Poster Presentation ANZSCDB National Scientific Meeting 2019

Investigation of how the epigenetic regulator Smchd1 regulates Hox gene expression. (#Poster 15)

Natalia Benetti 1 , Natasha Jansz 1 , Tamara Beck 1 , Megan Iminitoff 1 , Kelsey Breslin 1 , Siew Fen Lisa Wong 2 , Edwina McGlinn 2 , Marnie Blewitt 1
  1. Epigenetics and Development Division, Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria, Australia
  2. EMBL Australia, Australian Regenerative Medicine Institute, Monash University, Clayton, Victoria, Australia

Structural maintenance of chromosomes flexible hinge domain containing 1 (Smchd1) is a non-canonical SMC protein that plays a key role in X chromosome inactivation and the epigenetic silencing of several clustered gene families [1-6]. One such example of a clustered gene family that is silenced by Smchd1 is the Hox genes [5, 6], and the mechanism/s by which this occurs, as well as the consequences of Smchd1 deletion on Hox regulation is the focus of this project. Jansz et al., found that Smchd1-null embryos displayed a loss of silencing of the Hox genes responsible for posterior vertebral patterning and consequential homeotic transformations in their skeletons, compared to Smchd1 wildtype embryos, indicating that Smchd1 plays an important role in Hox gene silencing [6]. Jansz et al., also recently reported that the targeting of Smchd1 to the inactive X chromosome is dependent on the H2AK119 ubiquitination activity of Ring1A and Ring1B (components of PRC1) [7]. Given that polycomb group proteins such as PRC1 are well-known epigenetic silencers of Hox genes, this poses the question as to whether or not the ubiquitination activity of PRC1 is also required for Smchd1 to be targeted to the Hox gene clusters for their maintained silencing [8]. To test this, we plan to perform ChIP-sequencing of Smchd1-bound DNA 3 days post Ring1B deletion in Ring1A-/-Ring1Bfl/fl mouse embryonic fibroblasts (MEFs). We also plan to perform RNA-sequencing on presomitic mesoderm tissue dissected from somite-matched male Smchd1-null and Smchd1wildtype embryos at E8.5, 9.5 and 10.5 to analyse differential Hox gene expression at each time point and to compare it with the results of Jansz et al., at E9.5 [6, 9].

  1. Blewitt, M.E., et al., SmcHD1, containing a structural-maintenance-of-chromosomes hinge domain, has a critical role in X inactivation. Nat Genet, 2008. 40(5): p. 663-9.
  2. Blewitt, M.E., et al., An N-ethyl-N-nitrosourea screen for genes involved in variegation in the mouse. Proc Natl Acad Sci U S A, 2005. 102(21): p. 7629-34.
  3. Mould, A.W., et al., Smchd1 regulates a subset of autosomal genes subject to monoallelic expression in addition to being critical for X inactivation. Epigenetics & Chromatin, 2013. 6(1): p. 19.
  4. Gendrel, A.V., et al., Epigenetic functions of smchd1 repress gene clusters on the inactive X chromosome and on autosomes. Mol Cell Biol, 2013. 33(16): p. 3150-65.
  5. Chen, K., et al., Genome-wide binding and mechanistic analyses of Smchd1-mediated epigenetic regulation. Proc Natl Acad Sci U S A, 2015. 112(27): p. E3535-44.
  6. Jansz, N., et al., Smchd1 regulates long-range chromatin interactions on the inactive X chromosome and at Hox clusters. Nat Struct Mol Biol, 2018. 25(9): p. 766-777.
  7. Jansz, N., et al., Smchd1 Targeting to the Inactive X Is Dependent on the Xist-HnrnpK-PRC1 Pathway. Cell Rep, 2018. 25(7): p. 1912-1923.e9.
  8. Lewis, E.B., A gene complex controlling segmentation in Drosophila. Nature, 1978. 276(5688): p. 565-70.
  9. Wong, S.F., et al., Independent regulation of vertebral number and vertebral identity by microRNA-196 paralogs. Proc Natl Acad Sci U S A, 2015. 112(35): p. E4884-93.