The TCL1Gene Is Involved, Other Than in Lymphoid Differentiation and Early Embryogenesis, Also in the Development of the Hair Follicle.

The TCL1(T-cell leukaemia lymphoma1)oncogene plays a causative role in the onset of T and B cell leukaemia of mature phenotype, such as T-prolymphocytic leukema T-(PLL) in human and mice and B-cell-chroni lymphatic leukaemia (B-CLL) in mice due to its overexpression. Moreover, Tcl1−/− mice show that this gene is also important during the early embryogenesis and lymphocyte differentiation. An undiscovered role was found for TCL1 gene in the skin. In this work, we show evidences that give Tcl1a new, important role in mouse hair follicle (HF) and skin homeostasis. In fact, Tcl1−/− adult mice develop premature hair loss leading to alopecia followed by extensive skin lesions, starting from the dorsal region. The expression pattern of Tcl1in the skin throughout the different stages of hair and skin differentiation, by in vivoimmunofluorescence and fluorescent in situ hybridization experiments, shows a high level of the mRNA and protein in HF mainly in the secondary hair germ cells and hair bulge but not in dermal papilla (DP), both in early anagen and late catagen phases, and to less extent in the epidermis in all the stages examined.