The Medical Research Council's Paul Burgoyne led a team that used transgenic mice and microarrays to find a gene that contributes to the post-meiotic silencing of genes on the long arm of the mouse Y chromosome MSYq, information that "is crucial for postmeiotic repression of the sex chromosomes and for sperm differentiation." With mice made to produce siRNAs targeting the MSYq gene Sycp3-like Y-linked, or Sly, they found that less Sly expression led to mice with "major sperm differentiation problems together with a remarkable postmeiotic derepression of genes encoded on the X and Y chromosomes." The work appears in this week's PLoS Biology.
In a flood of papers in PLoS Genetics, scientists take on the maize genome, published last week in Science. In one, University of California, Berkeley researchers used genetic and molecular techniques to find that a Pol IV-type subunit protein is involved in maintaining epigenetic silencing. Mutations in the gene called required to maintain repression7 lead to different functional isoforms of the Pol IV-type RNAP.
In other work, scientists led by David Schwartz at the University of Wisconsin, Madison, have constructed a genome-wide, high-resolution optical map of the maize B73 genome from genomic DNA molecules without using genetic markers. They say the map will be useful for validating sequence assemblies and "demonstrates the inherent advantages of single molecule platforms." Rod Wing led a group that also sequenced the B73 genome, creating a "minimum tiling path (MTP) of over 16,000 BAC clones across the genome." In another large study led by Wing and Washington University's Rick Wilson, they sequenced and annotated a 22-mb sequence from chromosome 4 and found 544 genes that have transposable elements, representing 84 percent of the sequence. In more work, researchers performed a computational genome-wide survey of maize miRNAs and discovered 150 high-confidence genes within 26 miRNA families.
In PLoS One this week, Hong-Wen Deng and Jian Li at the University of Missouri, Kansas City, led a study looking at copy number variation among Caucasians and Asians. While much has been learned about CNVs, "knowledge is still inadequate on fundamental CNV characteristics such as occurrence rate, genomic distribution and ethnic differentiation," they write in the abstract. In this work, they used Affy arrays to find 3,019 CNVs from both populations, and that among these, 190 had greater than one percent frequency in at least one ethnic group while 109 showed "significant ethnic differences in frequencies."