The process of development in mammals is always accompanied with high amounts of brain plasticity. Similarly, the maturation of sex organs during puberty in mammals serves as the foundation for important cognitive development. Researching centers of high plasticity could lead to key discoveries for the molecular basis of behavior. The medial preoptic area (MPOA) is an example of a very active site in pubertal gene expression. Estrogen-receptor 1, or Esr1, is a gene that is essential for hormone binding. We aim to gain insights on the neural basis of behavior by analyzing Esr1’s level of control in the MPOA, and on sexual behavior. This was completed by identifying single-cell types, determining the full transcriptome of the MPOA, and then observing any changes in gene expression after selectively knocking out the Esr1 gene. We utilized scRNA sequencing to identify single-cell types. The mating behaviors of mice was also studied to pinpoint any phenotypic differences. We have found that the deletion of Esr1 leads to severe hinderances in maturation, as well as sexual behavior, due to reduced function of Cis-regulatory elements. This provides important clarity regarding the key effectors of brain development in the pubertal stages. We aim to apply this approach to uncover the transcriptional dynamics of other areas in the brain, eventually forming a full, detailed representation of the brain. This would be a massive step forward in understanding the neural foundation governing sexual behavior.

Leptin and ghrelin are two hormones essential to maintaining and regulating energy levels and food intake. These hormones have opposite effects on feeding behavior where leptin suppresses feeding and ghrelin potentiates it. While the roles of these two hormones have been widely researched, their relative effects on distinct neural populations are still largely undetermined. Previous electrophysiological and in vivo imaging experiments have shown that the activity of individual populations of glutamatergic hypothalamic projection neurons are differentially affected by feeding hormones. This data leads to the question of whether or not the projection populations have a bias for leptin and ghrelin receptors that could account for the difference in sensitivity. We hypothesize that Lepr and Ghsr will be expressed at different levels within the different projection populations. To study this, we injected two retrogradely trafficked viruses into the target locations, lateral habenula (Lhb) and ventral tegmental area (VTA), in Mus musculus and performed fluorescent in situ hybridization experiments in the lateral hypothalamus (LHA), dorsomedial hypothalamic nucleus (DMH), ventromedial hypothalamus (VMH), paraventricular nucleus (PVH), and arcuate nucleus (ARC) for viral based fluorophores as well as leptin and ghrelin receptors. The viral expression was imaged using fluorescence microscopy and quantified for within individual hypothalamic neurons. Analysis is currently underway to reveal any differences in fluorescence between the two projection populations and therefore, determine any disparities in hormone receptor expression. The objective of this research is to understand whether differences in expression of Lepr and Ghsr exist within LHb- and VTA-projecting glutamatergic hypothalamic neurons. This study could be indicative of how hormones regulate feeding behavior and their particular effects on the hypothalamus projection neurons. Further research concerning the downstream impacts of these opposing hormonal pathways could shed light on the neural networks that govern food and energy balance.