Core splicing architecture and early spliceosomal recognition determine microexon sensitivity to SRRM3/4

Area of Science:

• Molecular Biology
• Genetics
• Cell Biology

Background:

• Microexons are vital for neuronal and pancreatic endocrine cell function.
• Splicing factors SRRM3 and SRRM4 (SRRM3/4) regulate microexon inclusion.
• Differential sensitivity of microexons to SRRM3/4 in different cell types is not well understood.

Purpose of the Study:

• Investigate the regulatory mechanisms underlying differential microexon sensitivity to SRRM3/4.
• Determine the role of cis-acting elements and splicing architecture in microexon regulation.
• Explore the evolutionary conservation of microexon sensitivity.

Main Methods:

• Utilized massively parallel splicing assays to test 28,535 variants.
• Analyzed spliceosome activity in the absence of SRRM3/4.
• Developed a mathematical model to simulate microexon recruitment dynamics.

Main Results:

• Demonstrated conserved sensitivity to SRRM4 across vertebrates.
• Identified interplay between core splicing architecture and length constraints as key determinants of microexon sensitivity.
• Observed distinct spliceosome activities correlating with microexon sensitivity.

Conclusions:

• Microexon sensitivity to SRRM4 is evolutionarily conserved.
• Splicing architecture and length constraints, rather than solely regulatory factor levels, dictate microexon sensitivity.
• A model of early spliceosomal component recruitment efficiency explains differential microexon behavior.