Loss of Gata6 causes dilation of the hair follicle canal and sebaceous duct

The uppermost aspect of the hair follicle, known as the infundibulum or hair canal, provides a passageway for hair shaft egress and sebum secretion. Recent studies have indicated that the infundibulum and sebaceous ducts are lined by molecularly distinct differentiated cells expressing markers including Keratin 79 and Gata6. Here, we ablated Gata6 from the skin and observed dilation of both the hair canal and sebaceous ducts, independent of gender and hair cycle stage. Constitutive loss of Gata6 yielded only a mild delay in depilation‐induced entry into anagen, while unperturbed mutant mice possessed overtly normal skin and hair. Furthermore, we noted that Keratin 79 and Gata6 expression and localization did not depend upon each other. Our findings implicate Gata6 in maintaining the upper hair follicle and suggest that regulation of this transcription factor may be compromised in pathologies such as acne or infundibular cystic diseases that are characterized by abnormal expansion of this follicular domain.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/149235/1/exd13757_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/149235/2/exd13757-sup-0001-FigS1-S9.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/149235/3/exd13757.pd

Inflammation and Gli2 Suppress Gastrin Gene Expression in a Murine Model of Antral Hyperplasia

<div><p>Chronic inflammation in the stomach can lead to gastric cancer. We previously reported that gastrin-deficient (<em>Gast^−/−</em>) mice develop bacterial overgrowth, inflammatory infiltrate, increased Il-1β expression, antral hyperplasia and eventually antral tumors. Since Hedgehog (Hh) signaling is active in gastric cancers but its role in precursor lesions is poorly understood, we examined the role of inflammation and Hh signaling in antral hyperplasia. <em>LacZ</em> reporter mice for <em>Sonic hedgehog</em> (<em>Shh</em>), <em>Gli1</em>, and <em>Gli2</em> expression bred onto the <em>Gast^−/−</em> background revealed reduced <em>Shh</em> and <em>Gli1</em> expression in the antra compared to wild type controls (WT). <em>Gli2</em> expression in the <em>Gast^−/−</em> corpus was unchanged. However in the hyperplastic <em>Gast^−/−</em> antra, <em>Gli2</em> expression increased in both the mesenchyme and epithelium, whereas expression in WT mice remained exclusively mesenchymal. These observations suggested that <em>Gli2</em> is differentially regulated in the hyperplastic <em>Gast^−/−</em> antrum versus the corpus and by a Shh ligand-independent mechanism. Moreover, the proinflammatory cytokines Il-1β and Il-11, which promote gastric epithelial proliferation, were increased in the <em>Gast^−/−</em> stomach along with Infγ. To test if inflammation could account for elevated epithelial <em>Gli2</em> expression in the <em>Gast^−/−</em> antra, the human gastric cell line AGS was treated with IL-1β and was found to increase <em>GLI2</em> but decrease <em>GLI1</em> levels. IL-1β also repressed human <em>GAST</em> gene expression. Indeed, GLI2 but not GLI1 or GLI3 expression repressed gastrin luciferase reporter activity by ∼50 percent. Moreover, chromatin immunoprecipitation of GLI2 in AGS cells confirmed that GLI2 directly binds to the <em>GAST</em> promoter. Using a mouse model of constitutively active epithelial GLI2 expression, we found that activated GLI2 repressed <em>Gast</em> expression but induced <em>Il-1β</em> gene expression and proliferation in the gastric antrum, along with a reduction of the number of G-cells. In summary, epithelial Gli2 expression was sufficient to stimulate <em>Il-1β</em> expression, repress <em>Gast</em> gene expression and increase proliferation, leading to antral hyperplasia.</p> </div

Epithelial activation of Gli2 induced Il-1β and reduced <i>Gast</i> expression and G-cell number.

<p><b>A</b>) <i>Gast</i> gene expression is reduced after Gli2 activation in <i>Shh-Cre;R26-LSL-rtTA;tetO-GLI2</i>ΔN (GLI2ΔN) mice after 3 days of treatment with doxycycline. <b>B</b>) <i>Il-1β</i> was induced in the antra of GLI2ΔN mice antra. <b>C</b>) Representative images of hematoxylin-eosin staining (top panels), MYC staining to detect epitope-tagged GLI2?N (red), Gast staining (green) and merged images (lower panel) of the antrum of control and GLI2ΔN mice after 3 days of doxycycline. <b>D</b>) Representative images of proliferation marker Ki-67 staining in control and GLI2ΔN mice after 3 days of doxycycline. Data presented as mean±SEM. N = 2 mice per group per time. Bars are 100 µm in panel <b>C)</b> and 50 µm in panel <b>D)</b>.</p

Distinct mechanisms for sebaceous gland self-renewal and regeneration provide durability in response to injury

Summary: Sebaceous glands (SGs) release oils that protect our skin, but how these glands respond to injury has not been previously examined. Here, we report that SGs are largely self-renewed by dedicated stem cell pools during homeostasis. Using targeted single-cell RNA sequencing, we uncovered both direct and indirect paths by which resident SG progenitors ordinarily differentiate into sebocytes, including transit through a Krt5+PPARγ+ transitional basal cell state. Upon skin injury, however, SG progenitors depart their niche, reepithelialize the wound, and are replaced by hair-follicle-derived stem cells. Furthermore, following targeted genetic ablation of >99% of SGs from dorsal skin, these glands unexpectedly regenerate within weeks. This regenerative process is mediated by alternative stem cells originating from the hair follicle bulge, is dependent upon FGFR2 signaling, and can be accelerated by inducing hair growth. Altogether, our studies demonstrate that stem cell plasticity promotes SG durability following injury

Epithelial expression of Gli2 in the <i>Gast^−/−</i> antrum.

<p>The antral expression of Hedgehog pathway molecules was determined in 9–13 month-old littermate controls (<i>Gast^+/+</i>) (panels <b>A</b>, <b>C</b> and <b>E</b>) and <i>Gast^−/−</i> (panels <b>B</b>, <b>D</b> and <b>F</b>) mice by X-gal staining of LacZ reporter mice for Sonic hedgehog (<i>Shh</i>) (<b>A</b> and <b>B</b>), <i>Gli1</i> (<b>C</b> and <b>D</b>) and <i>Gli2</i> (<b>E</b> and <b>F</b>). A high power field of Gli2-LacZ staining is shown in F, where nuclear (yellow arrows) and perinuclear (black arrows) staining was observed along with cytoplasmic reporter accumulation. Whole stomachs from <i>Gast^+/+</i> and <i>Gast^−/−</i> were analyzed for gene expression of <i>Shh</i> (<b>G</b>), <i>Gli1</i> (<b>H</b>), and <i>Gli2</i> (<b>I</b>). Bars in panels <b>A</b> to <b>F</b> are 100 µm. Data presented as mean±SEM. N = 8 per group. *P≤0.05.</p

Gli2 expression is not increased in the <i>Gast^−/−</i> corpus.

<p>Representative X-gal staining of corpi of <i>Gast^+/+</i> and <i>Gast^−/−</i> mice harboring the <i>LacZ</i> reporter for Sonic hedgehog (<i>Shh</i>) (<b>A</b> and <b>B</b>), <i>Gli1</i> (<b>C</b> and <b>D</b>) and <i>Gli2</i> (<b>E</b> and <b>F</b>). Bars are 100 µm.</p

Niche-Specific Factors Dynamically Regulate Sebaceous Gland Stem Cells in the Skin.

Oil-secreting sebaceous glands (SGs) are critical for proper skin function; however, it remains unclear how different factors act together to modulate SG stem cells. Here, we provide functional evidence that each SG lobe is serviced by its own dedicated stem cell population. Upon ablating Notch signaling in different skin subcompartments, we find that this pathway exerts dual counteracting effects on SGs. Suppressing Notch in SG progenitors traps them in a hybrid state where stem and differentiation features become intermingled. In contrast, ablating Notch outside of the SG stem cell compartment indirectly drives SG expansion. Finally, we report that a K14:K5→K14:K79 keratin shift occurs during SG differentiation. Deleting K79 destabilizes K14 in sebocytes, and attenuates SGs and eyelid meibomian glands, leading to corneal ulceration. Altogether, our findings demonstrate that SGs integrate diverse signals from different niches and suggest that mutations incurred within one stem cell compartment can indirectly influence another