Radiological evolution of peri-odontoid pannus in a patient with Chiari I malformation: a case-based review.

INTRODUCTION: The Chiari I malformation (CIM) is commonly encountered by neurosurgeons and can have different etiologies and clinical presentations. CASE REPORT: We report a CIM patient who presented with symptoms of ventral brain stem compression and was found to have a large peri-odontoid pannus. Posterior fossa decompression was performed with a planned second-stage odontoidectomy. However, at the 6-month follow-up, postoperative images demonstrated a mostly resolved pannus and improvement of the brain stem compression symptoms, and the patient progressed uneventfully without the need for odontoidectomy. CONCLUSIONS: This case illustrates the resolution of a significant and symptomatic peri-odontoid pannus in a patient with CIM without craniocervical fusion or odontoidectomy. Such a case indicates that not all peri-odontoid pannus formations in CIM patients are due to hypermobility at the craniocervical junction.

IL-7 functionally segregates the pro-B cell stage by regulating transcription of recombination mediators across cell cycle.

Ag receptor diversity involves the introduction of DNA double-stranded breaks during lymphocyte development. To ensure fidelity, cleavage is confined to the G(0)-G(1) phase of the cell cycle. One established mechanism of regulation is through periodic degradation of the RAG2 recombinase protein. However, there are additional levels of protection. In this paper, we show that cyclical changes in the IL-7R signaling pathway functionally segregate pro-B cells according to cell cycle status. In consequence, the level of a downstream effector of IL-7 signaling, phospho-STAT5, is inversely correlated with cell cycle expression of Rag, a key gene involved in recombination. Higher levels of phopho-STAT5 in S-G(2) correlate with decreased Rag expression and Rag relocalization to pericentromeric heterochromatin. These cyclical changes in transcription and locus repositioning are ablated upon transformation with v-Abl, which renders STAT5 constitutively active across the cell cycle. We propose that this activity of the IL-7R/STAT5 pathway plays a critical protective role in development, complementing regulation of RAG2 at the protein level, to ensure that recombination does not occur during replication. Our data, suggesting that pro-B cells are not a single homogeneous population, explain inconsistencies in the role of IL-7 signaling in regulating Igh recombination.

Supernumerary Abducens Nerves: A Comprehensive Review.

BACKGROUND: Branching and/or replication of the abducens nerve is not an uncommon occurrence. Although numerous variations have been documented, the rarest forms are duplicated or triplicated nerves, where multiple nerve roots originate from the brainstem, travel intracranially, and attach to the lateral rectus as separate entities. METHODS: We conducted a systematic literature search on the topic of supernumerary abducens nerve, using PubMed and Google Scholar. RESULTS: After screening, 16 studies were included: 11 cadaveric studies and 6 case reports. CONCLUSIONS: In this paper, we review the literature on variations found, discuss current hypotheses and clinical relevance, and propose future studies. Neurosurgeons should be aware of such nerve variants when viewing imaging or operating in the regions traversed by the abducens nerve.

Higher-order looping and nuclear organization of Tcra facilitate targeted rag cleavage and regulated rearrangement in recombination centers.

V(D)J recombination is essential for generating a diverse array of B and T cell receptors that can recognize and combat foreign antigens. As with any recombination event, tight control is essential to prevent the occurrence of genetic anomalies that drive cellular transformation. One important aspect of regulation is directed targeting of the RAG recombinase. Indeed, RAG accumulates at the 3' end of individual antigen receptor loci poised for rearrangement; however, it is not known whether focal binding is involved in regulating cleavage, and what mechanisms lead to enrichment of RAG in this region. Here, we show that monoallelic looping out of the 3' end of the T cell receptor α (Tcra) locus, coupled with transcription and increased chromatin/nuclear accessibility, is linked to focal RAG binding and ATM-mediated regulation of monoallelic cleavage on looped-out 3' regions. Our data identify higher-order loop formation as a key determinant of directed RAG targeting and the maintenance of genome stability.