Pixel walking along the boreal forest-Arctic tundra ecotone: Large scale ground-truthing of satellite-derived greenness (NDVI).

In this Technical Advance, we describe a novel method to improve ecological interpretation of remotely sensed vegetation greenness measurements that involved sampling 24,395 Landsat pixels (30 m) across 639 km of Alaska's central Brooks Range. The method goes well beyond the spatial scale of traditional plot-based sampling and thereby more thoroughly relates ground-based observations to satellite measurements. Our example dataset illustrates that, along the boreal-Arctic boundary, vegetation with the greatest Landsat Normalized Difference Vegetation Index (NDVI) is taller than 1 m, woody, and deciduous; whereas vegetation with lower NDVI tends to be shorter, evergreen, or non-woody. The field methods and associated analyses advance efforts to inform satellite data with ground-based vegetation observations using field samples collected at spatial scales that closely match the resolution of remotely sensed imagery.

Keratinocyte-specific deletion of SHARPIN induces atopic dermatitis-like inflammation in mice.

Spontaneous mutations in the SHANK-associated RH domain interacting protein (Sharpin) resulted in a severe autoinflammatory type of chronic proliferative dermatitis, inflammation in other organs, and lymphoid organ defects. To determine whether cell-type restricted loss of Sharpin causes similar lesions, a conditional null mutant was created. Ubiquitously expressing cre-recombinase recapitulated the phenotype seen in spontaneous mutant mice. Limiting expression to keratinocytes (using a Krt14-cre) induced a chronic eosinophilic dermatitis, but no inflammation in other organs or lymphoid organ defects. The dermatitis was associated with a markedly increased concentration of serum IgE and IL18. Crosses with S100a4-cre resulted in milder skin lesions and moderate to severe arthritis. This conditional null mutant will enable more detailed studies on the role of SHARPIN in regulating NFkB and inflammation, while the Krt14-Sharpin-/- provides a new model to study atopic dermatitis.

Integrin beta 1 inhibition alleviates the chronic hyperproliferative dermatitis phenotype of SHARPIN-deficient mice.

SHARPIN (Shank-Associated RH Domain-Interacting Protein) is a component of the linear ubiquitin chain assembly complex (LUBAC), which enhances TNF-induced NF-κB activity. SHARPIN-deficient (Sharpincpdm/cpdm) mice display multi-organ inflammation and chronic proliferative dermatitis (cpdm) due to TNF-induced keratinocyte apoptosis. In cells, SHARPIN also inhibits integrins independently of LUBAC, but it has remained enigmatic whether elevated integrin activity levels in the dermis of Sharpincpdm/cpdm mice is due to increased integrin activity or is secondary to inflammation. In addition, the functional contribution of increased integrin activation to the Sharpincpdm/cpdm phenotype has not been investigated. Here, we find increased integrin activity in keratinocytes from Tnfr1-/- Sharpincpdm/cpdm double knockout mice, which do not display chronic inflammation or proliferative dermatitis, thus suggesting that SHARPIN indeed acts as an integrin inhibitor in vivo. In addition, we present evidence for a functional contribution of integrin activity to the Sharpincpdm/cpdm skin phenotype. Treatment with an integrin beta 1 function blocking antibody reduced epidermal hyperproliferation and epidermal thickness in Sharpincpdm/cpdm mice. Our data indicate that, while TNF-induced cell death triggers the chronic inflammation and proliferative dermatitis, absence of SHARPIN-dependent integrin inhibition exacerbates the epidermal hyperproliferation in Sharpincpdm/cpdm mice.

Loss of FAS/FASL signalling does not reduce apoptosis in Sharpin null mice.

Mice with mutations in SHANK-associated RH domain interactor (Sharpin) develop a hypereosinophilic auto-inflammatory disease known as chronic proliferative dermatitis. Affected mice have increased apoptosis in the keratinocytes of the skin, oesophagus and forestomach driven by extrinsic TNF receptor-mediated apoptotic signalling pathways. FAS receptor signalling is an extrinsic apoptotic signalling mechanism frequently involved in inflammatory skin diseases. Compound mutations in Sharpin and Fas or Fasl were created to determine whether these death domain proteins influenced the cutaneous phenotype in Sharpin null mice. Both Sharpin/Fas and Sharpin/Fasl compound mutant mice developed an auto-inflammatory phenotype similar to that seen in Sharpin null mice, indicating that initiation of apoptosis by FAS signalling is likely not involved in the pathogenesis of this disease.

Skin fragility in the wild-derived, inbred mouse strain Mus pahari/EiJ.

Mus pahari is a wild-derived, inbred mouse strain. M. pahari colony managers observed fragility of this strain's skin resulting in separation of tail skin from the mouse if handled incorrectly. Tail skin tension testing of M. pahari resulted in significantly lowered force threshold for caudal skin rupture and loss in comparison to closely related inbred mouse species and subspecies and even more than a model for junctional epidermolysis bullosa. Histologically, the tail skin separated at the subdermal level with the dermis firmly attached to the epidermis, excluding the epidermolysis bullosa complex of diseases. The dermal collagen bundles were abnormally thickened and branched. Elastin fiber deposition was focally altered in the dermis adjacent to the hair follicle. Collagens present in the skin could not be differentiated between the species in protein gels following digestion with pepsin. Together these data suggest that M. pahari have altered extracellular matrix development resulting in separation of the skin below the level of the dermis with moderate force similar to the African spiny mouse (Acomys spp.).

Dysregulated expression of sterol O-acyltransferase 1 (Soat1) in the hair shaft of Hoxc13 null mice.

The cholesterol-metabolizing enzyme sterol O-acetyltransferase (SOAT1) is implicated in an increasing number of biological and pathological processes in a number of organ systems, including the differentiation of the hair shaft. While the functional and regulatory mechanisms underlying these diverse functional roles remain poorly understood, the compartment of the hair shaft known as medulla, affected by mutations in Soat1, may serve as a suitable model for defining some of these mechanisms. A comparative analysis of mRNA and protein expression patterns of Soat1/SOAT1 and the transcriptional regulator Hoxc13/HOXC13 in postnatal skin of FVB/NTac mice indicated co-expression in the most proximal cells of the differentiating medulla. This finding combined with the significant downregulation of Soat1 expression in postnatal skin of both Hoxc13 gene-targeted and transgenic mice based on previously reported DNA microarray results suggests a potential regulatory relationship between the two genes. Non-detectable SOAT1 expression in the defective hair follicle medulla of Hoxc13(tm1Mrc) mice and evidence for binding of HOXC13 to the Soat1 upstream control region obtained by ChIP assay suggests that Soat1 is a downstream regulatory target for HOXC13 during medulla differentiation.

Dsp rul: a spontaneous mouse mutation in desmoplakin as a model of Carvajal-Huerta syndrome.

Studies of spontaneous mutations in mice have provided valuable disease models and important insights into the mechanisms of human disease. Ruffled (rul) is a new autosomal recessive mutation causing abnormal hair coat in mice. The rul allele arose spontaneously in the RB156Bnr/EiJ inbred mouse strain. In addition to an abnormal coat texture, we found diffuse epidermal blistering, abnormal electrocardiograms (ECGs), and ventricular fibrosis in mutant animals. Using high-throughput sequencing (HTS) we found a frameshift mutation at 38,288,978bp of chromosome 13 in the desmoplakin gene (Dsp). The predicted mutant protein is truncated at the c-terminus and missing the majority of the plakin repeat domain. The phenotypes found in Dsp(rul) mice closely model a rare human disorder, Carvajal-Huerta syndrome. Carvajal-Huerta syndrome (CHS) is a rare cardiocutaneous disorder that presents in humans with wooly hair, palmoplantar keratoderma and ventricular cardiomyopathy. CHS results from an autosomal recessive mutation on the 3' end of desmoplakin (DSP) truncating the full length protein. The Dsp(rul) mouse provides a new model to investigate the pathogenesis of CHS, as well as the underlying basic biology of the adhesion molecules coded by the desmosomal genes.

Crisp1 and alopecia areata in C3H/HeJ mice.

Alopecia areata (AA), a cell mediated autoimmune disease, is the second most common form of hair loss in humans. While the autoimmune disease is responsible for the underlying pathogenesis, the alopecia phenotype is ultimately due to hair shaft fragility and breakage associated with structural deficits. Quantitative trait genetic analyses using the C3H/HeJ mouse AA model identified cysteine-rich secretory protein 1 (Crisp1), a hair shaft structural protein, as a candidate gene within the major AA locus. Crisp1 transcripts in the skin at various times during disease development were barely detectable. In situ hybridization identified Crisp1 expression within the medulla of hair shafts from clinically normal strains of mice but not C3H/HeJ mice with AA. Follow-up work with 5-day-old C3H/HeJ mice with normal hair also had essentially no expression of Crisp1. Other non-inflammatory based follicular dystrophy mouse models with similar hair shaft abnormalities also have little or no Crisp1 expression. Shotgun proteomics, used to determine strain difference in hair proteins, confirmed that there was very little CRISP1 within normal C3H/HeJ mouse hair in comparison to 11 other strains. However, mutant mice with hair medulla defects also had undetectable levels of CRISP1 in their hair. Crisp1 null mice had normal skin, hair follicles, and hair shafts indicating that the lack of the CRISP1 protein does not translate directly into defects in the hair shaft or hair follicle. These results suggest that CRISP1 may be an important structural component of mouse hair and that its strain-specific dysregulation may indicate a predisposition to hair shaft disease such as AA.

Chronic proliferative dermatitis in Sharpin null mice: development of an autoinflammatory disease in the absence of B and T lymphocytes and IL4/IL13 signaling.

SHARPIN is a key regulator of NFKB and integrin signaling. Mice lacking Sharpin develop a phenotype known as chronic proliferative dermatitis (CPDM), typified by progressive epidermal hyperplasia, apoptosis of keratinocytes, cutaneous and systemic eosinophilic inflammation, and hypoplasia of secondary lymphoid organs. Rag1(-/-) mice, which lack mature B and T cells, were crossed with Sharpin(-/-) mice to examine the role of lymphocytes in CDPM. Although inflammation in the lungs, liver, and joints was reduced in these double mutant mice, dermatitis was not reduced in the absence of functional lymphocytes, suggesting that lymphocytes are not primary drivers of the inflammation in the skin. Type 2 cytokine expression is increased in CPDM. In an attempt to reduce this aspect of the phenotype, Il4ra(-/-) mice, unresponsive to both IL4 and IL13, were crossed with Sharpin(-/-) mice. Double homozygous Sharpin(-/-) , Il4ra(-/-) mice developed an exacerbated granulocytic dermatitis, acute system inflammation, as well as hepatic necrosis and mineralization. High expression of CHI3L4, normally seen in CPDM skin, was abolished in Sharpin(-/-) , Il4ra(-/-) double mutant mice indicating the crucial role of IL4 and IL13 in the expression of this protein. Cutaneous eosinophilia persisted in Sharpin(-/-) , Il4ra(-/-) mice, although expression of Il5 mRNA was reduced and the expression of Ccl11 and Ccl24 was completely abolished. TSLP and IL33 were both increased in the skin of Sharpin(-/-) mice and this was maintained in Sharpin(-/-) , Il4ra(-/-) mice suggesting a role for TSLP and IL33 in the eosinophilic dermatitis in SHARPIN-deficient mice. These studies indicate that cutaneous inflammation in SHARPIN-deficient mice is autoinflammatory in nature developing independently of B and T lymphocytes, while the systemic inflammation seen in CPDM has a strong lymphocyte-dependent component. Both the cutaneous and systemic inflammation is enhanced by loss of IL4 and IL13 signaling indicating that these cytokines normally play an anti-inflammatory role in SHARPIN-deficient mice.

R164C mutation in FOXQ1 H3 domain affects formation of the hair medulla.

A number of single gene mutations in laboratory mice produce hair follicle defects resulting in deformed hair shafts. The radiation-induced (SB/LeJ-Foxq1(sa)) satin mutant mice have a satin-like sheen to their hair and dilute colouration. This sheen is due to failure of the hair shafts to develop normal medullas, while the pigment dilution is due to the unrelated beige (lysosomal trafficking regulator, Lyst(bg)) mutation. A new allelic mutation, Foxq1(sa-J), arose spontaneously on the albino (tyrosinase, Tyr(c)) MRL/MpJ-Fas(lpr) background. The Foxq1(sa-J) allele has a C to T transition at position 490. By contrast, the Foxq1(sa) mutant allele was confirmed to be a 67 base pair deletion followed by two base changes (GA to AT). Morphologic changes were similar to those seen in Hoxc13 transgenic and targeted mutant mice. This new allelic mutation provides yet another tool to investigate formation of the interior structures of hair shafts.

Molecular diagnosis of a laboratory mouse papillomavirus (MusPV).

MusPV, a novel papillomavirus (PV) that naturally infects laboratory mice, was isolated and characterized from a colony of NMRI-Foxn1(nu)/Foxn1(nu) (nude) mice in India. Because MusPV may have been missed during routine pathogen screening of mice in colonies worldwide, a variety of detection methods are described to detect MusPV. The clinical and histologic lesions of productive MusPV infections fit PV-associated features, including papillomas, koilocytes within the stratum granulosum of the hyperplastic/acanthotic papillomatous epithelium, and the presence of intranuclear virus particles in koilocytotic cells visualized by electron microscopy. Antiserum against disrupted PV virions, isolated from another species (canine), identified conserved viral antigens in productively infected cells by immunohistochemistry. A rolling circle technique was used to amplify viral circular DNAs followed by endonuclease restriction enzyme digestion to determine the correct size of PV DNA. Consensus PV degenerative primers, My09/11, commonly used to detect many different types of PVs by polymerase chain reaction (PCR), particularly mucosotropic HPVs, also identified MusPV and all rodent PVs tested. Since there was one nucleotide mismatch between the My09/11 primer set and the MusPV template, a new primer set, MusPV-My09/11, was designed to specifically detect MusPV in latent infections and spontaneous MusPV-induced papillomas. Southern blot analysis verified the presence of full size PV DNA in infected tissues. Virus-like particles (VLPs), generated from MusPV L1 genes, provided a substrate for serological testing of naturally and experimentally infected mice. In summary, a series of diagnostic assays were developed and validated to detect MusPV infection in skin tumors and serological response in laboratory mice.

SHARPIN is a key regulator of immune and inflammatory responses.

Mice with spontaneous mutations in the Sharpin gene develop chronic proliferative dermatitis that is characterized by eosinophilic inflammation of the skin and other organs with increased expression of type 2 cytokines and dysregulated development of lymphoid tissues. The mutant mice share phenotypic features with human hypereosinophilic syndromes. The biological function of SHARPIN and how its absence leads to such a complex inflammatory phenotype in mice are poorly understood. However, recent studies identified SHARPIN as a novel modulator of immune and inflammatory responses. The emerging mechanistic model suggests that SHARPIN functions as an important adaptor component of the linear ubiquitin chain assembly complex that modulates activation of NF-κB signalling pathway, thereby regulating cell survival and apoptosis, cytokine production and development of lymphoid tissues. In this review, we will summarize the current understanding of the ubiquitin-dependent regulatory mechanisms involved in NF-κB signalling, and incorporate the recently obtained molecular insights of SHARPIN into this pathway. Recent studies identified SHARPIN as an inhibitor of ß1-integrin activation and signalling, and this may be another mechanism by which SHARPIN regulates inflammation. Furthermore, the disrupted lymphoid organogenesis in SHARPIN-deficient mice suggests that SHARPIN-mediated NF-κB regulation is important for de novo development of lymphoid tissues.

SHARPIN is an endogenous inhibitor of ß1-integrin activation.

Regulated activation of integrins is critical for cell adhesion, motility and tissue homeostasis. Talin and kindlins activate ß1-integrins, but the counteracting inhibiting mechanisms are poorly defined. We identified SHARPIN as an important inactivator of ß1-integrins in an RNAi screen. SHARPIN inhibited ß1-integrin functions in human cancer cells and primary leukocytes. Fibroblasts, leukocytes and keratinocytes from SHARPIN-deficient mice exhibited increased ß1-integrin activity, which was fully rescued by re-expression of SHARPIN. We found that SHARPIN directly binds to a conserved cytoplasmic region of integrin α-subunits and inhibits recruitment of talin and kindlin to the integrin. Therefore, SHARPIN inhibits the critical switching of ß1-integrins from inactive to active conformations.

Predicting bison migration out of Yellowstone National Park using bayesian models.

Long distance migrations by ungulate species often surpass the boundaries of preservation areas where conflicts with various publics lead to management actions that can threaten populations. We chose the partially migratory bison (Bison bison) population in Yellowstone National Park as an example of integrating science into management policies to better conserve migratory ungulates. Approximately 60% of these bison have been exposed to bovine brucellosis and thousands of migrants exiting the park boundary have been culled during the past two decades to reduce the risk of disease transmission to cattle. Data were assimilated using models representing competing hypotheses of bison migration during 1990-2009 in a hierarchal bayesian framework. Migration differed at the scale of herds, but a single unifying logistic model was useful for predicting migrations by both herds. Migration beyond the northern park boundary was affected by herd size, accumulated snow water equivalent, and aboveground dried biomass. Migration beyond the western park boundary was less influenced by these predictors and process model performance suggested an important control on recent migrations was excluded. Simulations of migrations over the next decade suggest that allowing increased numbers of bison beyond park boundaries during severe climate conditions may be the only means of avoiding episodic, large-scale reductions to the Yellowstone bison population in the foreseeable future. This research is an example of how long distance migration dynamics can be incorporated into improved management policies.

The nude mutant gene Foxn1 is a HOXC13 regulatory target during hair follicle and nail differentiation.

Among the Hox genes, homeobox C13 (Hoxc13) has been shown to be essential for proper hair shaft differentiation, as Hoxc13 gene-targeted (Hoxc13(tm1Mrc)) mice completely lack external hair. Because of the remarkable overt phenotypic parallels to the Foxn1(nu) (nude) mutant mice, we sought to determine whether Hoxc13 and forkhead box N1 (Foxn1) might act in a common pathway of hair follicle (HF) differentiation. We show that the alopecia exhibited by both the Hoxc13(tm1Mrc) and Foxn1(nu) mice is because of strikingly similar defects in hair shaft differentiation and that both mutants suffer from a severe nail dystrophy. These phenotypic similarities are consistent with the extensive overlap between Hoxc13 and Foxn1 expression patterns in the HF and the nail matrix. Furthermore, DNA microarray analysis of skin from Hoxc13(tm1Mrc) mice identified Foxn1 as significantly downregulated along with numerous hair keratin genes. This Foxn1 downregulation apparently reflects the loss of direct transcriptional control by HOXC13 as indicated by our results obtained through co-transfection and chromatin immunoprecipitation (ChIP) assays. As presented in the discussion, these data support a regulatory model of keratinocyte differentiation in which HOXC13-dependent activation of Foxn1 is part of a regulatory cascade controlling the expression of terminal differentiation markers.

Desmoglein 4 is regulated by transcription factors implicated in hair shaft differentiation.

The hair fiber is made of specialized keratinocytes, known as trichocytes, that primarily express hair keratins, which are cemented by a multitude of keratin-associated proteins (KAPs). The hair keratins form the intermediate filament cytoskeleton of the trichocytes, which are linked to abundant cell-cell adhesion junctions, called desmosomes. Desmoglein 4 (DSG4) is the major desmosomal cadherin expressed in the hair shaft cortex where the hair keratins are highly expressed. In humans, mutations affecting either the hair keratins or DSG4 lead to beaded hair phenotypes with features of monilethrix. In this work, we postulated that the regulatory pathways governing the expression of hair shaft components, such as hair keratins and DSG4, are shared. Therefore, we studied the transcriptional regulation of DSG4 by transcription factors/pathways that are known regulators of hair keratin or KAP expression. We show that HOXC13, LEF1 and FOXN1 repress DSG4 transcription and provide in vitro and in vivo evidence correlating the Notch pathway with the activation and/or maintenance of DSG4 expression in the hair follicle.

Evidence that the satin hair mutant gene Foxq1 is among multiple and functionally diverse regulatory targets for Hoxc13 during hair follicle differentiation.

It is increasingly evident that the molecular mechanisms underlying hair follicle differentiation and cycling recapitulate principles of embryonic patterning and organ regeneration. Here we used Hoxc13-overexpressing transgenic mice (also known as GC13 mice), known to develop severe hair growth defects and alopecia, as a tool for defining pathways of hair follicle differentiation. Gene array analysis performed with RNA from postnatal skin revealed differential expression of distinct subsets of genes specific for cells of the three major hair shaft compartments (cuticle, cortex, and medulla) and their precursors. This finding correlates well with the structural defects observed in each of these compartments and implicates Hoxc13 in diverse pathways of hair follicle differentiation. The group of medulla-specific genes was particularly intriguing because this included the developmentally regulated transcription factor-encoding gene Foxq1 that is altered in the medulladefective satin mouse hair mutant. We provide evidence that Foxq1 is a downstream target for Hoxc13 based on DNA binding studies as well as co-transfection and chromatin immunoprecipitation assays. Expression of additional medulla-specific genes down-regulated upon overexpression of Hoxc13 requires functional Foxq1 as their expression is ablated in hair follicles of satin mice. Combined, these results demonstrate that Hoxc13 and Foxq1 control medulla differentiation through a common regulatory pathway. The apparent regulatory interactions between members of the mammalian Hox and Fox gene families shown here may establish a paradigm for "cross-talk" between these two conserved regulatory gene families in different developmental contexts including embryonic patterning as well as organ development and renewal.