Mouse paracentric inversion In(3)55Rk mutates the urate oxidase gene

Area of Science:

• Genetics
• Molecular Biology
• Nephrology

Background:

• Paracentric inversions can disrupt gene function and lead to phenotypic consequences.
• Uricase (Uox) deficiency in mice results in nephropathy.
• Characterizing radiation-induced mutations is crucial for understanding genetic alterations.

Purpose of the Study:

• To characterize the genetic and molecular basis of the paracentric inversion In(3)55Rk on mouse Chromosome 3.
• To investigate the impact of this inversion on the urate oxidase (Uox) gene and its associated phenotype.
• To determine if the induced mutation is a null mutation.

Main Methods:

• Induction of paracentric inversion using cesium irradiation.
• Genetic crosses and linkage analysis to map breakpoints.
• Giemsa banding for cytogenetic analysis.
• Southern blot and cDNA analysis to assess Uox gene integrity.
• Fluorescence in situ hybridization (FISH) to analyze chromosomal rearrangements.
• Clinical, histopathological, and Northern blot analyses.

Main Results:

• The paracentric inversion In(3)55Rk was mapped to mouse Chromosome 3, with breakpoints in bands 3A2 and 3H3.
• Homozygous inversion mice exhibited nephropathy linked to uricase deficiency.
• Southern blot revealed RFLPs in the mutant Uox gene, and cDNA analysis showed a truncation.
• FISH analysis demonstrated a 5' segment of the Uox allele transposed from the distal to the proximal breakpoint.
• Clinical and molecular data suggest the mutation, uox(In), is a putative null.

Conclusions:

• The paracentric inversion In(3)55Rk disrupts the mouse Uox gene, causing a putative null mutation.
• This radiation-induced mutation leads to nephropathy, highlighting the link between Uox deficiency and kidney disease.
• The study refines the breakpoint locations and provides detailed molecular characterization of the Uox mutation.