A genetic melanotic neoplasm of Drosophila melanogaster

Abstract

Tuml is a sex-linked recessive lethal mutation. The major pathological consequence of this mutation is hypertrophy of the larval lymph gland followed by the encapsulation of the anterior midgut, i.e., the formation of melanotic pseudotumors. Injection of the Tuml larval lymph gland into adult female hosts results in severe melanization, growth of the injected tissue, and premature death of the host animals. The tissue recovered from a host injected with Tuml larval lymph glands grows in subsequent hosts, causes the premature death of those hosts, and may or may not give rise to melanizations. None of these effects is seen in hosts injected with other Tuml tissues, including encapsulated midgut tissue or in hosts injected with wild-type larval lymph gland tissue. Ultrastructural studies reveal that the neoplastic tissue derived from hosts injected with Tuml lymph glands contain cells which resemble Drosophila blood cells both structurally and functionally. This evidence suggests that the Tuml mutation expresses a true melanotic neoplasm in which neoplastic cells capable of encapsulating and melanizing are continuously produced. This is the first demonstration of a melanotic neoplasm associated with a melanotic tumor mutation.