Expression of keratohyalin-trichohyalin hybrid granules in molluscum contagiosum.
BACKGROUND
Recently, in the filiform papillae epithelium of mouse dorsal tongue, we showed the presence of hybrid granules in which filaggrin and trichohyalin were both present, but physically segregated. Further, trichohyalin was also detected in scattered granular cells of a number of hyperplastic skin diseases.


METHODS
The epidermis infected with molluscum contagiosum virus (MCV) was studied by conventional electron microscopy in conjunction with light and electron-microscopic immunohistochemistry, using both antifilaggrin and antitrichohyalin antibodies as probes.


RESULTS
We found that the granular cells of MCV-infected epidermis contained both filaggrin and trichohyalin. Subsequent electron-microscopic examination showed that the granular cells contained morphologically heterogeneous granules that appeared to be composed of discrete areas of distinct electron densities. Double-labeling, using antibodies to filaggrin and trichohyalin, clearly indicated that filaggrin and trichohyalin were both present in the hybrid granules and that the electron-dense regions contained trichohyalin while the more electron-lucent regions contained filaggrin.


CONCLUSIONS
The expression of trichohyalin was a common feature observed in the epidermis from a heterogenous group of hyperplastic conditions, including MCV infection. This finding has led us to speculate that trichohyalin may be specifically or preferentially involved in interacting with the hyperproliferation-related keratin pair (K6/K16), whereas the function of filaggrin is more closely linked to the skin-type keratin pair (K1/K10) that are normal keratins found in the differentiated epidermis.
Manabe
M
M
Department of Dermatology, Juntendo University School of Medicine, Tokyo, Japan.
Yaguchi
H
H
Butt
K I
KI
O'Guin
W M
WM
Sun
T T
TT
Ogawa
H
H
D002454:Cell Differentiation; D002455:Cell Division; D003594:Cytoplasmic Granules / Q000648:ultrastructure*; D004817:Epidermis / Q000648:ultrastructure; D000091344:Filaggrin Proteins; D005786:Gene Expression Regulation; D006801:Humans; D006818:Hyalin / Q000737:chemistry*; D002479:Inclusion Bodies / Q000648:ultrastructure; D007381:Intermediate Filament Proteins / Q000032:analysis / Q000235:genetics; D007633:Keratins / Q000032:analysis* / Q000235:genetics; D008854:Microscopy, Electron; D016253:Microscopy, Immunoelectron; D008976:Molluscum Contagiosum / Q000473:pathology*; D008977:Molluscum contagiosum virus / Q000648:ultrastructure; D011498:Protein Precursors / Q000032:analysis* / Q000235:genetics
C000717249:FLG protein, human; D000091344:Filaggrin Proteins; D007381:Intermediate Filament Proteins; D011498:Protein Precursors; C001500:keratohyalin; C016159:trichohyalin; D007633:Keratins