homeostasis/metabolism
• defects in stratum corneum (SC) formation result in total loss of epidermal barrier function
• epidermal defects are associated with selective loss of both proteolytically processed filaggrin monomer units and the NH2-terminal filaggrin S-100 regulatory protein, with severe accumulation of profilaggrin and aberrant profilaggrin-processing products in the SC
• epidermal deficiency is not corrected with time or by systemic expression of Matriptase/MT-SP1
• prolonged exposure of neonatal mutant transplanted skin to dehydration (air) leads to severe compensatory hyperproliferative ichthyosis
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integument
• newborn homozygotes exhibit defective proteolytic processing of profilaggrin and incorporation of aberrantly processed profilaggrin into the SC during terminal corneocyte differentiation
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• defects in stratum corneum (SC) formation result in total loss of epidermal barrier function
• epidermal defects are associated with selective loss of both proteolytically processed filaggrin monomer units and the NH2-terminal filaggrin S-100 regulatory protein, with severe accumulation of profilaggrin and aberrant profilaggrin-processing products in the SC
• epidermal deficiency is not corrected with time or by systemic expression of Matriptase/MT-SP1
• prolonged exposure of neonatal mutant transplanted skin to dehydration (air) leads to severe compensatory hyperproliferative ichthyosis
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• at 3 wks after transplantation onto nude mice, neonatal mutant skin displays absence of erupted pelage hairs; only a few pelage hair shafts are found as thin, broken fibers surrounded by dense sheaths of cornified debris
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• newborn homozygotes display numerous defects in stratum corneum (SC) formation
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• mutant corneocyte envelopes (CEs) isolated from newborn homozygotes are enlarged by 15% relative to wild-type CEs
• however, the shape, surface morphology, and mechanical integrity of mutant CEs remain unaffected
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• newborn homozygotes exhibit lipid matrix defects, as shown by a ~50% reduction in free fatty acids, a ~25% increase in cholesterol, and a nearly 10-fold decrease in sterol esters in total epidermis and SC, along with a >2-fold increase in phospholipid content in the SC relative to control littermates
• mutant intercorneocyte lipids appear poorly organized with short and misaligned lipid lamellae
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• at 3 wks after transplantation onto nude mice, neonatal mutant skin displays severe hyperkeratosis, associated with hyperproliferation of basal keratinocytes and keratin-6 overexpression
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• unlike wild-type controls, where the SC is completely removed exposing the lower epidermal layers after 12 successive rounds of tape stripping, newborn homozygotes display only minimal SC removal with a significant reduction in SC protein loss after tape stripping, indicating increased mechanical resistance
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• newborn homozygotes display rare and poorly formed lamellar bodies with wavy, short, and disorganized lipid structures in the granular layer of the epidermis
(J:86715)
• tight junctions are poorly defined
(J:153070)
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acanthosis
(
J:86715
)
• at 3 wks after transplantation onto nude mice, neonatal mutant skin displays profound acanthosis
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• at 3 wks after transplantation onto nude mice, neonatal mutant skin displays grotesque epidermal thickening
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scaly skin
(
J:86715
)
• at 3 wks after transplantation onto nude mice, neonatal mutant skin displays large plate-like epidermal scales
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cellular
• newborn homozygotes exhibit defective proteolytic processing of profilaggrin and incorporation of aberrantly processed profilaggrin into the SC during terminal corneocyte differentiation
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