Mitchell-Riley syndrome iPSCs exhibit reduced pancreatic endoderm differentiation due to a mutation in RFX6

Area of Science:

• Developmental Biology
• Genetics
• Endocrinology

Background:

• Mitchell-Riley syndrome (MRS) is a genetic disorder characterized by pancreatic hypoplasia and neonatal diabetes.
• MRS results from recessive mutations in the regulatory factor X6 gene (RFX6).
• The precise mechanism by which RFX6 mutations lead to the specific loss of pancreatic endocrine cells remains unclear.

Purpose of the Study:

• To investigate the role of RFX6 in pancreatic development and the etiology of endocrine cell deficiency in MRS.
• To determine the spatio-temporal expression pattern of RFX6 during human pancreatic embryogenesis.
• To elucidate why RFX6 deficiency specifically impairs pancreatic endocrine cell formation.

Main Methods:

• Micro-computed tomography (micro-CT) imaging of an MRS fetus.
• Derivation and differentiation of induced pluripotent stem cells (iPSCs) from MRS fetal tissue.
• Gene targeting to create an RFX6 reporter allele (RFX6HA) in human embryonic stem cells.
• In situ hybridization for RFX6 expression in human embryonic pancreatic buds.

Main Results:

• Micro-CT revealed absence of the pancreas body and tail in an MRS fetus.
• In vitro differentiation of MRS iPSCs showed significantly reduced pancreatic endoderm generation.
• RFX6 expression was identified in a subset of PDX1-expressing pancreatic endoderm cells both in vitro and in vivo.
• RFX6 is essential for the efficient differentiation of pancreatic endoderm.

Conclusions:

• RFX6 plays a critical role in the development of pancreatic endoderm.
• Absence of functional RFX6 impairs the formation of pancreatic endocrine cells, particularly in the pancreas head and tail.
• This finding explains the specific endocrine cell deficiency observed in individuals with Mitchell-Riley syndrome.