Synaptonemal complex analysis of B-chromosome behavior in meiotic prophase I in the East-Asiatic mouse <i>Apodemus peninsulae</i> (Muridae, Rodentia)

Abstract

The mitotic and meiotic chromosomes of four male East-Asiatic mice, Apodemus peninsulae, having three to seven chromosomes in addition to the standard karyotype (2n = 48), were investigated. B-chromosomes were represented by medium-sized metacentric and dotlike chromosomes. Mosaicism of bone marrow cells due to a numerical variation of accessory chromosomes was established for the males examined. Capacity of B-chromosomes to- form axial elements and synaptonemal cornplexes in meiotic prophase I was revealed by electron microscopy. The occurrence of univalents of different morphology, bivalents, and multivalents, corresponding to B-chromosomes, was demonstrated. An increase in the number of B-chromosomes was found in spermatocytes at zygotene-pachytene relative to the number in bone marrow cells, which may be evidence of B-chromosome accumulation in the germ cell line of the East-Asiatic mouse.

B chromosomes of Korean field mouse <i>Apodemus peninsulae</i> (Rodentia, Murinae) analysed by microdissection and FISH

“…Populations of A. peninsulae are highly polymorphic for number and morphology of B chromosomes (Volobuev and Timina, 1980;Kolomiets et al, 1988;Borisov, 1990;Boeskorov et al, 1995;Kartavtseva, 1999). B chromosomes were also found in several other species of this genus: A. flavicollis (Sablina et al, 1985;Vujoevi and Ivkovi, 1987;Vujoevi, 1992;Blagojevi and Vujoevi, 1994;Tanic et al, 2000), A. speciosus, A. microps and A. sylvaticus (Orlov and Bulatova, 1983) and in one population of A. agrarius (Kartavtseva, 1999).…”

B chromosomes in the wood mice (genus Apodemus )

“…In a population of A. flavicollis the frequency of B chromosome stayed rather constant over several generations (Vujosevic 1992). Studies addressing the possibility of a preferential segregation of B chromosomes during meiosis yielded ambiguous results (Kolomiets et al 1988, Vujosevic et al 1989. In A. peninsulae transcriptional activity during the pachytene was shown to be lacking in B chromosomes (Ishak et al 1991).…”

Lateral element lengths and nuclear disposition in Lolium

“…These synaptic configurations are essentially the same as those observed in a reconstructed B chromosome of L. perenne (Jenkins, 1985a), and in surface-spread univalent B chromosomes of Vulpus fulvus (Switonski et a!., 1987) and Secale cereale Jiménez et al, 1994). The intrachromosomal SCs formed in these cases are nonhomologous and contrast with the homologous interarm SCs formed within supernumerary isochromosomes of species such as Euthystira brachyptera and Myrmeleotettix maculatus (Fletcher & Hewitt, 1988), Apodemus peninsulae (Kolomiets et al, 1988), Crepis capillaris and Secale cereale (Santos eta!., 1995).…”