Rdh54 stabilizes Rad51 at displacement loop intermediates to regulate genetic exchange between chromosomes.

Homologous recombination (HR) is a double-strand break DNA repair pathway that preserves chromosome structure. To repair damaged DNA, HR uses an intact donor DNA sequence located elsewhere in the genome. After the double-strand break is repaired, DNA sequence information can be transferred between donor and recipient DNA molecules through different mechanisms, including DNA crossovers that form between homologous chromosomes. Regulation of DNA sequence transfer is an important step in effectively completing HR and maintaining genome integrity. For example, mitotic exchange of information between homologous chromosomes can result in loss-of-heterozygosity (LOH), and in higher eukaryotes, the development of cancer. The DNA motor protein Rdh54 is a highly conserved DNA translocase that functions during HR. Several existing phenotypes in rdh54Δ strains suggest that Rdh54 may regulate effective exchange of DNA during HR. In our current study, we used a combination of biochemical and genetic techniques to dissect the role of Rdh54 on the exchange of genetic information during DNA repair. Our data indicate that RDH54 regulates DNA strand exchange by stabilizing Rad51 at an early HR intermediate called the displacement loop (D-loop). Rdh54 acts in opposition to Rad51 removal by the DNA motor protein Rad54. Furthermore, we find that expression of a catalytically inactivate allele of Rdh54, rdh54K318R, favors non-crossover outcomes. From these results, we propose a model for how Rdh54 may kinetically regulate strand exchange during homologous recombination.

Clear cell meningiomas-case presentation, review of radiographic identifiers, and treatment approaches.

Spinal clear cell meningiomas (CCMs) are a rare histological subtype of meningiomas that pose preoperative diagnostic challenges due to their radiographic similarities with other lesions. They are also more aggressive, exhibiting higher rates of recurrence, particularly in pediatric patients. Overcoming diagnostic challenges of these tumors can improve patient outcomes. In this report, we describe a case of a pediatric patient presenting with a lumbar CCM in whom we were able to obtain gross total resection. Our report reviews previously identified predictors of CCM recurrence, including the Ki-67 proliferation index, number of spinal segments involved, and hormonal influences related to age and sex. We describe the characteristic radiographic features that differentiate spinal CCMs from other tumors to improve pre-operative diagnosis. Furthermore, we provide our rationale for adjuvant therapy for pediatric patients to refine treatment protocols for these rare tumors.

Three-dimensional imaging in craniofacial surgery: utilization of a novel 3D mobile application to evaluate the surgical outcomes of a skull recontouring procedure for cephalohematoma.

OBJECTIVE: Cranial abnormalities are common birth defects that frequently alter skull shape and appearance. Despite their prevalence, objective quantification of defect severity pre- and posttreatment is limited. The authors evaluated the ability of MirrorMe3D, a novel 3D mobile iPhone application, to measure changes in the contour of the skull for patients undergoing contouring of a calcified cephalohematoma. METHODS: The heads of two 20-month-old patients with disfiguring right parietal cephalohematomas undergoing a skull recontouring operation were scanned pre- and postsurgery. Four scans of the cranial abnormality were taken throughout the procedure and intraoperative 3D models were generated. Models of the head were overlapped pre- and postsurgery and compared using a depth analyzer built into MirrorMe3D. RESULTS: Depth analysis revealed 6.0-mm and 9.9-mm differences for patients 1 and 2, respectively. Volume analysis revealed 33-cm3 and 85-cm3 differences for patients 1 and 2, respectively. Currently, no standard for quantitative measurement of the surgical outcomes of a skull reconstruction procedure exists. CONCLUSIONS: MirrorMe3D provides an efficient method for monitoring patients with simple topographic scans that create accurate models of the head. The authors show the app's ability to capture the severity of a calcified cephalohematoma and quantify the changes in the contour of the skull before and after surgery.

Clinical Features and Management of Skull Base Fractures in the Pediatric Population: A Systematic Review.

Pediatric basilar skull fractures (BSFs) are a rare type of traumatic head injury that can cause debilitating complications without prompt treatment. Here, we sought to review the literature and characterize the clinical features, management, and outcomes of pediatric BSFs. We identified 21 relevant studies, excluding reviews, meta-analyses, and non-English articles. The incidence of pediatric BSFs ranged from 0.0001% to 7.3%, with falls from multi-level heights and traffic accidents being the primary causes (9/21). The median presentation age ranged from 3.2 to 12.8 years, and the mean age of patients across all studies was 8.68 years. Up to 55% of pediatric BSFs presented with intracranial hematoma/hemorrhage, along with pneumocephalus and edema. Cranial nerve palsies were a common complication (9/21), with the facial nerve injured most frequently (7/21). While delayed cranial nerve palsy was reported in a few studies (4/21), most resolved within three months post-admission. Other complications included CSF leaks (10/21) and meningitis (4/21). Management included IV fluids, antiemetics, and surgery (8/21) to treat the fracture directly, address a CSF leak, or achieve cranial nerve compression. Despite their rarity, pediatric skull base fractures are associated with clinical complications, including CSF leaks and cranial nerve palsies. Given that some of these complications may be delayed, patient education is critical.