Contrasting levels of hybridization across the two contact zones between two hedgehog species revealed by genome-wide SNP data.

Hybridization and introgression have played important roles in the history of various species, including lineage diversification and the evolution of adaptive traits. Hybridization can accelerate the development of reproductive isolation between diverging species, and thus valuable insight into the evolution of reproductive barrier formation may be gained by studying secondary contact zones. Hedgehogs of the genus Erinaceus, which are insectivores sensitive to changes in climate, are a pioneer model in Pleistocene phylogeography. The present study provides the first genome-wide SNP data regarding the Erinaceus hedgehogs species complex, offering a unique comparison of two secondary contact zones between Erinaceus europaeus and E. roumanicus. Results confirmed diversification of the genus during the Pleistocene period, and detected a new refugial lineage of E. roumanicus outside the Mediterranean basin, most likely in the Ponto-Caspian region. In the Central European zone, the level of hybridization was low, whereas in the Russian-Baltic zone, both species hybridise extensively. Asymmetrical gene flow from E. europaeus to E. roumanicus suggests that reproductive isolation varies according to the direction of the crosses in the hybrid zones. However, no loci with significantly different patterns of introgression were detected. Markedly different pre- and post-zygotic barriers, and thus diverse modes of species boundary maintenance in the two contact zones, likely exist. This pattern is probably a consequence of the different age and thus of the different stage of evolution of reproductive isolating mechanisms in each hybrid zone.

Regulation of Smoothened ubiquitylation and cell surface expression through a Cul4-DDB1-Gß E3 ubiquitin ligase complex.

Hedgehog (Hh) transduces signals by promoting cell surface accumulation and activation of the G-protein-coupled receptor (GPCR)-family protein Smoothened (Smo) in Drosophila, but the molecular mechanism underlying the regulation of Smo trafficking remains poorly understood. Here, we identified the Cul4-DDB1 E3 ubiquitin ligase complex as being essential for Smo ubiquitylation and cell surface clearance. We found that the C-terminal intracellular domain of Smo recruits Cul4-DDB1 through the ß subunit of trimeric G protein (Gß), and that Cul4-DDB1-Gß promotes the ubiquitylation of both Smo and its binding partner G-protein-coupled-receptor kinase 2 (Gprk2) and induces the internalization and degradation of Smo. Hh dissociates Cul4-DDB1 from Smo by recruiting the catalytic subunit of protein kinase A (PKA) to phosphorylate DDB1, which disrupts its interaction with Gß. Inactivation of the Cul4-DDB1 complex resulted in elevated Smo cell surface expression, whereas an excessive amount of Cul4-DDB1 blocked Smo accumulation and attenuated Hh pathway activation. Taken together, our study identifies an E3 ubiquitin ligase complex targeting Smo for ubiquitylation and provides new insight into how Hh signaling regulates Smo trafficking and cell surface expression.

Complete mitochondrial genome of the Amur hedgehog Erinaceus amurensis (Erinaceidae) and higher phylogeny of the family Erinaceidae.

We sequenced and characterized the complete mitogenome (KX964606) of the Amur hedgehog Erinaceus amurensis to provide more data for comparative mitogenomics of the genus Erinaceus (Erinaceidae). The mitogenome of E. amurensis is a circular molecule 16,941 bp long, consisting of a control region and a conserved set of 37 genes containing 13 protein-coding genes, 22 tRNA genes, and two rRNA genes (12S rRNA and 16S rRNA). The mitogenome of E. amurensis is AT-biased, with a nucleotide composition of 33.9% A, 21.1% C, 32.6% T, and 12.4% G. The mitogenomes of E. amurensis and the closely related hedgehog species E. europaeus, excluding the control region (66.7%), share over 90% sequence similarity. According to the inter-generic relationship based on six mitogenomes described from five genera of Erinaceidae, the subfamilies Erinaceinae and Galericinae are strongly supported as monophyletic groups, with each genus well placed within its own subfamily. Within the subfamily Erinaceinae, E. amurensis is a sister species to E. europaeus, and the relationship between Hemiechinus and Erinaceus is strongly supported. Within the subfamily Galericinae, the clade of Hylomys + Neotetracus was sister to that of Echinosorex, with clades supported by high values. Our findings will help to understand the codon usage pattern and molecular evolution of E. amurensis, and provide insight into inter-generic relationships within the family Erinaceidae. In future studies, the inclusion of mitogenomes from other genera would greatly enhance our understanding of higher phylogeny within the Erinaceidae.

A genome-wide association meta-analysis implicates Hedgehog and Notch signaling in Dupuytren's disease.

Dupuytren's disease (DD) is a highly heritable fibrotic disorder of the hand with incompletely understood etiology. A number of genetic loci, including Wnt signaling members, have been previously identified. Our overall aim was to identify novel genetic loci, to prioritize genes within the loci for functional studies, and to assess genetic correlation with associated disorders. We performed a meta-analysis of six DD genome-wide association studies from three European countries and extensive bioinformatic follow-up analyses. Leveraging 11,320 cases and 47,023 controls, we identified 85 genome-wide significant single nucleotide polymorphisms in 56 loci, of which 11 were novel, explaining 13.3-38.1% of disease variance. Gene prioritization implicated the Hedgehog and Notch signaling pathways. We also identified a significant genetic correlation with frozen shoulder. The pathways identified highlight the potential for new therapeutic targets and provide a basis for additional mechanistic studies for a common disorder that can severely impact hand function.

Epigenetic Effects of Resveratrol on Oncogenic Signaling in Breast Cancer.

The crosstalk between oncogenic signaling pathways plays a crucial role in driving cancer development. We previously demonstrated that dietary polyphenols, specifically resveratrol (RSV) and other stilbenoids, epigenetically target oncogenes for silencing via DNA hypermethylation in breast cancer. In the present study, we identify signal transduction regulators among RSV-hypermethylated targets and investigate the functional role of RSV-mediated DNA hypermethylation in the regulation of Hedgehog and Wnt signaling. Non-invasive ER-positive MCF-7 and highly invasive triple-negative MCF10CA1a human breast cancer cell lines were used as experimental models. Upon 9-day exposure to 15 µM RSV, pyrosequencing and qRT-PCR were performed to assess DNA methylation and expression of GLI2 and WNT4, which are upstream regulators of the Hedgehog and Wnt pathways, respectively. Our results showed that RSV led to a DNA methylation increase within GLI2 and WNT4 enhancers, which was accompanied by decreases in gene expression. Consistently, we observed the downregulation of genes downstream of the Hedgehog and Wnt signaling, including common targets shared by both pathways, CCND1 and CYR61. Further analysis using chromatin immunoprecipitation identified increased H3K27 trimethylation and decreased H3K9 and H3K27 acetylation, along with abolishing OCT1 transcription factor binding. Those changes indicate a transcriptionally silent chromatin state at GLI2 and WNT4 enhancers. The inhibition of the Wnt signal transduction was confirmed using a phospho-antibody array that demonstrated suppression of positive and stimulation of negative Wnt regulators. In conclusion, our results provide scientific evidence for dietary polyphenols as epigenetics-modulating agents that act to re-methylate and silence oncogenes, reducing the oncogenic signal transduction. Targeting such an action could be an effective strategy in breast cancer prevention and/or adjuvant therapy.

Population biology of establishment in New Zealand hedgehogs inferred from genetic and historical data: conflict or compromise?

The crucial steps in biological invasions, related to the shaping of genetic architecture and the current evolution of adaptations to a novel environment, usually occur in small populations during the phases of introduction and establishment. However, these processes are difficult to track in nature due to invasion lag, large geographic and temporal scales compared with human observation capabilities, the frequent depletion of genetic variance, admixture and other phenomena. In this study, we compared genetic and historical evidence related to the invasion of the West European hedgehog to New Zealand to infer details about the introduction and establishment. Historical information indicates that the species was initially established on the South Island. A molecular assay of populations from Great Britain and New Zealand using mitochondrial sequences and nuclear microsatellite loci was performed based on a set of analyses including approximate Bayesian computation, a powerful approach for disentangling complex population demographies. According to these analyses, the population of the North Island was most similar to that of the native area and showed greatest reduction in genetic variation caused by founder demography and/or drift. This evidence indicated the location of the establishment phase. The hypothesis was corroborated by data on climate and urbanization. We discuss the contrasting results obtained by the molecular and historical approaches in the light of their different explanatory power and the possible biases influencing the description of particular aspects of invasions, and we advocate the integration of the two types of approaches in invasion biology.

Synanthropic and Wild Animals as Sentinels of Zoonotic Agents: A Study of Leptospira Genotypes Circulating in Northeastern Italy.

Leptospirosis is an infectious disease widely reported in veterinary practice and a worldwide zoonosis. In Northeastern Italy, different serogroups and genotypes of Leptospira have been described in ill dogs, the most commonly detected being Icterohaemorragiae (ICT) ST 17, Australis (AUS) ST 24 and ST 198, Pomona (POM) ST 117 and ST 289, and Sejroe (SEJ) ST 155. However, there is little information available on the environmental exposure to Leptospira of wild and synanthropic animals. The aim of this study was to identify the circulating genotypes in potential reservoirs to fill this gap of knowledge. Between 2015 and 2022, 681 animal carcasses collected by the Public Veterinary Service were analyzed for Leptospira with a real-time PCR-based screening test, while positive samples were genotyped by multi-locus sequence typing analysis. To carry out our study, we tested 330 hedgehogs, 105 red foxes, 108 Norway rats, 79 mice, 22 coypus, 10 bank voles, 13 grey wolves, 5 common shrews and 9 greater mouse-eared bats. Five sequence types (STs) common in dogs were also found in wild animals: ST 24, ST 198, ST 17 and ST 155 in hedgehogs, ST 17 and ST 24 in foxes, ST 17 in rats, ST 17 and ST 155 in mice, and ST 117 in a wolf. In addition, to the best of the authors' knowledge, this is the first Italian report of SEJ ST 197 in a bank vole. Furthermore, this study described a previous survey conducted in 2009 on coypus (30 animals from the province of Trento and 41 from the province of Padua), referring to a serological positivity (L. Bratislava) without any molecular detection of Leptospira. This study on Leptospira in synanthropic and wild animals highlighted the importance of increasing our epidemiological knowledge of leptospirosis and its zoonotic risks.

Unveiling the connection: Long-chain non-coding RNAs and critical signaling pathways in breast cancer.

Breast cancer is a complex and diverse condition that disrupts multiple signaling pathways essential for cell proliferation, survival, and differentiation. Recently, the significant involvement of long-chain non-coding RNAs (lncRNAs) in controlling key signaling pathways associated with breast cancer development has been discovered. This review aims to explore the interaction between lncRNAs and various pathways, including the AKT/PI3K/mTOR, Wnt/ß-catenin, Notch, DNA damage response, TGF-ß, Hedgehog, and NF-κB signaling pathways, to gain a comprehensive understanding of their roles in breast cancer. The AKT/PI3K/mTOR pathway regulates cell growth, survival, and metabolic function. Recent data suggests that specific lncRNAs can influence the functioning of this pathway, acting as either oncogenes or tumor suppressors. Dysregulation of this pathway is commonly observed in breast cancer cases. Moreover, breast cancer development has been associated with other pathways such as Wnt/ß-catenin, Notch, TGF-ß, Hedgehog, and NF-κB. Emerging studies have identified lncRNAs that modulate breast cancer's growth, progression, and metastasis by interacting with these pathways. To advance the development of innovative diagnostic tools and targeted treatment options, it is crucial to comprehend the intricate relationship between lncRNAs and vital signaling pathways in breast cancer. By fully harnessing the therapeutic potential of lncRNAs, there is a possibility of developing more effective and personalized therapy choices for breast cancer patients. Further investigation is necessary to comprehensively understand the role of lncRNAs within breast cancer signaling pathways and fully exploit their therapeutic potential.

Recent expansion of a new Ingi-related clade of Vingi non-LTR retrotransposons in hedgehogs.

Autonomous non-long terminal repeat (non-LTR) retrotransposons and their repetitive remnants are ubiquitous components of mammalian genomes. Recently, we identified non-LTR retrotransposon families, Ingi-1_AAl and Ingi-1_EE, in two hedgehog genomes. Here we rename them to Vingi-1_AAl and Vingi-1_EE and report a new clade "Vingi," which is a sister clade of Ingi that lacks the ribonuclease H domain. In the European hedgehog genome, there are 11 non-autonomous families of elements derived from Vingi-1_EE by internal deletions. No retrotransposons related to Vingi elements were found in any of the remaining 33 mammalian genomes nearly completely sequenced to date, but we identified several new families of Vingi and Ingi retrotransposons outside mammals. Our data suggest the horizontal transfer of Vingi elements to hedgehog, although the vertical transfer cannot be ruled out. The compact structure and trans-mobilization of nonautonomous derivatives of Vingi can make them useful for in vivo retrotransposition assay system.

Microevolution of sympatry: landscape genetics of hedgehogs Erinaceus europaeus and E. roumanicus in Central Europe.

We used the mitochondrial control region and nuclear microsatellites to assess the distribution patterns, population structure, demography and landscape genetics for the hedgehogs Erinaceus europaeus and Erinaceus roumanicus in a transect of the mid-European zone of sympatry. E. roumanicus was less frequent and restricted to regions with lower altitudes. Demographic analyses suggested recent population growth in this species. A comparison of patterns in the spatial variability of mitochondrial and nuclear DNA indicated less sex-biased dispersal and higher levels of gene flow in E. roumanicus. No evidence of recent hybridisation or introgression was detected. We interpreted these results by comparing with phylogeographic and palaeontological studies as well as with the occurrence of hybridisation in the Russian contact zone. We propose that Central Europe was colonised by E. roumanicus by the beginning of the Neolithic period and that there was a subsequent reinforcement stage as well as the formation of a zone of sympatry after the complete reproductive isolation of both species.

Gene cloning, expression and functional characterization of a proliferation-inducing ligand (APRIL) from hedgehog (Erinaceus europaeus).

Here we describe the identification of the hedgehog Erinaceus europaeus homologue of a proliferation-inducing ligand (APRIL) of the TNF family (designated heAPRIL). Hedgehog APRIL contains two cysteine residues (Cys(196) and Cys(211)), a furin protease cleavage site and a conserved putative N-glycosylation site (Asn(124)). Real-time quantitative PCR (qPCR) analysis revealed that heAPRIL could be detected in various tissues. MTT assays and flow cytometric analysis revealed that Nus-hesAPRIL and hesAPRIL could promote the survival/proliferation of splenic B cells. Laser scanning confocal microscopy analysis showed GFP-hesAPRIL could successfully bind to the APRIL receptors of lymphocytes.

Signatures of conserved and unique molecular features in Afrotheria.

Afrotheria is a clade of African-origin species with striking dissimilarities in appearance and habitat. In this study, we compared whole proteome sequences of six Afrotherian species to obtain a broad viewpoint of their underlying molecular make-up, to recognize potentially unique proteomic signatures. We find that 62% of the proteomes studied here, predominantly involved in metabolism, are orthologous, while the number of homologous proteins between individual species is as high as 99.5%. Further, we find that among Afrotheria, L. africana has several orphan proteins with 112 proteins showing < 30% sequence identity with their homologues. Rigorous sequence searches and complementary approaches were employed to annotate 156 uncharacterized protein sequences and 28 species-specific proteins. For 122 proteins we predicted potential functional roles, 43 of which we associated with protein- and nucleic-acid binding roles. Further, we analysed domain content and variations in their combinations within Afrotheria and identified 141 unique functional domain architectures, highlighting proteins with potential for specialized functions. Finally, we discuss the potential relevance of highly represented protein families such as MAGE-B2, olfactory receptor and ribosomal proteins in L. africana and E. edwardii, respectively. Taken together, our study reports the first comparative study of the Afrotherian proteomes and highlights salient molecular features.

Genetic structure of the European hedgehog (Erinaceus europaeus) in Denmark.

OBJECTIVES: Low genetic diversity can lead to reduced average fitness in a population or even extinction. Preserving genetic connectivity across fragmented landscapes is therefore vital to counteract the negative consequences of genetic drift and inbreeding. This study aimed to assess the genetic composition and consequently the conservation status of a nationwide sample of European hedgehogs (Erinaceus europaeus) in Denmark. METHODS: We applied an adaptation of the genotyping by sequencing (GBS) technique to 178 individuals from six geographically distinct populations. We used a Bayesian clustering method to subdivide individuals into genetically distinct populations. We estimated individual observed (iHO), observed (HO), and unbiased expected (uHE) heterozygosity, inbreeding coefficient (FIS), percentage of polymorphic loci (P%) and tested for deviations from Hardy-Weinberg equilibrium (HWE). We used linear models to test for potential anthropogenic effects on the genetic variability of hedgehogs with iHO, uHE, P% and FIS as response variables, and assessed the demographic history of the population. RESULTS: The Danish hedgehog population is composed of three genetic clusters. We found a mean P% of 54.44-94.71, a mean uHE of 0.126-0.318 and a mean HO of 0.124-0.293 in the six populations. The FIS was found to be significantly positive for three of the six populations. We detected a large heterogeneity of iHO values within populations, which can be due to inbreeding and/or fragmentation. FIS values decreased with increasing farmland density, but there was no significant association with human population or road density. CONCLUSIONS: We found a low level of genetic variability and evidence for genetic substructure and low effective population size, which are all consequences of habitat fragmentation. We failed to detect signs of a recent population bottleneck or population increase or decline. However, because the test only identifies recent changes in population size, we cannot reject the possibility of a longer-term decline in the Danish hedgehog population.

Transcriptome analysis reveals the genetic basis underlying the development of skin appendages and immunity in hedgehog (Atelerix albiventris).

The expression of hair features is an evolutionary adaptation resulting from interactions between many organisms and their environment. Elucidation of the mechanisms that underlie the expression of such traits is a topic in evolutionary biology research. Therefore, we assessed the de novo transcriptome of Atelerix albiventris at three developmental stages and compared gene expression profiles between abdomen hair and dorsal spine tissues. We identified 328,576 unigenes in our transcriptome, among which 4,435 were differentially expressed between hair- and spine-type tissues. Dorsal and abdomen skin tissues 5 days after birth were compared and the resulting DEGs were mainly enriched in keratin filament, epithelium cell differentiation, and epidermis development based on GO enrichment analysis, and tight junction, p53, and cell cycle signaling pathways based on KEGG enrichment analysis. MBP8, SFN, Wnt1 and KRT1 gene may involve in the development of hedgehog skin and its appendages. Strikingly, DEGs in hair-type tissues were also significantly enriched in immune-related terms and pathways with hair-type tissues exhibiting more upregulated immune genes than spine-type tissues. Our study provided a list of potential genes involved in skin appendage development and differentiation in A. albiventris, and the candidate genes provided valuable information for further studies of skin appendages.

MicroRNA­1 regulates the development of osteoarthritis in a Col2a1­Cre­ERT2/GFPfl/fl­RFP­miR­1 mouse model of osteoarthritis through the downregulation of Indian hedgehog expression.

The present study assessed the effects of microRNA­1 (miR­1) on the development of osteoarthritis using human tissues and a Col2a1­Cre­ERT2/GFPfl/fl­RFP­miR­1 mouse model of osteoarthritis. Human cartilage tissues (n=20) were collected for reverse transcription­quantitative polymerase chain reaction (RT­qPCR), histological analysis and immunohistochemistry experiments. A transgenic mouse model of osteoarthritis was established by subjecting Col2a1­Cre­ERT2/GFPfl/fl­RFP­miR­1 transgenic mice to anterior cruciate ligament transection (ACLT). Mice were subjected to radiography and in vivo fluorescence molecular tomography (FMT), while mouse tissues were collected for histological analysis, RT­qPCR and Safranin O staining. It was found that the miR­1 level was downregulated, whereas the levels of Indian hedgehog (Ihh), as well as those of its downstream genes were upregulated in human osteoarthritic cartilage. In the transgenic mice, treatment with tamoxifen induced miR­1, as well as collagen, type II (Col2a1) and Aggrecan (Acan) expression; however, it decreased Ihh, glioma­associated oncogene homolog (Gli)1, Gli2, Gli3, smoothened homolog (Smo), matrix metalloproteinase (MMP)­13 and collagen type X (Col10) expression. Safranin O staining revealed cartilage surface damage in the non­tamoxifen + ACLT group, compared with that in the tamoxifen + ACLT group. Histologically, an intact cartilage surface and less fibrosis were observed in the tamoxifen + ACLT group. Immunohistochemistry revealed that the protein expression of Ihh, Col10, and MMP­13 was significantly higher in the joint tissues of the non­tamoxifen + ACLT group than in those of the tamoxifen + ACLT group. However, Col2a1 expression was lower in the joint tissues of the non­tamoxifen + ACLT group than in those of the tamoxifen + ACLT group. The results of RT­qPCR and FMT further confirmed these findings. On the whole, the findings of the present study demonstrate that miR­1 expression protects against osteoarthritis­induced cartilage damage and gene expression by inhibiting Ihh signaling.

[The first genetic evidence of hybridization between west European and northern white-breasted hedgehogs (Erinaceus europaeus and E. roumanicus) in Moscow Region].

The complex genetic examination of hedgehogs from the vicinity of the village of Nikolina Gora (Moscow region, Odintsovskii district) showed both Erinaceus europaeus and E. roumanicus in the sample. One of the hedgehogs was designated as E. roumanicus by the nucleotide sequence of 1 TTR intron but possessed mitochondrial DNA of E. europeus. Only one of the chromosomal pairs that differ in E. europeus and E. roumanicus was heteromorphic in this specimen. Its hybridous origin as the offspring of one or several back-crosses between F1 hybrid and E. roumanicus was suggested.

Epigenetic regulation of mammalian Hedgehog signaling to the stroma determines the molecular subtype of bladder cancer.

In bladder, loss of mammalian Sonic Hedgehog (Shh) accompanies progression to invasive urothelial carcinoma, but the molecular mechanisms underlying this cancer-initiating event are poorly defined. Here, we show that loss of Shh results from hypermethylation of the CpG shore of the Shh gene, and that inhibition of DNA methylation increases Shh expression to halt the initiation of murine urothelial carcinoma at the early stage of progression. In full-fledged tumors, pharmacologic augmentation of Hedgehog (Hh) pathway activity impedes tumor growth, and this cancer-restraining effect of Hh signaling is mediated by the stromal response to Shh signals, which stimulates subtype conversion of basal to luminal-like urothelial carcinoma. Our findings thus provide a basis to develop subtype-specific strategies for the management of human bladder cancer.

Taxonomic revision of the genus Mesechinus (Mammalia: Erinaceidae) with description of a new species.

Hedgehogs in the genus Mesechinus (Family Erinaceidae), which include two currently recognized species (M. dauuricus and M. hughi), are distributed from northeast Mongolia to the upper Amur Basin in Russia and adjacent areas in northeast and northern China. In recent years, a population of Mesechinus hedgehogs was discovered from Mt. Gaoligong, southwestern Yunnan, China, far from the known distribution range of the genus. Furthermore, these hedgehogs are the only known population to be distributed at elevations higher than 2 100 m and in sympatry with gymnures. To evaluate the taxonomic status of these hedgehogs, we examined specimens representing Mesechinus taxa in China and further conducted morphometric and karyotypic analyses. Our results supported the existence of four species in China. Specifically, we identified the hedgehogs from Mt. Gaoligong as a new species, Mesechinus wangi sp. nov., and recognized M. miodon, previously considered as a synonym of either M. dauuricus or M. hughi, as a distinct species. Interestingly, we observed a supernumerary M4 on all specimens of Mesechinus wangi sp. nov., which is an extremely rare event in the evolution of mammalian dentition.

Sulforaphene Inhibition of Adipogenesis via Hedgehog Signaling in 3T3-L1 Adipocytes.

Obesity is a risk factor for numerous metabolic disorders. In this study, we investigated the effects of the isothiocyanates sulforaphane (SA) and sulforaphene (SE) on adipogenesis in 3T3-L1 adipocytes. SE, a compound that is abundant in radish, inhibited adipogenesis by suppressing the adipogenic transcription factors peroxisome proliferator-activated receptor γ (PPARγ, 69.2 ± 2.4%, P < 0.05) and CCAAT/enhancer-binding protein α (C/EBPα, 36.1 ± 3.1%, P < 0.05), thereby reducing fat accumulation in 3T3-L1 adipocytes (45.6 ± 2.7%, P < 0.05); SA was less effective. SE exerted these activities through the activation of the Hedgehog (Hh) signaling pathway by restoring Smo ((2.1 ± 0.2)-fold, P < 0.05) and Gli1 ((2.8 ± 0.1)-fold, P < 0.05) expression, which was suppressed by adipogenic signals. These effects of SE were abrogated by treatment with the Hh inhibitor vismodegib. Thus, SE inhibits adipocyte differentiation via Hh signaling and may be an effective natural agent for preventing adipocyte hyperplasia and obesity.

The role of Hedgehog-responsive fibroblasts in facial nerve regeneration.

BACKGROUND: Facial nerve paralysis is a significant cause of morbidity, affecting facial appearance, emotional expression, speech, oral competence, and vision. A more complete understanding of the complex cellular events required for successful nerve regeneration may reveal new therapeutic targets. The role of fibroblasts in regeneration, and the process by which the nerve reforms its three-dimensional structure after a transection injury, are not fully understood. The Hedgehog signaling pathway has been shown to mediate nerve sheath formation during development. We therefore sought to characterize the role of Hedgehog-responsive cells following transection of the facial nerve. METHODS: Two transgenic mouse lines with reporters for the downstream effector of Hedgehog signaling, Gli1, were used. The animals underwent a unilateral facial nerve transection injury, and the contralateral side served as a control. Facial nerves were analyzed via immunohistochemistry and immunofluorescence at predetermined time points as the facial nerve regenerated after the transection injury. RESULTS: There was a statistically significant increase in Gli1+ cells both at the site of injury and within the distal nerve segment over time. Gli1+ cells are fibroblasts within the nerve and appear to contribute to the reformation of the nerve sheath after injury. CONCLUSION: These findings describe a key signaling pathway by which fibroblasts participate in motor nerve regeneration. Fibroblasts that reside within the nerve respond to injury and may represent a novel therapeutic target in the context of facial nerve regeneration after transection injury.