Forkhead box (Fox) family transcription factors are highly conserved and play essential roles in a wide range of cellular and developmental processes. This family was named after the ectopic head structures observed in mutants of the Drosophila gene forkhead (fkh). Since the discovery of fkh, hundreds of Fox genes have been identified in organisms ranging from yeasts to humans, making it one of the largest but least explored families of higher eukaryotic transcription factors. The NIH Undiagnosed Diseases Program (NIH UDP), a clinical site of the NIH Undiagnosed Diseases Network (UDN), identified a variant (p.M280L) in a single allele of the FOXR1 gene in an individual with severe neurological symptoms including postnatal microcephaly, progressive brain atrophy, and global developmental delay. The de novo missense variant in FOXR1 converts a highly conserved methionine residue at amino acid 280 to leucine and was predicted to contribute to the individual’s disease. The goal of this research is to investigate the biological role of FOXR1 and to determine how the M280L mutant leads to disease pathogenesis.
At the protein level, the M280L mutant impaired FOXR1 expression and induced a nuclear aggregate phenotype when overexpressed in HEK 293T and COS7 cells due to protein misfolding and proteolysis. A FOXR1 C-terminal truncation mutant mimicked the M280L phenotype, suggesting that the C-terminal sequences of FOXR1 are important for FOXR1 protein stability. RNAseq and pathway analysis in HEK 293T cells indicated that FOXR1 acts as both transcriptional activator and repressor, playing central roles in heat shock response, chaperone cofactor-dependent protein refolding, and cellular response to stress. Indeed, FOXR1 expression is increased in HEK 293T in response to cellular stress, a process in which FOXRI directly controls HSPA6, HSPA1A and DHRS2 transcription. In contrast, the ability of the M280L mutant to respond to stress is compromised, in part due to impaired regulation of downstream target genes that are involved in the stress response pathway. Combined, these results suggest that FOXR1 plays a role in cellular stress and that impairment of these functions may contribute to the disease phenotypes seen in the individual with the FOXRI M280L variant.
| Identifer | oai:union.ndltd.org:bu.edu/oai:open.bu.edu:2144/42669 |
| Date | 07 June 2021 |
| Creators | Mota, Andressa |
| Contributors | Ho, Angela, Beffert, Uwe |
| Source Sets | Boston University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
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