Biology subjects

Engle, S. E.

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

3 recordsLinked to original sources

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↗