Allelic expression analysis for the new candidate imprinted gene Axl in mouse. Shown here are cDNA amplified using Axl primers digested with Hpy188III enzyme that cuts a polymorphic sequence specifically on the C57BL/6 allele. Direction of the cross (Maternal X Paternal) is indicated as BXC or CXB (B = C57BL/6; C = Cast). The lanes are as follows: 1: M (marker); 2: B, for digestion (control); 3: C, for no digestion (control); 4: BL (blastocyst); 5: 6.5E (6.5 dpc embryonic tissue); 6: 6.5EE (6.5 dpc extra-embryonic tissue); 7: 7.5E (7.5 dpc embryonic tissue); 8: 7.5EE (7.5 dpc extra-embryonic tissue); 9: 8.5E (8.5 dpc embryo); 10: 8.5P (8.5 dpc placenta); 11 and 16: 9.5E (9.5 dpc embryo); 12 and 17: 9.5P (9.5 dpc placenta); 13: 17.5L (17.5 dpc liver); 14: 17.5B (17.5 dpc brain); 15: 17.5P (17.5 dpc placenta); 18: +/+P (9.5 dpc Dnmt1 +/+ placenta); and 19: −/−P = 9.5 dpc Dnmt1 −/− placenta. Exclusive maternal expression of Axl was detected starting in blastocyst (n = 2), in the extra-embryonic tissues of all examined E6.5 concepti (n = 6), and subsequently in variable proportions of extra-embryonic tissues of 7.5 dpc (2/4), 8.5 dpc (1/4), and 9.5 dpc (6/9) mice. Embryonic tissues from 6.5 dpc (4/4), 7.5 dpc (4/4), 8.5 dpc (4/4), 9.5 dpc (8/9), and 17.5 dpc (2/2) concepti, as well as from 17.5 dpc placentas (2/2), showed equal maternal and paternal expression. While 4/6 placentas from 9.5 dpc Dnmt1 (n allele) +/+ mice showed biased maternal expression, all Dnmt1 −/− placentas exhibited equal expression from the parental alleles (n = 3).
