Essential Palatal Myoclonus and Clicking Tinnitus in a Nine-Year-Old Boy-A Case Report.

The work describes a case of palatal myoclonus with distressing tinnitus in a 9-year-old boy and its successful treatment with injections of botulinum toxin. This case report discusses common questions about myoclonic-induced clicking tinnitus and provides answers. Laryngoscope, 134:397-399, 2024.

Inactivation of Autophagy in Keratinocytes Reduces Tumor Growth in Mouse Models of Epithelial Skin Cancer.

Autophagy is a ubiquitous degradation mechanism, which plays a critical role in cellular homeostasis. To test whether autophagy suppresses or supports the growth of tumors in the epidermis of the skin, we inactivated the essential autophagy gene Atg7 specifically in the epidermal keratinocytes of mice (Atg7∆ep) and subjected such mutant mice and fully autophagy-competent mice to tumorigenesis. The lack of epithelial Atg7 did not prevent tumor formation in response to 7, 12-dimethylbenz(a)anthracene (DMBA) as the initiator and 12-O tetradecanoylphorbol-13-acetate (TPA) as the promoter of tumor growth. However, the number of tumors per mouse was reduced in mice with epithelial Atg7 deficiency. In the K5-SOS EGFRwa2/wa2 mouse model, epithelial tumors were initiated by Son of sevenless (SOS) in response to wounding. Within 12 weeks after tumor initiation, 60% of the autophagy-competent K5-SOS EGFRwa2/wa2 mice had tumors of 1 cm diameter and had to be sacrificed, whereas none of the Atg7∆ep K5-SOS EGFRwa2/wa2 mice formed tumors of this size. In summary, the deletion of Atg7 reduced the growth of epithelial tumors in these two mouse models of skin cancer. Thus, our data show that the inhibition of autophagy limits the growth of epithelial skin tumors.

Autophagy protects murine preputial glands against premature aging, and controls their sebum phospholipid and pheromone profile.

ABBREVIATIONS: ATG7: autophagy related 7; BODIPY: boron dipyrromethene; DAG: diacyl glycerides; DBI: diazepam binding inhibitor; GFP: green fluorescent protein; KRT14: keratin 14; HPLC-MS: high performance liquid chromatography-mass spectrometry; LD: lipid droplet; MAP1LC3/LC3: microtubule-associated protein 1 light chain 3; MSI: mass spectrometric imaging; ORO: Oil Red O; PC: phosphatidylcholine; PE: phosphatidylethanolamine; PG: preputial gland; PLIN2: perilipin 2; PtdIns: phosphatidylinositol; PL: phospholipids; POPC: 1-palmitoyl-2-oleoyl-PC; PS: phosphatidylserine; qRT-PCR: quantitative reverse transcribed PCR; SG: sebaceous gland; scRNAseq: single-cell RNA sequencing; TAG: triacylglycerides; TLC: thin layer chromatography.

The Trichohyalin-Like Protein Scaffoldin Is Expressed in the Multilayered Periderm during Development of Avian Beak and Egg Tooth.

Scaffoldin, an S100 fused-type protein (SFTP) with high amino acid sequence similarity to the mammalian hair follicle protein trichohyalin, has been identified in reptiles and birds, but its functions are not yet fully understood. Here, we investigated the expression pattern of scaffoldin and cornulin, a related SFTP, in the developing beaks of birds. We determined the mRNA levels of both SFTPs by reverse transcription polymerase chain reaction (RT-PCR) in the beak and other ectodermal tissues of chicken (Gallus gallus) and quail (Coturnix japonica) embryos. Immunohistochemical staining was performed to localize scaffoldin in tissues. Scaffoldin and cornulin were expressed in the beak and, at lower levels, in other embryonic tissues of both chickens and quails. Immunohistochemistry revealed scaffoldin in the peridermal compartment of the egg tooth, a transitory cornified protuberance (caruncle) on the upper beak which breaks the eggshell during hatching. Furthermore, scaffoldin marked a multilayered peridermal structure on the lower beak. The results of this study suggest that scaffoldin plays an evolutionarily conserved role in the development of the avian beak with a particular function in the morphogenesis of the egg tooth.

The Whey Acidic Protein WFDC12 Is Specifically Expressed in Terminally Differentiated Keratinocytes and Regulates Epidermal Serine Protease Activity.

WFDC proteins such as peptidase inhibitor 3 and SLPI inhibit proteases in the epidermis and other tissues. In this study, we tested the hypothesis that further WFDC protein family members might contribute to epidermal homeostasis. We found that in addition to peptidase inhibitor 3 and SLPI, WFDC5 and WFDC12 were expressed in human epidermis. In contrast to WFDC5, the expression of WFDC12 was induced during the late differentiation of keratinocytes and was restricted to the outermost layer of live cells. Single-cell RNA sequencing demonstrated that WFDC12-positive keratinocytes were characterized by the upregulation of LCE mRNA expression and downregulated the expression of keratins and claudins. Immunogold-electron microscopy revealed the colocalization of WFDC12 with corneodesmosomes in the lower stratum corneum. WFDC12 was elevated in the affected skin of patients with psoriasis, atopic dermatitis, and Darier disease. By contrast, WFDC12 expression was strongly upregulated not only in the affected but even more so in clinically normal-appearing skin of patients with Netherton syndrome. Finally, functional analysis showed distinct inhibitory activity of WFDC12 on neutrophil elastase and epidermal kallikrein‒related peptidase. Altogether, our study identified WFDC12 as a marker of the last stage of epidermal keratinocyte differentiation and suggests that WFDC12 contributes to the control of protease activity in the stratum corneum.

PIWIL-2 and piRNAs are regularly expressed in epithelia of the skin and their expression is related to differentiation.

PIWI proteins play multiple roles in germline stem cell maintenance and self-renewal. PIWI-interacting RNAs (piRNAs) associate with PIWI proteins, form effector complexes and maintain genome integrity and function in the regulation of gene expression by epigenetic modifications. Both are involved in cancer development. In this study, we investigated the expression of PIWIL-2 and piRNAs in normal human skin and epithelial tumors and its regulation during keratinocyte (KC) differentiation. Immunohistochemistry showed that PIWIL-2 was regularly expressed in the epidermis and adnexal tissue with strongest expression in sebaceous glands. Cell culture studies revealed an association of PIWIL-2 expression with the state of differentiated KC. In contrast, the PIWIL-2 expression pattern did not correlate with stem cell compartments or malignancy. piRNAs were consistently detected in KC in vitro by next-generation sequencing and the expression levels of numerous piRNAs were regulated during KC differentiation. Epidermal piRNAs were predominantly derived from processed snoRNAs (C/D-box snoRNAs), tRNAs and protein coding genes. Our data indicate that components of the PIWIL-2-piRNA pathway are present in epithelial cells of the skin and are regulated in the context of KC differentiation, suggesting a role of somatic gene regulation. However, putative roles in the maintenance of stem cell compartments or the development of malignancy in the skin were not supported by this study.

Bradykinin Receptor B1 and C-Reactive Protein as Prognostic Factors for Pharyngocutaneous Fistula Development After Laryngectomy.

Pharyngocutaneous fistulae (PCF) are one of the most common complications after laryngectomy. Predisposing risk factors have been studied, yet knowledge to determine which patients are prone to developing a fistula remains scarce. This study aims to establish prognostic parameters to identify individual patients at risk for PCF development. As PCF and inflammation seem to be interwoven, this work focuses on markers able to detect an inflammatory response. We retrospectively analyzed all patients who had undergone a laryngectomy at our clinic in the years 2007 to 2017 (n = 182). Immunohistochemical expression of bradykinin type 1 and 2 receptor and vascular endothelial growth factor receptor 2 was studied in all available tumor samples. Additionally, the clinical inflammation parameters 'body temperature', 'pain', 'c-reactive protein (CRP)', and 'leucocytes' were postoperatively tracked in all patients. The times between fistula diagnosis, therapeutic approach, and hospital discharge were recorded. We found a strong correlation between inflammation and the formation of a fistula. High bradykinin 1 receptor expression in the tumor samples correlated with postoperative PCF development. Persistently elevated CRP and leukocyte levels beyond the 6th postoperative day were also risk factors. A decreased time lapse between PCF diagnosis and surgical revision clearly correlated with a shorter hospital stay. In this study, we identified a bradykinin 1 receptor positive patient group at high risk for development of PCF. We recommend close monitoring for fistula formation in these patients to ensure timely intervention.

Adjustment of Vocal Tract Shape via Biofeedback: Influence on Vowels.

The study assessed 30 nonprofessional singers to evaluate the effects of vocal tract shape adjustment via increased resonance toward an externally applied sinusoidal frequency of 900 Hz without phonation. The amplification of the sound wave was used as biofeedback signal and the intensity and the formant position of the basic vowels /a/, /e/, /i/, /o/, and /u/ were compared before and after a vocal tract adjustment period. After the adjustment period, the intensities for all vowels increased and the measured changes correlated with the participants' self-perception.The diferences between the second formant position of the vowels and the applied frequency influences the changes in amplitude and in formant frequencies. The most significant changes in formant frequency occurred with vowels that did not include a formant frequency of 900 Hz, while the increase in amplitude was the strongest for vowels with a formant frequency of about 900 Hz.

Distinct Distribution of RTN1A in Immune Cells in Mouse Skin and Lymphoid Organs.

The endoplasmic reticulum-associated protein reticulon 1A (RTN1A) is primarily expressed in neuronal tissues but was recently identified also specifically in cells of the dendritic cell (DC) lineage, including epidermal Langerhans cells (LCs) and dermal DCs in human skin. In this study, we found that in mice major histocompatibility complex class II (MHCII)+CD207+ LCs but not dermal DCs express RTN1A. Further, RTN1A expression was identified in CD45+MHCII+CD207+ cells of the lymph node and spleen but not in the thymus. Of note, RTN1A was expressed in CD207 low LCs in adult skin as well as emigrated LCs and DCs in lymph nodes and marginally in CD207 hi cells. Ontogeny studies revealed that RTN1A expression occurred before the appearance of the LC markers MHCII and CD207 in LC precursors, while dermal DC and T cell precursors remained negative during skin development. Analogous to the expression of RTN1A in neural tissue, we identified expression of RTN1A in skin nerves. Immunostaining revealed co-localization of RTN1A with nerve neurofilaments only in fetal but not in newborn or adult dermis. Our findings suggest that RTN1A might be involved in the LC differentiation process given its early expression in LC precursors and stable expression onward. Further analysis of the RTN1A expression pattern will enable the elucidation of the functional roles of RTN1A in both the immune and the nervous system of the skin.

Quality of Voice and Prognostic Markers for the Recovery of Vocal Fold Paralysis After Thyroid Surgery.

OBJECTIVES: This study is set to analyze clinicopathological factors predicting the recovery of unilateral vocal fold paralysis (UVP) in patients after thyroid gland surgery. The quality of voice was additionally assessed in these patients. METHODS: The charts and videolaryngostroboscopy (VLS) examinations of 84 consecutive patients with a complete UVP after surgery of the thyroid gland were retrospectively reviewed. Patients were divided into 2 groups: patients who fully recovered from vocal fold paralysis and those who failed to recover after a follow-up of 12 months. The quality of voice was analyzed among other things by determining the Voice Handicap Index (VHI). RESULTS: The UVP fully recovered in 52 of 84 (61.9%) patients. Positive mucosal waves (pMWs) on the paralyzed side, a minimal glottic gap <3 mm seen at the first postoperative VLS, age ≤50 years, and surgery duration ≤120 minutes were associated factors for a complete recovery of nerve function. The voice parameters improved independently from recovery of the paralysis in 90% of the patients. CONCLUSIONS: For patients with a poor prognosis of a UVP, early intervention may be beneficial. Thus, predicting factors for a full recovery of vocal fold motion would be a valuable tool. In our cohort, about 60% of recoveries could have been predicted using the above-mentioned parameters. Good quality of voice was independently reached in 90% of the cases.

Cornification of nail keratinocytes requires autophagy for bulk degradation of intracellular proteins while sparing components of the cytoskeleton.

Epidermal keratinocytes undergo cornification to form the cellular building blocks of hard skin appendages such as nails and the protective layer on the surface of the skin. Cornification requires the cross-linking of structural proteins and the removal of other cellular components to form mechanically rigid and inert corneocytes. Autophagy has been proposed to contribute to this intracellular remodelling process, but its molecular targets in keratinocytes, if any, have remained elusive. Here, we deleted the essential autophagy factor Atg7 in K14-positive epithelia of mice and determined by proteomics the impact of this deletion on the abundance of individual proteins in cornified nails. The genetic suppression of autophagy in keratinocytes resulted in a significant increase in the number of proteins that survived cornification and in alterations of their abundance in the nail proteome. A broad range of enzymes and other non-structural proteins were elevated whereas the amounts of cytoskeletal proteins of the keratin and keratin-associated protein families, cytolinker proteins and desmosomal proteins were either unaltered or decreased in nails of mice lacking epithelial autophagy. Among the various types of non-cytoskeletal proteins, the subunits of the proteasome and of the TRiC/CCT chaperonin were most strongly elevated in mutant nails, indicating a particularly important role of autophagy in removing these large protein complexes during normal cornification. Taken together, the results of this study suggest that autophagy is active during nail keratinocyte cornification and its substrate specificity depends on the accessibility of proteins outside of the cytoskeleton and their presence in large complexes.

Inactivation of autophagy leads to changes in sebaceous gland morphology and function.

We have reported recently that inactivation of the essential autophagy-related gene 7 (Atg7) in keratinocytes has little or no impact on morphology and function of the epidermal barrier in experimental animals. When these mice aged, mutant males, (Atg7 ΔKC), developed an oily coat. As the keratin 14 promoter driven cre/LoxP system inactivates floxed Atg7 in all keratin 14 (K14) expressing cells, including sebocytes, we investigated whether the oily hair phenotype was the consequence of changes in function of the skin sebaceous glands. Using an antibody to the GFP-LC3 fusion protein, autophagosomes were detected at the border of sebocyte disintegration in control but not in mutant animals, suggesting that autophagy was (a) active in normal sebaceous glands and (b) was inactivated in the mutant mice. Detailed analysis established that dorsal sebaceous glands were about twice as large in all Atg7 ΔKC mice compared to those of controls (Atg7 F/F), and their rate of sebocyte proliferation was increased. In addition, male mutant mice yielded twice as much lipid per unit hair as age-matched controls. Analysis of sebum lipids by thin layer chromatography revealed a 40% reduction in the proportion of free fatty acids (FFA) and cholesterol, and a 5-fold increase in the proportion of fatty acid methyl esters (FAME). In addition, the most common diester wax species (58-60 carbon atoms) were increased, while shorter species (54-55 carbon atoms) were under-represented in mutant sebum. Our data show that autophagy contributes to sebaceous gland function and to the control of sebum composition.

The Reticulum-Associated Protein RTN1A Specifically Identifies Human Dendritic Cells.

RTN1 is an endoplasmic reticulum-associated protein that was initially identified in neuronal tissues. Here we show that the main isoform RTN1A is a marker for dendritic cells. In the skin, HLA-DR+CD1ahighCD207+CD11cweak Langerhans cells were the only cells in the epidermis, and HLA-DR+CD11c+ dendritic cells were the main cells in the dermis, expressing this protein. RTN1A+ dendritic cells were also found in gingiva, trachea, tonsil, thymus, and peripheral blood. During differentiation of MUTZ-3 cells into Langerhans cells, expression of RTN1A mRNA and protein preceded established Langerhans cell markers CD1a and CD207, and RTN1A protein partially co-localized with the endoplasmic reticulum marker protein disulfide isomerase. In line with this observation, we found that RTN1A was expressed by around 80% of Langerhans cell precursors in human embryonic skin. Our findings show that RTN1A is a marker for cells of the dendritic lineage, including Langerhans cells and dermal dendritic cells. This unexpected finding will serve as a starting point for the elucidation of the, until now, elusive functional roles of RTN1A in both the immune and the nervous system.

Inactivation of DNase1L2 and DNase2 in keratinocytes suppresses DNA degradation during epidermal cornification and results in constitutive parakeratosis.

The stratum corneum of the epidermis constitutes the mammalian skin barrier to the environment. It is formed by cornification of keratinocytes, a process which involves the removal of nuclear DNA. Here, we investigated the mechanism of cornification-associated DNA degradation by generating mouse models deficient of candidate DNA-degrading enzymes and characterizing their epidermal phenotypes. In contrast to Dnase1l2 -/- mice and keratinocyte-specific DNase2 knockout mice (Dnase2 Δep ), Dnase1l2 -/- Dnase2 Δep mice aberrantly retained nuclear DNA in the stratum corneum, a phenomenon commonly referred to as parakeratosis. The DNA within DNase1L2/DNase2-deficient corneocytes was partially degraded in a DNase1-independent manner. Isolation of corneocytes, i.e. the cornified cell components of the stratum corneum, and labelling of DNA demonstrated that corneocytes of Dnase1l2 -/- Dnase2 Δep mice contained DNA in a nucleus-shaped compartment that also contained nucleosomal histones but lacked the nuclear intermediate filament protein lamin A/C. Parakeratosis was not associated with altered corneocyte resistance to mechanical stress, changes in transepidermal water loss, or inflammatory infiltrates in Dnase1l2 -/- Dnase2 Δep mice. The results of this study suggest that cornification of epidermal keratinocytes depends on the cooperation of DNase1L2 and DNase2 and indicate that parakeratosis per se does not suffice to cause skin pathologies.

Delivered adipose-derived stromal cells improve host-derived adipose tissue formation in composite constructs in vivo.

OBJECTIVES/HYPOTHESIS: Adipose tissue engineering aims to provide functional tissue surrogates for the restoration of soft tissue defects and contour deformities in the face. Many studies involve the delivery of cells; however, the impact and the exact role of the implanted cells is not yet fully elucidated. STUDY DESIGN: Animal research. METHODS: In this study, we used a mouse model for the development of volume-stable adipose tissue using polyurethane scaffolds combined with a long-term stable fibrin gel and adipose-derived stromal cells to investigate the influence of cell delivery on tissue development. RESULTS: After 12 weeks in vivo, the emerging tissue in these constructs was shown to be exclusively of host origin by human-specific vimentin staining. Comparison of unseeded versus seeded scaffolds revealed a significant effect of the delivered cells on adipose tissue development as shown by histological staining and histomorphometric quantification of adipocytes, whereas blood vessel formation was not affected by delivery of adipose-derived stromal cells at this time point. CONCLUSIONS: This is evidence for an indirect action of the implanted cells, providing a proadipogenic microenvironment within constructs, which was further boosted by adipogenic precultivation of the seeded constructs. Especially in peripheral areas of the constructs, the number of adipocytes was significantly elevated in seeded scaffolds compared to nonseeded controls, suggesting that the implanted cells likely triggered the invasion and differentiation of host cells. This is supported by the fact that the provision of a fat rich environment (by coverage of the constructs with a fat flap upon implantation) additionally stimulated adipose tissue formation. LEVEL OF EVIDENCE: NA. Laryngoscope, 127:E428-E436, 2017.

Holocrine Secretion of Sebum Is a Unique DNase2-Dependent Mode of Programmed Cell Death.

Sebaceous glands produce sebum via holocrine secretion, a largely uncharacterized mode of programmed cell death that contributes to the homeostasis and barrier function of the skin. To determine the mechanism of DNA degradation during sebocyte cell death, we have inactivated candidate DNA-degrading enzymes by targeted gene deletions in mice. DNase1 and DNase1-like 2 were dispensable for nuclear DNA degradation in sebocytes. By contrast, epithelial cell-specific deletion of lysosomal DNase2 blocked DNA degradation in these cells. DNA breakdown during sebocyte differentiation coincided with the loss of LAMP1 and was accelerated by the abrogation of autophagy, the central cellular program of lysosome-dependent catabolism. Suppression of DNA degradation by the deletion of DNase2 resulted in aberrantly increased concentrations of residual DNA and decreased amounts of the DNA metabolite uric acid in secreted sebum. These results define holocrine secretion as a DNase2-mediated form of programmed cell death and suggest that autophagy-dependent metabolism, DNA degradation, and the molecular composition of sebum are mechanistically linked.

The Expression of the Endogenous mTORC1 Inhibitor Sestrin 2 Is Induced by UVB and Balanced with the Expression Level of Sestrin 1.

Sestrin 2 (SESN2) is an evolutionarily conserved regulator of mechanistic target of rapamycin complex 1 (mTORC1) which controls central cellular processes such as protein translation and autophagy. Previous studies have suggested that SESN2 itself is subjected to regulation at multiple levels. Here, we investigated the expression of SESN2 in the skin and in isolated skin cells. SESN2 was detected by immunofluorescence analysis in fibroblasts and keratinocytes of human skin. Differentiation of epidermal keratinocytes was not associated with altered SESN2 expression and siRNA-mediated knockdown of SESN2 did not impair stratum corneum formation in vitro. However, SESN2 was increased in both cell types when the expression of its paralog SESN1 was blocked by siRNA-mediated knock down, indicating a compensatory mechanism for the control of expression. Irradiation with UVB but not with UVA significantly increased SESN2 expression in both keratinocytes and fibroblasts. Upregulation of SESN2 expression could be completely blocked by suppression of p53. These results suggest that SESN2 is dispensable for normal epidermal keratinization but involved in the UVB stress response of skin cells.

Nanofiltrated C1-esterase-inhibitor in the prophylactic treatment of bradykinin-mediated angioedema.

BACKGROUND: Patients suffering from bradykinin-induced angioedema show recurrent swelling of subcutaneous and submucosal structures. Increased bradykinin levels lead to an increase in vascular permeability and edema formation. Current therapy consists of B2 bradykinin receptor antagonists, C1-esterase-inhibitor (C1-INH) concentrate, or the kallikrein inhibitor ecallantide. In most cases the treatment of acute attacks is sufficient. Prophylactic therapy is recommended only in severe cases. C1-INHc has been shown a safe and efficient option. Its effect on the quality of life has not yet been analyzed. STUDY DESIGN AND METHODS: Patients with inadequate disease control despite an "on-demand therapy" including C1-INHc and/or the B2 receptor antagonist icatibant were switched to long-term prophylaxis consisting in an individual dose of intravenous C1-INHc (Cinryze). None of the patients had been previously treated with ecallantide. Disease-specific quality-of-life questionnaires and patient records were used for evaluation. Disease control, quality of life, adverse events, and administered dosage per month were compared for 6 months on on-demand therapy and the following 6 months under prophylactic therapy. RESULTS: Data of seven patients with hereditary angioedema (HAE) and one patient with acquired angioedema were evaluated. Prophylactic therapy with Cinryze led to a significant and clinically relevant reduction in the overall attack frequency from 6.7 to 2.3 per month without relevant side effects. The frequency of severe attacks was reduced by 89% and quality of life significantly improved. CONCLUSION: Prophylaxis with Cinryze led to a significantly improved quality of life in our cohort of patients with high-frequency bradykinin-induced angioedema attacks that were not sufficiently treated with on-demand medication.

Keratins K2 and K10 are essential for the epidermal integrity of plantar skin.

BACKGROUND: K1 and K2 are the main type II keratins in the suprabasal epidermis where each of them heterodimerizes with the type I keratin K10 to form intermediate filaments. In regions of the ears, tail, and soles of the mouse, only K2 is co-expressed with K10, suggesting that these keratins suffice to form a mechanically resilient cytoskeleton. OBJECTIVE: To determine the effects of the suppression of both main keratins, K2 and K10, in the suprabasal plantar epidermis of the mouse. METHODS: Krt2(-/-) Krt10(-/-) mice were generated by crossing Krt2(-/-) and Krt10(-/-) mice. Epidermal morphology of soles of hind-paws was examined macroscopically and histologically. Immunofluorescence analysis and quantitative PCR analysis were performed to analyze the expression of keratins in sole skin of wildtype and Krt2(-/-) Krt10(-/-) mice. Highly abundant proteins of the sole stratum corneum were determined by electrophoretic and chromatographic separation and subsequent mass spectrometry. RESULTS: K2 and K10 are the most prominent suprabasal keratins in normal mouse soles with the exception of the footpads where K1, K9 and K10 predominate. Mice lacking both K2 and K10 were viable and developed epidermal acanthosis and hyperkeratosis in inter-footpad epidermis of the soles. The expression of keratins K1, K9 and K16 was massively increased at the RNA and protein levels in the soles of Krt2(-/-) Krt10(-/-) mice. CONCLUSIONS: This study demonstrates that the loss of the main cytoskeletal components of plantar epidermis, i.e. K2 and K10, can be only partly compensated by the upregulation of other keratins. The thickening of the epidermis in the soles of Krt2(-/-) Krt10(-/-) mice may serve as a model for pathomechanistic aspects of palmoplantar keratoderma.

Trichohyalin-like proteins have evolutionarily conserved roles in the morphogenesis of skin appendages.

S100 fused-type proteins (SFTPs) such as filaggrin, trichohyalin, and cornulin are differentially expressed in cornifying keratinocytes of the epidermis and various skin appendages. To determine evolutionarily conserved, and thus presumably important, features of SFTPs, we characterized nonmammalian SFTPs and compared their amino acid sequences and expression patterns with those of mammalian SFTPs. We identified an ortholog of cornulin and a previously unknown SFTP, termed scaffoldin, in reptiles and birds, whereas filaggrin was confined to mammals. In contrast to mammalian SFTPs, both cornulin and scaffoldin of the chicken are expressed in the embryonic periderm. However, scaffoldin resembles mammalian trichohyalin with regard to its expression in the filiform papillae of the tongue and in the epithelium underneath the forming tips of the claws. Furthermore, scaffoldin is expressed in the epithelial sheath around growing feathers, reminiscent of trichohyalin expression in the inner root sheath of hair. The results of this study show that SFTP-positive epithelia function as scaffolds for the growth of diverse skin appendages such as claws, nails, hair, and feathers, indicating a common evolutionary origin.