Update README.md

Author: liliw-w

README.md

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 Figure: Three main steps in trans-PCO pipeline. The first step of trans-PCO pre-processes RNA-seq data to reduce false positive trans-eQTL associations due to read alignment errors. The second step involves grouping genes into gene sets, such as co-expression modules or biological pathways. The last step tests for trans-eQTLs of each gene set by a PC-based multivariate association test.
 
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