P33 C-MYC, MAX AND BIN1 EXPRESSION IN HUMAN ANAGEN HAIR FOLLICLES.

Barajon I., Donetti E., Rumio C., Imberti A., Castano P.; Institute of Human Anatomy, University of Milan, Via Mangiagalli 31, 20133 Milan, Italy.

Recently, we have shown the presence of c-Myc immunoreactivity in three distinct zones of the IRS, corresponding to the level where terminal differentiation takes place in Henle’s, cuticle’s and Huxley’s layers. On this background we have decided to extend our investigations to two others regulatory molecules participating to the so-called “Myc network”: Max and Bin1.

Human scalp microislets were processed for immunofluorescence and immunohistochemical detection of c-Myc, Max and Bin1 and Western blot analysis was performed for the latter. The subcellular localization of the immunoreactivity was mostly cytoplasmic. Max immunostaining was present in all the three layers of the IRS, starting where they become distinguishable at the level of the bulb. Bin1 immunostaining could be detected in Huxley’s layer and in the cuticle starting from the keratogenic zone. Both for Max and Bin1, the labeling stopped in each layer at the level of the corresponding c-Myc positive ring where there was a rather complete overlapping among the immunoreactivies. Clear-cut Bin1 immunostaining was also present in the companion layer of the ORS up to the infundibular region. A correlation between the immunostaining for Max and Bin1 and changes in the morphological features of cells could be clearly observed at the level of the c-Myc rings, consisting in a rather abrupt disappearance of putative trichoyalin granules, nuclear picnosis and changes in the appearance of the cytoplasm. The results of the present study indicate that behind the biochemical events leading to terminal differentiation of hair follicle keratinocytes there is complex balance of Myc-interacting molecules suggesting also that this small organ could provide a useful model to investigate the expression of genes usually involved in cell transformation, tumorigenesis and tumor suppression.