Endocrine Abstracts

Aryl hydrocarbon receptor-interacting protein (AIP) is a highly expressed, evolutionary conserved little-known co-chaperone molecule that can bind to client proteins. Heterozygous loss-of-function mutations of AIP are associated with pituitary adenomas. Multiple lines of evidence suggest that AIP has important functions beyond the pituitary gland. Homozygous loss of AIP is lethal, with cardiac abnormalities seen in mice and failure-to-thrive seen in fruit flies and C.elegans. The mechanisms of AIP lethality are unclear. We generated aip loss of function zebrafish line using CRISPR/Cas9 with 29 base pair (bp) deletion in exon 2, leading to a premature stop codon. Fluorescent-labelled larval fish feed (paramecia) intake assay was conducted to measure their food intake. Heart size and functions were assessed using microscopy. In larval fish, in situ hybridization of atrial myosin heavy chain (amhc) and ventricular myosin heavy chain (vmhc) and H&E staining were used to characterise cardiac phenotypes. Somatotroph cells were assessed by in situ hybridisation for growth hormone 1 (gh1). There were no pituitary abnormalities noted at larval stages. The majority of aip^-/- individuals died between 6 and 11 dpf regardless of feeding. Only 4% of aip^-/- larvae survived until approximately 20 dpf and the remaining fish were significantly smaller, comparable to that 5 dpf larvae. The food intake assay suggested no significant difference between aip^+/+, aip^+/- and aip^-/- at 7 dpf, suggesting that while the intake is normal, animals are unable to absorb and metabolise nutrients. The cardiac assessment showed several cardiovascular abnormalities, including an elevated heart rate, severe pericardial oedema and the presence of ventricular hypertrophy after 4 dpf. Our findings establish the key role of AIP in cardiac development and function. Zebrafish provide an ideal model for exploring the mechanisms behind AIP-related growth failure and cardiac dysfunction and identification of potential therapeutic approaches for individuals with AIP-related disorders.