Biology subjects

Engle, S. E.

Publications and source records attributed to Engle, S. E..

5 recordsLinked to original sources

bioRxiv2023

Ciliary ARL13B prevents obesity in mice

Primary cilia are sensory cellular appendages that regulate diverse developmental and homeostatic processes, including energy homeostasis. In animal models and humans, their dysfunction can lead to hyperphagia and obesity. ARL13B is a regulatory GTPase enriched in cilia. We engineered an Arl13b mouse allele, Arl13bV358A, that disrupts ARL13B from localizing to primary cilia. Homozygous Arl13bV358A/V358A mice become hyperphagic, obese, and insulin resistant. Restoring wildtype ARL13B to cilia in 4-week-old Arl13bV358A/V358A mice fully rescued the obesity and metabolic dysfunction. Additionally, the selective exclusion of ARL13B from cilia in the nervous system caused obesity. Together, these findings establish that ciliary ARL13B function within the nervous system is necessary for body weight regulation. Our ability to genetically uncouple the ciliary and non-ciliary functions of ARL13B in a cell-type-specific manner enables us to define its cilia-specific role and offers new insights into the molecular mechanisms underlying primary cilia control of energy homeostasis.

genetics↗

bioRxiv2022

Physiological Condition Dependent Changes in Ciliary GPCR Localization in the Brain

Primary cilia are small immotile cellular appendages which mediate diverse types of singling and are found on most mammalian cell types including throughout the central nervous system. Cilia are known to localize certain G protein-coupled receptors (GPCRs) and are critical for mediating the signaling of these receptors. Several of these neuronal GPCRs have recognized roles in feeding behavior and energy homeostasis. Heterologous cell line and model systems like C. elegans and Chlamydomonas have implicated both dynamic GPCR cilia localization and cilia length and shape changes as key for signaling. However, it is unclear if mammalian ciliary GPCRs utilize similar mechanisms in vivo and under what physiological conditions these processes may occur. Here, we use the ciliary GPCRs, melanin concentrating hormone receptor 1 (MCHR1) and neuropeptide-Y receptor 2 (NPY2R) as model ciliary receptors to determine if dynamic localization to cilia occurs. We tested physiological conditions in which these GPCRs have been implicated such as feeding behavior, obesity, and circadian rhythm. Cilia were imaged using confocal microscopy and analyzed with a computer assisted approach allowing for unbiased and high throughput analysis of cilia. We analyzed GPCR positive cilia, cilia frequency as well as cilia length and receptor occupancy. Interestingly we observed changes in ciliary length, receptor occupancy, and cilia frequency under different conditions, but no consistent theme across GPCRs or brain nuclei was observed. A better understanding of the subcellular localization dynamics of ciliary GPCRs could reveal unrecognized molecular mechanisms regulating behaviors like feeding. Significance StatementOften, primary cilia localize specific G protein-coupled receptors (GPCRs) for subcellular signaling. Cell lines and model systems have indicated that cilia deploy dynamic GPCR localization and change their shape or length to modulate signaling. We used mice to assess neuronal cilia GPCRs under physiological conditions associated with both the receptors known functions and ciliopathy clinical features like obesity. We show that certain cilia with specific GPCRs appear to dynamically alter their length while others appear relatively stable under these conditions. These results implicate multiple themes across cilia GPCR mediated signaling and indicate that not all cilia modulate GPCR signaling using the same mechanisms. These data will be important for potential pharmacological approaches to target cilia GPCR-mediated signaling.

neuroscience↗

bioRxiv2021

The hedgehog signaling pathway is expressed in the adult mouse hypothalamus and modulated by fasting

The importance of the primary cilium was initially highlighted by the class of human genetic disorders known as ciliopathies. Patients with ciliopathies such as Bardet-Biedl and Alstrom syndrome exhibit hyperphagia-associated obesity as a core clinical phenotype. How primary cilia contribute to energy homeostasis and feeding behavior is complex and unclear, but cilia appear important in both developmental and homeostatic processes. Primary cilia are important signaling centers, required for hedgehog signaling and localization of specific G protein-coupled receptors (GPCRs) with known roles in feeding behavior in mammals. The hedgehog pathway is best known for its role in developmental patterning, but now has recognized roles in adult tissues as well. In the postnatal brain, cilia and hedgehog signaling are important for growth and maintenance of neural progenitors, however, the role of hedgehog signaling in the differentiated adult brain is less clear. Here, we provide a detailed analysis of the expression of core components of the hedgehog signaling pathway in the adult mouse hypothalamus with an emphasis on feeding centers. We show that hedgehog pathway genes continue to be expressed in differentiated neurons important for regulation of feeding behavior. Furthermore, we demonstrate for the first time that pathway activity is regulated at the transcriptional level by fasting. These data suggest that hedgehog signaling is involved in the proper functioning of brain regions which regulate feeding behavior and that hedgehog pathway dysfunction may play a role in the obesity observed in certain ciliopathies. Significance StatementHere we investigate the expression of hedgehog pathway components in the adult mouse hypothalamus. Using dual labeling in situ hybridization we show that core components of the signaling pathway are expressed in multiple neuronal cell types within the hypothalamic feeding centers. Our findings also support previous findings that astrocytes are responsive to hedgehog signaling, as determined by Gli1 and Ptch1 expression. Using qPCR analysis, we show that hypothalamic hedgehog pathway activity is upregulated in response to fasting and this response is nuclei specific. These data not only provide a more detailed understanding of hedgehog pathway expression in the adult mouse hypothalamus but also provide direct evidence of a novel role for hedgehog signaling in the physiological response to fasting.

neuroscience↗

bioRxiv2021

Artificial Intelligence Approaches to Assessing Primary Cilia

Cilia are microtubule based cellular appendages that function as signaling centers for a diversity of signaling pathways in many mammalian cell types. Cilia length is highly conserved, tightly regulated, and varies between different cell types and tissues and has been implicated in directly impacting their signaling capacity. For example, cilia have been shown to alter their lengths in response to activation of ciliary G protein-coupled receptors. However, accurately and reproducibly measuring the lengths of numerous cilia is a time-consuming and labor-intensive procedure. Current approaches are also error and bias prone. Artificial intelligence (Ai) programs can be utilized to overcome many of these challenges due to capabilities that permit assimilation, manipulation, and optimization of extensive data sets. Here, we demonstrate that an Ai module can be trained to recognize cilia in images from both in vivo and in vitro samples. After using the trained Ai to identify cilia, we are able to design and rapidly utilize applications that analyze hundreds of cilia in a single sample for length, fluorescence intensity and colocalization. This unbiased approach increased our confidence and rigor when comparing samples from different primary neuronal preps in vitro as well as across different brain regions within an animal and between animals. Moreover, this technique can be used to reliably analyze cilia dynamics from any cell type and tissue in a high-throughput manner across multiple samples and treatment groups. Ultimately, Ai-based approaches will likely become standard as most fields move toward less biased and more reproducible approaches for image acquisition and analysis. SUMMARYThe use of Artificial Intelligence (Ai) to analyze images is emerging as a powerful, less biased, and rapid approach compared with commonly used methods. Here we trained Ai to recognize a cellular organelle, primary cilia, and analyze properties such as length and staining intensity in a rigorous and reproducible manner.

cell biology↗

bioRxiv2020

A Bbs5 mouse model reveals pituitary cilia contributions to developmental abnormalities.

Primary cilia are critical sensory and signaling compartments present on most mammalian cell types. These specialized structures require a unique signaling protein composition relative to the rest of the cell to carry out their functions. Defects in ciliary structure and signaling result in a broad group of disorders collectively known as ciliopathies. One ciliopathy, Bardet-Biedl Syndrome (BBS; OMIM 209900), presents with diverse clinical features, many of which are attributed to defects in ciliary signaling during both embryonic development and postnatal life. For example, patients exhibit obesity, polydactyly, hypogonadism, developmental delay, and skeletal abnormalities along with sensory and cognitive deficits, but for many of these phenotypes it is uncertain which are developmental in origin. A subset of BBS proteins assembles into the BBSome complex, which is responsible for mediating transport of membrane proteins into and out of the cilium, establishing it as a sensory and signaling hub. Here we describe two new mouse models for BBS resulting from a congenital null and conditional allele of Bbs5. Bbs5 null mice develop a complex phenotype including craniofacial defects, skeletal shortening, ventriculomegaly, infertility, and pituitary anomalies. Utilizing the conditional allele, we show that the male fertility defects, ventriculomegaly, and pituitary abnormalities are only found when Bbs5 is mutated prior to P7 indicating a developmental origin. In contrast, mutation of Bbs5 results in obesity independent of the age of Bbs5 loss. Compared to other animal models of BBS, Bbs5 mutant mice exhibit pathologies that suggest a specialized role for Bbs5 in ciliary function.

developmental biology↗