Visualization of mosaicism in tissues of normal and mismatch-repair-deficient mice carrying a microsatellite-containing transgene.
To determine the frequency of mutation in different cell types of mammals, transgenic mice that allow mutant cells to be visualized in situ were used. These mice carry a defective allele of the human placental alkaline phosphatase (PLAP) gene. The allele does not produce enzyme because the reading frame is shifted by an insertion of 7 G:C basepairs. The insertion is adjacent to four existing G:C basepairs, so the allele has a tract of 11Gs. The G11 PLAP allele was studied in wildtype mice and in mice deficient in mismatch-repair (MMR) due to lack of either Pms2 or Mlh1. PLAP(+) cells were counted in brain, heart, kidney, and liver. In wildtype mice, there was an average of between 5 and 30 PLAP(+) events per million cells. No cells with alkaline phosphatase activity were detected in tissues from mice lacking the PLAP gene. In MMR-deficient mice, the number of PLAP(+) allele was increased by at least three-order of magnitude in brain, heart and kidney, but <10-fold in liver. These data show that MMR is vital to maintaining repeat stability in brain, heart and kidney cells. The reason for the different results in the liver is not clear. Cells in the liver were shown to be capable of expressing of PLAP enzyme and PLAP mRNA was present in this organ.
Hersh
Megan N
MN
Department of Molecular Genetics, Biochemistry and Microbiology, College of Medicine, University of Cincinnati, OH 45267-0524, USA.
Stambrook
Peter J
PJ
Stringer
James R
JR
D048868:Adaptor Proteins, Signal Transducing; D000251:Adenosine Triphosphatases / Q000172:deficiency* / Q000502:physiology; D000469:Alkaline Phosphatase; D000483:Alleles; D000818:Animals; D020137:Base Pair Mismatch / Q000235:genetics*; D052160:Benzothiazoles; D002352:Carrier Proteins; D004260:DNA Repair / Q000235:genetics*; D045643:DNA Repair Enzymes; D004268:DNA-Binding Proteins / Q000172:deficiency* / Q000502:physiology; D003959:Diamines; D005260:Female; D005456:Fluorescent Dyes; D058851:GPI-Linked Proteins; D006801:Humans; D007211:Indoles; D007527:Isoenzymes / Q000235:genetics*; D008099:Liver / Q000201:enzymology; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D008822:Mice, Transgenic / Q000235:genetics*; D018895:Microsatellite Repeats / Q000235:genetics*; D008856:Microscopy, Fluorescence; D000070976:Mismatch Repair Endonuclease PMS2; D009030:Mosaicism; D000070957:MutL Protein Homolog 1; D016254:Mutagenesis, Insertional; D009154:Mutation; D009363:Neoplasm Proteins / Q000172:deficiency* / Q000502:physiology; D009580:Nitroblue Tetrazolium; D009687:Nuclear Proteins; D009928:Organ Specificity; D009930:Organic Chemicals; D009943:Organophosphorus Compounds; D011799:Quinazolines; D052999:Quinazolinones; D011804:Quinolines; D012333:RNA, Messenger / Q000032:analysis; D013194:Staining and Labeling; D019076:Transgenes / Q000235:genetics*
D048868:Adaptor Proteins, Signal Transducing; D052160:Benzothiazoles; D002352:Carrier Proteins; D004268:DNA-Binding Proteins; D003959:Diamines; D005456:Fluorescent Dyes; D058851:GPI-Linked Proteins; D007211:Indoles; D007527:Isoenzymes; C501486:MLH1 protein, human; C501485:Mlh1 protein, mouse; D009363:Neoplasm Proteins; D009687:Nuclear Proteins; D009930:Organic Chemicals; D009943:Organophosphorus Compounds; D011799:Quinazolines; D052999:Quinazolinones; D011804:Quinolines; D012333:RNA, Messenger; C079177:2-(5'-chloro-2'-phosphoryloxyphenyl)-6-chloro-4-(3H)-quinazolinone; C098022:SYBR Green I; D009580:Nitroblue Tetrazolium; C035455:5-bromo-4-chloro-3-indoxyl phosphate; D000469:Alkaline Phosphatase; C019839:alkaline phosphatase, placental; D000251:Adenosine Triphosphatases; C094934:PMS2 protein, human; C499533:Pms2 protein, mouse; D000070976:Mismatch Repair Endonuclease PMS2; D000070957:MutL Protein Homolog 1; D045643:DNA Repair Enzymes