Dataset Information

Evolutionary strata on the mouse X chromosome correspond to strata on the human X chromosome.

ABSTRACT: Lahn and Page previously observed that genes on the human X chromosome were physically arranged along the chromosome in "strata," roughly ordered by degree of divergence from related genes on the Y chromosome. They hypothesized that this ordering results from a historical series of suppressions of recombination along the mammalian Y chromosome, thereby allowing formerly recombining X and Y chromosomal genes to diverge independently. Here predictions of this hypothesis are confirmed in a nonprimate mammalian order, Rodentia, through an analysis of eight gene pairs from the X and Y chromosomes of the house mouse, Mus musculus. The mouse X chromosome has been rearranged relative to the human X, so strata were not found in the same physical order on the mouse X. However, based on synonymous evolutionary distances, X-linked genes in M. musculus fall into the same strata as orthologous genes in humans, as predicted. The boundary between strata 2 and 3 is statistically significant, but the boundary between strata 1 and 2 is not significant in mice. An analysis of smaller fragments of Smcy, Smcx, Zfy, and Zfx from seven species of Mus confirmed that the strata in Mus musculus were representative of the genus Mus.

SUBMITTER: Sandstedt SA

PROVIDER: S-EPMC327101 | biostudies-literature | 2004 Feb

REPOSITORIES: biostudies-literature

ACCESS DATA

Publications

Evolutionary strata on the mouse X chromosome correspond to strata on the human X chromosome.

Sandstedt Sara A SA Tucker Priscilla K PK

Genome research 20040201 2

Lahn and Page previously observed that genes on the human X chromosome were physically arranged along the chromosome in "strata," roughly ordered by degree of divergence from related genes on the Y chromosome. They hypothesized that this ordering results from a historical series of suppressions of recombination along the mammalian Y chromosome, thereby allowing formerly recombining X and Y chromosomal genes to diverge independently. Here predictions of this hypothesis are confirmed in a nonprima ...[more]

PMID: 14762062

Similar Datasets

Project description:BackgroundX chromosome inactivation is the transcriptional silencing of one X chromosome in the somatic cells of female mammals. In eutherian mammals (e.g. humans) one of the two X chromosomes is randomly chosen for silencing, with about 15% (usually in younger evolutionary strata of the X chromosome) of genes escaping this silencing. In contrast, in the distantly related marsupial mammals the paternally derived X is silenced, although not as completely as the eutherian X. A chromosome wide examination of X inactivation, using RNA-seq, was recently undertaken in grey short-tailed opossum (Monodelphis domestica) brain and extraembryonic tissues. However, no such study has been conduced in Australian marsupials, which diverged from their American cousins ~80 million years ago, leaving a large gap in our understanding of marsupial X inactivation.ResultsWe used RNA-seq data from blood or liver of a family (mother, father and daughter) of tammar wallabies (Macropus eugenii), which in conjunction with available genome sequence from the mother and father, permitted genotyping of 42 expressed heterozygous SNPs on the daughter's X. These 42 SNPs represented 34 X loci, of which 68% (23 of the 34) were confirmed as inactivated on the paternally derived X in the daughter's liver; the remaining 11 X loci escaped inactivation. Seven of the wallaby loci sampled were part of the old X evolutionary stratum, of which three escaped inactivation. Three loci were classified as part of the newer X stratum, of which two escaped inactivation. A meta-analysis of previously published opossum X inactivation data revealed that 5 of 52 genes in the old X stratum escaped inactivation.ConclusionsWe demonstrate that chromosome wide inactivation of the paternal X is common to an Australian marsupial representative, but that there is more escape from inactivation than reported for opossum (32% v 14%). We also provide evidence that, unlike the human X chromosome, the location of loci within the oldest evolutionary stratum on the marsupial X does not correlate with their probability of escape from inactivation.

Project description:Snakes exhibit genetic sex determination, with female heterogametic sex chromosomes (ZZ males, ZW females). Extensive cytogenetic work has suggested that the level of sex chromosome heteromorphism varies among species, with Boidae having entirely homomorphic sex chromosomes, Viperidae having completely heteromorphic sex chromosomes, and Colubridae showing partial differentiation. Here, we take a genomic approach to compare sex chromosome differentiation in these three snake families. We identify homomorphic sex chromosomes in boas (Boidae), but completely heteromorphic sex chromosomes in both garter snakes (Colubridae) and pygmy rattlesnake (Viperidae). Detection of W-linked gametologs enables us to establish the presence of evolutionary strata on garter and pygmy rattlesnake sex chromosomes where recombination was abolished at different time points. Sequence analysis shows that all strata are shared between pygmy rattlesnake and garter snake, i.e., recombination was abolished between the sex chromosomes before the two lineages diverged. The sex-biased transmission of the Z and its hemizygosity in females can impact patterns of molecular evolution, and we show that rates of evolution for Z-linked genes are increased relative to their pseudoautosomal homologs, both at synonymous and amino acid sites (even after controlling for mutational biases). This demonstrates that mutation rates are male-biased in snakes (male-driven evolution), but also supports faster-Z evolution due to differential selective effects on the Z. Finally, we perform a transcriptome analysis in boa and pygmy rattlesnake to establish baseline levels of sex-biased expression in homomorphic sex chromosomes, and show that heteromorphic ZW chromosomes in rattlesnakes lack chromosome-wide dosage compensation. Our study provides the first full scale overview of the evolution of snake sex chromosomes at the genomic level, thus greatly expanding our knowledge of reptilian and vertebrate sex chromosomes evolution.

Dataset Information

Evolutionary strata on the mouse X chromosome correspond to strata on the human X chromosome.

Publications

Evolutionary strata on the mouse X chromosome correspond to strata on the human X chromosome.

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure

Tweets