POLYMORPHIC INSERTIONS DELETIONS OF BOTH 1550 NT AND 100 NT IN 2 MICROSATELLITE-CONTAINING, LINE-RELATED INTRONIC REGIONS OF THE RABBIT KAPPA-CASEIN GENE/

The most frequent allele of the rabbit kappa-casein (kappa-Cas)-encodi ng gene (A allele) has previously been shown to possess two sequences similar to those found in the 5' end of long interspersed repeated ele ments (LINE). Part of an inverted rabbit LINE is present in the first intron and part of a direct rabbit LINE in the fourth intron. We descr ibe herewith a less frequent allele (B allele) that lacks both 100 bp in the first intron and 1550 bp in the fourth intron. It was not possi ble to identify any allele exhibiting only one of the deletions in a p opulation of 55 rabbits. The 100 bp present in the first intron of the A allele, but absent from the B allele, are located at the 5' end of the inverse complementary LINE and include the poly (T) track of the L INE. The 1550 bp present in the fourth intron of the A allele, but abs ent from the B allele, include the entire direct LINE sequence. Theref ore, the B allele only possesses one partial LINE sequence that is loc ated in the first intron and is truncated when compared to the copy fo und in the first intron of the A allele. The B allele might thus be mo re recent than the A. allele. Differences between the sequences of tra nscripts corresponding to each allele are limited to two silent mutati ons and three modifications in the 3' UTR. In the mammary glands of la ctating rabbits, which are homozygous for both alleles, kappa-Cas mRNA accumulate to similar levels and are translated into identical kappa- Cas that are secreted at similar concentrations into milk. (C) 1998 El sevier Science B.V. All rights reserved.