Structure of BTK kinase domain with the second-generation inhibitors acalabrutinib and tirabrutinib.

Bruton's tyrosine kinase (BTK) is the target of the therapeutic agent, Ibrutinib, that treats chronic lymphocyte leukemia (CLL), mantle cell lymphoma (MCL) and other B cell malignancies. Ibrutinib is a first in class, covalent BTK inhibitor that limits B-cell survival and proliferation. Designing new inhibitors of BTK has been an important objective for advancing development of improved therapeutic agents against cancer and autoimmune disorders. Based on the success of Ibrutinib, several second-generation irreversible BTK inhibitors have been developed that exhibit fewer off-target effects. However, the binding-mode and their interaction with Btk have not been experimentally determined and evaluated at atomic resolution. Here we determined the first crystal structure of the BTK kinase domain in complex with acalabrutinib. In addition, we report a structure of the BTK/tirabrutinib complex and compare these structures with previously solved structures. The structures provide insight in the superior selectivity reported for acalabrutinb and guide future BTK inhibitor development.

Pediatric Forefoot Deformities.

This article explores different pediatric forefoot deformities including syndactyly, polydactyly, macrodactyly, curly toe, and congenital hallux varus. The epidemiology and genetic background are reviewed for each condition. Preferred treatment options and recommended surgical techniques are discussed with review of the current literature.

Single Electrospun PLLA and PCL Polymer Nanofibers: Increased Molecular Orientation with Decreased Fiber Diameter.

Electrospinning has become a widely-used method for fabricating polymer nanofibers for various applications including filtration, drug delivery, and tissue engineering. Due to the high extensional forces during the electrospinning process, and the rapid crystallization and solidification during solvent evaporation, molecular orientation may develop within the resulting fibers. The properties of electrospun fibers are expected to be sensitive to level of orientation in the fibers. Various reports have shown an increased modulus with decreased fiber diameter, and molecular orientation has been used to explain this trend. However, there have been relatively few studies of the detailed relationship between fiber diameter and molecular orientation, especially at the single fiber level. Here we report a quantitative study of the orientation in individual electrospun poly(caprolactone) (PCL) and poly(L-lactic acid) (PLLA) fibers using low-dose electron microscopy and diffraction techniques. Our results confirmed that for electrospun fibers of PCL and PLLA processed under similar experimental conditions, the molecular orientation decreased as the fiber diameter increased. The extent of orientation remained high for quite large fiber diameters, with azimuthal orientation of 20 degrees seen up to ~500 nm for PCL and ~2000 nm for PLLA.

Cocaine alters Homer1 natural antisense transcript in the nucleus accumbens.

Natural antisense transcripts (NATs) are an abundant class of long noncoding RNAs that have recently been shown to be key regulators of chromatin dynamics and gene expression in nervous system development and neurological disorders. However, it is currently unclear if NAT-based mechanisms also play a role in drug-induced neuroadaptations. Aberrant regulation of gene expression is one critical factor underlying the long-lasting behavioral abnormalities that characterize substance use disorder, and it is possible that some drug-induced transcriptional responses are mediated, in part, by perturbations in NAT activity. To test this hypothesis, we used an automated algorithm that mines the NCBI AceView transcriptomics database to identify NAT overlapping genes linked to addiction. We found that 22% of the genes examined contain NATs and that expression of Homer1 natural antisense transcript (Homer1-AS) was altered in the nucleus accumbens (NAc) of mice 2h and 10days following repeated cocaine administration. In in vitro studies, depletion of Homer1-AS lead to an increase in the corresponding sense gene expression, indicating a potential regulatory mechanisms of Homer1 expression by its corresponding antisense transcript. Future in vivo studies are needed to definitely determine a role for Homer1-AS in cocaine-induced behavioral and molecular adaptations.

CTR1 phosphorylates the central regulator EIN2 to control ethylene hormone signaling from the ER membrane to the nucleus in Arabidopsis.

The gaseous phytohormone ethylene C(2)H(4) mediates numerous aspects of growth and development. Genetic analysis has identified a number of critical elements in ethylene signaling, but how these elements interact biochemically to transduce the signal from the ethylene receptor complex at the endoplasmic reticulum (ER) membrane to transcription factors in the nucleus is unknown. To close this gap in our understanding of the ethylene signaling pathway, the challenge has been to identify the target of the CONSTITUTIVE TRIPLE RESPONSE1 (CTR1) Raf-like protein kinase, as well as the molecular events surrounding ETHYLENE-INSENSITIVE2 (EIN2), an ER membrane-localized Nramp homolog that positively regulates ethylene responses. Here we demonstrate that CTR1 interacts with and directly phosphorylates the cytosolic C-terminal domain of EIN2. Mutations that block the EIN2 phosphorylation sites result in constitutive nuclear localization of the EIN2 C terminus, concomitant with constitutive activation of ethylene responses in Arabidopsis. Our results suggest that phosphorylation of EIN2 by CTR1 prevents EIN2 from signaling in the absence of ethylene, whereas inhibition of CTR1 upon ethylene perception is a signal for cleavage and nuclear localization of the EIN2 C terminus, allowing the ethylene signal to reach the downstream transcription factors. These findings significantly advance our understanding of the mechanisms underlying ethylene signal transduction.

Aligned electrospun nanofibers specify the direction of dorsal root ganglia neurite growth.

Nerve injury, a significant cause of disability, may be treated more effectively using nerve guidance channels containing longitudinally aligned fibers. Aligned, electrospun nanofibers direct the neurite growth of immortalized neural stem cells, demonstrating potential for directing regenerating neurites. However, no study of neurite guidance on these fibers has yet been performed with primary neurons. Here, we examined neurites from dorsal root ganglia explants on electrospun poly-L-lactate nanofibers of high, intermediate, and random alignment. On aligned fibers, neurites grew radially outward from the ganglia and turned to follow the fibers upon contact. Neurite guidance was robust, with neurites never leaving the fibers to grow on the surrounding cover slip. To compare the alignment of neurites to that of the nanofiber substrates, Fourier methods were used to quantify the alignment. Neurite alignment, however striking, was inferior to fiber alignment on all but the randomly aligned fibers. Neurites on highly aligned substrates were 20 and 16% longer than neurites on random and intermediate fibers, respectively. Schwann cells on fibers assumed a very narrow morphology compared to those on the surrounding coverslip. The robust neurite guidance demonstrated here is a significant step toward the use of aligned, electrospun nanofibers for nerve regeneration. (c) 2007 Wiley Periodicals, Inc. J Biomed Mater Res, 2007.

Osteogenesis imperfecta presenting as simultaneous bilateral tibial tubercle avulsion fractures in a child: a case report.

This is a case report of a unique presentation of a mild form of osteogenesis imperfecta (OI) (type IA) in a 9-year-old African-American boy who presented with simultaneous bilateral tibial tubercle avulsion fractures. The boy presented to the authors' emergency room complaining of acute bilateral knee pain. He could not perform a straight leg raise. Other than his orthopaedic examination, significant findings included blue sclera and irregular teeth. Radiographs and magnetic resonance imaging (MRI) confirmed bilateral tibia tubercle avulsion fractures. The patient underwent open reduction and internal fixation of his fractures, and postoperative genetic testing confirmed that the patient was heterozygous for OI. The authors present the fourth reported case of simultaneous bilateral tibial tubercle fractures. To their knowledge this is the first case of OI presenting with these fractures, the youngest reported case, and the first case with MRI documentation.