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Neuroendocrinology and Pituitary

SAT-122 - Induced Pluripotent Stem Cell (Ipsc)-Models for Investigating FOXA2'S Role in Human Pituitary Differentiation and Hormone Deficiencies

Saturday, June 13, 2026
9:30 AM - 4:30 PM CT
Location: ENDOExpo; Poster Floor
Forkhead Box A2 (FOXA2) is a pioneer transcription factor required for pancreas, liver, and neuronal development; however, its involvement in pituitary organogenesis remains unknown. Candidate FOXA2 variants were proposed in the etiology of congenital hypopituitarism, but additional evidence is necessary to define strong genotype-phenotype associations. Induced pluripotent stem cells (iPSCs) can self-renew and differentiate into all body cell types, thus they represent a useful tool for human-genetic disease modeling. We previously reported a congenital hypopituitarism (CH) patient carrying a novel heterozygous FOXA2 variant (c.686C>A; p.S229*). In this study, we aimed to evaluate the mechanism of the FOXA2;p.S229* variant and the putative role of FOXA2 in pituitary development. To that end, we generated patient-derived iPSCs by reprogramming the patient’s blood cells and a FOXA2 knockout iPSC model via the CRISPR/Cas9 editing tool. All iPSC lines, including control healthy donor-derived iPSCs, were validated for pluripotency, genomic stability, and spontaneous differentiation capacity into the three germ layers. To induce pituitary specification, a monolayer protocol was applied to the FOXA2-deficient and control iPSCs by 15-day culture induction with bone morphogenetic protein 4, fibroblast growth factor, and sonic hedgehog pathway agonist. Pituitary-associated markers, FOXA2-homolog FOXA1, and putative FOXA2 interactors (GLI, GLI2, NOTCH2) were analyzed at differentiation days 0 (pluripotency), 4 (non-neural ectoderm), 7, and 15 (pituitary precursor) by real-time quantitative RT-PCR. Over 15 days, all three iPSC lines progressed toward a pituitary lineage. However, differential expression trends were detected. FOXA2-deficient cells showed decreased placodal marker SIX1 mRNA expression and increased FOXA1 and GLI1 mRNA at pituitary progenitor stages, alongside a significant increase in pituitary stem-cell marker SOX2 at day 7 (*P < 0.05). In agreement, immunofluorescence protein expression assays confirmed an increased percentage of SOX2-positive cells (54% ± 3% FOXA2 KO vs 18% ± 8% control iPSCs, day 15). PITX2, a key regulator of gonadotroph and thyrotroph differentiation, was found to be decreased in the KO model at early stages, suggesting an altered temporal progression during pituitary progenitor specification. In conclusion, we successfully generated human in vitro models to identify the molecular mechanism of FOXA2 in hypopituitarism and its contribution during pituitary-cell specification. Additional experiments are necessary to define the roles of GLI proteins and the FOXA1 homolog as FOXA2 protein interaction partners during pituitary differentiation. Future work will extend differentiation for the comparison of the hormone-cell maturation stage between FOXA2-deficient and wild-type iPSCs.

*Unless otherwise noted, all abstracts presented at ENDO must not be released to the press or the public until the date and time of presentation. For oral presentations, the abstracts are embargoed until the session begins. The Endocrine Society reserves the right to lift the embargo on specific abstracts that are selected for promotion prior to or during ENDO.*