Title: An androgenic gland membrane-anchored gene associated with the crustacean insulin-like androgenic gland hormone
Abstract: Summary Crustacean male sexual differentiation is governed by the androgenic gland (AG) and specifically by the secreted insulin-like AG hormone (IAG), thus far identified in several decapod species including the Australian red claw crayfish Cherax quadricarinatus (termed Cq-IAG). While few insulin-like AG genes have been identified in crustaceans, other AG-specific genes have not been documented until now. In the present study we describe the recent identification of a non-IAG AG-specific transcript obtained from the C. quadricarinatus AG cDNA library. This transcript, termed C. quadricarinatus membrane-anchored AG-specific factor (Cq-MAG), was fully sequenced and found to encode a putative product of 189 amino acids including a signal anchoring peptide. Expression of a recombinant GFP fusion protein lacking the signal anchor encoding sequence dramatically affected recombinant protein localization pattern. While the expression of the deleterious fusion protein was observed throughout most of the cell, the native GFP::Cq-MAG fusion protein was observed mainly surrounding the periphery of the nucleus, demonstrating an ER-like localization pattern. Moreover, co-expressing the wild-type Cq-MAG (fused to GFP) and the Cq-IAG hormone revealed that these peptides indeed co-localize. This study is the first to report a protein specifically associated with the insulin-like androgenic gland hormone in addition to the finding of another AG-specific transcript in crustaceans. Previous knowledge suggests that insulin/insulin-like factor secretion involves tissue-specific transcripts and membrane anchored proteins. On this note, Cq-MAG's tissue specificity, anchoring properties, and intracellular co-localization with Cq-IAG suggest that it may play a role in the processing and secretion of this insulin-like androgenic gland hormone.