piRNAs and Piwi proteins have been implicated in transposon control and are linked to transposon methylation in mammals. Here, we examined the construction of the piRNA system in the restricted developmental window in which methylation patterns are set during mammalian embryogenesis. We find robust expression of two Piwi family proteins, MIWI2 and MILI. Their associated piRNA profiles reveal differences from Drosophila wherein large piRNA clusters act as master regulators of silencing. Instead, in mammals, dispersed transposon copies initiate the pathway, producing primary piRNAs, which predominantly join MILI in the cytoplasm. MIWI2, whose nuclear localization and association with piRNAs depend upon MILI, is enriched for secondary piRNAs antisense to the elements that it controls. The Piwi pathway lies upstream of known mediators of DNA methylation, since piRNAs are still produced in Dnmt3L mutants, which fail to methylate transposons. This implicates piRNAs as specificity determinants of DNA methylation in germ cells.

Several novel myelin-associated/oligodendrocytic basic protein (MOBP) isoforms were identified in this study by cDNA cloning. They are small, highly basic polypeptides comprising 69, 81, and 99 amino acids (8.2, 9.7, and 11.7 kDa, respectively) and show no significant homology with described proteins or domain structures. All (as yet) identified MOBP isoforms are identical in amino acids 1-68 but differ in the length and polarity of the C-terminal region. One isoform, designated MOBP81, was shown to be expressed abundantly during development. Interestingly, MOBP81 has a significant clustering of positively charged residues at positions 69-81, a feature that also has been observed for myelin basic protein (MBP) and Po. As demonstrated by in situ hybridization, MOBP gene expression occurs during development of the rat optic nerve later than that of MBP and proteolipid protein and coincides exactly with the beginning of myelin compaction. The 2.6 kb MOBP81-A transcript is localized in the processes of oligodendrocytes, whereas the 3.8 kb MOBP81-B transcript is restricted to the perinuclear region. Therefore, MOBP81-A and related mRNAs seem to be transported to the periphery of the oligodendrocytes, as is known for the transcripts of the MBP gene. The late developmental expression of the MOBP gene suggests that the MOBP proteins act at the late steps of myelin formation, possibly in myelin compaction and in the maintenance of the myelin sheath.

Specific sequences are designated for de novo DNA methylation at CpG dinucleotides in mammalian germ cells. The result is the long-term transcriptional silencing of the methylated sequences, most of which are retrotransposons and CpG-rich sequences associated with imprinted genes. There is profound sexual dimorphism in both the nature of the sequences that undergo de novo methylation in germ cells and in the mechanism by which de novo methylation is regulated. The restriction of future gene expression by the imposition of heritable methylation patterns in germ cell genomes is characteristic of mammals but is rare in other taxa.

Without the RAD51 strand exchange protein, Saccharomyces cerevisiae cannot repair a double-strand break (DSB) by gene conversion. However, cells can repair DSBs by recombination-dependent, break-induced replication (BIR). RAD51-independent BIR is initiated more than 13 kb from the DSB. Repair depends on a 200-bp sequence adjacent to ARS310, located ∼34 kb centromere-proximal to the DSB, but does not depend on the origin activity of ARS310. We conclude that the ability of a recombination-induced replication fork to copy >130 kb to the end of the chromosome depends on a special site that enhances assembly of a processive repair replication fork. Break-induced DNA replication (BIR) plays a key role in the repair of double-strand breaks (DSBs) in eukaryotic chromosomes. BIR is likely to be important in restarting DNA replication after the collapse of a replication fork (for reviews, see Haber 1999; Michel 2000), but it also functions to repair DSBs created in other ways. In Saccharomyces cerevisiae, when there is homology with another chromosomal template only centromere-proximal to the DSB, repair may occur by recombination-dependent DNA replication, forming a nonreciprocal translocation (Bosco and Haber 1998). Similar types of events have been documented when linearized plasmids are introduced into yeast cells and initiate DNA replication from a template chromosome, travelling as much as several hundred kilobases to the end of the chromosome (Dunn et al. 1984;Morrow et al. 1997). BIR also may account for the analogous ALT mechanism of telomere maintenance of human tumor cells in the absence of telomerase, as well as similar types of telomere maintenance in budding yeast (Lundblad and Blackburn 1993;Le et al. 1999;Teng and Zakian 1999;Dunham et al. 2000;Teng et al. 2000).BIR is a recombination-dependent mechanism to initiate DNA synthesis. By creating a DSB in G 1 cells, we showed that this replicative process can occur before the initiation of normal DNA replication, at least in wildtype cells (Bosco and Haber 1998). BIR may be closely related to the mechanism of gene conversion induced by a DSB, based on gene conversion that appears to involve both leading-and lagging-strand DNA synthesis (Holmes and Haber 1999). Both processes may initiate in the same way, by the invasion of a single-stranded DNA end that is produced by 5Ј to 3Ј resection of the DSB, to establish a modified replication fork. In gene conversion, this process would terminate when the second end of the DSB engaged the replication structure, whereas in BIR, the replication process would continue to the end of the chromosome. In some circumstances, BIR and gene conversion appear to be alternative, competing outcomes of DSB-initiated recombination (Esposito 1978; VoelkelMeiman and Roeder 1990;Malkova et al. 2000).Nevertheless, there are significant differences between BIR and gene conversion (Malkova et al. 1996). Surprisingly, BIR can occur in the absence of the Rad51p strand exchange protein, whereas gene conversion is completely abolished (Fig. 1)....

We have isolated several new genes that are specifically expressed by oligodendrocytes in the CNS. This was achieved by differential screening of a rat spinal cord cDNA library with probes derived from normal and from oligodendrocyte‐free spinal cord mRNAs. Four of these genes are exclusively expressed by oligodendrocytes: Three of these are not related to known genes, whereas one encodes the myelin oligodendrocyte glycoprotein (MOG). Four other genes are expressed by oligodendrocytes as well as by Schwann cells. One gene codes for apolipoprotein D, which is thought to be involved in lipid metabolism. A second cDNA sequence codes for the recently identified galactosylceramide‐synthesizing enzyme UDP‐galactose:ceramide galactosyl‐transferase. The third gene encodes a small protein with four putative transmembrane domains that is related to a T‐lymphocyte‐specific membrane protein, MAL. The fourth gene encodes the rat homologue of the stearyl‐CoA‐desaturase 2 (SCD2) gene, which is specifically expressed in the nervous system and involved in the synthesis and regulation of long‐chain unsaturated fatty acids essential for myelination. Finally, we found that a member of the β‐tubulin family is highly expressed in oligodendrocytes as well as neurons. The identification of several new proteins that may play a role in myelin synthesis and sheath formation will lead to new insight into this complex mechanism.

Stauffer's syndrome is a paraneoplastic phenomenon associated with renal cell carcinoma (RCC) characterized by cholestatic hepatitis. We explore the effects of perioperative immunotherapy in a case of Stauffer's syndrome. A 70-year-old female with a locally advanced clear cell RCC (ccRCC) developed severe hyperbilirubinemia. The patient's cholestasis progressed despite initial systemic immunotherapy, but improved after cytoreductive nephrectomy. The patient continued immunotherapy post-operatively and regained normalized hepatic function. To our knowledge, this is the first case reporting use of systemic immunotherapy with surgery in Stauffer's syndrome, and we provide clinical insight into a treatment regimen which may be employed in future cases.

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Attention-deficit/hyperactivity disorder may have substantial impact on family life, peer interactions, and quality of life. Stimulants are recommended as first-line pharmacotherapy for ADHD. OROS(®) MPH (Concerta(®)) is a long-acting preparation with duration of effect for up to 12 h. In this 8-week, prospective, open-label, non-interventional trial the impact of therapy with OROS(®) MPH on functioning in four different areas of life (school, recreation, family life, and peer interaction), severity of disease, and quality of life (QoL) as well as tolerability were investigated under daily routine care. 306 patients, aged 10.2±2.3 years, were either transitioned to OROS(®) MPH from short-acting, immediate-release MPH (-IR) preparations (n=231; 75%), or treatment was initiated with OROS(®) MPH in MPH-naïve patients (n =75; 25%). In both groups, therapy with OROS(®) MPH was associated with significant improvements in daily functioning, severity of disease, and QoL. Adverse events (AE) were documented in 160 patients (52.3%). In 95 patients (31.0%) a causal relationship was assessed as at least possible. Four serious AEs were reported in 2 patients and rated as doubtfully related to study medication. Most frequent AEs (≥5% of patients) were insomnia, anorexia, ineffectiveness of medication, and headache. In 12.1% of patients AE led to discontinuation of study participation. Considering the limitations of this non-interventional study, the results refer to the importance of a therapy that covers not only school-time, but also takes other areas of life into account. Initiating treatment with long-acting preparations, such as OROS(®) MPH in MPH-naïve patients might be a feasible option.