Gain-of-function mutation of microRNA-140 in human skeletal dysplasia

Area of Science:

• Genetics
• Molecular Biology
• Developmental Biology

Background:

• MicroRNAs (miRNAs) are crucial gene regulators, and loss-of-function mutations are linked to human disorders.
• Neomorphic (gain-of-new-function) mutations in miRNAs have not been previously reported.
• The MIR140 gene, encoding miR-140, is vital for chondrocytes and associated with super-enhancers.

Purpose of the Study:

• To report the first instance of a neomorphic, gain-of-function mutation in a microRNA gene.
• To investigate the molecular mechanisms underlying a novel autosomal dominant human skeletal dysplasia.
• To characterize the effects of a seed region mutation in miR-140.

Main Methods:

• Identification and characterization of a novel neomorphic seed region mutation in the MIR140 gene.
• Generation and analysis of a mouse model with the corresponding single nucleotide substitution.
• Assessment of miRNA expression, target derepression/repression, and RNA-binding protein competition in chondrocytes.

Main Results:

• A novel autosomal dominant skeletal dysplasia is associated with a neomorphic mutation in the MIR140 gene.
• The mutant mouse model exhibits skeletal abnormalities distinct from miR-140-null mice.
• The mutation leads to both loss-of-function and gain-of-function effects by altering target interactions and competing with Ybx1.

Conclusions:

• This study presents the first evidence of a pathogenic gain-of-function mutation in a microRNA.
• The neomorphic miR-140 mutation provides molecular insights into the potent regulatory actions of mutant and emerging miRNAs.
• Understanding these neomorphic mutations is critical for diagnosing and potentially treating related congenital disorders.