Biology subjects

Johnston, N.

Publications and source records attributed to Johnston, N..

3 recordsLinked to original sources

bioRxiv2025

Esr1-Dependent Signaling and Transcriptional Maturation in the Medial Preoptic Area of the Hypothalamus Shapes the Development of Mating Behavior during Adolescence

Mating and other behaviors emerge during adolescence through the coordinated actions of steroid hormone signaling throughout the nervous system and periphery. In this study, we investigated the transcriptional dynamics of the medial preoptic area (MPOA), a critical region for reproductive behavior, using single-cell RNA sequencing (scRNAseq) and in situ hybridization techniques in male and female mice throughout adolescence development. Our findings reveal that estrogen receptor 1 (Esr1) plays a pivotal role in the transcriptional maturation of GABAergic neurons within the MPOA during adolescence. Deletion of the estrogen receptor gene, Esr1, in GABAergic neurons (Vgat+) disrupted the developmental progression of mating behaviors in both sexes, while its deletion in glutamatergic neurons (Vglut2+) had no observable effect. In males and females, these neurons displayed distinct transcriptional trajectories, with hormone-dependent gene expression patterns emerging throughout adolescence and regulated by Esr1. Esr1 deletion in MPOA GABAergic neurons, prior to adolescence, arrested adolescent transcriptional progression of these cells and uncovered sex-specific gene-regulatory networks associated with Esr1 signaling. Our results underscore the critical role of Esr1 in orchestrating sex-specific transcriptional dynamics during adolescence, revealing gene regulatory networks implicated in the development of hypothalamic controlled reproductive behaviors. One Sentence SummarySingle cell RNA sequencing reveals how adolescent sex hormones sculpt hypothalamic cell types required for mating behavior.

neuroscience↗

bioRxiv2022

Structure of phage lambda Red-beta(177) annealase shows how it anneals DNA strands during single-strand annealing homologous DNA recombination

The bacteriophage {lambda} red recombination system catalyzes the single-strand annealing homologous DNA recombination reaction, in which Red{beta} annealase protein plays a critical role. Using cryogenic electron microscopy, we were able to determine a structure of a C-terminally truncated Red{beta} with the residues 1-177 bound to two complementary 27mer oligonucleotides forming an annealing intermediate, to a final resolution of 3.3 [A]. This structure validates and rationalizes decades of experimental observations on the biochemistry of Red{beta}. Definition of the interaction surfaces between subunits explains not only the DNA binding properties of Red{beta}, but also its propensity to oligomerize into long helical filaments, which are also formed by almost all annealases and are known to be functionally important. In addition, this annealing intermediate structure provides a detailed picture of the hydrogen bonding network that positions the DNA strands in a planar orientation to facilitate base pairing. Residues 133-138, which are missing from our structure, form a flexible loop. Molecular dynamics simulations were used to model the range of motion of the flexible loop, which suggested that it has a crucial role in keeping the DNA strands in the DNA-binding groove long enough to allow homology searching. The combination of structural and computational observations has allowed us to propose a detailed mechanism for the action of Red{beta}. More than half a century after its discovery, our work shines a light not only on the structure and mechanisms of Red{beta}, but also of other proteins within the annealase superfamilies. Significance StatementSingle-strand annealing homologous DNA recombination is a process that is conserved throughout evolution from bacteriophages to humans, highlighting its importance and indispensability. It is a process that repairs double-stranded DNA breaks and is particularly vital in dsDNA viruses. The Red{beta} protein from the bacteriophage lambda is the archetypal annealase protein, forming the basis of our knowledge about this class of proteins. Along with the exonuclease {lambda}Exo, these two proteins not only form the model system for single-strand annealing homologous recombination, but are also used in thousands of laboratories worldwide for performing genetic manipulations. After its discovery in 1966, we report the first structure of the DNA-binding and oligomerization domain of Red{beta}, providing details about the mechanism of homologous DNA annealing.

biochemistry↗

bioRxiv2021

Pubertal sex hormones control transcriptional trajectories in the medial preoptic area

Pubertal maturation aids development of emotion, cognition, and reproduction. We investigated transcriptional dynamics in the medial preoptic area (MPOA), a hypothalamic center for reproductive behaviors, in male and female mice at single-cell resolution (scRNAseq) during puberty. Defined subsets of neurons expressing Slc32a1 and Esr1 (Vgat+ Esr1+) were the most transcriptionally dynamic compared to other cell types throughout puberty. These cell type specific transcriptional progressions towards adulthood were bidirectionally controlled by the levels of circulating testosterone and estradiol. Selective deletion of Esr1 in Slc32a1-expressing cells in the MPOA prior to puberty arrested transcriptional progression and revealed a sexually dimorphic gene-regulatory network governed by Esr1. Deletion of Esr1 in Vgat+ cells prevented the development of mating behavior in both sexes. These analyses reveal both sexually common and dimorphic transcriptional progressions during puberty as well as their regulatory mechanisms, which have important implications towards understanding adaptative and maladaptive processes governing adolescent brain development.

neuroscience↗