Identifying biological pathways that underlie primordial short stature using network analysis.

Area of Science:

• Genetics and Molecular Biology
• Cellular Biology
• Endocrinology

Background:

• 3-M syndrome is a common primordial growth disorder caused by mutations in CUL7, OBSL1, and CCDC8, leading to disordered ubiquitination.
• Associated abnormalities include impaired p53 function, growth hormone (GH)/insulin-like growth factor 1 (IGF1) resistance, and IGF2 deficiency.
• The precise molecular mechanisms linking these factors to growth restriction are not fully understood.

Purpose of the Study:

• To define key cellular pathways and biological functions associated with growth failure in 3-M syndrome by generating a 3-M interactome.
• To investigate the molecular link between disordered ubiquitination and growth restriction in 3-M syndrome.

Main Methods:

• Immunoprecipitation/mass spectrometry and transcriptomic studies were employed to create a 3-M interactome.
• Proteins interacting with CUL7, OBSL1, and CCDC8 were identified and networked.
• Differential gene expression in 3-M fibroblasts was compared with controls to refine the 3-M network.
• An exogenous insulin receptor (INSR) minigene system was used to assess alternative splicing.

Main Results:

• A 3-M network of 131 proteins was generated, with mRNA splicing/processing identified as the most significant biological pathway.
• Alternative splicing of exon 11 of the insulin receptor (INSR) was significantly altered in cells with modified CUL7, OBSL1, CCDC8 expression and in 3-M fibroblasts.
• This aberrant splicing resulted in reduced expression of the mitogenic INSR isoform in 3-M syndrome.

Conclusions:

• Disordered ubiquitination may lead to aberrant mRNA splicing in 3-M syndrome.
• Reduced expression of the mitogenic INSR isoform is a consequence of altered splicing in 3-M syndrome.
• Further investigation is required to determine if these splicing changes contribute to growth failure in 3-M syndrome.