Biology subjects

Palmert, M. R.

Publications and source records attributed to Palmert, M. R..

5 recordsLinked to original sources

bioRxiv2023

Age, sex, and cell type-resolved hypothalamic gene expression across the pubertal transition in mice

Although the hypothalamus plays a critical role in the regulation of puberty, more research is needed to identify the gene regulatory networks that control pubertal timing. Here, we investigate the age-, sex- and cell-type-specific gene regulation in the hypothalamus across the pubertal transition. We used RNA-seq to profile hypothalamic gene expression in male and female mice at five time points spanning the onset of puberty (postnatal days (PD) 12, 22, 27, 32, and 37). By combining this data with hypothalamic scRNA-seq data of pre- and post-pubertal mice, we were able to assign gene expression changes to their cell types of origin. In our colony, pubertal onset occurs earlier in male mice allowing us to focus on genes whose expression is dynamic across ages and offset between sexes and to explore bases of sex effects. Our age-by- sex pattern of expression enriched for biological pathways involved hormone production, neuronal activation, and glial maturation. Additionally, we found a dramatic expansion of oligodendrocytes precursor cells into mature oligodendrocytes spanning the pre-pubertal (PD12) to peri-pubertal (PD27) timepoints, and that genes driving this expansion enrich for genes involved in pubertal regulation. Together, by incorporating multiple biological timepoints with male and female mice simultaneously, our work furthers the understanding of gene and cell-type changes that accompany the development of secondary sex characteristics in both sexes.

genomics↗

bioRxiv2022

Postnatal developmental trajectory of sex-biased gene expression in the mouse pituitary gland

The pituitary gland regulates essential physiological processes such as growth, pubertal onset, stress response, metabolism, reproduction, and lactation. While sex biases in these functions and hormone production have been described, the underlying identity, temporal deployment, and cell-type specificity of sex-biased pituitary gene regulatory networks are not fully understood. To capture sex differences in pituitary gene regulation dynamics during postnatal development, we performed 3 untranslated region sequencing and small RNA sequencing to ascertain gene and microRNA expression respectively across five postnatal ages (postnatal days 12, 22, 27, 32, 37) that span the pubertal transition in female and male C57BL/6J mouse pituitaries (n=5-6 biological replicates for each sex at each age). We observed over 900 instances of sex-biased gene expression and 17 sex-biased microRNAs, with the majority of sex differences occurring with puberty. Using miRNA-gene target interaction databases, we identified 18 sex-biased genes that were putative targets of 5 sex-biased microRNAs. In addition, by combining our bulk RNA-seq with publicly available male and female mouse pituitary single-nuclei RNA-seq data, we obtained evidence that cell-type proportion sex differences exist prior to puberty and persist post-puberty for three major hormone-producing cell types: somatotropes, lactotropes, and gonadotropes. Finally, we predicted sex-biased genes in these three pituitary cell types after accounting for cell-type proportion differences between sexes. Our study reveals the identity and postnatal developmental trajectory of sex-biased gene expression in the mouse pituitary. This work also highlights the importance of considering sex biases in cell-type composition when understanding sex differences in the processes regulated by the pituitary gland. HighlightsO_LIMale and female mouse pituitary gland gene and miRNA expression was profiled across five postnatal ages spanning pubertal development C_LIO_LIAbundant sex differences in pituitary gene expression exist prior to puberty and become more prominent upon puberty C_LIO_LICombining expression data from genes and miRNAs revealed 18 putative sex-biased gene targets of 5 sex-biased miRNAs C_LIO_LISex differences in the proportions of somatotropes, lactotropes, and gonadotropes are predicted to occur prior to puberty C_LI

genomics↗

bioRxiv2021

Mouse models of immune dysfunction: Their neuroanatomical differences reflect their anxiety-behavioural phenotype

Extensive evidence supports the role of the immune system in modulating brain function and behaviour. However, past studies have revealed striking heterogeneity in behavioural phenotypes produced from immune system dysfunction. Using magnetic resonance imaging (MRI), we studied the neuroanatomical differences among 11 distinct genetically-modified mouse lines (n=371), each deficient in a different element of the immune system. We found a significant and heterogeneous effect of immune dysfunction on the brains of both male and female mice. However, by imaging the whole brain and using bayesian hierarchical modelling, we were able to identify patterns within the heterogeneous phenotype. Certain structures -- such as the corpus callosum, midbrain, and thalamus -- were more likely to be affected by immune dysfunction. A notable brain-behaviour relationship was identified with neuroanatomy endophenotypes across mouse models clustering according to anxiety-like behaviour phenotypes reported in literature, such as altered volume in brains regions associated with promoting fear response (e.g., the lateral septum and cerebellum). Interestingly, genes with preferential spatial expression in the most commonly affected regions are also associated with multiple sclerosis and other immune-mediated diseases. In total, our data suggest that the immune system modulates anxiety behaviour through well-established brain networks.

neuroscience↗

bioRxiv2020

Exposure to maternal high-fat diet induces extensive changes in the brain of adult offspring

Maternal environmental exposures, such as high-fat diets, diabetes and obesity, can induce long term effects in offspring. These effects include increased risk of neurodevelopmental disorders (NDDs) including autism spectrum disorder (ASD), attention deficit hyperactivity disorder (ADHD), depression and anxiety. The mechanisms underlying these late-life neurologic effects are unknown. In this article, we measured changes in the offspring brain and determined which brain regions are sensitive to maternal metabolic milieu and therefore may mediate NDD risk. We showed that mice exposed to maternal high-fat diet display extensive brain changes in adulthood despite being switched to low-fat diet at weaning. Brain regions impacted by early-life diet include the extended amygdalar system, which plays an important role in reward-seeking behaviour. Genes preferentially expressed in these regions have functions related to feeding behavior, while also being implicated in human NDDs, such as autism. Our data demonstrated that exposure to maternal high-fat diet in early-life leads to brain alterations that persist into adulthood, even after dietary modifications.

neuroscience↗

bioRxiv2017

Mouse MRI shows brain areas larger in males emerge earlier than those larger in females

2Sex differences exist in behaviours, disease and neuropsychiatric disorders. Sexual dimorphisms however, have yet to be studied across the whole brain and across a comprehensive time course of postnatal development. We used manganese-enhanced MRI (MEMRI) to longitudinally image male and female C57BL/6J mice across 9 time points, beginning at postnatal day 3. We recapitulated findings on canonically dimorphic areas, demonstrating the ability of MEMRI to study neuroanatomical sex differences. We discovered, upon whole-brain volume correction, that neuroanatomical regions larger in males develop early in life, while regions larger in females develop in peripubertal life. Furthermore, we found groups of areas with shared sexually dimorphic developmental trajectories that reflect behavioural and functional networks, and expression of genes involved with sex processes. Our results demonstrate the ability of MEMRI to reveal comprehensive developmental differences between male and female brains, which will improve our understanding of sex-specific predispositions to various neuropsychiatric disorders.

neuroscience↗