SRA053222
Ascaris suum Chromatin Diminution
This is an update for our aim to build comprehensive Ascaris genomic resources for the study of various aspects of parasitic nematode biology including developmental, chromosomal, and molecular biology. Specifically, this study addresses Ascaris chromatin diminution, the programmed elimination of specific DNA sequences, which occurs during early embryonic cleavages and leads to the loss of germline genome sequences and the formation of a distinct genome in somatic cells. We used high-throughput sequencing to characterize the content of Ascaris chromatin diminution by comparing the sequences of the germline (sperm) and somatic (intestine) genomes from a single male nematode and between male and female nematodes.
Chromatin diminution is the programmed elimination of specific DNA sequences during development. It occurs in diverse species, but the function(s) of diminution and the specificity of sequence loss remain largely unknown. Diminution in the nematode Ascaris suum occurs during early embryonic cleavages and leads to the loss of germline genome sequences and the formation of a distinct genome in somatic cells. We found that ~43 Mb (~13%) of genome sequence is eliminated in A. suum somatic cells, including ~12.7 Mb of unique sequence. The eliminated sequences and location of the DNA breaks are the same in all somatic lineages from a single individual and between different individuals. At least 685 genes are eliminated. These genes are preferentially expressed in the germline and during early embryogenesis. We propose that diminution is a mechanism of germline gene regulation that specifically removes a large number of genes involved in gametogenesis and early embryogenesis.