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Shiverer jimpy double mutant mice. V. Correlation of genotype and myelin proteins
A Sinclair1, Y Raz, D A Kirschner
1Department of Neurology, Childrens Hospital, Boston, Mass.
Abstract:
We have reexamined the levels of myelin basic protein (MBP) and proteolipid protein (PLP) in the brains of mice bred to carry both the shi/shi and jp/Y hypomyelination defects. The genotype of each putative double mutant was confirmed by direct DNA analysis: shi/shi by Southern blot analysis, and jp/Y by restriction enzyme analysis of polymerase chain reaction-amplified fragments. MBP and PLP levels were assessed by immunoblotting. All putative double mutants were found to be shi/shi. However, examination of the PLP locus revealed both jp and wild-type genotypes, the latter produced by an expected crossover. Animals proven to be shi/shi*jp/Y had no detectable MBP or PLP; those proven to be shi/shi*+/Y (the crossover) had no MBP but had PLP. These results differ from an earlier report of both MBP and PLP in the brains of presumed shi*jp animals.
Insights
This study re-evaluates myelin basic protein (MBP) and proteolipid protein (PLP) levels in mice with hypomyelination defects. Results show shi/shi*jp/Y mice lack both MBP and PLP, differing from prior findings.
Area of Science:
- Neuroscience
- Genetics
- Molecular Biology
Background:
- Hypomyelination is a neurological disorder characterized by reduced myelin.
- The shi and jp mutations in mice are known models for studying hypomyelination.
- Understanding the combined effects of these mutations is crucial for myelin research.
Purpose of the Study:
- To re-examine myelin basic protein (MBP) and proteolipid protein (PLP) levels in mice with combined shi/shi and jp/Y hypomyelination defects.
- To clarify discrepancies with previous reports on MBP and PLP levels in double mutant mice.
- To investigate the genetic interactions and their impact on myelin protein expression.
Main Methods:
- Genotyping of double mutant mice using Southern blot analysis (shi/shi) and PCR-RFLP (jp/Y).
- Quantification of MBP and PLP levels via immunoblotting.
- Analysis of the PLP locus to identify wild-type alleles resulting from recombination.
Main Results:
- All analyzed double mutants were confirmed to be shi/shi.
- Mice with the shi/shi*jp/Y genotype showed no detectable MBP or PLP.
- Mice with the shi/shi*+/Y genotype (resulting from a crossover) lacked MBP but retained PLP.
Conclusions:
- The combined shi/shi and jp/Y mutations result in a severe deficiency of both MBP and PLP.
- The presence of a wild-type allele at the PLP locus can restore PLP expression in shi/shi mice.
- These findings refine our understanding of hypomyelination genetics and provide a more accurate model for studying myelin disorders.