| First Author | Beechey CV | Year | 1992 |
| Journal | Mouse Genome | Volume | 90 |
| Issue | 3 | Pages | 423-24 |
| Mgi Jnum | J:2497 | Mgi Id | MGI:51020 |
| Citation | Beechey CV, et al. (1992) Mapping studies of distal chromosome 2 including the imprinting region. Mouse Genome 90(3):423-24 |
| abstractText | Full text of Mouse Genome contribution: Research News: 1. Mapping studies of distal chromosome 2 including the imprinting region. The distal Chr 2 imprinting region causing opposite anomalous phenotypes and neonatal lethality was recently defined as lying between the breakpoints of T(2;4)lGo and T(2;16)28H in central H3 and proximal H4 respectively (Cattanach et a1 Mouse Genome 89:255-256, 1991). Further work however showed that the proximal boundary of the imprinting region was more distal in H3 and is now defined by the T(2;8)2Wa breakpoint (Cattanach et al Mouse Genome 90:82, 1992). We have commenced mapping studies with these translocations against Chr 2 genetic markers, as follows: a) Backcrosses of alpha T1Go +/alpha1 +ls males to homozygous alpha1 ls females were carried out and offspring test mated to distinguish between alpha1/alpha1 and alpha1/alpha genotypes as well as their T1Go status. The following offspring were successfully classified: 11 T1Go, 16 alpha1 ls, 0 alpha1 T1Go, 1 ls, 4 T1Go ls, 2 alpha1, 0 alpha1 T1Go ls and 1 +, total 35. Thus the RF between T1Go and alpha1 is 5.7 +/- 3.9% while that between alpha1 and ls is 20.0 +/- 6.8%, similar to the value given on the locus map of the mouse (Hillyard et al, Mouse Genome 90: 8-21, 1992). The order judging by the rarity of double recombinants could be either alpha-T1Go-1s or T1Go-alpha-1s. However, it is known that the G band breakpoints of 2 reciprocal translocations at the alpha locus, T(2;8)26H and T(2;11)30H, are in 2H1 whereas T1Go is central in 2H3 (de Boer and van Gijsen, Cytogenet. Cell Genet. 13:489-510, 1974 and Washburn and Eicher MNL 57:23, 1977; Cattanach et al, 1991, ibid). Thus the likely order is alpha1-T1Go-1s. In addition crosses of Adab + Ra/Adaa T1Go + males to Adaa+ +/Adaa + + females with subsequent testing of progeny for Ada and T1Go gave the following progeny: 46 ADA-A TlGo, 29 ADA-AB Ra, 1 ADA-A Ra, 0 ADA-AB TIGo, 12 ADA-A TlGo Ra, 12 ADA-AB, 1 ADA-AB TlGo Ra and 0 ADA-A, total 101. The RFs are: Ada to TlGo 2.0 +/- 1.4%, TIGo to Ra 24.8 +/- 4.3%, Ada to Ra 24.8 +/- 4.3%; this latter RF is somewhat greater than the published value of 13.8 +/- 2.7% found by Abbott et a1 (Abbott et a1 Biochem. Genet. 29:537-544, 1991) but in reasonable agreement with the value of 21.0 +/- 2.8% found by Le Tissier (Le Tissier Ph.D thesis University of Reading 1990). The order could be either Ada-TlGo-Ra or TIGo-Ada-Ra. The close linkage of Ada and TlGo is consistent with their cytogenetic localizations for both have been placed previously in 2H3 (Abbott et al; Cattanach et a1 1992 ibid). b) Backcrosses of + T2Wa +/alpha1 +ls males or females to homozygous alpha1 ls with subsequent testing of progeny for T2Wa gave the following progeny: 71 T2Wa, 48 alpha1 ls, 0 alpha1 T2Wa, 3 ls, 19 T2Wa ls, 15 alpha1, 2 alpha1 T2Wa ls, and 1 +, total 159. Thus the RF between T2Wa and alpha1 is 3.8 +/- 1.5 % with 23.3 +/- 3.3% between T2Wa and ls. The RF between alpha1 and ls is 23.3 +/- 3.3 %, in reasonable agreement with the published distance of 19 cM (Hillyard et al, ibid). The order could either be alpha1-T2Wa-ls or T2Wa-alpha1-ls. However the G-band breakpoint of T2Wa is distal in H3 so for the same reasons as given in (a) the most likely order is alpha1-T2Wa-ls. In these crosses it has proved difficult to order the closest marker in respect of the translocation breakpoint because of the occurrence of double crossovers. This could be due to the high frequency of chiasmata found in the region of bands H3/H4 in distal Chr 2 (Evans pers. comm. and Gorlov et al, Genetika 23:63-70, in Russian). (Beechey,Peters, Ball). |
