| First Author | Sweet HO | Year | 1995 |
| Journal | Mouse Genome | Volume | 93 |
| Issue | 1 | Pages | 149-150 |
| Mgi Jnum | J:24317 | Mgi Id | MGI:72061 |
| Citation | Sweet HO, et al. (1995) Genetic distance between hammertoe and reeler. Mouse Genome 93(1):149-150 |
| abstractText | Full text of Mouse Genome contribution: Genetic distance between hammertoe and reeler. The close linkage of hammertoe (Hm) and reeler (rl) on mouse Chromosome (Chr) 5 allowed the construction of stocks that used Hm as a marker for early recognition of rl/rl homozygotes. Two such stocks were created and maintained for many years in the Mouse Mutant Stock Center to be used by other investigators interested in studying the effects of the reeler gene in early development. The first stock began on a C57BL/6J genetic background. Seven years later a second Hm rl/+ + line was constructed by one of us (HOS) to be used in a cross with Robertsonian chromosome, Rb(5.15)15Rma, to map more accurately the distance of reeler from the centromere (Davisson and Akeson, Genetics 1993; 133:649-667). Because we still get requests for Hm and rl on the same chromosome, we would like to explain here why the stocks were discontinued. First, other investigators had difficulty distinguishing accurately between Hm/Hm and Hm/+. Second, our inability to distinguish these phenotypes reliably before 7-8 days of age made early postnatal identification difficult. Finally, because several groups are attempting to clone the rl gene, it will soon be possible to detect presymptomatic rl/rl homozygotes using probes. Data from the colony matings provide a recombination estimate for the genetic distance between Hm and rl. Although both stocks were discontinued by the early 1980s, these data were never published. We present below the data from colony matings between 1976 and 1981 to provide a more accurate estimate of the distance between these two genes than is currently available. Colony records for both Hm - rl stocks show very few recombinant progeny or matings discarded because one parent had a recombinant chromosome. The only published data on the Hm Ð rl interval, however, give a combined estimate of 8.0 +/- 3.5 from crosses in which Hm and rl were not together on the same chromosome (Davisson and Akeson, Genetics 1993; 133:649-667). It is unclear why these crosses have a higher recombination frequency than was observed in the colony. Because the sample size was small (n = 95 from 4 current crosses combined) and the standard error, consequently, fairly large, we believe the data presented below provide a better estimate for the Hm - rl distance. To construct the first stock a C57BL/6J-Hm/+ female was crossed to a C57BL/6J +/rl male and all Hm +/+ ? progeny were mated together to test for the presence of reeler. These two types of crosses were repeated backcrossing Hm +/+ rl mice to the reeler strain at alternated generations. The Hm rl chromosome was recovered at N5F9. A female Hm rl/+ + was outcrossed to a B6C3Fe-a/a-Fl (C57BL/6J x C3HeB/FeJ-a/a)Fl hybrid male. All Hm ?/+ + progeny were mated together and progeny tested for the presence of rl. The second stock was produced similarly using the B6C3Fe-a/a genetic background. The data below are all from the hybrid background stock matings. From the matings Hm rl/+ + x Hm rl/+ +, only one phenotypically detectable recombinant mouse was seen in a total of 1326 progeny produced (+ +, 375; Hm rl, 247; Hm +/+ ?, 703; Hm rl/ + rl, 1). Because not all recombinant classes were recovered, the entire data set can not be used to calculate a recombination estimate by standard methods for analyzing an intercross. An estimate can be calculated, however, from the rl/rl classes: one recombinant chromosome in a total of 496 rl/rl chromosomes = .2 +/- .2 % This estimate for the Hm Ð rl interval combined with mapping data for Hm and rl with molecular markers from crosses by other investigators cloning these genes will more precisely define the proximal mouse Chr 5 linkage map. We recognize Dr. Margaret C. Green and Priscilla W. Lane for their foresight in creating the original crosses and are indebted to them for their advice and encouragement while we were making the second cross. We also thank Dr. Green for helping with the data analysis. (Sweet and Davisson) |
