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Functional interaction of transcriptional regulators in endocrine lineage specification

Award Number: R01DK135032
ORGANIZATION: NATIONAL INSTITUTE OF DIABETES & DIGESTIVE & KIDNEY DISEASES
OPDIV: NIH
AWARD CLASS: DISCRETIONARY
AWARD ACTIVITY TYPE: SCIENTIFIC/HEALTH RESEARCH (INCLUDES SURVEYS)
PERIOD OF PERFORMANCE START DATE: 01/01/2023
PERIOD OF PERFORMANCE END DATE: 12/31/2027

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Functional interaction of transcriptional regulators in endocrine lineage specification - SUMMARY Reduction in functional insulin-secreting β cells underlies the progression of all forms of diabetes, underscoring the translational relevance of deciphering molecular pathways regulating the formation, growth, and function of β cells. The transcriptional networks critical for the proper development, differentiation, and expansion of β cells work through islet enhancers, super enhancers, and active promoters that form 3D hubs. The homeodomain transcription factor Pdx1 is a critical member of the β-cell transcriptional network during development and in postnatal β-cell function. Pdx1 is mutated in monogenic forms of human diabetes and plays critical roles in early pancreas specification, regulation of organ size, and in β-cell formation, proliferation, and identity. Our preliminary data reveal that developing β cells exhibit altered subnuclear localization and reduced levels of Pdx1 protein as they advance through the cell cycle. Further, ectopically elevated levels of Pdx1 prevent cell cycle progression, suggesting that dynamic regulation of expression is required for effective β-cell expansion. We identify an intrinsically disordered protein region (IDPR) in the Pdx1 C-terminus (aa 207-223). IDPRs, commonly found within transcription factors, lack fixed secondary structure and are amenable to flexible conformations and phase separation. IDPRs promote protein-protein interactions and transcriptional hub formation at super enhancers necessary for coordinated gene regulation. We have found that the Pdx1 C-terminus mediates interaction with the one cut homeodomain transcription factor Oc1 in multipotent pancreatic progenitor cells to establish the endocrine gene program, with long-term impact on postnatal islet function and β-cell compensation. We previously identified the E3 ubiquitin ligase substrate adaptor SPOP as a PDX1 C-terminus partner (via aa224-238) that mediates ubiquitination and proteasomal degradation of PDX1. Our preliminary data suggest that SPOP and Oc1 compete for interaction with the Pdx1 C-terminus and that Oc1 protects Pdx1 from SPOP- mediated degradation. Notably, the C-terminus harbors several diabetes-associated human mutations, one of which we recently found disrupts the PDX1/SPOP interaction. Thus, we hypothesize that PDX1/OC1 interactions, in part mediated by their IDPRs, regulate Pdx1 stability, cell cycle progression, and pancreatic endocrine differentiation. This hypothesis will be tested in 3 Aims: (1) To determine the mechanisms whereby Pdx1 and Oc1 cooperate to establish a chromatin landscape permissive for endocrine differentiation and proliferation; (2) To define the roles of the Pdx1 and Oc1 IDPRs in protein-protein interaction and pancreas development; and (3) To define the molecular mechanisms by which the Pdx1 C-terminal domain regulates protein stability and function during pancreas organogenesis and endocrine differentiation. The impact of human diabetes-associated mutations will be investigated in this context. Our studies will determine a novel and cohesive role for unstudied structural features of the Pdx1 C-terminus in β-cell development. Results of our studies will inform therapeutic efforts to optimize β-cell expansion for cell-based therapies.


Issue Date FY	Funding FY	Legal Entity Name	Legal Entity Address	Legal Entity City	Legal Entity State	Legal Entity Zip Code	Legal Entity COUNTY	Legal Entity COUNTRY	Assistance Listing	Award Code	Budget Year	Action Date	Action Type	Action Amount

Issue Date FY: 2026 ( Subtotal = $690,551 )
2026	2026	TRUSTEES OF THE UNIVERSITY OF PENNSYLVANIA, THE	3451 WALNUT STREET	PHILADELPHIA	PA	19104	PHILADELPHIA	USA	Diabetes, Digestive, and Kidney Diseases Extramural Research	000	4	12/16/2025	NON-COMPETING CONTINUATION	$690,551
														Subtotal = $690,551

Issue Date FY: 2025 ( Subtotal = $696,480 )
2025	2025	TRUSTEES OF THE UNIVERSITY OF PENNSYLVANIA, THE	3451 WALNUT ST STE 440A	PHILADELPHIA	PA	19104	PHILADELPHIA	USA	Diabetes, Digestive, and Kidney Diseases Extramural Research	000	3	12/9/2024	NON-COMPETING CONTINUATION	$626,833
2025	2025	TRUSTEES OF THE UNIVERSITY OF PENNSYLVANIA, THE	3451 WALNUT ST STE 440A	PHILADELPHIA	PA	19104	PHILADELPHIA	USA	Diabetes, Digestive, and Kidney Diseases Extramural Research	001	3	6/12/2025	NON-COMPETING CONTINUATION	$69,647
														Subtotal = $696,480

Issue Date FY: 2024 ( Subtotal = $674,130 )
2024	2024	TRUSTEES OF THE UNIVERSITY OF PENNSYLVANIA, THE	3451 WALNUT ST STE 440A	PHILADELPHIA	PA	19104	PHILADELPHIA	USA	Diabetes, Digestive, and Kidney Diseases Extramural Research	000	2	12/8/2023	NON-COMPETING CONTINUATION	$631,999
2024	2024	TRUSTEES OF THE UNIVERSITY OF PENNSYLVANIA, THE	3451 WALNUT ST STE 440A	PHILADELPHIA	PA	19104	PHILADELPHIA	USA	Diabetes, Digestive, and Kidney Diseases Extramural Research	001	2	5/3/2024	NON-COMPETING CONTINUATION	$42,131
														Subtotal = $674,130

Issue Date FY: 2023 ( Subtotal = $754,659 )
2023	2023	TRUSTEES OF THE UNIVERSITY OF PENNSYLVANIA, THE	3451 WALNUT ST STE 440A	PHILADELPHIA	PA	19104	PHILADELPHIA	USA	Diabetes, Digestive, and Kidney Diseases Extramural Research	000	1	12/16/2022	NEW	$754,659
														Subtotal = $754,659

Grand Total All Awards = $2,815,820

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Functional interaction of transcriptional regulators in endocrine lineage specification

Award Number: R01DK135032

ORGANIZATION: NATIONAL INSTITUTE OF DIABETES & DIGESTIVE & KIDNEY DISEASES

OPDIV: NIH

AWARD CLASS: DISCRETIONARY

AWARD ACTIVITY TYPE: SCIENTIFIC/HEALTH RESEARCH (INCLUDES SURVEYS)

PERIOD OF PERFORMANCE START DATE: 01/01/2023

PERIOD OF PERFORMANCE END DATE: 12/31/2027

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