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- 2009, BS Biology, Loyola Marymount University
MT1-MMP-Deficient Mice Develop Dwarfism, Osteopenia, Arthritis, and Connective Tissue Disease due to Inadequate Collagen Turnover (Holbeck, K et. al. )
Figure 1 (Media:Figure 1.jpg) of the article MT1-MMP-Deficient Mice Develop Dwarfism, Osteopenia, Arthritis, and Connective Tissue Disease due to Inadequate Collagen Turnover (Holbeck, K et. al. )  describes the targeting of MT1-MMP and the results. Panel A gives the targeting vector, the endogenous gene, the targeted gene and the overall outlook of the protein. In order to disrupt expression of the MT1-MMP gene, a targeting vector with a 3.35 kb segment that contained sequences from the 3' half of intron 1 through the 3' end of exon 5 was replaced with a PGK controlled HPRT minigene (a selection cassette used for gene targeting in mouse embryonic stem cells). The endogenous gene contains Bgl II / Hind III (6675 kb) and Hind III (3600 kb) fragments. Through recombination with the endogenous gene, the targeted gene was developed. The targeted gene consists of Bgl II /Hind III (5337 kb) and Hind III (3150 kb). The overall protein shows that the all but five residues of the prodomain and all but eight residues of the catalytic domain have been deleted. Panel B is the identification of transgenic mice by a southern blot analysis. Hind III restricted samples were size fractionated and hybridized to the P3' probe and Bgl II / Hind III restricted samples were size fractionated and hybridized to the P5' probe. In this panel we see that wild type mice (+/+) only express the Hind III (3600). Heterozygous mice (+/-) express Hind III (3600) and Hind III (3150). Homozygous mice (-/-) express only Hind III (3150). The Hind III / Bgl II (6675) fragment is only expressed in wild type mice. Both the Hind III/ Bgl II (6675) and the Hind III/ Bgl II (5537) fragments are expressed in heterozygous mice. The Hind III /Bgl II (5337) fragment is only expressed in the homozygous mice. Panel C is a detection of the expression of the MT1-MMP mRNA in total neonate RNA by Northern blot analysis. In wild type mice it can be seen that the MT1-MMP mRNA is expressed. In the heterozygous mice it can be seen that there is less expression of the MT1-MMP mRNA because these mice still have one copy of the endogenous gene, however, there is less expression than the wild type mice. The homozygous mice show no expression of the MT1-MMP gene. The two shaded boxes at the bottom are the control (using ribosomal RNA). This shows that there is no change in the ribosomal RNA expression in all of these mice. Panel D is a dorsal view of 10 day old mice. The top mouse is the homozygous and the bottom is the heterozygous. It can be seen that there is a relative difference in the sizeof these mice. Panel E is a close-up view of of a 79 day old homozygous mouse. After Day 50 most of these mice experienced progressive wasting, patchy hair loss, reduced mobility, kinking of the wrist, and hyperlordosis/hyperkyphosis.
Figure 2 (Media:Figure 2.jpg) displays the bone development of the MT1-MMP deficient and wild type mice. Panel A shows alizarin red and alican blue staining that was used to identify skull structure of the MT1-MMP deficient and wild type mice. We can see that by day 5 the wild type mice have larger fontanelles and gradually increasing cranial dysmorphism of mutant mice. Panel B is a lateral X-Ray image of an 80 day old MT1-MMP deficient mouse. When compared to Panel D, an X-Ray image of an 80 day old wild type mouse, we can see that there is a severe difference in cranial structure, spine, and limb development. Panel C shows the magnification of the cranial vault from panel B. The arrowheads show the wide sutures and the displacement of the interparietal bone. Panel E shows an X-Ray of the hind limbs of the wild type mouse. When compared to Panel F , the MT1-MMP deficient mouse hind limb X-Ray, we can see that the hind limbs are severely shorter than the wild type mouse. By day 45 the hind limb bones of the MT1-MMP deficient mice grew to approximately 65% less than the wild type mouse. Panels G and I is the histology of the femora of 60 day old MT1-MMP deficient mice. Panels H and J is the histology of the femora of 60 day old wild type mice. Osteopenia became increasingly apparent and bone mass was severely reduced in the MT1-MMP deficient mice. The MT1-MMP deficient mice also developed severe generalized arthritis.
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- Mark Ptashne. A genetic switch. Cold Spring Harbor, N.Y.: Cold Spring Harbor Laboratory Press, 2004. isbn:0879697164.