A sex-biased obesity gene on the X chromosome

The leading cause of death in women in the United States is cardiovascular disease (CVD). Progress in reducing CVD in women has lagged behind progress in men. Obesity is a prevalent risk factor for CVD, and becomes more prevalent in women following menopause. We have shown that XX chromosome complement promotes increased adiposity in female compared to male mice, and this effect is amplified when gonadal hormone levels are diminished, as occurs after menopause in humans. We have identified the Kdm5c gene on the X chromosome as a key contributor to XX effects on adiposity. Kdm5c is expressed at higher levels in female compared to male humans and mice due to escape from X chromosome inactivation. Kdm5c encodes a histone demethylase that modulates chromatin structure and gene expression. Reducing Kdm5c gene dosage in XX females to that normally present in XY males reduces adipose tissue mass and alters histone marks in preadipocytes to favor induction of beige adipocytes and enhanced whole body energy expenditure. We hypothesize that sex differences in histone modifications throughout the genome, which likely change in hypogonadal states such as menopause, influence sex differences in adipose tissue function. We will investigate key questions regarding the role of Kdm5c gene dosage, and more generally, histone modifications and gene regulation, as determinants of sex differences in adipose tissue. Aim 1: Is Kdm5c gene dosage a determinant of weight/fat gain in hypogonadal states? We hypothesize that Kdm5c gene dosage is partially responsible for the impact of X chromosome dosage on weight gain when gonadal hormone levels are diminished. We will test the impact of Kdm5c gene dosage on weight gain, adiposity, and energy balance in female and male mice with preadipocyte Kdm5c deficiency under normal and reduced hormone levels. Aim 2: What is the effect of sex, gonadal hormones, and Kdm5c gene dosage on adipocyte histone and gene expression profiles at the tissue and single-cell levels? We will map the histone landscape and corresponding gene expression profile in adipose tissue to identify effects of sex, gonadal hormones, and Kdm5c gene dosage (A) at the tissue level using CUT&RUN and RNA-seq, and (B) and the single-nucleus level using Paired-Tag to simultaneously profile histone marks and gene expression in individual nuclei. Aim 3: How do sex and gonadal hormone status impact the histone landscape in human adipocytes? There is a dearth of information regarding the effect of sex on histone modifications in human adipose tissue, and whether changes in histone profile underlie alterations in adipose tissue following menopause/andropause. We will map histone profiles in adipose tissue of women vs. men, and in pre- vs. post-menopausal women. Our studies will shed light on how sex influences the epigenetic regulation of adipose tissue gene expression, composition, and function through histone modifications. This knowledge may inform therapeutic strategies to prevent excess adiposity and CVD risk in both women and men, including adipose tissue accrual in response to diminished hormone levels in mid-life.