A Function for Rac1 in the Terminal Differentiation and Pigmentation of Hair

January 2012 in “ Journal of cell science ”

Kristina Behrendt, Jennifer E. Klatte, Ruth Pofahl, Wilhelm Bloch, Neil Smyth, Michael Tscharntke, Thomas Krieg, Ralf Paus, Carien M. Niessen, Catherin Niemann, Cord Brakebusch, Ingo Haase

Rac1 terminal differentiation pigmentation hair loss basal epidermal layer outer root sheath epidermis-specific deletion medulla cells pigment distribution cortical keratin-filled spikes desmosomal cadherin Dsc2

Studysummary This study demonstrates that Rac1 activity is essential for normal hair follicle formation but influences hair structure and pigmentation, in terminal differentiation, through alterations in hair shaft, cuticle, and pigmentation organization.

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The study demonstrated that Rac1 played a crucial role in the terminal differentiation and pigmentation of hair. By expressing a constitutively active mutant of Rac1 (L61Rac1) in the basal epidermal layer and outer root sheath of mice with an epidermis-specific deletion of endogenous Rac1, researchers were able to rescue severe hair loss, resulting in a full hair coat. However, the hair quality in these rescue mice was abnormal, appearing grey and dull compared to the black and shiny hair of wild-type mice. Hair analysis revealed structural alterations, disorganized medulla cells, and disrupted pigment distribution. The absence of cortical, keratin-filled spikes and reduced desmosomal cadherin Dsc2 were also noted. This study identified Rac1's regulatory functions in hair structure and pigmentation, highlighting its role in terminal differentiation.

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