AIP Mutation Leads to Significant Alterations in Gene Expression, Altered Sensitivity to AHR Ligands, and Early Lethality in Zebrafish

Aip mutant zebrafish (Danio rerio) lines were generated using CRISPR-Cas9 technology. Deletions were generated in exon 2 (aipwh86) or exon 5 (aipwh239), both resulting in an early stop codon. Zebrafish homozygous for either mutation died at 7–10-days post-fertilization (dpf).

No such effect was observed in ahr mutant lines. Larvae from the aipwh239 line were exposed to four toxic AHR ligands from diverse chemical classes. Homozygous mutant larvae exposed to PCB126, 5-nitroacenaphthene, and benzo(k)fluoranthene showed reduced sensitivity compared to both heterozygous and wildtype larvae.

However, changes in sensitivity were ligand-dependent. In contrast, homozygous larvae demonstrated increased sensitivity to leflunomide. mRNA sequencing was performed at 5 dpf in unexposed larvae from both aip lines. Around one thousand DEGs and alternative splicing products were observed in homozygous mutants from both lines.

Gene sets and binding motifs involved in cellular stress, apoptosis, innate immune response, proteolysis, replication, and metabolism were enriched. Our findings highlight the context-dependent nature of Aip in Ahr modulation and the critical roles that Aip plays in regulating cellular homeostasis.