Cytogenetic and Genome Research

We investigated subinterval 6E on the human Y chromosome, a region frequently deleted in infertile males. YAC yOX17, mapped within subinterval 6E by STS-PCR, was analyzed for the presence of new genes. TSPYq1, a member of the TSPY multi-copy gene family, was isolated and character- ized from a yOX17 cosmid subclone. PCR and FISH analysis performed on normal subjects and on patients with microdeletions of Yq suggested the presence of multiple copies of TSPY in Yq.   

PRG4 (proteoglycan 4) has been identified as megakaryocyte stimulating factor and articular superficial zone protein. PRG4 has characteristic motifs including somatomedin B and hemopexin domains, a chondroitin sulfate-attachment site and mucin-like repeats. During a screen of genes implicated in ectopic ossification, we found a novel mouse gene highly homologous to human and bovine PRG4 genes. Here, we report isolation, characterization and mapping of the gene, <i>Prg4</i> together with characterization of its human orthologue. <i>Prg4</i> cDNA was 3,320 bp long, encoding a 1,054 amino-acid protein. Human and mouse PRG4 genes each consisting of 12 exons spanned 18 and 16 kb, respectively. Characteristic motifs were conserved across species; however, the mucin-like repeat regions were highly diverse in length between species with a tendency that larger animals had longer repeats. Expression of human and mouse PRG4 genes was similar and found not only in cartilage, but also in liver, heart, lung, and bone. Expression of the mouse gene increased with progression of ectopic ossification. Multiple tissue-specific splicing variants lacking some of the motifs were found in both human and mouse. Although a specific role in the articular joint has previously been reported, the presence of multi-functional motifs as well as unique expression and alternative splicing patterns suggest that PRG4 functions in several distinctive biological process including regulation of ossification.   

Retrons are distinct DNA sequences that code for a reverse transcriptase (RT) similar to the RTs produced by retroviruses and other types of retroelements. Retron DNAs are commonly associated with prophage DNA and are found in the genomes of a wide variety of different bacteria. The retron RT is used to synthesize a strange satellite DNA known as msDNA. msDNA is actually a complex of DNA, RNA, and probably protein. It is composed of a small, single-stranded DNA, linked to a small, single-stranded RNA molecule. The 5′ end of the DNA molecule is joined to an internal guanosine residue of the RNA molecule by a unique 2′-5′ phosphodiester bond. msDNA is produced in many hundreds of copies per cell, but its function remains unknown. Although retrons are absent from the genome of most members of a population of related bacteria, retrons may not be entirely benign DNAs. Evidence is beginning to suggest that retron elements may produce small but potentially significant effects on the host cell. This includes the generation of repeated copies of the msDNA sequence in the genome, and increasing the frequency of spontaneous mutations. Because these events involve the retron RT, this may represent a source of reverse transcription in the bacterial cell. Thus, the process of reverse transcription, a force that has profoundly affected the content and structure of most eukaryotic genomes, may likewise be responsible for changes in some prokaryotic genomes.   

Systemic lupus erythematosus (SLE) is a systemic autoimmune disorder characterized by the presence of auto-antibodies to nuclear antigens, immune complex deposition, and subsequent tissue destruction. Early studies in twins suggested that SLE has, at least in part, a genetic basis, and a role for class II alleles in the major histocompatibility complex has been known for over 30 years. Through both linkage studies and candidate gene studies, numerous additional genetic risk factors have been identified. The recent publication of two SNP-based genome-wide association studies (GWAS) has resulted in the confirmation of a number of previously identified genetic risk loci and has identified new previously unappreciated loci conferring risk for development of SLE. A role for gene copy number variation (CNV) in SLE has also been appreciated through studies of the complement component 4 (C4) loci and more recent work in the IgG Fc receptor loci. The availability of large SNP-based GWAS datasets will undoubtedly lead to the genome-wide analysis and identification of copy number variants related to genetic susceptibility for development of SLE. We review current studies of CNV in SLE susceptibility that include reports of association between SLE and CNV in <i>C4</i>, IgG Fc receptors, <i>TLR7,</i> and <i>CCL3L1</i>.

The eggs, after being washed out from the genital tract, are put into hypotonic (1%) sodium citrate and left to stand at room temperature for 5–15 minutes. The duration of treatment is not very critical, but later stages, especially blastocysts, need longer treatment. A microdrop of this solution together with the eggs is placed on a grease-free slide. A few drops of acetic alcohol (3 parts of absolute ethyl alcohol, 1 part of glacial acetic acid) are immediately expelled from another pipette, whose tip is brought just over the microdrop containing eggs. The optimal number of drops of fixative has been found to be three in the case of eggs from the one cell to eight cell stage and five or even more in the case of blastocysts. These indications were calculated for drops measuring approximately 0.02 ml in volume. Air-dried preparations are stained in lactic-acetic-orcein or in 2% aqueous solution of toluidine blue. The method can be applied to all stages from diakinesis of the first meiotic division to blastocyst. It enables one to obtain excellent scattering of nuclei and metaphase plates and good spreading of chromosomes. The remnants of cytoplasm are negligible.