Aromatase expression in extragonadal tissues of the Sebright chicken is controlled by a retroviral promoter.

These studies have clarified a number of issues regarding the genetic control of extragonadal aromatase expression in birds carrying the henny-feathering trait. The marked increased in extragonadal aromatase expression of a unique species of aromatase mRNA is apparently controlled by a retrovirus. We have not yet established whether this promoter is the consequence of a new retroviral insertion or is due to a mutation in a preexisting retrovirus. It is of interest in this regard that the chicken aromatase gene is located in a region of chromosome 1 known to be rich in retroviral insertions. Second, the relationship of the henny-feathering trait to normal and abnormal extragonadal aromatase expression in man remains to be determined. At one extreme, it is possible that a similar mechanism may underlie syndromes typified by increases in extraglandular aromatase expression. Even if the parallel proves to be less exact, the Sebright chicken provides important insight into how aromatase expression may be modulated differently in different tissues. Finally, the discovery that retroviral sequences appear to modulate the expression of aromatase in extragonadal tissues represents an unusual method by which the genetic control of genes can be altered. In the case of the henny-feathering trait, the alteration in the dimorphic feathering pattern was the principal clue to the altered regulation of extragonadal aromatase. This relation is in keeping with the other examples of altered gene expression caused by retroviruses that have also caused morphologic alterations such as changes in coat color or the appearance of neoplasms (for examples, see Refs. 14-16).(ABSTRACT TRUNCATED AT 250 WORDS)