Differential regulation of uncoupling protein-2 and uncoupling protein-3 gene expression in brown adipose tissue during development and cold exposure.

The expression of the two novel uncoupling proteins genes, UCP2 and UCP3, is differentially regulated during prenatal maturation of brown adipose tissue in the mouse. UCP2 gene is expressed early in prenatal development, when neither UCP1 nor UCP3 gene expression yet occurs. UCP3 mRNA is absent at any stage of fetal life; it appears suddenly at birth and reaches adult levels in a few hours. UCP2 mRNA increased after birth but more slowly than UCP3 and UCP1 mRNA. Short-time exposure of adult mice to cold caused a rise in UCP2 or UCP1 mRNA levels but not in that of UCP3. The postnatal rise in UCP2 gene expression appears to be a response to the thermic stress associated with birth, similarly to UCP1, whereas different biological signals may be responsible for the surge in UCP3 gene expression at birth.