Inherited macrocytic anaemias in the house mouse

Journal of Genetics - The geneW in the mouse has no measurable effect on the blood in heterozygotes, regardless of the amount of variegation present. Mice heterozygous forW V have macrocytic red...     

Chromosomal variation in the house mouse

Although the standard karyotype of the western house mouse, Mus musculus domesticus , consists entirely of acrocentric chromosomes, there are 97 distinct 'populations' that are characterized by various combinations of metacentric chromosomes that have arisen by Robertsonian (Rb) fusions and whole-arm reciprocal translocations (WARTs). In this review we discuss the processes behind the origin and fixation of these rearrangements and then present a unified list of all known metacentric populations and evaluate their phylogenetic relationships. Eleven independent phylogeographical 'systems', each consisting of 2–25 metacentric populations, were identified in Scotland, Denmark, Northern Europe–Northern Switzerland, Southern Switzerland, Northern Italy, Croatia, Spain, Central–Southern Italy, Peloponnesus, Mainland Greece and Madeira. There are six isolated metacentric populations that do not belong to any of these systems. To generate phylogenies of the metacentric populations within each system, we determined those outcomes with the fewest steps regarding accumulation of metacentrics by Rb fusions, WARTs and zonal raciation and taking into account geographical proximity. These phylogenies should be viewed as working hypotheses that will be refined with further chromosomal and molecular data and improvements in methods of phylogenetic reconstruction. The list of metacentric populations and our phylogenies are also published electronically and can be accessed at http://www.studenec.ivb.cz/Projects/RobertsonianMice/ .  © 2005 The Linnean Society of London, Biological Journal of the Linnean Society , 2005, 84 , 535–563.     

Total sex-linkage in the house mouse

Summary 1. A totally sex-linked gene, Tabby (Ta), in the house mouse is described. It is semi-dominant in females. Mutant males resemble homozygous females, which shows that there is no homologue on the Y-chromosome.2. Heterozygous females have transverse black markings, visible only in agoutis. Homozygous females and hemizygous males have a number of defects exactly resembling those produced by the autosomal recessive crinkled.3. Brindled and Mottled are shown also to be totally sex-linked, by means of linkage tests with Tabby in doubly heterozygous females. Both Brindled and Mottled recombine with Tabby with a frequency of about 4%. This proves that crossing-over takes place in the differential segment of the X-chromosome in females.

---

Zusammenfassung 1. Tabby (Ta) ist ein völlig geschlechtsgebundenes Gen in der Hausmaus. In Weibchen zeigt es unvollkommene Dominanz. Männchen mit dieser Mutante gleichen homozygoten Weibchen, ein Beweis, daß das Y-Chromosom kein homologes Gen enthält.2. Heterozygote Weibchen haben schwarze Querstreifen, die nur auf Agouti-Hintergrund erkennbar sind. Homozygote Weibchen und hemizygote Männchen zeigen eine Anzahl von Abnormitäten, die genau den von dem recessiven Autosomalfaktor crinkled hervorgerufenen gleichen.3. Brindled und Mottled sind gleichfalls völlig geschlechtsgebunden; das geht hervor aus Koppelungsversuchen mit Weibchen, die heterozygot für Tabby und eines dieser Gene sind. Sowohl Brindled und Mottled haben Tabby gegenüber eine Rekombinationshäufigkeit von ungefähr 4%. Das beweist das Vorkommen von crossing-over in dem Differentialsegment des X-Chromosoms in Weibchen.

---

---

With 1 figure in the text.

---

Agricultural Research Council Scientific Staff.     

Gametic and pleiotropic defects in mouse fetuses with Hertwig''s macrocytic anemia

Pleiotropic effects on germ cell number, hematologic status, and body size are described in 12- to 15-day WBB6F1 normal (+/-) and defective (an/an) mouse fetuses, with special emphasis on gametogenesis. Differences between genotypes were apparent by Day 12. At 12 days, normal testes contained many germ cells and frequent normal mitoses, and the number of germ cells increased rapidly from Day 12 to Day 15. By contrast, 12-day an/an testes contained fewer germ cells, frequently degenerating, and many abnormal mitoses. Their number of germ cells decreased rapidly, so that almost none persisted to Day 15. Normal ovaries contained many germ cells, with much normal mitosis on Day 12 and 13, followed by meioses, but the smaller an/an ovaries contained few germ cells, with little mitosis, some meiosis, and very much degeneration. The erythrocyte counts of both normal and anemic fetuses increased approximately fourfold between 12 and 15 days, but at comparable ages, total counts were always lower in an/an fetuses than in normal littermates. At all ages, Hertwig's anemic (an/an) fetuses were somewhat smaller than their normal littermates. Although both W/Wv and Sl/Sld mice also show macrocytic anemia and germ cell failure, the great difference in etiology of their germ cell defects indicates that an/an gene action must be qualitatively different from that in either W/Wv or Sl/Sld mice.     

Inherited differences in mouse kidney carnosinase activity

Carnosinase is a peptidase which cleaves B-alanyl-l-histidine (carnosine) and closely related dipeptides. Its activity in kidney cytosol of various mouse strains varies more than 50-fold. The highest activity occurs in random-bred CD-1 and inbred NZB/BINJ mice, while it is barely detectable in BALB/cJ, C57BL/6J, and AU/SsJ among others. Carnosinase is immunologically and enzymologically identical in all high-activity strains. This is the first report of quantitative interstrain differences in carnosinase activity. No other peptidase activity has been reported which exhibits the same strain distribution shown here. In matings and backcrosses between the NZB/BINJ and the BALB/cJ strains, the levels of kidney carnosinase activity in the progeny behave as a classical Mendelian trait.     

Centromeric heterochromatin polymorphism in the house mouse

Polymorphism of Giemsa-specific centromeric heterochromatin (C.H.) has been described in the laboratory and wild mice. All examined wild mice and inbred mouse strains display some chromosomes with considerably reduced or enlarged C.H. regions. The quantity of C.H. could be an inherent property of a chromosome as inferred from (a) the finding of the identical C.H. pattern within inbred strains, (b) the finding that two genetically related inbred strains, C3H and CBA, separated from each other for more than 150 generations, possess the same two chromosome pairs with tiny C.H. marker regions. These chromosomes were identified as No. 1 (l.g. XIII) and No. 14 (l.g.III) by means of T(14;15)6Ca translocation, and C- and G-band analysis. The neutrality of C.H. polymorphism in murine genome is inferred from the heterozygosity for the C.H. variants found in all studied wild mice. The possible relationship of C.H. polymorphism to the centromere interference phenomenon is hypothesized.     

Asymmetrical reproductive character displacement in the house mouse

Our study addressed reproductive character displacement between two subspecies of the house mouse, Mus musculus musculus and Mus musculus domesticus that hybridize in Europe along a zone where selection against hybridization is known to occur. Based on a multi-population approach, we investigated spatial patterns of divergence of mate preference in the two taxa. Mate preference was significantly higher in the contact zone than in allopatry in both subspecies, suggesting that reproductive character displacement occurs. Moreover, patterns of preference were stronger in M. m. musculus than in M. m. domesticus, indicating an asymmetrical divergence between the two. In the context of selection against hybridization, our results may provide empirical support for the hypothesis of reinforcement in a parapatric hybrid zone. We discuss factors that could explain the asymmetrical pattern of divergence and the possible impact of a unimodal structure on the maintenance of premating divergence between the two subspecies.     

Estimating total genic diversity in the house mouse

In a survey of variation in both electrophoretic charge and thermostability at 14 structural loci in 40 strains of Mus musculus, 27 electromorphs (polypeptides differing in electrophoretic charge) and 20 thermomorphs (polypeptides differing in thermostability) were found. Electrophoresis detected 11 new variants within thermomorphs, and the heat denaturation technique detected four new variants within electromorphs. From these data, and making the assumption that both techniques are independent of each other, it is estimated that the actual total number of alleles at the 14 loci is 53, or an average of 3.79 per locus (1.96 per electromorph), and that electrophoresis apparently detects one-third of the variants, thus describing about 50% of the alleles at structural gene loci in the house mouse.     

Variation in aggressiveness in house mouse populations

Clearly the ability of 'house mice' to vary their social structures is an important feature contributing to their success in a wide range of habitats. Social structure is strongly influenced by aggressiveness and other behaviours in male and female mice. Material is presented illustrating how genotype, intrauterine location and social experiences influence dyadic encounters in this 'species'.