ESR1 and obesity due to melanocortin 4 receptor deficiency: Of note, as will be described in detail in the following section, targeted ablation of ER⍺ in the amygdala using the SIM1-Cre mouse revealed a role of estrogen signaling at this site in the modulation of body weight, so that mice with selective ablation of ER⍺ in SIM1 neurons displayed an obesity phenotype [70].