Validation of candidate genes involved in X chromosome inactivation

Abstract

Due to the unequal genetic makeup of homogametic males and heterogametic females, placental mammals have to equalize the expression of X-linked genes between both sexes. This dosage balance is achieved by a process known as X chromosome inactivation (XCI). Originally described by Mary Lyon, XCI has been intensively studied given its importance in functional cell physiology This has contributed to a greater understanding of the molecular events involved in XCI. A milestone in the history of XCI marks the discovery of Xist which is now known to take on a central role in driving X-inactivation. However, knowledge gaps still exist in this field as players involved in Xist-mediated gene silencing and maintenance of XCI remain unidentified. Here, we performed a cell-based RNAi assay to assess the role of 9 candidates genes in XCI. We constructed 9 shRNA constructs and individually transfected genetically engineered mouse ES cell line( Av3.1.12) with single shRNA. Of the 9 validated genes, only 2 genes (X6" & X7") whose knockdown led to a small increase in viability of Av3.1.12. While this suggest a possible role of both genes in XCI, the lack of significant cell rescuing effect did not seem to provide a strong evidence to support this implication. Further research are needed to study the two genes in greater details.