Pattern Skin Research Articles

A Trustworthy Framework for Skin Cancer Detection Using a CNN with a Modified Attention Mechanism

The early and accurate detection of skin cancer can reduce mortality rates and improve patient outcomes, but requires advanced diagnostics. The integration of artificial intelligence (AI) into healthcare enables the precise and timely detection of skin cancer. However, significant challenges remain including the difficulty in differentiating visually similar skin conditions and the limitations of diverse, representative datasets. In this study, we proposed DCAN-Net, a novel deep-learning framework designed for the early detection of skin cancer. The model leverages an efficient backbone architecture optimized for capturing diverse skin patterns, utilizing carefully tuned parameters to enhance the discrimination capabilities and refine the extracted features using modified attention modules, thereby prioritizing relevant foreground information while minimizing background noise. Furthermore, the Grad-CAM explainable AI method was employed, highlighting the most salient features within dermatoscopic images. The fused optimal feature representations significantly enhanced the dermatoscopic image analysis. When evaluated on the HAM10000 dataset, DCAN-Net achieved a precision, recall, F1-score, and accuracy of 97.00%, 97.57%, 97.10%, and 97.57%, respectively. Moreover, the application of advanced data augmentation techniques mitigated data imbalance issues and reduced false-positive and false-negative rates across the original and augmented datasets. These findings demonstrate the potential of DCAN-Net for improving clinical outcomes and advancing AI-driven skin cancer diagnostics.

A Deterministic Model for Harmful Algal Bloom (HAB) Patterns Under Turing’s Instability Perspective

Turing’s instability has been widely introduced to explain the formation of several biological and ecological patterns, such as the skin patterning of fish or animals, wings of butterflies, pigmentation, and labyrinth patterns of the cerebral cortex of mammals. Such a mechanism may occur in the ecosystem due to the differential diffusion dispersal that happen if one of the constituent species results in the activator or the prey, showing a tendency to undergo autocatalytic growth. The diffusion of the constituent species activator is a random mobility function called passive diffusion. If the other species in the system (the predator/inhibitor) disperses sufficiently faster than the activator, then the spatially uniform distribution of species becomes unstable, and the system will settle into a stationary state. This paper introduced Turing’s mechanism in our reaction–taxis–diffusion model to simulate the harmful algal bloom (HAB) pattern. A numerical approach, the Runge–Kutta method, was used to deal with this system of reaction–taxis–diffusion equations, and the findings were qualitatively compared to the aerial patterns obtained by a drone flying over Torment Lake in Nova Scotia (Canada) during the bloom season of September 2023.

B-cell infiltration distinguishes mucosal from skin patterns of rejection in facial vascularized composite allografts.

Rejection monitoring in facial vascularized composite allotransplantation (fVCA) traditionally focuses on skin biopsies. However, mucosal rejection frequently presents with more pronounced signs of immune activity. To explore mechanistic differences between skin and mucosal rejection, rejection and non-rejection biopsies from allograft skin and oral mucosa of nine fVCA recipients were retrospectively analyzed using histology, multiplex immunostaining, and gene expression profiling, with peripheral blood mononuclear cells (PBMCs) quantified via mass cytometry (CyTOF). Both skin and mucosa exhibited similar patterns of granzyme B expressing (GZMB+) T-cells, indicating T-cell-mediated rejection in both tissues. However, mucosa demonstrated additional CD19+ B-cell infiltration and occasional plasma cells, which were absent in skin. These intramucosal B-cells expressed AHNAK and CD43, suggesting they may be innate-like B-cells (Bin cells). CD8+/GZMB+ cells and B-cell populations were enriched in PBMCs during combined skin and mucosal rejection but not isolated skin rejection. These findings suggest distinct rejection mechanisms in skin and mucosa, with mucosa uniquely involving B-cells. Current skin-focused rejection monitoring may overlook important mucosal rejection events, emphasizing the need to monitor both tissues concurrently. Mucosal biopsies could improve the accuracy in detecting acute rejection.

Re‐identification of patterned animals by multi‐image feature aggregation and geometric similarity

AbstractImage‐based re‐identification of animal individuals allows gathering of information such as population size and migration patterns of the animals over time. This, together with large image volumes collected using camera traps and crowdsourcing, opens novel possibilities to study animal populations. For many species, the re‐identification can be done by analysing the permanent fur, feather, or skin patterns that are unique to each individual. In this paper, the authors study pattern feature aggregation based re‐identification and consider two ways of improving accuracy: (1) aggregating pattern image features over multiple images and (2) combining the pattern appearance similarity obtained by feature aggregation and geometric pattern similarity. Aggregation over multiple database images of the same individual allows to obtain more comprehensive and robust descriptors while reducing the computation time. On the other hand, combining the two similarity measures allows to efficiently utilise both the local and global pattern features, providing a general re‐identification approach that can be applied to a wide variety of different pattern types. In the experimental part of the work, the authors demonstrate that the proposed method achieves promising re‐identification accuracies for Saimaa ringed seals and whale sharks without species‐specific training or fine‐tuning.

Ligand-Independent Vitamin D Receptor Actions Essential for Keratinocyte Homeostasis in the Skin.

Recently, we demonstrated that the alopecia observed in vitamin D receptor gene-deficient (Vdr-KO) rats is not seen in rats with a mutant VDR(R270L/H301Q), which lacks ligand-binding ability, suggesting that the ligand-independent action of VDR plays a crucial role in maintaining the hair cycle. Since Vdr-KO rats also showed abnormalities in the skin, the relationship between alopecia and skin abnormalities was examined. To clarify the mechanism of actions of vitamin D and VDR in the skin, protein composition, and gene expression patterns in the skin were compared among Vdr-KO, Vdr-R270L/H301Q, and wild-type (WT) rats. While Vdr-R270L/H301Q rats exhibited normal skin formation similar to WT rats, Vdr-KO rats showed remarkable hyperkeratosis and trans-epidermal water loss in the skin. RNA sequencing and proteomic analysis revealed that the gene and protein expression patterns in Vdr-KO rats significantly differed from those in WT and Vdr-R270L/H301Q rats, with a marked decrease in the expression of factors involved in Shh, Wnt, and Bmp signaling pathways, a dramatic reduction in the expression of hair keratins, and a substantial increase in the expression of epidermal keratins. This study clearly demonstrated that non-liganded VDR is significantly involved in the differentiation, proliferation, and cell death of keratinocytes in hair follicles and the epidermis.

Pigment granule architecture varies across yellow, red, and brown chromatophores in squid Doryteuthis pealeii

Cephalopods produce dynamic colors and skin patterns for communication and camouflage via stratified networks of neuronally actuated yellow, red, and brown chromatophore organs, each filled with thousands of pigment granules. While compositional analysis of chromatophore granules in Doryteuthis pealeii reveals the pigments as ommochromes, the ultrastructural features of the granules and their effects on bulk coloration have not been explored. To investigate this, we isolated granules from specific colored chromatophores and imaged them using multiple modalities. The brown granules are largest with smooth surface coatings. Red granules are intermediate in size with irregular surface textures, and yellow granules are smallest, with rough, porous surfaces. Many of the granules contain sub-granular features that also vary in presentation with color. Correlated light and electron microscopy reveal that differences in hue of individual granules are similarly associated with size, shape, and texture, suggesting that granules may be structurally adapted to modify the dominant visible colors presented within the chromatophores. These findings suggest that granule ultrastructure, not just chemical composition, may be significant in producing the range of colors presented in cephalopod chromatophores.

Dermoscopy of syphilitic chancre: Report of five cases

Dermoscopy is a non-invasive tool which helps in the visualization of skin structures and patterns not visible to the naked eye. This study evaluates the effectiveness of dermoscopy in diagnosing primary syphilis, which typically presents as a painless ulcer at the site of Treponema pallidum inoculation. In this study, dermoscopic patterns such as vascular structures and background colour changes were analyzed in patients with confirmed primary syphilis. Results indicate that primary syphilis lesions often display unique dermoscopic features, including polymorphic vessels and orange, red-purple backgrounds. These patterns can facilitate the early detection and diagnosis of syphilis, improving clinical outcomes through earlier intervention. The study concludes that integrating dermoscopy into the clinical assessment of suspected syphilis lesions can enhance diagnostic accuracy.

A Force-Thermal-Magnetic Trimodal Flexible Sensor for Ultrafine Recognition of Metallic Materials.

Humans possess the remarkable ability to perceive the intricate world by integrating multiple senses. However, the challenge of enabling humanoid robots to achieve multimodal sensing and fine recognition of metallic materials persists. In this study, we propose a flexible tactile sensor that mimics the sensory patterns of human skin, which is assembled by a flexible electromagnetic coil that is engraved on the surface of a polyimide substrate and porous MXene/CNT aerogel. This sensor is capable of detecting pressure, temperature, and inductive signals with minimal interference via three disparate response mechanisms of the piezoresistive sensing, the thermoelectric principle, and the electromagnetic induction effect, allowing the device with the abilities of sensing grasp forces and selectively identifying ferromagnetic and nonferromagnetic metals, which has a high accuracy rate of 99.2% in distinguishing mixed metals with varying ratios based on the fusion algorithm of multimodal sensory data. Further, the sensor was integrated on a humanoid robotic hand to demonstrate its recognition capacity of objects used in a kitchen setting and a simulated scenario of mineral exploration, achieving a remarkable ultrafine accuracy of 100% in distinguishing 16 common metal products. These findings will pave the way for humanoid robots to attain heightened levels of perception and recognition.

Novel use of deep neural networks on photographic identification of epaulette sharks (Hemiscyllium ocellatum) across life stages.

Photographic identification (photo ID) is an established method that is used to count animals and track individuals' movements. This method performs well with some species of elasmobranchs (i.e., sharks, skates, and rays) where individuals have distinctive skin patterns. However, the unique skin patterns used for ID must be stable through time to allow re-identification of individuals in future sampling events. More recently, artificial intelligence (AI) models have substantially decreased the labor-intensive process of matching photos in extensive photo ID libraries and increased the reliability of photo ID. Here, photo ID and AI are used for the first time to identify epaulette sharks (Hemiscyllium ocellatum) at different life stages for approximately 2 years. An AI model was developed to assess and compare the reliability of human-classified ID patterns in juvenile and neonate sharks. The model also tested the persistence of unique patterns in adult sharks. Results indicate that immature life stages are unreliable for pattern identification, using both human and AI approaches, due to the plasticity of these subadult growth forms. Mature sharks maintain their patterns through time and can be identified by AI models with approximately 86% accuracy. The approach outlined in this study has the potential of validating the stability of ID patterns through time; however, testing on wild populations and long-term datasets is needed. This study's novel deep neural network development strategy offers a streamlined and accessible framework for generating a reliable model from a small data set, without requiring high-performance computing. Since many photo ID studies commence with limited datasets and resources, this AI model presents practical solutions to such constraints. Overall, this approach has the potential to address challenges associated with long-term photo ID data sets and the application of AI for shark identification.

A Ball Python Colour Morph Implicates MC1R in Melanophore-Xanthophore Distribution and Pattern Formation.

Reptiles showcase an extensive array of skin colours and patterns, yet little is known about the genetics of reptile colouration. Here, we investigate the genetic basis of the Clown colour morph found in captive-bred ball pythons (Python regius) to study skin pigmentation and patterning in snakes. We obtained samples by crowdsourcing shed skin from commercial breeders and hobbyists. We applied a case-control design, whole-genome pool sequencing, variant annotation, histological analyses, and electron microscopy imaging. We identified a missense mutation in a transmembrane region of the melanocortin-1 receptor (MC1R) associated with the Clown phenotype. In classic avian and mammalian model species, MC1R is known for controlling the type and amount of melanin produced. In contrast, our results suggest that MC1R signalling might play a key role in pattern formation in ball pythons, affecting xanthophore-melanophore distribution. This work highlights the varied functions of MC1R across different vertebrate lineages and promotes a novel model system to study reptile colouration.

The relationship between spectral signals and retinal sensitivity in dendrobatid frogs.

Research on visually driven behavior in anurans has often focused on Dendrobatoidea, a clade with extensive variation in skin reflectance, which is perceived to range from cryptic to conspicuous coloration. Because these skin patterns are important in intraspecific and interspecific communication, we hypothesized that the visual spectral sensitivity of dendrobatids should vary with conspecific skin spectrum. We predicted that the physiological response of frog retinas would be tuned to portions of the visible light spectrum that match their body reflectance. Using wavelength-specific electroretinograms (ERGs; from 350-650 nm), spectrometer measurements, and color-calibrated photography of the skin, we compared retinal sensitivity and reflectance of two cryptic species (Allobates talamancae and Silverstoneia flotator), two intermediate species (Colostethus panamansis and Phyllobates lugubris), and two conspicuous aposematic species (Dendrobates tinctorius and Oophaga pumilio). Consistent with the matched filter hypothesis, the retinae of cryptic and intermediate species were sensitive across the spectrum, without evidence of spectral tuning to specific wavelengths, yielding low-threshold broadband sensitivity. In contrast, spectral tuning was found to be different between morphologically distinct populations of O. pumilio, where frogs exhibited retinal sensitivity better matching their morph's reflectance. This sensory specialization is particularly interesting given the rapid phenotypic divergence exhibited by this species and their behavioral preference for sympatric skin reflectances. Overall, this study suggests that retinal sensitivity is coevolving with reflective strategy and spectral reflectance in dendrobatids.

The Expression of Cytokines and Chemokines Potentially Distinguishes Mild and Severe Psoriatic Non-Lesional and Resolved Skin from Healthy Skin and Indicates Different Stages of Inflammation

In the psoriatic non-lesional (PS-NL) skin, the tissue environment potentially influences the development and recurrence of lesions. Therefore, we aimed to investigate mechanisms involved in regulating tissue organization in PS-NL skin. Cytokine, chemokine, protease, and protease inhibitor levels were compared between PS-NL skin of patients with mild and severe symptoms and healthy skin. By comparing mild and severe PS-NL vs. healthy skin, differentially expressed cytokines and chemokines suggested alterations in hemostasis-related processes, while protease inhibitors showed no psoriasis severity-related changes. Comparing severe and mild PS-NL skin revealed disease severity-related changes in the expression of proteases, cytokines, and chemokines primarily involving methyl-CpG binding protein 2 (MECP2) and extracellular matrix organization-related mechanisms. Cytokine and chemokine expression in clinically resolved versus healthy skin showed slight interleukin activity, differing from patterns in mild and severe PS-NL skin. Immunofluorescence analysis revealed the severity-dependent nuclear expression pattern of MECP2 and decreased expression of 5-methylcytosine and 5-hydroxymethylcytosine in the PS-NL vs. healthy skin, and in resolved vs. healthy skin. Our results suggest distinct cytokine–chemokine signaling between the resolved and PS-NL skin of untreated patients with varying severities. These results highlight an altered inflammatory response, epigenetic regulation, and tissue organization in different types of PS-NL skin with possibly distinct, severity-dependent para-inflammatory states.

Controlled atmosphere storage enhances Korean melon shelf life and quality: A comparative metabolic analysis with reefer container export

Korean melons are renowned for their taste and nutritional qualities but face challenges such as chilling injury and browning during post-harvest storage, limiting their export potential. To address these issues, we compared melons stored in Controlled Atmosphere (CA) containers to those in Reefer Container (CON) under simulated export conditions. This study examines the effects of CA storage on the quality, metabolite changes, and volatile organic compounds (VOC) of Korean melons (Cucumis melo var. makuwa). CA-stored Korean melons showed increased concentrations of cutin monomers, suggesting reduced browning due to the expression of cutin-related genes. VOCs analysis revealed distinctive patterns in both Korean melon skin and juice, with specific compounds elevated in CA storage. The breakdown of linolenic acid into (E,Z)-2,6-nonadienal was reduced by approximately 30 % under CA storage, likely due to reduced oxygen availability. Twister-assisted VOCs analysis highlighted aroma differences, indicating potential effects on sensory perception. Solubility changes showed a 15 % increase in glyceric acid and a 20 % decrease in oxalate levels under CA storage, suggesting improved flavor and reduced harmful compounds. The freshness model based on VOCs indicated that CA-treated melons remained fresh approximately 4 d longer than control melons. In conclusion, CA storage improves the quality, freshness, and nutritional profile of Korean melons and offers valuable insights for refining post-harvest storage practices. Further research is warranted to explore the long-term effects of CA storage on other fruits and vegetables.

B-350 The application of MALDI-TOF imaging to biomarker discovery in a mouse model of papillomavirus associated tumorigenesis

Abstract Background Human papillomavirus (HPV) can cause infection and dysplasia in cutaneous epithelium of immunodeficient patients. An animal model has been developed to study HPV-associated tumorigenesis using Nude mouse (Foxn1nu) and mouse papillomavirus (MmuPV1). This study applies MALDI-TOF imaging to compare the expression pattern of small molecules between viral-infected dysplastic mouse skin and mock-infected control tissue. Three sets of molecules showing distinct patterns are identified in correlation with the upregulation of an enzyme in related biosynthetic pathway. Methods Nude mice were wounded on tail and inoculated with MmPV1 suspension (1×109 viral DNA genomes per infected site) or PBS 24 hours later for treatment and control group, respectively. Tail skins were harvested 4 weeks post-infection and processed for cryosectioning. Tissue sections were analyzed using timsTOF flex (Bruker) under negative ion mode with 9-aminoacridine as the matrix. Viral infection (MmuPV1-L1 antigen) and enzyme expression (3'-phosphoadenosine 5'-phosphosulfate synthetase 1, PAPSS1) were assessed by immunofluorescence on adjacent sections. Results Three peaks demonstrated distinct distribution patterns in mouse skin. One peak at m/Z = 465 was identified as cholesterol sulfate (CS) by tandem MS and comparing with the standard. CS was enriched in keratinocytes, hair follicles, and blood vessels in normal skins, and it increased in dysplastic skins with enhanced angiogenesis. The combined peaks at m/Z = 327 & 329 were tentatively identified as docosahexaenoic acid (DHA) and docosapentaenoic acid (DPA). These long chain polyunsaturated fatty acids (LC-PUFAs) were present in the dermis as foci partially co-localized with CS, and they also increased in virus-infected skins. The peak at m/Z = 426 may represent a combination of ADP and APS. Although these two isobars cannot be separated by tandem MS, APS was revealed by the presence of sulfur isotopes at expected natural abundance (34S and 32S). They were present at a low level in the epidermis of normal skins but significantly increased after virus infection. APS and ADP were closely associated with the proliferating cells, and the signal intensity also increased with the degree of tissue dysplasia. As a single factor, APS & ADP demonstrated a fair differential power for MmuPV1-induced dysplastic skin and normal control (AUC of ROC curve = 0.75). The bifunctional enzyme PAPSS1 catalyzes the conversion of ATP to 3’-phosphonato-5’-adenyl sulfate (PAPS) via APS as an intermediate. Interestingly, immunofluorescence showed the expression of PAPSS1 also increased significantly with the severity of tissue dysplasia and MmuPV1 infection. Conclusions MALDI-TOF imaging reveals three sets of molecules with distinct patterns in mouse skin, and their levels are increased during MmuPV1-induced epithelium dysplasia. As a precursor of the common sulfate donor (PAPS), increased APS and ADP in the epidermis of virus-infected skins indicate an upregulation of sulfation pathway and adenine metabolism. This finding is supported by enhanced expression of enzyme PAPSS1 and an increased sulfation reaction product, CS. In addition, DHA and DPA are also increased in the dermis of virus-infected skins, implying a disturbance in LC-PUFA metabolism. This study demonstrates combined use of MALDI-TOF imaging and immunostaining in the search of novel biomarkers of HPV-associated tumorigenesis.

Structure, function and formation of the amniote skin pattern

From feather and hair dotted arrays to pigmented stripes and spots, the spatial distribution of skin appendages and colouration often forms visible ornaments crucial for fitness in the coat of birds and mammals. These geometrical motifs are extremely diverse in nature. Yet, phenotypic surveys evidenced common themes in variation: the orientation, appendage-specificity or pigmentation of a given region may be conserved across groups or species. Here, we review naturalist observations of natural variation in the anatomy and ecological function of the skin pattern in amniotes. We then describe several decades of genetics, mathematical modelling and experimental embryology work aiming at understanding the molecular and morphogenetic mechanisms responsible for pattern formation. We discuss how these studies provided evidence that the morphological trends and differences representative of the phenotypic landscape of skin patterns in wild amniote species is rooted in the mechanisms controlling the production of distinct compartments in the embryonic skin.

PMEL is involved in snake colour pattern transition from blotches to stripes

Corn snakes are emerging models for animal colouration studies. Here, we focus on the Terrazzo morph, whose skin pattern is characterized by stripes rather than blotches. Using genome mapping, we discover a disruptive mutation in the coding region of the Premelanosome protein (PMEL) gene. Our transcriptomic analyses reveal that PMEL expression is significantly downregulated in Terrazzo embryonic tissues. We produce corn snake PMEL knockouts, which present a comparable colouration phenotype to Terrazzo and the subcellular structure of their melanosomes and xanthosomes is also similarly impacted. Our single-cell expression analyses of wild-type embryonic dorsal skin demonstrate that all chromatophore progenitors express PMEL at varying levels. Finally, we show that in wild-type embryos PMEL-expressing cells are initially uniformly spread before forming aggregates and eventually blotches, as seen in the adults. In Terrazzo embryos, the aggregates fail to form. Our results provide insights into the mechanisms governing colouration patterning in reptiles.

Antibiotic sensitivity pattern of deep skin and soft tissue infections in Pakistan.

Objective: To determine the antibiotic spectrum of deep skin and soft tissue infections in Pakistan. Study Design: Cross-sectional study. Setting: Department of Dermatology at Madinah Teaching Hospital, Faisalabad. Period: June, 2023 to December 2023. Methods: Inclusion criteria covered consenting patients aged 15-60, excluding those with specific conditions. The study aimed to ascertain antibiotic sensitivity patterns in deep skin and soft tissue infections. Ethical approval was obtained, and subjects meeting criteria were enrolled after informed consent, contributing valuable insights into healthcare-associated infections. Results: Examining 60 patients, the age distribution indicates a prevalent cohort up to 50 years (61.7%), highlighting potential health concerns in earlier years. Those above 50 constitute 38.3%, signifying distinct challenges in older age. With 61.7% males, Gram stain analysis reveals microbial diversity. Notably, Ciprofloxacin (90%) and Cefipime (98.3%) exhibit high resistance, while Cephradine (48.3%) and Cefoxitin (20%) show sensitivity. Meropenem and Vancomycin display moderate resistance (28.3% and 25%), while Tigecycline (10%) and Teicoplanin (1.7%) exhibit lower resistance, offering insights for effective treatment strategies. Conclusion: Our study reveals notable antibiotic resistance, with Ciprofloxacin (90%) and Cefipime (98.3%) exhibiting high resistance. Conversely, Cephradine (48.3%) and Cefoxitin (20%) show sensitivity, guiding tailored treatment strategies for deep skin and soft tissue infections.

Visual acuity of the summer flounder (Paralichthys dentatus) captures spatial information relevant to dynamic camouflage at close range.

Dynamic camouflage is the capacity to rapidly change skin color and pattern, often for the purpose of background-matching camouflage. Summer flounder (Paralichthys dentatus) are demersal fish with an exceptional capacity for dynamic camouflage, but with eyes that face away from the substrate, it is unknown if this behavior is mediated by vision. Past studies have shown that summer flounder skin can match the pattern (i.e., spatial detail) of substrate with a high degree of precision, and for that to be achieved using sight, one testable assumption is that the resolution of vision must match the degree of detail produced in color-change performance. To test this, approaches in morphology and behavior were used to estimate visual acuity, which is the capacity of the visual system to resolve static spatial detail. Using image processing techniques, we then compared the degree of spatial detail from a relevant substrate with what may be detectable by summer flounder spatial vision. The morphological and behavioral estimates of visual acuity were calculated as 3.62 cycles per degree (CPD) ± 0.8 (s.d.) and 4.06 CPD ± 0.4 (s.d.), respectively. These estimates fall within a range of acuities known among other flatfishes and appear adequate for detecting the spatial information needed for background-matching camouflage, though only at close distances. These data provide new knowledge about summer flounder visual acuity and suggest the capacity of flounder vision to support dynamic camouflage of the skin.

State-dependent dynamics of cuttlefish mantle activity.

Cuttlefish skin is a powerful rendering device, capable of producing extraordinary changes in visual appearance over a broad range of temporal scales. This unique ability is typically associated with camouflage; however, cuttlefish often produce skin patterns that do not appear connected with the surrounding environment, such as fast large-scale fluctuations with wave-like characteristics. Little is known about the functional significance of these dynamic patterns. In this study, we developed novel tools for analyzing pattern dynamics, and demonstrate their utility for detecting changes in feeding state that occur without concomitant changes in sensory stimulation. Under these conditions, we found that the dynamic properties of specific pattern components differ for different feeding states, despite no measurable change in the overall expression of those components. Therefore, these dynamic changes are not detectable by conventional analyses focusing on pattern expression, requiring analytical tools specifically targeted to pattern dynamics.

The dynamic behavior of chromatophores marks the transition from bands to spots in leopard geckos

Reptilian skin coloration is spectacular and diverse, yet little is known about the ontogenetic processes that govern its establishment and the molecular signaling pathways that determine it. Here, we focus on the development of the banded pattern of leopard gecko hatchlings and the transition to black spots in the adult. With our histological analyses, we show that iridophores are present in the white and yellow bands of the hatchling and they gradually perish in the adult skin. Furthermore, we demonstrate that melanophores can autonomously form spots in the absence of the other chromatophores both on the regenerated skin of the tail and on the dorsal skin of the Mack Super Snow (MSS) leopard geckos. This color morph is characterized by uniform black coloration in hatchlings and black spots in adulthood; we establish that their skin is devoid of xanthophores and iridophores at both stages. Our genetic analyses identified a 13-nucleotide deletion in the PAX7 transcription factor of MSS geckos, affecting its protein coding sequence. With our single-cell transcriptomics analysis of embryonic skin, we confirm that PAX7 is expressed in iridophores and xanthophores, suggesting that it plays a key role in the differentiation of both chromatophores. Our in situ hybridizations on whole-mount embryos document the dynamics of the skin pattern formation and how it is impacted in the PAX7 mutants. We hypothesize that the melanophores-iridophores interactions give rise to the banded pattern of the hatchlings and black spot formation is an intrinsic capacity of melanophores in the postembryonic skin.