Tob is a potential marker gene for the basal layer of the epidermis and is stably expressed in human primary keratinocytes.
BACKGROUND
Epidermis consists of multiple layers, from the proliferating basal layer to terminal differentiated cornified layers, and these layers are defined by differentiation status. Tob gene product is known to be a member of the BTG antiproliferative protein family. We investigated the expression pattern of Tob gene product to understand the possible role in differentiation of keratinocytes and epidermis.


OBJECTIVE
In this study, we examined the expression of Tob gene product in the primary cultured human keratinocytes and in the in vivo epidermis.


METHODS
The expression of Tob gene product was assessed by Western blotting analysis. Cellular localization of Tob was detected using the green fluorescent protein-tagged Tob cDNA expression construct. In vivo expression of Tob gene product in the epidermis was determined by immunohistochemistry with paraffin sections.


RESULTS
Tob family members are degraded by the ubiquitine-proteasome system triggered by the growth signal. Tob is stably and abundantly expressed in primary cultured human keratinocytes. Furthermore, the expression of Tob in the keratinocytes persists during the differentiation induced by calcium; however, it was not detected in primary cultured fibroblasts. Also, the subcellular localization of Tob is mainly in the cellular membrane in the primary human keratinocytes. We evaluated Tob expression in normal skin, oral mucosa and different diseases, such as psoriasis, X-linked ichthyosis and squamous cell carcinoma (SCC). Using immunohistochemical analysis, we observed that Tob was selectively expressed in the basal layer of X-linked ichythyosis and the hyperproliferative basal layer of psoriasis and oral mucosa as well as in normal epidermis. In SCC, the expression of Tob gene product was relatively decreased.


CONCLUSIONS
Tob is stably expressed in primary human keratinocytes and it is specifically expressed in the basal layer of in vivo epidermis.
Park
G T
GT
Clinical Research Centre, Samsung Biomedical Research Institute, Seoul, Korea.
Seo
E Y
EY
Lee
K M
KM
Lee
D Y
DY
Yang
J M
JM
D015153:Blotting, Western; D002294:Carcinoma, Squamous Cell / Q000378:metabolism; D002478:Cells, Cultured; D018076:DNA, Complementary / Q000235:genetics; D004817:Epidermis / Q000378:metabolism*; D015870:Gene Expression; D005819:Genetic Markers; D006801:Humans; D016114:Ichthyosis, X-Linked / Q000378:metabolism; D007124:Immunoenzyme Techniques; D047908:Intracellular Signaling Peptides and Proteins / Q000235:genetics / Q000378:metabolism*; D015603:Keratinocytes / Q000378:metabolism*; D009061:Mouth Mucosa / Q000378:metabolism; D009363:Neoplasm Proteins / Q000378:metabolism; D011565:Psoriasis / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction / Q000379:methods; D012878:Skin Neoplasms / Q000378:metabolism; D014162:Transfection; D025521:Tumor Suppressor Proteins / Q000235:genetics / Q000378:metabolism*
D018076:DNA, Complementary; D005819:Genetic Markers; D047908:Intracellular Signaling Peptides and Proteins; D009363:Neoplasm Proteins; D012333:RNA, Messenger; C098669:TOB1 protein, human; D025521:Tumor Suppressor Proteins