Dimerization defective MODY mutations of hepatocyte nuclear factor 4α

Area of Science:

• Molecular Endocrinology
• Genetics of Diabetes
• Protein Biochemistry

Background:

• Hepatocyte Nuclear Factor 4 alpha (HNF4α) is implicated in Maturity Onset Diabetes of the Young type 1 (MODY1), a monogenic diabetes form.
• Reduced HNF4α activity impairs insulin secretion and beta-cell function, with numerous mutations identified in patients.
• HNF4α, a nuclear receptor, functions as a homodimer, crucial for transcriptional regulation.

Purpose of the Study:

• To investigate the impact of mutations directly affecting the HNF4α dimerization interface.
• To characterize the functional consequences of disrupting HNF4α homodimerization.
• To confirm that MODY1 mutations represent loss-of-function events.

Main Methods:

• Analysis of two MODY1 mutations (L332P and L328del) located at the HNF4α dimerization interface.
• Assessment of dimerization disruption, protein stability, and transcriptional activity.
• In vitro characterization of mutant HNF4α protein function.

Main Results:

• The L332P and L328del mutations directly disrupt HNF4α dimerization.
• These mutations also affect protein stability and reduce transcriptional activity.
• The findings demonstrate that impaired dimerization leads to loss-of-function of HNF4α.

Conclusions:

• HNF4α dimerization is essential for its optimal function and normal physiological roles.
• Mutations disrupting HNF4α dimerization are a cause of MODY1.
• This study provides direct evidence for dimerization disruption as a pathogenic mechanism in MODY1.