Recombination within the myelin basic protein gene created the dysmyelinating shiverer mouse mutation

Area of Science:

• Neuroscience
• Genetics
• Molecular Biology

Background:

• The shiverer (shi) mutation in mice results in a near-complete absence of central nervous system (CNS) myelin.
• Myelin basic protein (MBP) is a critical component of CNS myelin, and its four forms are undetectable in shi mutant brains.
• Previous studies suggested a significant rearrangement within the MBP gene in shi mutants.

Purpose of the Study:

• To precisely characterize the molecular nature and extent of the MBP gene rearrangement in the shiverer (shi) mouse mutant.
• To elucidate the genetic mechanism underlying the myelin deficiency observed in shi mice.

Main Methods:

• Detailed molecular analysis of the myelin basic protein (MBP) gene in shiverer (shi) mutant mice.
• Mapping of the 5' and 3' breakpoints of the deletion within the MBP gene.
• Sequence analysis of the recombination junction to identify structural features and potential mechanisms.

Main Results:

• A 20-kilobase deletion within the MBP gene was identified in shi mutant mice.
• The 5' breakpoint was mapped to the second intron, and the 3' breakpoint was located 2 kilobases downstream of the final MBP exon.
• The deletion junction contained a region rich in alternating purine-pyrimidine sequences, associated with Z-DNA and gene rearrangements, and exhibited features consistent with a partially homologous recombination event.

Conclusions:

• The extensive deletion within the MBP gene is the direct cause of the absence of MBP and the severe myelin deficiency in shiverer (shi) mice.
• The recombination junction structure suggests a model of partially homologous recombination, involving alignment in a homologous region followed by staggered cutting and joining.
• Understanding this specific gene rearrangement provides insights into the mechanisms of DNA recombination and their role in genetic mutations affecting neurological development.