Tonight I watched Quentin Gouil from the Walter and Eliza Hall Institute of Medical Research in Australia speak at the Nanopore Community Meeting in Singapore about “Measuring skewed X inactivation by adaptive nanopore sequencing.” Gouil explained that there are ~2000 genes on the X chromosome, and males are more affected by X-linked diseases. They described how one of the X chromosomes is condensed into a “bar body” with unique methylation. X inactivation happens early in development, is stochastic, and has a mosaic pattern. Gouil explained that X inactivation can be skewed: regional, tissue-specific, or even global. They collaborated with clinicians and obtained buccal swabs, blood, and saliva from patients. They extracted ~20 Kb DNA and ran on PromethION flow cells. Adaptive sampling helped the team load multiple samples on one PromethION flow cell. However, enrichment deficiency was highly dependent on size distribution of library. Haplotype blocks could be identified. Gouil then searched for methylation-based clustering with NanoMethViz. This information helped classify skews in X inactivation. The skew may be either beneficial or dangerous. Gouil emphasized that X inactivation skew can be calculated by nanopore long-read sequencing. Females are mosaic and the X-linked skew is important to keep in mind. Females are also affected by X-linked diseases. Gouil noted that differences in inactivation can impact the phenotype and methylation patterns can help without the need for parental data.
