Endocrine Abstracts

Introduction: Heterozygote loss-of-function mutations in AIP (Aryl hydrocarbon receptor interacting protein) predispose to young-onset pituitary adenomas. Homozygote murine knockout model of AIP leads to lethality. While the majority of the 75 published AIP mutations result in truncated or missing proteins, missense mutations are more difficult to characterise and to establish their pathogenic role. We have identified the orthologue of AIP, CG1847, in Drosophila melanogaster. This protein has high level of homology with human AIP.

Methods: We generated a CG1847 deficiency via RNAi knockdown (using two different RNAi-lines) or via knocking out two of the three exons of CG1847 by imprecise excision of a transposable P-element located in the 5′-UTR of CG1847.

To functionally test the homology between human AIP and CG1847, a UAS::humanAIP construct was made by inserting the human AIP coding sequence, downstream of the GAL4-dependent UAS promoter into the pUASK10attB vector. Microinjection of this construct into fruitfly embryos harbouring attP40 landing sites enabled us to obtain transgenic fruitflies with human AIP sequence on the second chromosome balanced over CyO. We tested whether this UAS::humanAIP transgene was able to rescue CG1847^exon1_2 mutants by expressing it with a ubiquitous driver during fly development.

Results: Our data show that both in the knockdown and knockout of CG1847 results in lethality in the fruitfly. Strikingly, we found that human AIP gene can rescue the lethality of Drosophila melanogaster knockout model of AIP orthologue, demonstrating that CG1847 is the functional homolog of AIP.

Conclusions: We are able to rescue the lethality of fruitfly CG1847^exon1_2 mutant with human AIP, confirming that CG1847 is a highly conserved gene throughout evolution. This system can be used to test human AIP missense variants, where pathogenicity cannot be easily determined based on clinical data.

Acknowledgments: This work was supported by the William Harvey Research Foundation (grant number #2011-5).