TRIP13 was originally discovered to be an interactor with rat thyroid receptor beta (THRB; [54]), but the relationship between THRB and TRIP13 in meiosis is unknown. Interestingly, we observed that THRB is distributed diffusely throughout wild-type spermatocyte nuclei but is excluded from the XY (sex) body (unpublished observations), a compartmentalized nuclear domain beginning in pachynema, in which the sex chromosomes become heterochromatinized and transcriptionally silenced in the process of MSCI [55]. However, the XY body appeared intact in most mutant spermatocytes upon probing with several markers of XY heterochromatinization (unpublished observations). Considering that THRB knockout mice are viable and fertile [56], the functional relationship between TRIP13 and its receptor THRB in meiosis is unclear.