LEP and obesity due to melanocortin 4 receptor deficiency: (a) In the lipostatic model of obesity originally defined by Kennedy, 1953, circulating concentrations of the leptin hormone signal the amount of energy stored in fat cells to the brain. The plot shows gene ESμ (y-axis) for each cell type (x-axis, ordered by increasing values of expression specificity, ESμ) with BMI-prioritized cell types from the Mouse Nervous System dataset highlighted.