Effects of Brn2 overexpression on eccrine sweat gland development in the mouse paw

Eccrine sweat glands regulate body temperature by secreting water and electrolytes. In humans, eccrine sweat glands are ubiquitous in the skin, except in the lips and external genitalia. In mice, eccrine sweat glands are present only in the paw pad. Brn2 is a protein belonging to a large family of transcription factors. A few studies have examined Brn2 in melanoma cells and epidermal keratinocytes. This study investigated changes in the skin in the K5-Brn2 transgenic mouse, which overexpresses Brn2 and contains the keratin 5 promotor. Interestingly, the volume of eccrine sweat glands was reduced markedly in the K5-Brn2 transgenic mouse compared with the wild-type, while the expression of aquaporin 5, important molecule in sweat secretion, was increased in each sweat gland cell, probably to compensate for the reduction in gland development. However, sweating response to a pilocarpine injection in the hind paw was significantly decreased in the K5-Brn2 transgenic mouse compared with the wild-type. The paw epidermis was thicker in the K5-Brn2 transgenic mouse compared with the wild-type. Taken together, eccrine sweat gland development and sweat secretion were suppressed markedly in the K5-Brn2 transgenic mouse. These results may be associated with dominant development of the epidermis by Brn2 overexpression in the paw skin.