Immunohistochemical evaluation of epidermal proliferation, differentiation and melanocytic density in symmetrical acrokeratoderma

Calcium-sensing receptor deletion in the mouse esophagus alters barrier function

Calcium-sensing receptor (CaSR) is the molecular sensor by which cells respond to small changes in extracellular Ca²⁺ concentrations. CaSR has been reported to play a role in glandular and fluid secretion in the gastrointestinal tract and to regulate differentiation and proliferation of skin keratinocytes. CaSR is present in the esophageal epithelium, but its role in this tissue has not been defined. We deleted CaSR in the mouse esophagus by generating keratin 5 CreER;CaSR^Flox+/+compound mutants, in which loxP sites flank exon 7 of CaSR gene. Recombination was initiated with multiple tamoxifen injections, and we demonstrated exon 7 deletion by PCR analysis of genomic DNA. Quantitative real-time PCR and Western blot analyses showed a significant reduction in CaSR mRNA and protein expression in the knockout mice (^EsoCaSR^-/-) as compared with control mice. Microscopic examination of ^EsoCaSR^-/- esophageal tissues showed morphological changes including elongation of the rete pegs, abnormal keratinization and stratification, and bacterial buildup on the luminal epithelial surface. Western analysis revealed a significant reduction in levels of adherens junction proteins E-cadherin and β catenin and tight junction protein claudin-1, 4, and 5. Levels of small GTPase proteins Rac/Cdc42, involved in actin remodeling, were also reduced. Ussing chamber experiments showed a significantly lower transepithelial resistance in knockout (KO) tissues. In addition, luminal-to-serosal-fluorescein dextran (4 kDa) flux was higher in KO tissues. Our data indicate that CaSR plays a role in regulating keratinization and cell-cell junctional complexes and is therefore important for the maintenance of the barrier function of the esophagus.NEW & NOTEWORTHY The esophageal stratified squamous epithelium maintains its integrity by continuous proliferation and differentiation of the basal cells. Here, we demonstrate that deletion of the calcium-sensing receptor, a G protein-coupled receptor, from the basal cells disrupts the structure and barrier properties of the epithelium.

Symmetrical acral keratoderma revisited: proposal for a new term, 'pigmented carpotarsal hyperkeratosis'

First reported from Taiwan mistakenly as acral acanthosis nigricans in 1991, pigmented carpotarsal hyperkeratosis or hyperkeratosis nigricans carpi et tarsi displays a peculiar distribution of velvety brown-grey hyperpigmented plaques symmetrically on the flexural side of the wrists and ankles and on the dorsal sides of the hands and feet. A marked epidermal hyperkeratosis with typically mild acanthosis and papillomatosis is observed in histology. Whitish maceration upon perspiration or water exposure, with exacerbation in summer but remission in winter, is common. The association with obesity, endocrine disorders, atopic dermatitis, ichthyosis or malignancy is unknown. Familial occurrence and hereditary patterns are ill-defined. There is preliminary evidence indicating a pathogenic role of missense mutation in the transcription factor 4 gene. Treatment is empirical, with good outcome with topical retinoids and keratolytic agents. Recurrence is common, and long-term prognosis is unclear. To be distinguished are acral acanthosis nigricans, palmoplantar keratoderma of the Nagashima type, palmoplantar keratoderma of the Bothnian type and aquagenic palmoplantar keratoderma. Most reported cases are from Southern China and are predominantly observed in men between the ages of 20 and 40 years. The currently used term 'symmetrical acral keratoderma' is non-specific and misleading and may lead to global unawareness, underreporting or misdiagnosis of this phenomenon. Further genetic and molecular studies are required to clarify its pathogenesis and relation to palmoplantar keratoderma.