title: The t(4;8) is mediated by homologous recombination between olfactory receptor gene clusters, but other 4p16 translocations occur at random.
abstract: The t(4;8)(p16;p23) is the second most common constitutional chromosomal translocation and is caused by an ectopic meiotic recombination between the olfactory receptor gene clusters (ORGC), located on chromosome 4p and 8p. Given that ORGCs are scattered across the genome and make-up about 0.1% of the human genome we reasoned that translocations between 4p16 and other chromosomes might be mediated by ectopic recombination between different ORGC. In 13 patients, we mapped the breakpoints of either a balanced or unbalanced translocation between chromosome 4p16 and different chromosomes. For all four t(4;8) cases, the breakpoints fall within the 4p and 8pter ORGC, confirming that non-allelic homologous recombination (NAHR) between the ORGC is the main mechanism of the t(4;8) formation. For the nine other translocations, the breakpoints on chromosome 4 mapped to different loci, one of them within the ORGC and in two flanking the ORGC. In these three cases, the translocation breakpoint at the reciprocal chromosome did not contain ORGC sequences. We conclude that only the t(4;8) is mediated by NAHR between ORGC.
authors.affiliation: Centre for Human-Genetics, University Hospital, Catholic University of Leuven, Leuven, Belgium.
authors.forename: N M C
authors.initials: NM
authors.lastname: Maas
authors.forename: S
authors.initials: S
authors.lastname: Van Vooren
authors.forename: F
authors.initials: F
authors.lastname: Hannes
authors.forename: G
authors.initials: G
authors.lastname: Van Buggenhout
authors.forename: M
authors.initials: M
authors.lastname: Mysliwiec
authors.forename: Y
authors.initials: Y
authors.lastname: Moreau
authors.forename: K
authors.initials: K
authors.lastname: Fagan
authors.forename: A
authors.initials: A
authors.lastname: Midro
authors.forename: O
authors.initials: O
authors.lastname: Engiz
authors.forename: S
authors.initials: S
authors.lastname: Balci
authors.forename: M J
authors.initials: MJ
authors.lastname: Parker
authors.forename: Y
authors.initials: Y
authors.lastname: Sznajer
authors.forename: K
authors.initials: K
authors.lastname: Devriendt
authors.forename: J P
authors.initials: JP
authors.lastname: Fryns
authors.forename: J R
authors.initials: JR
authors.lastname: Vermeesch
mesh_terms: D000328:Adult; D002894:Chromosomes, Human, Pair 4 / Q000235:genetics*; D005260:Female; D006801:Humans; D017404:In Situ Hybridization, Fluorescence; D007621:Karyotyping; D008297:Male; D005810:Multigene Family / Q000235:genetics*; D010641:Phenotype; D018035:Receptors, Odorant / Q000235:genetics*; D016615:Telomere / Q000235:genetics; D014178:Translocation, Genetic / Q000235:genetics*; D054877:Wolf-Hirschhorn Syndrome / Q000235:genetics*
chemical_list: D018035:Receptors, Odorant