Physical mapping of the murine casein locus

• Main Author: George, Sisilamma
• Published: University of Edinburgh 1996
• Subjects: 572.8
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.651392

The murine casein locus has been characterised by long range restriction mapping and the analysis of long fragment genomic clones. Cloned sequences from five mouse casein genes (α, β, γ, ?, κ) were used to screen a murine (strain 129) genomic library in a bacterial artificial chromosome vector (BAC). Of the nine clones isolated, two contained 3 casein genes α, β, γ and γ, ?, κ respectively. The following combinations were found in other clones - α + β; β + γ; γ + ?. Thus, I deduced that the gene order in the locus is α- β- γ- ?-κ. I have confirmed this order by restriction analysis of the clones. Expression studies of casein genes at various time points during pregnancy and lactation revealed a co-ordinate expression pattern for the three (α, β and γ) calcium sensitive genes from mid pregnancy to parturition. The genetic variation in the casein loci of <I>Mus musculus </I>(eight different strains) and <I>Mus spretus </I>was also examined as restriction fragment length variations (RFLV) using five restriction enzymes, <I>Bam</I>HI, <I>Sfi</I>I, <I>Hind</I>III, <I>Eco</I>RI and <I>Xba</I>I. The information obtained from the present mapping study and the clones isolated (129 strain) can be used to manipulate the casein locus in embryonic stem (ES) cells as most gene targeting experiments are carried out in ES cells isolated from 129 mice. Gene targeting is more effective if the targeting DNA is prepared from isogenic DNA. It is also advantageous to use isogenic DNA derived maps in targeting experiments. Thus, the results of this study could not only contribute to basic studies on genome structure and function but also in the longer term underpin applications in biotechnology and agriculture/industry.