056 Expression of the CCAAT/Enhancer-Binding Protein Transcription Factor Family in the Sebaceous Gland

J.J. Bull1, S. Müller-Röver2, C.C. Zouboulis3, R. Paus2, I.A. McKay1 and M.P. Philpott1. Centre for Cutaneous Research, St Bartholomew’s and the Royal London School of Medicine and Dentistry, Queen Mary College, University of London, UK1. University Hospital Eppendorf, University of Hamburg, Germany2. Department of Dermatology, Free University of Berlin, Germany3.

Although the precise function of the sebaceous gland remains to be determined, it appears to play a crucial role in the pathogenesis of pilosebaceous unit disorders such as acne vulgaris. The differentiation programme of basal sebaceous gland epithelia into lipid rich sebocytes has been hypothesised to be analogous to adipocyte differentiation in adipose tissue. The CCAAT/enhancer-binding proteins (C/EBPs) are a family of transcription factors known to play a crucial role in adipocyte differentiation and lipogenesis. We speculated that C/EBP family members (C/EBPa, C/EBPß, C/EBPd and Gadd153) have similar roles in the sebaceous gland. To determine C/EBP expression in sebaceous gland, immunohistochemistry was performed on cryosections of human hair bearing skin and dorsal skin from C57BL/6 mice. By use of immunocytochemistry, Western blotting and RT-PCR, we have also investigated C/EBP expression patterns in the human immortalised sebaceous gland cell line SZ95. Immunohistochemistry of both human and murine skin showed intense immunoreactivity for C/EBPa, C/EBPß and C/EBPd in the nuclei of both the basal undifferentiaited cells of the sebaceous gland and in the more differentiated sebocytes. Gadd153 was not detected in either human or murine sebaceous glands. In SZ95 cells, we detected C/EBPa, C/EBPß and C/EBPd expression by both RT-PCR and Western blotting. Immunocytochemistry of cultured SZ95 cells showed diffuse nuclear localisation of C/EBPß and C/EBPd, whereas C/EBPa exhibited a punctate, intranuclear localisation pattern. C/EBPa has previously been reported to trans-activate the adipocyte specific gene stearoyl CoA desaturase 1, a key enzyme in fatty acid synthesis. By RT-PCR, we have also detected stearoyl CoA desaturase 1 expression in SZ95 cells. Our results show specific C/EBP family members are expressed in the sebaceous gland and may therefore regulate the expression of genes crucial to sebocyte differentiation and lipogenesis.