TY - JOUR
T1 - Comprehensive phenotypic analysis of diverse FOXN1 variants
AU - Moses, Angela
AU - Bhalla, Pratibha
AU - Thompson, Austin
AU - Lai, Laijun
AU - Coskun, Fatma S.
AU - Seroogy, Christine M.
AU - de la Morena, Maria Teresa
AU - Wysocki, Christian A.
AU - van Oers, Nicolai S.C.
N1 - Publisher Copyright:
© 2023 The Authors
PY - 2023/11
Y1 - 2023/11
N2 - Background: Thymus hypoplasia due to stromal cell problems has been linked to mutations in several transcription factors, including Forkhead box N1 (FOXN1). FOXN1 supports T-cell development by regulating the formation and expansion of thymic epithelial cells (TECs). While autosomal recessive FOXN1 mutations result in a nude and severe combined immunodeficiency phenotype, the impact of single-allelic or compound heterozygous FOXN1 mutations is less well-defined. Objective: With more than 400 FOXN1 mutations reported, their impact on protein function and thymopoiesis remains unclear for most variants. We developed a systematic approach to delineate the functional impact of diverse FOXN1 variants. Methods: Selected FOXN1 variants were tested with transcriptional reporter assays and imaging studies. Thymopoiesis was assessed in mouse lines genocopying several human FOXN1 variants. Reaggregate thymus organ cultures were used to compare the thymopoietic potential of the FOXN1 variants. Results: FOXN1 variants were categorized into benign, loss- or gain-of-function, and/or dominant-negatives. Dominant negative activities mapped to frameshift variants impacting the transactivation domain. A nuclear localization signal was mapped within the DNA binding domain. Thymopoiesis analyses with mouse models and reaggregate thymus organ cultures revealed distinct consequences of particular Foxn1 variants on T-cell development. Conclusions: The potential effect of a FOXN1 variant on T-cell output from the thymus may relate to its effects on transcriptional activity, nuclear localization, and/or dominant negative functions. A combination of functional assays and thymopoiesis comparisons enabled a categorization of diverse FOXN1 variants and their potential impact on T-cell output from the thymus.
AB - Background: Thymus hypoplasia due to stromal cell problems has been linked to mutations in several transcription factors, including Forkhead box N1 (FOXN1). FOXN1 supports T-cell development by regulating the formation and expansion of thymic epithelial cells (TECs). While autosomal recessive FOXN1 mutations result in a nude and severe combined immunodeficiency phenotype, the impact of single-allelic or compound heterozygous FOXN1 mutations is less well-defined. Objective: With more than 400 FOXN1 mutations reported, their impact on protein function and thymopoiesis remains unclear for most variants. We developed a systematic approach to delineate the functional impact of diverse FOXN1 variants. Methods: Selected FOXN1 variants were tested with transcriptional reporter assays and imaging studies. Thymopoiesis was assessed in mouse lines genocopying several human FOXN1 variants. Reaggregate thymus organ cultures were used to compare the thymopoietic potential of the FOXN1 variants. Results: FOXN1 variants were categorized into benign, loss- or gain-of-function, and/or dominant-negatives. Dominant negative activities mapped to frameshift variants impacting the transactivation domain. A nuclear localization signal was mapped within the DNA binding domain. Thymopoiesis analyses with mouse models and reaggregate thymus organ cultures revealed distinct consequences of particular Foxn1 variants on T-cell development. Conclusions: The potential effect of a FOXN1 variant on T-cell output from the thymus may relate to its effects on transcriptional activity, nuclear localization, and/or dominant negative functions. A combination of functional assays and thymopoiesis comparisons enabled a categorization of diverse FOXN1 variants and their potential impact on T-cell output from the thymus.
KW - FOXN1
KW - T-cell immunodeficiency
KW - TRECs
KW - Thymopoiesis
KW - reaggregate thymus organ cultures
KW - thymus epithelial cells
UR - http://www.scopus.com/inward/record.url?scp=85171186613&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=85171186613&partnerID=8YFLogxK
U2 - 10.1016/j.jaci.2023.06.019
DO - 10.1016/j.jaci.2023.06.019
M3 - Article
C2 - 37419334
AN - SCOPUS:85171186613
SN - 0091-6749
VL - 152
SP - 1273-1291.e15
JO - Journal of Allergy and Clinical Immunology
JF - Journal of Allergy and Clinical Immunology
IS - 5
ER -