| Primary Identifier | MGI:1861183 | Allele Type | Radiation induced |
| Gene | Mp | Inheritance Mode | Semidominant |
| Strain of Origin | (101/Rl x C3H/Rl)F1 | Is Recombinase | false |
| Is Wild Type | false |
| description | Heterozygous mutant mice invariably have microphthalmia and often have reduced external ears. Homozygotes appear to be eyeless and have oligodactyly of the hindfeet. They are very small and die at about 12 days. The pinna is present and very probably of reduced size, but because homozygotes die before the ears open and the pinna expands, no accurate comparison with heterozygotes can be made (J:30712, J:187). |
| molecularNote | The radiation induced micropinna microphthalmia (Mp) mutation, which was discovered at the Oak Ridge National Laboratory in the 1960s, has been identified as a 660 kb inversion on Chr 18 with breakpoints in 3' introns of the terminal genes: intron 62 of fibrillin 2 (Fbn2), which is transcribed from the minus strand, and intron 4 of isochorismatase domain containing 1 (Isoc1). The transcript from the resultant Fbn2/Isoc1 fusion gene joins exon 62 of the 65-exon Fbn2 directly to the last (fifth) Isoc1 exon; the predicted protein contains amino acids 1-2646 of FBN2 - which do not include the last Ca2+-binding domain and the conserved furin cleavage site - followed by 11 amino acids and a stop codon encoded by the frame-shifted Isoc1 final exon. The reverse, Isoc1/Fbn2 fusion gene produces a transcript in which a frameshift-induced stop codon in the fifth of its seven exons is predicted to result in nonsense-mediated decay; consistent with this expectation is a ~50% lower level of Isoc1/Fbn2 than of wild-type Isoc1 mRNA in developing eyes, as measured by quatitative RT-PCR. |
