AgNOR variability among Robertsonian races of the house mouse from the island of Madeira: implications for patterns of Rb fusion formation and genetic differentiation

The island of Madeira harbours highly differentiated Robertsonian (Rb) races of the house mouse (Mus musculus domesticus), carrying several unique Rb fusions. The reproductive and geographical isolation between these races is expected to restrict gene flow severely, and contribute to their genetic differentiation. In the present study, the chromosomal distribution and frequency of transcriptionally active nucleolar organizer regions (AgNORs) between five Madeiran races was studied. The results showed that AgNORs were present in the centromeric regions of five chromosome pairs. Differences in NOR distribution were apparent within and between races. Comparison between races showed that AgNOR variation occurred independently of the Rb or non-Rb state of the chromosomes and of the NOR-bearing status of the partner chromosomes. The results indicated that Rb fusion formation does not interfere with the activity of rDNA genes. In addition our data provided no evidence that the presence of AgNOR sites inhibits Rb fusion. A cluster analysis showed that AgNOR differentiation was only partly congruent with the chromosomal divergence and geographical proximity between races. In particular, parapatrically distributed races showing the lowest chromosomal divergence exhibited high levels of AgNOR differentiation. If confirmed, this suggests that premating isolation may be reinforcing a barrier to gene flow between the races.

[1]  J. Piálek,et al.  Chromosomal variation in the house mouse , 2005 .

[2]  Elodie Gazave,et al.  The non-random occurrence of Robertsonian fusion in the house mouse. , 2003, Genetical research.

[3]  J. Auffray,et al.  Molecular studies on the colonization of the Madeiran archipelago by house mice , 2001, Molecular ecology.

[4]  J. Piálek,et al.  Raciation and speciation in house mice from the Alps: the role of chromosomes , 2001, Molecular ecology.

[5]  Maria da Luz Mathias,et al.  Environmental genetics: Rapid chromosomal evolution in island mice , 2000, Nature.

[6]  H. Hauffe,et al.  Chromosomal heterozygosity and fertility in house mice (Mus musculus domesticus) from Northern Italy. , 1998, Genetics.

[7]  T. Lenormand,et al.  CENTROMERIC INCOMPATIBILITIES IN THE HYBRID ZONE BETWEEN HOUSE MOUSE SUBSPECIES FROM DENMARK: EVIDENCE FROM PATTERNS OF NOR ACTIVITY , 1998, Evolution; international journal of organic evolution.

[8]  M. Nachman,et al.  Why is the house mouse karyotype so variable? , 1995, Trends in ecology & evolution.

[9]  K. Moriwaki,et al.  Chromosomal locations of Ag-NORs and clusters of ribosomal DNA in laboratory strains of mice , 1994, Mammalian Genome.

[10]  R. Kominami,et al.  Compensatory changes in silver-stainability of nucleolar organizer regions in mice. , 1992, Idengaku zasshi.

[11]  K. Kawasaki,et al.  Methylation status of ribosomal RNA gene clusters in the flow-sorted human acrocentric chromosomes , 1992, Mammalian Genome.

[12]  D. Miller,et al.  Inheritance of ribosomal gene activity and level of DNA methylation of individual gene clusters in a three generation family , 1991, Human Genetics.

[13]  K. Moriwaki,et al.  Variation in the distribution of silver-staining nucleolar organizer regions on the chromosomes of the wild mouse, Mus musculus. , 1990, Molecular biology and evolution.

[14]  C. Redi,et al.  Kinetics of oogenesis in mice heterozygous for Robertsonian translocation. , 1990, Differentiation; research in biological diversity.

[15]  F. Bonhomme,et al.  Evolutionary implication of heterogeneity of the nontranscribed spacer region of ribosomal DNA repeating units in various subspecies of Mus musculus. , 1986, Molecular biology and evolution.

[16]  D. A. Black,et al.  Controlled silver-staining of nucleolus organizer regions with a protective colloidal developer: a 1-step method , 1980, Experientia.

[17]  D. Miller,et al.  Nucleolus organizers in Mus musculus subspecies and in the RAG mouse cell line. , 1977, Genetics.

[18]  A. Henderson,et al.  Does the T-locus in the mouse include ribosomal DNA? , 1976, Cytogenetics and cell genetics.

[19]  F. Ruddle,et al.  Location of genes coding for 18S and 28S ribosomal RNA within the genome of Mus musculus , 1975, Chromosoma.

[20]  J. Forejt.  Centromeric heterochromatin polymorphism in the house mouse , 1973, Chromosoma.

[21]  Peter H. A. Sneath,et al.  Numerical Taxonomy: The Principles and Practice of Numerical Classification , 1973 .

[22]  M. Seabright.  A rapid banding technique for human chromosomes. , 1971, Lancet.

[23]  R. Greenberg.  Biometry , 1969, The Yale Journal of Biology and Medicine.

[24]  J. Cowell.  A photographic representation of the variability in the G-banded structure of the chromosomes in the mouse karyotype , 2004, Chromosoma.

[25]  A. Henderson,et al.  The chromosomal location of ribosomal DNA in the mouse , 2004, Chromosoma.

[26]  L. Monteagudo,et al.  Evidence of mendelian inheritance of the nucleolar organizer regions in the Spanish common rabbit. , 1989, The Journal of heredity.

[27]  G. Bulfield,et al.  Robertsonian karyotype Variation in the European house mouse, Mus musculus Survey of present knowledge and new observations , 1988 .

[28]  E. Capanna.  Robertsonian numerical variation in animal speciation: Mus musculus, an emblematic model. , 1982, Progress in clinical and biological research.

[29]  A. Gropp.  Consequences of Robertsonian heterozygosity: segregational impairment of fertility versus male-limited sterility. , 1982 .

[30]  H. Winking,et al.  Variable positions of NORs in Mus musculus. , 1980, Cytogenetics and cell genetics.

[31]  F. Elder,et al.  Yeast stimulation of bone marrow mitosis for cytogenetic investigations. , 1980, Cytogenetics and cell genetics.

[32]  P. Sneath,et al.  Numerical Taxonomy , 1962, Nature.