Retrospective Mid-Term Follow-Up of Posttraumatic and Iatrogenic Neurovascular Complications in Surgically Treated Paediatric Patients with Distal Humerus Fracture.

BACKGROUND: The purpose of the study was to investigate and describe neurovascular complications and mid-term clinical outcomes of operatively managed fractures of the distal humerus in a paediatric population. Neurovascular injuries are common in these fractures, but reports about their implications for mid-term clinical outcomes is sparse. METHODS: A single-centre retrospective study was conducted at a university teaching hospital investigating paediatric patients who underwent operative management of a distal humerus fracture between 2014 and 2018. Patient demographics, fracture classification, pre-, peri- and postoperative neurovascular complications were investigated. Mid-term follow up clinical examination and functional scoring using QuickDASH, the Broberg and Morrey Score (BMS), the Mayo Elbow Performance Score (MEPS) and the Numeric Rating Scale were performed. RESULTS: A total of 84 patients were identified, of which 34 met the inclusion criteria and were available for follow-up clinical examination. The average time to follow-up was 150 weeks (1049.44 days ± 448.54). Ten primary traumatic neurovascular complications were identified, the majority of which involved the median nerve. Primary traumatic dissection of the brachial artery was recorded in three patients. Secondary iatrogenic nerve injury was documented in five patients after previously normal clinical examination. At follow-up, the average QuickDASH score was 3.0 ± 4.3, BMS was 98.6 ± 3.4 and MEPS was 97.1 ± 3.3 points. CONCLUSIONS: The mid-term clinical outcome following surgical management of distal humerus fractures is excellent. There is, however, a considerable frequency of both primary and secondary neurovascular complications, which must be considered when opting to treat these injuries surgically.

CHD4 regulates the DNA damage response and RAD51 expression in glioblastoma.

Glioblastoma (GBM) is a lethal brain tumour. Despite therapy with surgery, radiation, and alkylating chemotherapy, most people have recurrence within 6 months and die within 2 years. A major reason for recurrence is resistance to DNA damage. Here, we demonstrate that CHD4, an ATPase and member of the nucleosome remodelling and deactetylase (NuRD) complex, drives a component of this resistance. CHD4 is overexpressed in GBM specimens and cell lines. Based on The Cancer Genome Atlas and Rembrandt datasets, CHD4 expression is associated with poor prognosis in patients. While it has been known in other cancers that CHD4 goes to sites of DNA damage, we found CHD4 also regulates expression of RAD51, an essential component of the homologous recombination machinery, which repairs DNA damage. Correspondingly, CHD4 suppression results in defective DNA damage response in GBM cells. These findings demonstrate a mechanism by which CHD4 promotes GBM cell survival after DNA damaging treatments. Additionally, we found that CHD4 suppression, even in the absence of extrinsic treatment, cumulatively increases DNA damage. Lastly, we found that CHD4 is dispensable for normal human astrocyte survival. Since standard GBM treatments like radiation and temozolomide chemotherapy create DNA damage, these findings suggest an important resistance mechanism that has therapeutic implications.

Evolution of the human gastrokine locus and confounding factors regarding the pseudogenicity of GKN3.

In a screen for genes expressed specifically in gastric mucous neck cells, we identified GKN3, the recently discovered third member of the gastrokine family. We present confirmatory mouse data and novel porcine data showing that mouse GKN3 expression is confined to mucous cells of the corpus neck and antrum base and is prominently expressed in metaplastic lesions. GKN3 was proposed originally to be expressed in some human populations and a pseudogene in others. To investigate that hypothesis, we studied human GKN3 evolution in the context of its paralogous genomic neighbors, GKN1 and GKN2. Haplotype analysis revealed that GKN3 mimics GKN2 in patterns of exonic SNP allocation, whereas GKN1 appeared to be more stringently selected. GKN3 showed signatures of both directional selection and population based selective sweeps in humans. One such selective sweep includes SNP rs10187256, originally identified as an ancestral tryptophan to premature STOP codon mutation. The derived (nonancestral) allele went to fixation in Asia. We show that another SNP, rs75578132, identified 5 bp downstream of rs10187256, exhibits a second selective sweep in almost all Europeans, some Latinos, and some Africans, possibly resulting from a reintroduction of European genes during African colonization. Finally, we identify a mutation that would destroy the splice donor site in the putative exon3-intron3 boundary, which occurs in all human genomes examined to date. Our results highlight a stomach-specific human genetic locus, which has undergone various selective sweeps across European, Asian, and African populations and thus reflects geographic and ethnic patterns in genome evolution.

The transcription factor MIST1 is a novel human gastric chief cell marker whose expression is lost in metaplasia, dysplasia, and carcinoma.

The lack of reliable molecular markers for normal differentiated epithelial cells limits understanding of human gastric carcinogenesis. Recognized precursor lesions for gastric adenocarcinoma are intestinal metaplasia and spasmolytic polypeptide expressing metaplasia (SPEM), defined here by ectopic CDX2 and TFF2 expression, respectively. In mice, expression of the bHLH transcription factor MIST1, normally restricted to mature chief cells, is down-regulated as chief cells undergo experimentally induced metaplasia. Here, we show MIST1 expression is also a specific marker of human chief cells. SPEM, with and without MIST1, is present in human lesions and, akin to murine data, likely represents transitional (TFF2(+)/MIST1(+) = "hybrid"-SPEM) and established (TFF2(+)/MIST1(-) = SPEM) stages. Co-visualization of MIST1 and CDX2 shows similar progressive loss of MIST1 with a transitional, CDX2(+)/MIST1(-) hybrid-intestinal metaplasia stage. Interinstitutional analysis and comparison of findings in tissue microarrays, resection specimens, and biopsies (n > 400 samples), comprising the entire spectrum of recognized stages of gastric carcinogenesis, confirm MIST1 expression is restricted to the chief cell compartment in normal oxyntic mucosa, rare in established metaplastic lesions, and lost in intraepithelial neoplasia/dysplasia and carcinoma of various types with the exception of rare chief cell carcinoma ( approximately 1%). Our findings implicate MIST1 as a reliable marker of mature, healthy chief cells, and we provide the first evidence that metaplasia in humans arises at least in part from the chief cell lineage.

RAB26 and RAB3D are direct transcriptional targets of MIST1 that regulate exocrine granule maturation.

Little is known about how differentiating cells reorganize their cellular structure to perform specialized physiological functions. MIST1, an evolutionarily conserved transcription factor, is required for the formation of large, specialized secretory vesicles in gastric zymogenic (chief) cells (ZCs) as they differentiate from their mucous neck cell progenitors. Here, we show that MIST1 binds to highly conserved CATATG E-boxes to directly activate transcription of 6 genes, including those encoding the small GTPases RAB26 and RAB3D. We next show that RAB26 and RAB3D expression is significantly downregulated in Mist1(-)(/)(-) ZCs, suggesting that MIST1 establishes large secretory granules by inducing RAB transcription. To test this hypothesis, we transfected human gastric cancer cell lines stably expressing MIST1 with red fluorescent protein (RFP)-tagged pepsinogen C, a key secretory product of ZCs. Those cells upregulate expression of RAB26 and RAB3D to form large secretory granules, whereas control, non-MIST1-expressing cells do not. Moreover, granule formation in MIST1-expressing cells requires RAB activity because treatment with a RAB prenylation inhibitor and transfection of dominant negative RAB26 abrogate granule formation. Together, our data establish the molecular process by which a transcription factor can directly induce fundamental cellular architecture changes by increasing transcription of specific cellular effectors that act to organize a unique subcellular compartment.

A necessary and sufficient determinant for protein-selective glycosylation in vivo.

A limited number of glycoproteins including luteinizing hormone and carbonic anhydrase-VI (CA6) bear N-linked oligosaccharides that are modified with beta1,4-linked N-acetylgalactosamine (GalNAc). The selective addition of GalNAc to these glycoproteins requires that the beta1,4-N-acetylgalactosaminyltransferase (betaGT) recognize both the oligosaccharide acceptor and a peptide recognition determinant on the substrate glycoprotein. We report here that two recently cloned betaGTs, betaGT3 and betaGT4, that are able to transfer GalNAc to GlcNAc in beta1,4-linkage display the necessary glycoprotein specificity in vivo. Both betaGTs transfer GalNAc to N-linked oligosaccharides on the luteinizing hormone alpha subunit and CA6 but not to those on transferrin (Trf). A single peptide recognition determinant encoded in the carboxyl-terminal 19-amino acid sequence of bovine CA6 mediates transfer of GalNAc to each of its two N-linked oligosaccharides. The addition of this 19-amino acid sequence to the carboxyl terminus of Trf confers full acceptor activity onto Trf for both betaGT3 and betaGT4 in vivo. The complete 19-amino acid sequence is required for optimal GalNAc addition in vivo, indicating that the peptide sequence is both necessary and sufficient for recognition by betaGT3 and betaGT4.

Metal-directed self-assembly of bimetallic dithiocarbamate transition metal cryptands and their binding capabilities.

A novel family of redox-active dinuclear transition metal based cryptands self-assembled from dithiocarbamate ligands has been synthesised; depending upon the nature of the spacer groups these new cryptand systems have been shown to electrochemically recognise the binding of cations or anions.