My lab focuses on human genetics and gene regulation. We study individual variation in gene expression, and use this variation to understand gene regulation. In this talk, I will discuss two projects. In the first part, I will describe the regulation of a histone demethylase, KDM4C, and show how individual differences in KDM4C expression affect its enzymatic activity and impact normal and cancer cell growth. In the second part, I will describe the discovery of RNA sequences that differ from their corresponding DNA sequences in human cells. These include known RNA editing sites and unknown events such as purine to pyrimidine transversions. I will describe the role of ADAR proteins in mediating some of these events, and our findings of when during transcription these RNA-DNA differences are formed. Overall, I will discuss the lessons we learned from studying natural variation in human gene expression, and the significance of our findings on basic understanding of gene regulation and disease manifestations.