Idiogram and fluorescence pattern of the chromosomes of the Indian muntjac

DNA content measurements and an improved idiogram for the Indian muntjac

The Indian muntjac, an asiatic deer, has the lowest diploid chromosome number among mammals (female 2N = 6; male 2N = 7). Using flow cytometric quantification of propidium iodide-stained cells, we determined the DNA content of muntjac cells to be 94% that of human. This suggests that the muntjac may serve as a model for investigation of karyotypic evolution and rearrangement. In order to facilitate future comparative gene mapping studies, computer-aided analysis of digitized metaphase chromosomes allowed development of a detailed Indian muntjac G-banded idiogram incorporating both ISCN-type nomenclature and quantitative estimates of the size of each band and position.

Chromosomal evolution in Cervidae

On the basis of chromosome data obtained on 30 species and 20 subspecies of Cervidae, a report is submitted on the karyosystematics of this family. The primitive karyotype of Cervidae may be inferred to be composed of 35 acrocentric pairs (2n = 70 FN = 70). During the phyletic evolution of this family different types of chromosome rearrangements were probably selected and the group may have differentiated karyologically into three branches: (1) the Cervinae that fixed a centric fusion resulting in a metacentric pair of autosomes (2n = 68, FN = 70), as shown by the basic karyotype of Cervus elaphus, and where Robertsonian fusions are the preeminent type of chromosome rearrangement; (2) the Odocoileinae, in which pericentric inversions and Robertsonian fusions were favored, yielding first a submetacentric X and then a submetacentric autosome pair. The most representative karyotype is 2n = 70, FN = 74--as in Odocoileus hemionus; and (3) the Muntiacinae, in which centric and tandem fusions were the most common chromosome rearrangements. While Muntiacus reevesi has a karyotype 2n = 46, FN = 46, the chromosome number drops down to 2n = 6 in the females of the M. muntjak vaginalis subspecies group and M. rooseveltorum. Therefore, while the karyotypes are conserved within the subfamilies Cervinae and Odocoileinae; the subfamily Muntiacinae appears to be the most chromosomally diversified group. The few karyological data on the Moschus berezovskii suggest that the Moschinae should be placed in a separate family, the Moschidae.

Direct evidence for the non-random localization of mammalian chromosomes in the interphase nucleus

Indirect immunofluorescence staining with human anti-centromere autoantibodies from a patient (LU 851) suffering from the CREST form of scleroderma was used to analyse chromosome topology in interphase nuclei of rat-kangaroo (PTO) and Indian muntjac (IM) cells. In some cells, centromeres were arranged in pairs suggesting association of homologous chromosomes. Clustering of centromeres at one pole of the nucleus (Rabl configuration) and other patterns suggesting higher order organization were also observed. In one fifth of the IM cells it was possible to identify the intranuclear location of each single chromosome on the basis of the morphology of the immunostained centromeres. In 30% of the IM cells in which centromeres could be identified, homologous chromosomes occupied adjacent territories within the interphase chromatin.

Immunological visualization of 5-methylcytosine-rich regions in Indian Muntjac metaphase chromosomes

Regions rich in 5-methylcytosine were localized in male metaphase chromosomes of the Indian muntjac deer (Muntiakus muntjak). Chromosomes were ultraviolet irradiated and subsequently photooxidized in the presence of methylene blue to induce maximum DNA denaturation. Following treatment with anti 5-methylcytosine antibody (anti 5-MeC), regions of antibody binding were visualized by an immunofluorescence or immunopreoxidase staining procedure. All chromosomes showed some level of antibody binding along their length and at centromeric regions, with intense binding evident in the centromere of chromosome 3 and the elongated centromeric "neck" of chromosome 3-X. The Y chromosome displayed low levels of antibody binding. The banding pattern observed with anti 5-MeC is the reverse of that obtained by quinacrine staining.

Quantitative cell fusion: derivation and application of theoretical models

Cell fusion experiments were made on ten cell lines representing seven mammalian species, using inactivated Sendai virus. The extent of fusion was determined microscopically and tabulated as frequencies of cell with different numbers of nuclei. Expected distributions were derived theoretically under certain assumptions concerning the fusion process. A random model was assumed according to which the tendency to fuse depends only on the cell size, expressed as the number of nuclei present in the cell. Three distributions were derived, which were referred to as the simple, additive, and multiplicative models. The additive model pertained to fusions made in cell suspensions and the multiplicative one mainly to fusions in fibroblast monolayers.

Constitutive heterochromatin of Indian muntjac chromosomes revealed by DNAse treatment and a C-banding technique

A karyotype of a female Indian muntjac, Muntiacus muntjak vaginalis, was described. The karyotype was unique in that No. 1 and No. 3 homologous pairs were heteromorphic with respect to the size of their secondary constrictions. In these pairs, one of the homologs always had a longer secondary constriction than that on the corresponding homolog. Heterochromatin in the secondary constriction region was visualized with difficulty by a C-banding technique, but was demonstrated clearly by a DNase treatment followed by Giemsa staining, which also revealed the size difference of the secondary constriction. Centromeric constitutive heterochromatin of No. 1 chromosome was also found to differ in size between the homologs. On the basis of the heteromorphic character of No. 3 chromosome, or an X-autosome complex, it was possible to confirm autoradiographically that X-inactivation had occurred at random.

THE CHARACTERIZATION OF TWO ESTABLISHED HETEROPLOID LINES (INDIAN MUNTJAC AND RAT KANGAROO) WITH A LOW CHROMOSOME NUMBER. II. CHROMOSOME IDENTIFICATION BY AUTORADIOGRAPHY AND SPECIFIC BANDING TECHNIQUES

Combined autoradiography, giemsa and fluorescence banding studies have been completed on the chromosomes of the rat kangaroo (Potorous tridactylis) and the Indian deer (Muntiacus muntjac). Autoradiographic analyses of these established heteroploid lines revealed an absence of a late replicating sex chromosome. For the muntjac complements there appeared to be a correlation between grain concentration and regions of bright fluorescence or dark giemsa stain. Specific banding studies revealed that numeric chromosome changes had taken place in the muntjac lines, with the chromosomes showing no obvious structural alterations from the diploid state. Karyotype changes in the rat kangaroo line were complex and involved structural rearrangements.