OR13-04 Nucleoredoxin Regulates WNT Signaling During Pituitary Stem Cell Differentiation

Abstract Disclosure: M.L. Brinkmeier: None. S. Yang: None. L.Y. Cheung: None. S.P. O'Connell: None. D.K. Gutierrez: None. Y. Ho: None. E.C. Rhoads: None. S.A. Camper: None. S.W. Davis: None. Nucleoredoxin (Nxn) encodes a multi-functional enzyme with oxidoreductase activity that regulates signaling pathways and cellular processes in a redox-dependent manner. We noted that homozygous mouse Nxn mutants have pituitary dysmorphology at embryonic day 14.5 (e14.5), a time when differentiated hormone producing cells are beginning to emerge. We sought to identify the basis for pituitary dysmorphology in Nxn mutants and to determine whether hormone cell differentiation was affected.We characterized a null allele of Nxn, (Nxnem1(IMPC)J or Nxn-/-). We confirmed that Nxn deficient mice are viable until birth, but do not survive. At e18.5 mutants had completely penetrant cleft palate, and variable penetrance of facial clefting and eye abnormalities. We analyzed skeletal preparations and found significant shortening of the head, nasal bone, and mandible (p<0.05). There was incomplete ossification of the basisphenoid bone (p<0.01).We examined Nxn expression and pituitary development in Nxn-/-. Nxn transcripts were present in the developing posterior, intermediate, and anterior lobes of the pituitary gland between e11.5 and e17.5, with predominant expression in the Sox2 expressing stem cells and other progenitors. Pituitary dysmorphology was evident at e10.5 and persisted throughout gestation. We employed scRNA sequencing to assess the proportions of various cell types and to identify differentially expressed genes in dissected pituitary tissue at e14.5. Not all hormone genes are expressed at this stage; we used pseudotime analysis to assist in identifying the relationships between the cell clusters present. We found reduced expression of the non-canonical Wnt5a in the infundibulum, but normal expression of Fgf8. The fraction of cells obtained in the clusters expressing Prop1 and Pou1f1 was altered, and there were fewer differentiated thyrotropes. Pseudotime density suggests that the mutants have more cells in mid-trajectory and fewer cells at the end. We found reduced expression of the canonical WNT responsive gene Lef1. Gene expression changes were confirmed by immunohistochemistry. Using TIME-coExpress, we identified gene pairs with altered coexpression patterns in the absence of Nxn.In conclusion, Nxn is expressed in the developing ventral diencephalon and pituitary gland, and it is required for normal pituitary development. Nxn deficiency altered WNT signaling in the canonical and planar cell polarity pathways, and it reduced the progression of progenitor cells to differentiated cells. NXN mutations are reported in some individuals with Robinow syndrome, which involves skeletal dysplasia, short stature, craniofacial dysmorphisms, and incompletely penetrant heart and palate defects. Our results suggest patients with Robinow syndrome could benefit from evaluation by endocrinologists for pituitary structural imaging and hormone insufficiency. Presentation: Sunday, July 13, 2025