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Articles by S Chun
Total Records ( 2 ) for S Chun
  S Chun and J. C. Fay

Each human carries a large number of deleterious mutations. Together, these mutations make a significant contribution to human disease. Identification of deleterious mutations within individual genome sequences could substantially impact an individual's health through personalized prevention and treatment of disease. Yet, distinguishing deleterious mutations from the massive number of nonfunctional variants that occur within a single genome is a considerable challenge. Using a comparative genomics data set of 32 vertebrate species we show that a likelihood ratio test (LRT) can accurately identify a subset of deleterious mutations that disrupt highly conserved amino acids within protein-coding sequences, which are likely to be unconditionally deleterious. The LRT is also able to identify known human disease alleles and performs as well as two commonly used heuristic methods, SIFT and PolyPhen. Application of the LRT to three human genomes reveals 796–837 deleterious mutations per individual, ~40% of which are estimated to be at <5% allele frequency. However, the overlap between predictions made by the LRT, SIFT, and PolyPhen, is low; 76% of predictions are unique to one of the three methods, and only 5% of predictions are shared across all three methods. Our results indicate that only a small subset of deleterious mutations can be reliably identified, but that this subset provides the raw material for personalized medicine.

  B Kim , Y Lee , Y Kim , K. H Lee , S Chun , K Rhee , J. T Seo , S. W Kim and J. S. Paick

DAZ is a male infertility gene located at the AZFc region of the Y chromosome. There are four copies of the DAZ gene that share a strong homology but are not identical to one another. In the present study, we carried out cDNA cloning and immunoblot analyses to determine whether all of the DAZ genes are actively expressed in the human testis.


AZFc deletion was detected by sequence-tagged site polymerase chain reaction (PCR) of genomic DNA isolated from blood samples. DAZ cDNAs were cloned with RT–PCR followed by sequence analysis. The expression of DAZ proteins in human testis was determined by immunoblot and compared with DAZ cDNA expression.


Immunoblot analysis revealed four DAZ protein bands in testis samples that showed no deletions in the AZFc region. No specific bands were observed in samples from AZFc deletion patients. Testis samples from individuals with the partial AZFc deletion, gr/gr, showed two DAZ-specific bands. Interestingly, the sizes of DAZ-specific bands varied among individuals. Analysis of DAZ transcripts in testis samples revealed that the DAZ proteins were translated from the largest of the multiple transcripts originating from each single DAZ gene.


All four DAZ genes are expressed in the human testis, and their products are highly polymorphic among men.

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