Free Access
Genet. Sel. Evol.
Volume 35, Number 2, March-April 2003
Page(s) 239 - 247
Genet. Sel. Evol. 35 (2003) 239-247
DOI: 10.1051/gse:2003006

Substitution of the $\alpha $-lactalbumin transcription unit by a CAT cDNA within a BAC clone silenced the locus in transgenic mice without affecting the physically linked Cyclin T1 gene

Solange Souliera, Marthe Hudrisiera, José Costa Da Silvaa, Caroline Maederb, Céline Vigliettab, Nathalie Besnarda and Jean-Luc Vilottea

a  Laboratoire de génétique biochimique et de cytogénétique, Département de génétique animale, Institut national de la recherche agronomique, 78352 Jouy-en-Josas Cedex, France
b  Laboratoire de biologie du développement et de biotechnologie, Département de physiologie animale, Institut national de la recherche agronomique, 78352 Jouy-en-Josas Cedex, France

(Received 12 December 2001; accepted 1 October 2002)

We recently reported that a goat bacterial artificial chromosome (BAC) clone conferred site-independent expression in transgenic mice of the two loci present within its insert, the ubiquitously expressed Cyclin T1 and the mammary specific $\alpha $-lactalbumin ( $\alpha $lac) genes. To assess if this vector could target mammary-restricted expression of cDNA, the CAT ORF was introduced by homologous recombination in Escherichia coli in place of the $\alpha $lac transcription unit. The insert of this modified BAC was injected into mice and three transgenic lines were derived. None of these lines expressed the CAT gene suggesting that the use of long genomic inserts is not sufficient to support the expression of intron-less transgenes. The physically linked goat Cyclin T1 locus was found to be active in all three lines. This observation reinforced the hypothesis that the two loci are localised in two separate chromatin domains.

Key words: bacterial artificial chromosome / homologous recombination / intron / transgenic mice / chromatin domain

Correspondence and reprints: Jean-Luc Vilotte

© INRA, EDP Sciences 2003