A bipartite element with allele-specific functions safeguards DNA methylation imprints at the Dlk1-Dio3 locus

Loss of imprinting (LOI) results in severe developmental defects, but the mechanisms preventing LOI remain incompletely understood. Here, we dissect the functional components of the imprinting control region of the essential Dlk1-Dio3 locus (called IG-DMR) in pluripotent stem cells. We demonstrate that the IG-DMR consists of two antagonistic elements: a paternally methylated CpG island that prevents recruitment of TET dioxygenases and a maternally unmethylated non-canonical enhancer that ensures expression of the Gtl2 lncRNA by counteracting de novo DNA methyltransferases. Genetic or epigenetic editing of these elements leads to distinct LOI phenotypes with characteristic alternations of allele-specific gene expression, DNA methylation, and 3D chromatin topology. Although repression of the Gtl2 promoter results in dysregulated imprinting, the stability of LOI phenotypes depends on the IG-DMR, suggesting a functional hierarchy. These findings establish the IG-DMR as a bipartite control element that maintains imprinting by allele-specific restriction of the DNA (de)methylation machinery.

QSER1 protects DNA methylation valleys from de novo methylation

DNA methylation is essential to mammalian development, and dysregulation can cause serious pathological conditions. Key enzymes responsible for deposition and removal of DNA methylation are known, but how they cooperate to regulate the methylation landscape remains a central question. Using a knockin DNA methylation reporter, we performed a genome-wide CRISPR-Cas9 screen in human embryonic stem cells to discover DNA methylation regulators. The top screen hit was an uncharacterized gene, QSER1, which proved to be a key guardian of bivalent promoters and poised enhancers of developmental genes, especially those residing in DNA methylation valleys (or canyons). We further demonstrate genetic and biochemical interactions of QSER1 and TET1, supporting their cooperation to safeguard transcriptional and developmental programs from DNMT3-mediated de novo methylation.

The Genetic Program of Pancreatic β-Cell Replication In Vivo

The molecular program underlying infrequent replication of pancreatic β-cells remains largely inaccessible. Using transgenic mice expressing green fluorescent protein in cycling cells, we sorted live, replicating β-cells and determined their transcriptome. Replicating β-cells upregulate hundreds of proliferation-related genes, along with many novel putative cell cycle components. Strikingly, genes involved in β-cell functions, namely, glucose sensing and insulin secretion, were repressed. Further studies using single-molecule RNA in situ hybridization revealed that in fact, replicating β-cells double the amount of RNA for most genes, but this upregulation excludes genes involved in β-cell function. These data suggest that the quiescence-proliferation transition involves global amplification of gene expression, except for a subset of tissue-specific genes, which are "left behind" and whose relative mRNA amount decreases. Our work provides a unique resource for the study of replicating β-cells in vivo.

Nuclear Retention of mRNA in Mammalian Tissues

mRNA is thought to predominantly reside in the cytoplasm, where it is translated and eventually degraded. Although nuclear retention of mRNA has a regulatory potential, it is considered extremely rare in mammals. Here, to explore the extent of mRNA retention in metabolic tissues, we combine deep sequencing of nuclear and cytoplasmic RNA fractions with single-molecule transcript imaging in mouse beta cells, liver, and gut. We identify a wide range of protein-coding genes for which the levels of spliced polyadenylated mRNA are higher in the nucleus than in the cytoplasm. These include genes such as the transcription factor ChREBP, Nlrp6, Glucokinase, and Glucagon receptor. We demonstrate that nuclear retention of mRNA can efficiently buffer cytoplasmic transcript levels from noise that emanates from transcriptional bursts. Our study challenges the view that transcripts predominantly reside in the cytoplasm and reveals a role of the nucleus in dampening gene expression noise.

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Genome-wide catalog of nuclear and cytoplasmic mRNA in mouse tissues

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Spliced, polyadenylated mRNA is retained in the nucleus for many protein-coding genes

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Retained genes include ChREBP and liver Nlrp6, co-localized with nuclear speckles

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Nuclear retention of mRNA reduces cytoplasmic gene expression noise

Transient acquisition of pluripotency during somatic cell transdifferentiation with iPSC reprogramming factors

Somatic cells can be transdifferentiated to other cell types without passing through a pluripotent state by ectopic expression of appropriate transcription factors^1,2. Recent reports have proposed an alternative transdifferentiation method in which fibroblasts are directly converted to various mature somatic cell types by brief expression of the induced pluripotent stem cell (iPSC) reprogramming factors Oct4, Sox2, Klf4 and c-Myc (OSKM) followed by cell expansion in media that promote lineage differentiation^3–6. Here we test this method using genetic lineage tracing for expression of endogenous Nanog and Oct4 and for X chromosome reactivation, as these events mark acquisition of pluripotency. We show that the vast majority of reprogrammed cardiomyocytes or neural stem cells obtained from mouse fibroblasts by OSKM-induced transdifferentiation pass through a transient pluripotent state, and that their derivation is molecularly coupled to iPSC formation mechanisms. Our findings underscore the importance of defining trajectories during cell reprogramming by different methods.

Derivation of novel human ground state naive pluripotent stem cells

Mouse embryonic stem (ES) cells are isolated from the inner cell mass of blastocysts, and can be preserved in vitro in a naive inner-cell-mass-like configuration by providing exogenous stimulation with leukaemia inhibitory factor (LIF) and small molecule inhibition of ERK1/ERK2 and GSK3β signalling (termed 2i/LIF conditions). Hallmarks of naive pluripotency include driving Oct4 (also known as Pou5f1) transcription by its distal enhancer, retaining a pre-inactivation X chromosome state, and global reduction in DNA methylation and in H3K27me3 repressive chromatin mark deposition on developmental regulatory gene promoters. Upon withdrawal of 2i/LIF, naive mouse ES cells can drift towards a primed pluripotent state resembling that of the post-implantation epiblast. Although human ES cells share several molecular features with naive mouse ES cells, they also share a variety of epigenetic properties with primed murine epiblast stem cells (EpiSCs). These include predominant use of the proximal enhancer element to maintain OCT4 expression, pronounced tendency for X chromosome inactivation in most female human ES cells, increase in DNA methylation and prominent deposition of H3K27me3 and bivalent domain acquisition on lineage regulatory genes. The feasibility of establishing human ground state naive pluripotency in vitro with equivalent molecular and functional features to those characterized in mouse ES cells remains to be defined. Here we establish defined conditions that facilitate the derivation of genetically unmodified human naive pluripotent stem cells from already established primed human ES cells, from somatic cells through induced pluripotent stem (iPS) cell reprogramming or directly from blastocysts. The novel naive pluripotent cells validated herein retain molecular characteristics and functional properties that are highly similar to mouse naive ES cells, and distinct from conventional primed human pluripotent cells. This includes competence in the generation of cross-species chimaeric mouse embryos that underwent organogenesis following microinjection of human naive iPS cells into mouse morulas. Collectively, our findings establish new avenues for regenerative medicine, patient-specific iPS cell disease modelling and the study of early human development in vitro and in vivo.

Deterministic direct reprogramming of somatic cells to pluripotency

Somatic cells can be inefficiently and stochastically reprogrammed into induced pluripotent stem (iPS) cells by exogenous expression of Oct4 (also called Pou5f1), Sox2, Klf4 and Myc (hereafter referred to as OSKM). The nature of the predominant rate-limiting barrier(s) preventing the majority of cells to successfully and synchronously reprogram remains to be defined. Here we show that depleting Mbd3, a core member of the Mbd3/NuRD (nucleosome remodelling and deacetylation) repressor complex, together with OSKM transduction and reprogramming in naive pluripotency promoting conditions, result in deterministic and synchronized iPS cell reprogramming (near 100% efficiency within seven days from mouse and human cells). Our findings uncover a dichotomous molecular function for the reprogramming factors, serving to reactivate endogenous pluripotency networks while simultaneously directly recruiting the Mbd3/NuRD repressor complex that potently restrains the reactivation of OSKM downstream target genes. Subsequently, the latter interactions, which are largely depleted during early pre-implantation development in vivo, lead to a stochastic and protracted reprogramming trajectory towards pluripotency in vitro. The deterministic reprogramming approach devised here offers a novel platform for the dissection of molecular dynamics leading to establishing pluripotency at unprecedented flexibility and resolution.

Resection arthrodesis of the knee in the treatment of tumours--a long-term follow-up

Limb salvage operations using large custom-made prostheses have become the treatment of choice for juxta-articular tumours at the knee. Resection-arthrodesis has been used since the 1920s and offers a satisfactory long term solution for young active patients. The good functional results after this procedure in 9 patients is presented here. This method should still be considered in selected cases.

Percutaneous laser nucleolysis of the intervertebral lumbar disc. An experimental study

Percutaneous laser discectomy has developed as a new modality in the treatment of herniated intervertebral discs. An experimental study of percutaneous nucleolysis using a carbon dioxide laser beam was performed in 10 dogs, each dog having 2 intervertebral disc spaces treated, for a total of 20 discs. The intradiscal pressure decreased in all instances with the drop ranging from 10% to 55% at the L2-L3 disc and 40% to 69% at the L4-L5 disc. The macroscopic and microscopic studies showed vaporization of the nucleus pulposus, and in 8 spaces, thermal damage to the end plate was observed. This study suggests that carbon dioxide laser nucleolysis is easy and effective, but 300 J of laser energy can damage the end plates in some intervertebral discs in dogs.

Percutaneous carbon dioxide laser nucleolysis with 2- to 5-year followup

A prospective study of 50 patients with low back and radicular pain caused by an L4-L5 protruded disc were treated by percutaneous laser nucleolysis with a carbon dioxide laser. The followup ranged from 2 to 5 years, and all the patients were evaluated clinically and by imaging with computed tomography scans and magnetic resonance images before and after the procedure. According to the Macnab criteria, 74% of the patients had excellent or good results and 26% had fair or poor results. The laser disc decompression opens up new options in the treatment of discogenic pain, but it is still an experimental procedure.

Tumoral calcinosis simulating osteomyelitis

A case of tumoral calcinosis simulating osteomyelitis and associated with bunion formation in a 20-year-old female is presented. The most striking findings in this patient were the soft tissue calcifications. There was no evidence of any of the known causes of heterotopic calcifications. This kind of simulation between tumoral calcinosis bunion formation and osteomyelitis has not been previously described.

Synovial chondromatosis of the hip joint

Synovial chondromatosis of the hip joint is uncommon entity. Two cases are presented, and the spectrum of the disease is discussed. Partial synovectomy with loose body removal is recommended as the treatment of choice. Joint replacement is performed only in patients with severe secondary osteoarthritis, and used only in selected cases.

Disc space infection and vertebral osteomyelitis as a complication of percutaneous lateral discectomy

Percutaneous lateral discectomy (PLD) in a 32-year-old man was followed by postoperative disc space infection and adjacent vertebral osteomyelitis caused by Staphylococcus aureus. The simplicity and decreased morbidity associated with PLD may be offset by severe infections. The small incision made in the annulus during PLD may not allow adequate drainage in the case of infection and may subsequently direct the infective process to the adjacent vertebral endplates. Meticulous aseptic technique, and possibly the use of prophylactic antibiotic therapy, is important in PLD.

Percutaneous discectomy of the lumbar spine

Ten patients with clinical and radiological evidence of herniated discs at lower lumbar levels were treated with partial discectomy by a lateral percutaneous approach. Eight patients had complete relief from radicular pain and were discharged within four days. They returned to normal daily activity within one month.

Musculocutaneous nerve injury after coracoid process transfer for clavicle instability. Report of three cases

During the last 10 years, we have treated 54 cases of fracture or dislocation of the lateral clavicle by transposing the coracoid process onto the clavicle. Recently, a postoperative musculocutaneous nerve injury was observed in 3 cases, all of which recovered spontaneously within 5 months. Our technique seems to entail a certain risk of causing stretch injury to the musculocutaneous nerve. Apart from resting the affected arm for a month or two, the condition does not require specific treatment.

Treatment of avulsed clavicle and recurrent subluxations of the ipsilateral shoulder by dynamic fixation

A new operative approach is presented for treatment of fractured distal end of clavicle associated with recurrent anterior shoulder subluxations. One case is presented in which open reduction of the fractured clavicle and stabilizing the anterior shoulder joint were accomplished by transfer of the coracoid process with its attached muscles under the subcapularis muscle onto the clavicle. The operation was followed by complete reduction of the fracture and a stable shoulder joint.

Total hip replacement in two patients with Paget's disease

Two patients suffering from Paget's disease, involving the hip joint, with pain and limitation of movement, were treated by total hip replacement. The operative course was normal and without excessive bleeding. At follow-up five years later, the patients are free of pain, and have almost complete range of motion; there is no sign of prosthetic loosening.

Hip arthroplasty in quiescent mycobacterial infection of hip

Three patients underwent hip arthroplasty--one total hip replacement and two, Thompson's hemiarthroplasty. The diagnosis was degenerative joint disease and subcapital fracture of the femur, respectively. Histologic and bacteriologic examination revealed mycobacterial infection. None of the patients had a past history of mycobacterial infection. In one instance, there was a reactivation of the infection eight months following surgery, which was treated successfully by antituberculosis drugs.

Salmonella osteomyelitis after internal fixation of fracture

A patient with Salmonella group D (Salmonella enteritidis) acute osteomyelitis of an operated femur is described. The patient failed to respond to chloramphenicol therapy and aztreonam therapy. The local infection that complicated the presence of a foreign body was eradicated only with the removal of the foreign body, an internal fixation plate.

The cardiac pacemaker patient with a femoral neck fracture

More than half the patients with permanent cardiac pacemakers (PCPMs) are over the age of 70 years. Patients in this age group are also more susceptible to fractures of the femoral neck requiring surgical intervention. The authors studied five patients with PCPMs who underwent surgery for femoral neck fracture. They discuss the special precautions necessary during surgery to prevent electromagnetic interference with the cardiac pacemaker as well as the special management of these patients.

Extra-appendicular carcinoid tumors of the gastrointestinal tract

During the years 1958-1978, seventeen patients were treated for extra-appendicular carcinoid tumors of the gastrointestinal tract in Tel-Hashomer and Belinson hospitals. Most of the tumors were located in the colon (eight cases) and in the rectum (four cases). A direct correlation between the tumor size and invasiveness has been noted, with distant metastases in eight of 12 patients with tumors more than 2 cm in size. Gastrointestinal bleeding was the most frequent clinical symptom, whereas the "carcinoid syndrome" appeared only in three patients. Curative surgery was performed in six patients, palliative procedure in two cases, explorative laparotomy was performed in four cases, and in two patients diagnosis was made in postmortem examination. Eight of the 17 patients (47%) had distant metastases at the time of the diagnosis, and six of the 15 operated patients (40%) died during the first year after the operation. The malignant nature of these tumors, together with the high incidence (23%) of associated malignant neoplasms is stressed. Radical resection is advocated in the cases where the tumor's size is more than 2 cm or in the presence of muscular invasion.

Walking cane designed to assist partial weight bearing

The device described indicates accurately the amount of weight borne on an affected leg. This device consists of two major elements: a weight measuring system incorporated in the walking cane's body, and a feedback mechanism situated in the cane's handle. By means of vibration or lights the patient and the therapist can determine whether or not the affected leg is bearing the prescribed weight. Thirty patients (10 with fractures, 10 with vascular disorders, and 10 below-knee amputees) and 10 healthy people participated in the study. The study concluded that young patients used the feedback information more readily than older patients. The intention in designing such a device is to help orthopedically disabled patients during their convalescence, to minimize strain on ischemic legs, and to assist amputees in monitoring weight-bearing postoperative walking.