J. Catalan et al., Spontaneous occurrence of a Robertsonian fusion involving chromosome 19 bysingle whole-arm reciprocal translocation (WART) in wild-derived house mice, CHROMOS RES, 8(7), 2000, pp. 593-601
Chromosomal races of the house mouse (Mus musculus domesticus) bear Roberts
onian (Rb) fusions, which consist of centric translocations between two non
-homologous acrocentric chromosomes. The high level of diversity of these f
usions in house mice is generated by de-novo formation of Rb fusions and su
bsequent whole-arm reciprocal exchanges (WARTs). This paper describes the s
pontaneous occurrence of a new Rb fusion, Rb(4.19), in progeny of wild-deri
ved house mice segregating for Rb(4.12). The chromosomal mutation was trace
d to a female which exhibited germline and somatic mosaicism indicating an
early embryonic origin of the mutation. FISH analysis of centromerically-lo
cated ribosomal genes suggested that no modification was observed on chromo
somes 12 and 19 prior to or following the occurrence of Rb(4.19). Distribut
ion of telomeric sequences showed that both Rb fusions lacked telomeres in
their centromeric regions. It is argued that this spontaneous mutation most
likely originated by single whole-arm reciprocal translocation (WART) betw
een Rb(4.12) and an acrocentric chromosome 19, resulting in Rb(4.19) and a
neo-acrocentric chromosome 12. Sequences required for centromeric function
and proximal telomeres would have been transferred to the neo-chromosome 12
from chromosome 19 during the translocation. The existence of such WARTs w
hich generate derived acrocentric chromosomes has several implications for
chromosomal evolution in house mice.