acid residue is located (i.e. where the SNPs lies)

16. Example: Sickle cell anemia
The SNP substitution creates a hydrophobic region on the outside of the protein’s structure
This region then ‘sticks’ to the hydrophobic region on adjacent hemoglobin molecule’s beta chain
This polymerization of mutant hemoglobin molecules results in the formation of rigid fibers

17. Example: Sickle cell anemia
Polymerization of mutant hemoglobin only occurs after red blood cells have released their oxygen molecules
As these red blood cells re-bind oxygen, the long fibers of mutant hemoglobin depolymerize and break apart into single molecules
Cycling between polymerization and depolymerization causes red blood cell membranes to become rigid

18. Example: Sickle cell anemia
The rigidity of the red blood cells, and their distorted shape when not carrying oxygen, can block small blood vessels
This blocking can produce micro vascular occlusions which can cause necrosis (death) of the tissue

19. Example: Sickle cell anemia
SCA is an autosomal recessive genetic disorder. For it to be expressed, a person must inherit two copies of the mutant (Hb S) variant or one copy of the mutant (Hb S) and one copy of another genetic variant
Carriers who have the normal HBB gene (Hb A) and one copy of the mutant (Hb S) are described as having sickle cell trait, but do not express the disease symptoms.

20. SNP profiles
There is now a concentrated effort to identify all the different SNPs in the human genome - hapmap
This will be used to generate a single map of the entire human genome and where each all the SNPs lie
The genomes of individuals will therefore contain a unique map of SNPs, thus providing individual SNP profiles

21. SNP profiles
These SNP profiles will be important for analyzing responses to disease treatments
SNP profiles are also thought to be important in explaining patients differential responses to drug treatment
Since SNPs are also good gene markers, SNP profiles will also be important in identifying the collection of genes that contribute to the development of complex diseases states

22. Conclusions
Many SNPs have no effect on cell function, but others could pre-dispose people to disease states or influence drug treatment responses
SNPs can either effect a proteins structure/function or they can effect regulatory aspects of gene expression
Mapping SNPs to the genome will produce useful individual SNP profiles and identify multiple genes associated with diseases
This makes SNPs extremely important for biomedical research and for developing pharmaceutical products or medical diagnostics

23. Useful Links
PDB ( )

24. The Big Picture http://www3.ncbi.nlm.nih.gov/Entrez/

25. Navigation By Data Source http://www. ncbi. nlm. nih
LocusLink
Chromosome
location
Genbank
All public
DNA sequences
RefSeq
Non-redundant
Sequences for
major organisms
Click on the computers to go to the resources

26. Navigation By Data Source http://www. ncbi. nlm. nih
Omim
Relate gene to
phenotype with
emphasis on disease
PubMed
The literature
reference to
all databases
PDB
3D Structure
Click on the computers to go to the resources