Over 40 putative NHRs have been identified in C. elegans so far. In insects such as Drosophila melanogaster, NHRs are known to be essential for developmental processes.
Nematodes also undergo a series of molts during development.
Recent work in D. immitis has identified homologs of the EcR and usp genes, which encode NHRs that heterodimerize to form the functional ecdysone receptor in Drosophila. The ecdysone signal in Drosophila is modulated by a number of transcription factors that are induced as a primary response to ecdysone. We have identified putative homologs of two of these Drosophila primary response genes, E75 and E78, both of which encode NHRs. Preliminary experiments in cultured adult females suggest that expression of these genes may be altered by ecdysone. NHRs may play a role in D. immitis development that is analogous to their role in Drosophila development.