Complex Structure of Lasiopodomys mandarinus vinogradovi Sex Chromosomes, Sex Determination, and Intraspecific Autosomal Polymorphism.

The mandarin vole, Lasiopodomys mandarinus, is one of the most intriguing species among mammals with non-XX/XY sex chromosome system. It combines polymorphism in diploid chromosome numbers, variation in the morphology of autosomes, heteromorphism of X chromosomes, and several sex chromosome systems the origin of which remains unexplained. Here we elucidate the sex determination system in Lasiopodomys mandarinus vinogradovi using extensive karyotyping, crossbreeding experiments, molecular cytogenetic methods, and single chromosome DNA sequencing. Among 205 karyotyped voles, one male and three female combinations of sex chromosomes were revealed. The chromosome segregation pattern and karyomorph-related reproductive performances suggested an aberrant sex determination with almost half of the females carrying neo-X/neo-Y combination. The comparative chromosome painting strongly supported this proposition and revealed the mandarin vole sex chromosome systems originated due to at least two de novo autosomal translocations onto the ancestral X chromosome. The polymorphism in autosome 2 was not related to sex chromosome variability and was proved to result from pericentric inversions. Sequencing of microdissection derived of sex chromosomes allowed the determination of the coordinates for syntenic regions but did not reveal any Y-specific sequences. Several possible sex determination mechanisms as well as interpopulation karyological differences are discussed

Make haste slowly: reproduction in the Zaisan mole-vole, Ellobius tancrei

Mole-voles are the most specialized subterranean members of the subfamily Arvicolinae. We assess the basic reproductive parameters of the Zaisan mole-vole and compare our data with the characteristics reported for other Ellobius species and surface-dwelling voles. In most respects reproduction of the E. tancrei (Blasius, 1884) follows the pattern that is typical for voles. Females undergo postpartum estrus, but rarely combine pregnancy with lactation. The rate of embryonic and postembryonic growth (respectively, 0.13 and 0.54 g/day) are slightly lower, while the relative neonate and weanling masses (respectively, 8% and 40% of maternal mass) are slightly higher than the respective values predicted for non-subterranean arvicolines. The combination of these trends results in the protracted pregnancy and lactation (both ~30 days). The age at first breeding is delayed (>2.5 months). Despite heavy weanlings, total maternal investment per litter in E. tancrei is low due to small litter size (2.31). While the species of Ellobius are similar to each other by the parameters of developmental time, they vary by litter size, total investment per litter, and possibly by relative neonate body mass. This is consistent with the idea that when body size effect is removed, fecundity variables and degree of precociality at birth are dissociated from timing variables.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author

Complex Structure of Lasiopodomys mandarinus vinogradovi Sex Chromosomes, Sex Determination, and Intraspecific Autosomal Polymorphism.

The mandarin vole, Lasiopodomys mandarinus, is one of the most intriguing species among mammals with non-XX/XY sex chromosome system. It combines polymorphism in diploid chromosome numbers, variation in the morphology of autosomes, heteromorphism of X chromosomes, and several sex chromosome systems the origin of which remains unexplained. Here we elucidate the sex determination system in Lasiopodomys mandarinus vinogradovi using extensive karyotyping, crossbreeding experiments, molecular cytogenetic methods, and single chromosome DNA sequencing. Among 205 karyotyped voles, one male and three female combinations of sex chromosomes were revealed. The chromosome segregation pattern and karyomorph-related reproductive performances suggested an aberrant sex determination with almost half of the females carrying neo-X/neo-Y combination. The comparative chromosome painting strongly supported this proposition and revealed the mandarin vole sex chromosome systems originated due to at least two de novo autosomal translocations onto the ancestral X chromosome. The polymorphism in autosome 2 was not related to sex chromosome variability and was proved to result from pericentric inversions. Sequencing of microdissection derived of sex chromosomes allowed the determination of the coordinates for syntenic regions but did not reveal any Y-specific sequences. Several possible sex determination mechanisms as well as interpopulation karyological differences are discussed

Rapid Karyotype Evolution in Lasiopodomys Involved at Least Two Autosome - Sex Chromosome Translocations.

The generic status of Lasiopodomys and its division into subgenera Lasiopodomys (L. mandarinus, L. brandtii) and Stenocranius (L. gregalis, L. raddei) are not generally accepted because of contradictions between the morphological and molecular data. To obtain cytogenetic evidence for the Lasiopodomys genus and its subgenera and to test the autosome to sex chromosome translocation hypothesis of sex chromosome complex origin in L. mandarinus proposed previously, we hybridized chromosome painting probes from the field vole (Microtus agrestis, MAG) and the Arctic lemming (Dicrostonyx torquatus, DTO) onto the metaphases of a female Mandarin vole (L. mandarinus, 2n = 47) and a male Brandt's vole (L. brandtii, 2n = 34). In addition, we hybridized Arctic lemming painting probes onto chromosomes of a female narrow-headed vole (L. gregalis, 2n = 36). Cross-species painting revealed three cytogenetic signatures (MAG12/18, 17a/19, and 22/24) that could validate the genus Lasiopodomys and indicate the evolutionary affinity of L. gregalis to the genus. Moreover, all three species retained the associations MAG1bc/17b and 2/8a detected previously in karyotypes of all arvicolins studied. The associations MAG2a/8a/19b, 8b/21, 9b/23, 11/13b, 12b/18, 17a/19a, and 5 fissions of ancestral segments appear to be characteristic for the subgenus Lasiopodomys. We also validated the autosome to sex chromosome translocation hypothesis on the origin of complex sex chromosomes in L. mandarinus. Two translocations of autosomes onto the ancestral X chromosome in L. mandarinus led to a complex of neo-X1, neo-X2, and neo-X3 elements. Our results demonstrate that genus Lasiopodomys represents a striking example of rapid chromosome evolution involving both autosomes and sex chromosomes. Multiple reshuffling events including Robertsonian fusions, chromosomal fissions, inversions and heterochromatin expansion have led to the formation of modern species karyotypes in a very short time, about 2.4 MY

Examples of fluorescence <i>in situ</i> hybridization.

<p>a–MAGX (green) and MAG13-14 (red) onto <i>L</i>. <i>mandarinus</i> chromosomes, b–DTO10-12 (green) and DTO2 (red) onto <i>L</i>. <i>mandarinus</i> chromosomes, c–DTO13 (green) and DTO9 (red) onto <i>L</i>. <i>gregalis</i> chromosomes, d–DTO2 (green) and DTO19 (red) onto <i>L</i>. <i>brandtii</i> chromosomes. Examples of fluorescence <i>in situ</i> hybridization of the 18S/28S-rDNA probe (green) and telomeric DNA probe (red): e–<i>L</i>. <i>mandarinus</i> (white arrows indicate localization of the largest interstitial telomeric blocks), f–<i>L</i>. <i>brandtii</i>, g–<i>L</i>. <i>gregalis</i>. Scale bar is 10 μm.</p

C-banding.

<p>a–<i>L</i>. <i>mandarinus</i>, b–<i>L</i>. <i>brandtii</i>, с –<i>L</i>. <i>gregalis</i>. Scale bar is 10 μm.</p

Distribution of shared syntenic segment associations.

<p>Distribution of shared syntenic segment associations.</p

Karyotype evolution pathways in three <i>Lasiopodomys</i> species.

<p>Tree topology is based on the molecular phylogeny of Arvicolinae species presented by [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0167653#pone.0167653.ref003" target="_blank">3</a>]. AAK–ancestral Arvicolinae karyotype, AMiK–ancestral karyotype of the tribe Arvicolini, LAK–ancestral karyotype of the genus <i>Lasiopodomys</i>, sLAK–ancestral karyotype of the subgenus <i>Lasiopodomys</i>. Chromosome numbers are indicated in AAK, LAK, and sLAK segments. *–see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0167653#sec008" target="_blank">Discussion</a>.</p