Exchange of subtelomeric regions between chromosomes 4q and 10q reverts the FSHD genotype and phenotype

The most common form of facioscapulohumeral dystrophy (FSHD1) is caused by a partial loss of the D4Z4 macrosatellite repeat array in the subtelomeric region of chromosome 4. Patients with FSHD1 typically carry 1 to 10 D4Z4 repeats, whereas nonaffected individuals have 11 to 150 repeats. The ~150-kilobyte subtelomeric region of the chromosome 10q exhibits a ~99% sequence identity to the 4q, including the D4Z4 array. Nevertheless, contractions of the chr10 array do not cause FSHD or any known disease, as in most people D4Z4 array on chr10 is flanked by the nonfunctional polyadenylation signal, not permitting the DUX4 expression. Here, we attempted to correct the FSHD genotype by a CRISPR-Cas9-induced exchange of the chr4 and chr10 subtelomeric regions. We demonstrated that the induced t(4;10) translocation can generate recombinant genotypes translated into improved FSHD phenotype. FSHD myoblasts with the t(4;10) exhibited reduced expression of the DUX4 targets, restored PAX7 target expression, reduced sensitivity to oxidative stress, and improved differentiation capacity.

Peptide nucleic acid-dependent artifact can lead to false-positive triplex gene editing signals

Triplex gene editing relies on binding a stable peptide nucleic acid (PNA) sequence to a chromosomal target, which alters the helical structure of DNA to stimulate site-specific recombination with a single-strand DNA (ssDNA) donor template and elicits gene correction. Here, we assessed whether the codelivery of PNA and donor template encapsulated in Poly Lactic-co-Glycolic Acid (PLGA)-based nanoparticles can correct sickle cell disease and x-linked severe combined immunodeficiency. However, through this process we have identified a false-positive PCR artifact due to the intrinsic capability of PNAs to aggregate with ssDNA donor templates. Here, we show that the combination of PNA and donor templates but not either agent alone results in different degrees of aggregation that result in varying but highly reproducible levels of false-positive signal. We have identified this phenomenon in vitro and confirmed that the PNA sequences producing the highest supposed correction in vitro are not active in vivo in both disease models, which highlights the importance of interrogating and eliminating carryover of ssDNA donor templates in assessing various gene editing technologies such as PNA-mediated gene editing.

Analysis of genes regulated by DUX4 via oxidative stress reveals potential therapeutic targets for treatment of facioscapulohumeral dystrophy

Muscles of patients with facioscapulohumeral dystrophy (FSHD) are characterized by sporadic DUX4 expression and oxidative stress which is at least partially induced by DUX4 protein. Nevertheless, targeting oxidative stress with antioxidants has a limited impact on FSHD patients, and the exact role of oxidative stress in the pathology of FSHD, as well as its interplay with the DUX4 expression, remain unclear. Here we set up a screen for genes that are upregulated by DUX4 via oxidative stress with the aim to target these genes rather than the oxidative stress itself. Immortalized human myoblasts expressing DUX4 (MB135-DUX4) have an increased level of reactive oxygen species (ROS) and exhibit differentiation defects which can be reduced by treating the cells with classic (Tempol) or mitochondria-targeted antioxidants (SkQ1). The transcriptome analysis of antioxidant-treated MB135 and MB135-DUX4 myoblasts allowed us to identify 200 genes with expression deregulated by DUX4 but normalized upon antioxidant treatment. Several of these genes, including PITX1, have been already associated with FSHD and/or muscle differentiation. We confirmed that PITX1 was indeed deregulated in MB135-DUX4 cells and primary FSHD myoblasts and revealed a redox component in PITX1 regulation. PITX1 silencing partially reversed the differentiation defects of MB135-DUX4 myoblasts. Our approach can be used to identify and target redox-dependent genes involved in human diseases.

•

Double homeobox transcription factor DUX4 misregulates hundreds of genes and induces oxidative stress in human myoblasts.

•

ROS, notably those of mitochondrial origin, contribute to the differentiation defects in myoblasts expressing DUX4.

•

A subset of genes is deregulated by DUX4 indirectly, via oxidative stress.

•

A strategy to identify the genes deregulated by DUX4 via oxidative stress was developed.

•

PITX1 is deregulated by DUX4 via oxidative stress and can be targeted to improve myogenesis in DUX4-expressing myoblasts.

Control of DUX4 Expression in Facioscapulohumeral Muscular Dystrophy and Cancer

DUX4, a gene encoding a transcription factor involved in early embryogenesis, is located within the D4Z4 subtelomeric repeat on chromosome 4q35. In most healthy somatic tissues, DUX4 is heavily repressed by multiple genetic and epigenetic mechanisms, and its aberrant expression is linked to facioscapulohumeral muscular dystrophy (FSHD) where it has been extensively studied. Recently, DUX4 expression has been implicated in oncogenesis, although this is much less explored. In this review, we discuss multiple levels of control of DUX4 expression, including enhancer-promoter interactions, DNA methylation, histone modifications, noncoding RNAs, and telomere positioning effect. We also connect disparate data on intrachromosomal contacts involving DUX4 and emphasize the feedback loops in DUX4 regulation. Finally, we bridge data on DUX4 in FSHD and cancer and discuss prospective approaches for future FSHD therapies and the potential outcomes of DUX4 inhibition in cancer.

Control of DNA integrity in skeletal muscle under physiological and pathological conditions

Skeletal muscle is a highly oxygen-consuming tissue that ensures body support and movement, as well as nutrient and temperature regulation. DNA damage induced by reactive oxygen species is present in muscles and tends to accumulate with age. Here, we present a summary of data obtained on DNA damage and its implication in muscle homeostasis, myogenic differentiation and neuromuscular disorders. Controlled and transient DNA damage appears to be essential for muscular homeostasis and differentiation while uncontrolled and chronic DNA damage negatively affects muscle health.

Genome- and Cell-Based Strategies in Therapy of Muscular Dystrophies

Muscular dystrophies are a group of heterogeneous genetic disorders characterized by progressive loss of skeletal muscle mass. Depending on the muscular dystrophy, the muscle weakness varies in degree of severity. The majority of myopathies are due to genetic events leading to a loss of function of key genes involved in muscle function. Although there is until now no curative treatment to stop the progression of most myopathies, a significant number of experimental gene- and cell-based strategies and approaches have been and are being tested in vitro and in animal models, aiming to restore gene function. Genome editing using programmable endonucleases is a powerful tool for modifying target genome sequences and has been extensively used over the last decade to correct in vitro genetic defects of many single-gene diseases. By inducing double-strand breaks (DSBs), the engineered endonucleases specifically target chosen sequences. These DSBs are spontaneously repaired either by homologous recombination in the presence of a sequence template, or by nonhomologous-end joining error prone repair. In this review, we highlight recent developments and challenges for genome-editing based strategies that hold great promise for muscular dystrophies and regenerative medicine.

DUX4-induced constitutive DNA damage and oxidative stress contribute to aberrant differentiation of myoblasts from FSHD patients

Facioscapulohumeral dystrophy (FSHD) is one of the three most common muscular dystrophies in the Western world, however, its etiology remains only partially understood. Here, we provide evidence of constitutive DNA damage in in vitro cultured myoblasts isolated from FSHD patients and demonstrate oxidative DNA damage implication in the differentiation of these cells into phenotypically-aberrant myotubes. Double homeobox 4 (DUX4), the major actor in FSHD pathology induced DNA damage accumulation when overexpressed in normal human myoblasts, and RNAi-mediated DUX4 inhibition reduced the level of DNA damage in FSHD myoblasts. Addition of tempol, a powerful antioxidant, to the culture medium of proliferating DUX4-transfected myoblasts and FSHD myoblasts reduced the level of DNA damage, suggesting that DNA alterations are mainly due to oxidative stress. Antioxidant treatment during the myogenic differentiation of FSHD myoblasts significantly reduced morphological defects in myotube formation. We propose that the induction of DNA damage is a novel function of the DUX4 protein affecting myogenic differentiation of FSHD myoblasts.

Facioscapulohumeral dystrophy myoblasts efficiently repair moderate levels of oxidative DNA damage

Facioscapulohumeral dystrophy (FSHD) is a progressive muscular dystrophy linked to a deletion of a subset of D4Z4 macrosatellite repeats accompanied by a chromatin relaxation of the D4Z4 array on chromosome 4q. In vitro, FSHD primary myoblasts show altered expression of oxidative-related genes and are more susceptible to oxidative stress. Double homeobox 4 (DUX4) gene, encoded within each D4Z4 unit, is normally transcriptionally silenced but is found aberrantly expressed in skeletal muscles of FSHD patients. Its expression leads to a deregulation of DUX4 target genes including those implicated in redox balance. Here, we assessed DNA repair efficiency of oxidative DNA damage in FSHD myoblasts and DUX4-transfected myoblasts. We have shown that the DNA repair activity is altered neither in FSHD myoblasts nor in immortalized human myoblasts transiently expressing DUX4. DNA damage caused by moderate doses of an oxidant is efficiently repaired while FSHD myoblasts exposed for 24 h to high levels of oxidative stress accumulated more DNA damage than normal myoblasts, suggesting that FSHD myoblasts remain more vulnerable to oxidative stress at high doses of oxidants.

Functional roles of HIV-1 Tat protein in the nucleus

Human immunodeficiency virus-1 (HIV-1) Tat protein is one of the most important regulatory proteins for viral gene expression in the host cell and can modulate different cellular processes. In addition, Tat is secreted by the infected cell and can be internalized by neighboring cells; therefore, it affects both infected and uninfected cells. Tat can modulate cellular processes by interacting with different cellular structures and signaling pathways. In the nucleus, Tat might be localized either in the nucleoplasm or the nucleolus depending on its concentration. Here we review the distinct functions of Tat in the nucleoplasm and the nucleolus in connection with viral infection and HIV-induced oncogenesis.

Does preoperative subscapularis fatty muscle infiltration really matter in anterosuperior rotator cuff tears repair outcomes? A prospective multicentric study

INTRODUCTION

Anterosuperior (AS) rotator cuff tear describes a combined tear of the subscapularis and the supraspinatus tendons. We hypothesized that results after AS tendon repairs might be influenced by the size of the subscapularis rupture and the preoperative subscapularis muscle fatty infiltration.

METHODS

A prospective multicentric study of 53 AS rotator cuff tears from five centers was performed (January 2008-January 2009). Subscapularis tendon retraction and fatty infiltration were assessed preoperatively. An ultrasonographic healing control was performed 1 year after surgery.

RESULTS

Patients were on average 60 years (range, 43-75 years) and were operated on average 16 months (range, 2-72 months) after the beginning of their symptoms. The incidence of AS tears was found to be 18%. Average follow-up was 15 months (range, 12-24). The Constant-Murley (CM) score for the patients with AS ruptures improved significantly from 49 points (range, 35-51 points) preoperatively to 73 points postoperatively (range, 50-95 points)(P=0.0205). CM score gains were 26 for Lafosse group 1 ruptures and 29 for Lafosse group 2 & 3 with pre- and postoperative P values at P<0.0000001 and P<0.000001, respectively. The last follow-up CM score according to the subscapularis fatty infiltration was 70 (range, 48-95) for groups 0-1, 70 (range, 56-87) for group 2, and 56 (range, 53-88) for groups 3-4 with pre- and postoperative P values at P<0.001, P<0.001, and P<0.004, respectively. The global retear rate was 6%.

DISCUSSION

Our study showed that the CM score after repairs of AS rotator cuff tears was lower in advanced subscapularis fatty infiltration. However, gains in CM scores were similar whatever the initial subscapularis fatty infiltration. The rate of tendon healing was correlated with subscapularis fatty infiltration. Subscapularis tendon rupture size was not significantly correlated with outcomes.

LEVEL OF EVIDENCE

Level III.

[Allograft-prosthesis composite arthroplasty for posttraumatic floating elbow]

Loss of bone stock in the elbow joint raises serious problems for reconstruction surgery. Total allograft-prosthesis composite arthroplasty is an attractive alternative to revision prosthesis and isolated osteoarticular allografts known to have many drawbacks. Use of this method is rather recent for revision procedures and tumor surgery and posttraumatic cases are rare (five reported cases). We report a case of posttraumatic floating elbow treated with this technique. At 75 months follow-up, the clinical result was excellent with the Mayo Clinic performance score at 100/100. Allograft-native bone fusion was complete and there were no complications, particularly no loosening. This composite technique is particularly well adapted for patients with major bone and joint loss. It can avoid the specific problems associated with each of the techniques used alone. The allograft reconstructs bone stock while the prosthetic component avoids the clinical expression of graft epiphyseal lysis.

Évaluation de la sensibilité à la lévofloxacine des souches isolées d'infections urinaires basses communautaires

The aim of this study was to evaluate the in vitro activity of levofloxacin (LVX) in comparison to nalidixic acid (NAL), ofloxacin (OFX), norfloxacin (NOR), amoxicillin (AMX), cefixime (CFM), cotrimoxazole (SXT) and nitrofurantoin (FT), against 402 strains recently isolated from urine specimens in outpatient women suffering from lower urinary tract infections for which short-term treatment was not indicated. MICs were determined by the agar dilution method on Mueller-Hinton medium (Bio-Rad) according to the recommendations of the Comite de l'Antibiogramme de la Societe Francaise de Microbiologie (CA-SFM). Strains were classified as susceptible (S), intermediate (I) or resistant (R) according to the CA-SFM recommended breakpoints. Quality control was carried out using three reference strains: Escherichia coli ATCC 25922, Staphylococcus aureus ATCC 25923 and Pseudomonas aeruginosa ATCC 27853. For E. coli, the most prevalent species (345 isolates: 85.3%), susceptibilities were as follows: AMX: 60.6%, CFM: 99.1%, NAL: 94.8%, NOR: 97.4%, OFX: 97.4%, LVX: 97.4%, SXT: 84.5%, FT: 98%. This study confirms the good in vitro activity of LVX, OFX, and CFM against strains isolated from urinary tract infections in the community and particularly against E. coli, which is by far the most prevalent pathogen, 90% of strains, with more than 97% of strains being susceptible.

[In vitro activity of the pristinamycin against the isolated staphylococci in the french hospitals in 1999-2000]

One thousand six hundred and fifty clinically significant, consecutive and non redundant strains of staphylococci, including 863 Staphylococcus aureus and 787 coagulase negative staphylococci (CNS), were isolated between October 1999 and March 2000 in 35 French hospital laboratories. Susceptibilities were determined in each center by a standard diffusion method according to the recommendations of CA-SFM. Strains with vancomycin zone size diameter <17 mm were sent to the central laboratory for MIC determination of vancomycin by agar dilution, as recommended by the CA-CSFM. Frequencies of resistance to oxacillin were 38.6% for S. aureus (MRSA), 54% for the CNS, all species and 62% for S. epidermidis, respectively. The antibiotics tested showed a good activity against strains of S. aureus susceptible to oxacillin, more than 95% of strains being susceptible except for erythromycin (82.6%). Against MRSA, vancomycin and prisitinamycin had the highest rates of susceptible strains, greater than 93% for the later antibiotic. More than 92% of strains of CNS susceptible or resistant to oxacillin were sensitive to pristinamycin. Pristinamycin displayed a good activity whether the strains were constitutively or inducibly resistant to MLS(B). It comes out from this in vitro study that the rate of resistance of staphylococci to pristinamycin remains weak and stable in France. Pristinamycin is a good alternative for oral treatment of staphylococcal infections.

[Developmental lumbar stenosis in eleven French Antilles patients]

PURPOSE OF THE STUDY

Developmental lumbar stenosis is a rare entity, exceptionally described in the literature. No study has been directly devoted to this condition. The purpose of the present study was to examine specific features, particularly clinical and anatomic expression, observed in a series of operated patients.

MATERIAL AND METHODS

Eleven patients from the French Antilles were treated for developmental lumbar stenosis between 1996 and 2000. The Verbiest criteria were used to define canal narrowness. Signs of degeneration and presence of discal herniation were exclusion criteria. Epidemiological and clinical data were collected for the 11 patients. The degree of sagittal stenosis (fixed diameter at the bone level and mobile diameter at the discal level) was measured on computed tomography images. Transverse stenosis was determined by measuring the interpedicular and interapophyseal distances. Lateral stenosis was determined by measuring the depth of the recessus.

RESULTS

These patients were young (mean age 42.4 years). Most of the clinical signs were monoradicular. Discal level stenosis predominated, generally at level L4-L5. It was generally central and lateral, sagittal and transverse. The interpedicular distance was the only diameter that remained within normal limits. Soft tissues (yellow ligaments and joint capsules) played an important role in the stenosis.

DISCUSSION

The rare reports of developmental lumbar stenosis describe decompensated stenosis due to discal herniation in the adolescent. Developmental lumbar stenosis is considered to be a genetic disease and its particular high frequency in the French Antilles favors this hypothesis. The stenosis results from bony (short pedicles, hypertrophic lateral masses) and ligament (hypertrophy of the yellow ligament and joint capsules) structures.

CONCLUSION

Developmental lumbar stenosis produces a global (sagittal, transverse, central, lateral) narrowing of the lumbar canal where soft tissue structures apparently play a greater role than usually thought. A prospective study examining the impact of ethnic origin is required to analyze the genetic hypothesis.

Susceptibility of Enterobacteriaceae to beta-lactam agents and fluoroquinolones: a 3-year survey in France

OBJECTIVE

To assess trends in the susceptibility to beta-lactam agents and to fluoroquinolones of clinically relevant Enterobacteriaceae isolated over a 3-year period in 14 French hospital laboratories.

METHODS

During the second quarter of 1996, 1997 and 1998, 180 consecutive non-duplicate isolates of Enterobacteriaceae were collected in each center. Sixteen beta-lactams and four quinolones were tested by the disk diffusion method. In addition, the double-disk synergy test was used to screen for the production of extended-spectrum beta-lactamase (ESBL).

RESULTS

Totals of 2507, 2312 and 2506 clinical isolates were obtained in each period, respectively. The distribution of Enterobacteriaceae species according to clinical specimens and wards was similar in each study period. No significant variation in the susceptibility rates to beta-lactams and fluoroquinolones was observed, except in Klebsiella pneumoniae and Enterobacter aerogenes. The prevalence of ESBL-producing isolates decreased from 18% to 9% in the former, while it increased from 32% to 54% in the latter. At the same time, the susceptibility to ofloxacin and pefloxacin increased for K. pneumoniae (P < 0.003) and cephalosporinase-producing species (P < 0.05), except Enterobacter spp.

CONCLUSION

Over the 3-year study period beta-lactams and fluoroquinolones remained highly active against Enterobacteriaceae clinical isolates, with the exception of E. aerogenes, probably as a result of the dissemination of multiresistant clones in French hospitals.

[Associated fracture of the posteromedial tubercle and the lateral process of the talus: a case report. Contribution of computed tomography]

PURPOSE OF THE STUDY

Fracture of lateral process of the talus is an uncommon injury, fracture of the posteromedial tubercle of the talus is quite rare, and association of the two lesions is not reported previously. We report a case of an associated fracture of posteromedial tubercle an lateral process of the talus.

PATIENT AND METHODS

The mechanism of injury was forced ankle dorsiflexion and pronation, this mechanism was responsible of an avulsion of the posteromedial tubercle by the postero talotibial ligament and a fracture of lateral process by compression between the lateral malleolus and the calcaneus.

RESULTS

Conventional radiographs permitted the diagnosis of the lateral process fracture but the fracture of the posteromedial tubercle was showed only on CT scans.

DISCUSSION

The fracture of the posteromedial tubercle was treated by internal fixation, through a posteromedial approach. At 12 months follow-up the patient was able to walk without pain and radiographic result was excellent (no avascular necrosis of the tubercle and no Arthrosis of subtalar joint).

[Elastic intramedullary nailing of the tibia with the Marchetti-Vicenzi nail. 43 treated cases]

PURPOSE OF THE STUDY

The purpose of this study was to analyse the results of tibial intramedullary nailing using an unreamed "Universal Elastic Bundle Nail".

MATERIAL AND METHODS

Forty-three intramedullary nailing of tibial shaft were done in 43 patients with recents fractures, from May 1993 and May 1996. There were 36 males and 7 females. The average age was 31.5 years (range 17-68 years). Thirty-three were injured in a traffic accident (20 motorcycles, 5 pedestrians and 8 car passengers), seven were injured in a home accident (fall) and three had a sport injury. There were 13 open fractures according to Gustilo: 5 grade I, 7 grade II and one grade III B. Eight fractures involved the proximal metaphyseal part of the tibia, 16 the distal metaphyseal part and 14 the tibial shaft; in five cases there were segmental fractures. According to AO classification there were: 10 fractures type A, 24 fractures type B and 9 fractures type C (5 segmental fractures). In 5 cases there were associated femoral fractures: three ipsilaterals and two controlaterals. All were treated in the same time: four by UEBN device and one by AO's nail. All the patients with type B and C fractures were positioned on a Maquet table with a boot traction or transcalcaneal pin traction (in the distal fractures). The nail was introduced after closed reduction through a vertical transpatellar tendon incision, without reaming procedure.

RESULTS

Forty one fractures healed after an average time of 96 days (60-120). In 11 open fractures bone union occurred after 98 days (85-120). The distal fractures healed after a mean time of 86 days (60-120), proximal fractures in 123 days and mid shaft fractures in 98 days. In type A fractures bone union occurred after an average time of 68 days, while bone union occurred after a mean time of 100 days in type B and C fractures. Two patients with an open proximal type B fracture, had a delayed union: both healed after proximal screws removal. Two fractures healed with a valgus angulaton 5 degrees and 10 degrees. No infection, no loss of reduction and no bundle migration has been noted.

DISCUSSION

The Marchetti-Vicenzi's nail (UEBN) permitted a stable fixation in tibial fractures. The use of this unreamed nailing coupled with an automatic distal locking in the metaphyseal cancellous bone, reduced operative time and shortened X Ray's radiation exposure. At the follow-up fracture healing occurred in 41 cases 95.3 p. 100 at four months. Two delayed union occurred after four months, the two cases were open fractures grade II. All the two cases healed after secondary procedure without any loss of function. Malunion occurred in two patients (in only one case there was a major valgus angulation 10 degrees), the two cases were related to technical error. We had no cases of infection or leg shortening or bundle migration in the ankle joint.

CONCLUSION

We believe that Universal Elastic Bundle Nail allows a stable and safety fixation in open or closed tibial fractures without pseudarthrosis and without infection (in our series).

[Reconstruction of a complex defect of the upper third of the humerus by pedicle transplant of the lateral edge of the scapula. A case report]

Vascularized bone transfer of the lateral border of the scapula is exceptionally used in orthopaedic surgery. The authors report a case of pedicle transfer of the lateral border of the scapula designed to reconstruct a nine centimetre bone defect of the upper third of the humerus following a gunshot wound. A complementary conventional bone graft was performed one month later and consolidation was achieved at the fourth month.

New susceptibility locus for rheumatoid arthritis suggested by a genome-wide linkage study

Rheumatoid arthritis (RA), the most common autoimmune disease, is associated in families with other autoimmune diseases, including insulin-dependent diabetes mellitus (IDDM). Its genetic component has been suggested by familial aggregation (lambdas = 5), twin studies, and segregation analysis. HLA, which is the only susceptibility locus known, has been estimated to account for one-third of this component. The aim of this paper was to identify new RA loci. A genome scan was performed with 114 European Caucasian RA sib pairs from 97 nuclear families. Linkage was significant only for HLA (P < 2.5.10(-5)) and nominal for 19 markers in 14 other regions (P < 0.05). Four of the loci implicated in IDDM potentially overlap with these regions: the putative IDDM6, IDDM9, IDDM13, and DXS998 loci. The first two of these candidate regions, defined in the RA genome scan by the markers D18S68-D18S61-D18S469 (18q22-23) and D3S1267 (3q13), respectively, were studied in 194 additional RA sib pairs from 164 nuclear families. Support for linkage to chromosome 3 only was extended significantly (P = 0.002). The analysis of all 261 families provided a linkage evidence of P = 0. 001 and suggested an interaction between this putative RA locus and HLA. This locus could account for 16% of the genetic component of RA. Candidate genes include those coding for CD80 and CD86, molecules involved in antigen-specific T cell recognition. In conclusion, this first genome scan in RA Caucasian families revealed 14 candidate regions, one of which was supported further by the study of a second set of families.

Genome search in celiac disease

Celiac disease (CD), a malabsorption disorder of the small intestine, results from ingestion of gluten. The HLA risk factors involved in CD are well known but do not explain the entire genetic susceptibility. To determine the localization of other genetic risk factors, a systematic screening of the genome has been undertaken. The typing information of 281 markers on 110 affected sib pairs and their parents was used to test linkage. Systematic linkage analysis was first performed on 39 pairs in which both sibs had a symptomatic form of CD. Replication of the regions of interest was then carried out on 71 pairs in which one sib had a symptomatic form and the other a silent form of CD. In addition to the HLA loci, our study suggests that a risk factor in 5qter is involved in both forms of CD (symptomatic and silent). Furthermore, a factor on 11qter possibly differentiates the two forms. In contrast, none of the regions recently published was confirmed by the present screening.

European Gene Mapping Project (EUROGEM): breakpoint panels for human chromosomes based on the CEPH reference families. Centre d'Etude du Polymorphisme Humain

Meiotic breakpoint panels for human chromosomes 2, 3, 4, 5, 6, 7, 8, 9, 10, 13, 14, 15, 17, 18, 20 and X were constructed from genotypes from the CEPH reference families. Each recombinant chromosome included has a breakpoint well-supported with reference to defined quantitative criteria. The panels were constructed at both a low-resolution, useful for a first-pass localization, and high-resolution, for a more precise placement. The availability of such panels will reduce the number of genotyping experiments necessary to order new polymorphisms with respect to existing genetic markers. This paper shows only a representative sample of the breakpoints detected. The complete data are available on the World Wide Web (URL http:/(/)www.icnet.uk/axp/hgr/eurogem++ +/HTML/data.html) or by anonymous ftp (ftp.gene.ucl.ac.uk in/pub/eurogem/maps/breakpoints).

A comprehensive genetic map of the human genome based on 5,264 microsatellites

The great increase in successful linkage studies in a number of higher eukaryotes during recent years has essentially resulted from major improvements in reference genetic linkage maps, which at present consist of short tandem repeat polymorphisms of simple sequences or microsatellites. We report here the last version of the Généthon human linkage map. This map consists of 5,264 short tandem (AC/TG)n repeat polymorphisms with a mean heterozygosity of 70%. The map spans a sex-averaged genetic distance of 3,699 cM and comprises 2,335 positions, of which 2,032 could be ordered with an odds ratio of at least 1,000:1 against alternative orders. The average interval size is 1.6 cM; 59% of the map is covered by intervals of 2 cM at most and 1% remains in intervals above 10 cM.

A radiation hybrid map of the human genome

We have developed a panel of whole-genome radiation hybrids by fusing irradiated diploid human fibroblasts with recipient hamster cells. This panel of 168 cell lines has been typed with microsatellite markers of known genetic location. Of 711 AFM genetic markers 404 were selected to construct a robust framework map that spans all the autosomes and the X chromosome. To demonstrate the utility of the panel, 374 expressed sequence tags (ESTs) previously assigned to chromosomes 1, 2, 14 and 16 were localized on this map. All of these ESTs could be positioned by pairwise linkage to one of the framework markers with a LOD score of greater than 8. The whole genome radiation hybrid panel described here has been used as the starting material for the Genebridge4 panel that is being made widely available for genome mapping projects.

An STS-based map of the human genome

A physical map has been constructed of the human genome containing 15,086 sequence-tagged sites (STSs), with an average spacing of 199 kilobases. The project involved assembly of a radiation hybrid map of the human genome containing 6193 loci and incorporated a genetic linkage map of the human genome containing 5264 loci. This information was combined with the results of STS-content screening of 10,850 loci against a yeast artificial chromosome library to produce an integrated map, anchored by the radiation hybrid and genetic maps. The map provides radiation hybrid coverage of 99 percent and physical coverage of 94 percent of the human genome. The map also represents an early step in an international project to generate a transcript map of the human genome, with more than 3235 expressed sequences localized. The STSs in the map provide a scaffold for initiating large-scale sequencing of the human genome.

Lack of additive effect between mechanisms of resistance to carbapenems and other beta-lactam agents in Pseudomonas aeruginosa

Eighty-nine clinical isolates resistant (n = 61) or susceptible (n = 28) to imipenem and exhibiting the main patterns of susceptibility to other beta-lactam agents (wild type pattern, penicillinase pattern, constitutive cephalosporinase pattern) were studied in order to investigate (i) the mechanism of resistance involved and (ii) whether resistance to carbapenems affects the level of resistance to other beta-lactam agents and, conversely, if resistance to other beta-lactam agents affects the level of resistance to carbapenems. For this purpose, the presence of OprD protein in the cell wall was detected by Western blot and beta-lactamase activity by spectrophotometric assay and isoelectric focusing. OprD expression was not detectable in the imipenem-resistant (MIC > or = 16 micrograms/ml) strains. It was decreased in half the strains for which MICs of imipenem were 2 to 8 micrograms/ml and was close to a normal level in the most susceptible strains (MIC < or = 1 microgram/ml), thus demonstrating a direct correlation between the level of susceptibility to imipenem and the level of OprD expression. No imipenemase activity was detected in imipenem-resistant strains. Synergy between imipenem or meropenem and BRL 42715 was observed for all of the strains, demonstrating the role of cephalosporinase in carbapenem resistance. Within each pattern of susceptibility, the mean MICs of beta-lactam agents other than carbapenems were similar, whether the strains were susceptible or resistant to imipenem. Conversely, the mean MICs of imipenem or meropenem for either the imipenem-resistant or the imipenem-susceptible strains were similar, regardless of the susceptibility of these strains to the other beta-lactam agents. Thus, when several mechanisms of resistance to beta-lactam agents are present in the same strain of Pseudomonas aeruginosa, there is no additive effect between these mechanisms.

Role of mutations in DNA gyrase genes in ciprofloxacin resistance of Pseudomonas aeruginosa susceptible or resistant to imipenem

In Pseudomonas aeruginosa, resistance to imipenem is mainly related to a lack of protein OprD and resistance to fluoroquinolones is mainly related to alterations in DNA gyrase. However, strains cross resistant to fluoroquinolones and imipenem have been selected in vitro and in vivo with fluoroquinolones. We investigated the mechanisms of resistance to fluoroquinolones in 30 clinical strains of P. aeruginosa resistant to ciprofloxacin (mean MIC, >8 micrograms/ml), 20 of which were also resistant to imipenem (mean MIC, >16 micrograms/ml). By immunoblotting, OprD levels were markedly decreased in all of the imipenem-resistant strains. Plasmids carrying the wild-type gyrA gene (pPAW207) or gyrB gene (pPBW801) of Escherichia coli were introduced into each strain by transformation. MICs of imipenem did not change after transformation, whereas those of ciprofloxacin and sparfloxacin dramatically decreased (25- to 70-fold) for all of the strains. For 28 of them (8 susceptible and 20 resistant to imipenem), complementation was obtained with pPAW207 but not with pPBW801. After complementation, the geometric mean MICs of ciprofloxacin and sparfloxacin (MICs of 0.3 microgram/ml and 0.5 microgram/ml, respectively) were as low as those for wild-type strains. Complementation was obtained only with pPBW801 for one strain and with pPAW207 and pPBW801 for one strain highly resistant to fluoroquinolones. These results demonstrate that in clinical practice, gyrA mutations are the major mechanism of resistance to fluoroquinolones even in the strains of P. aeruginosa resistant to imipenem and lacking OprD, concomitant resistance to these drugs being the result of the addition of at least two independent mechanisms.

[Treatment of posterior cruciate ligament rupture and recent knee dislocations by olecranisation of the patella without surgical repair]

Olecranisation of the patella was described and first used by Grammont (1984) to maintain reduction of the knee joint after posterior cruciate repair and reconstruction. Since 1985 we used this technique in 18 acute posterior ruptures and knee dislocations which did not undergo surgery. Knee laxity is assessed under general anaesthesia with radiographic control. A 4 or 5 mm. Steinmann pin is introduced medially at the top of the patella and drilled vertically through the bone to continue behind the patella tendon. After reduction of the posterior drawer, the pin is passed into the anterior part of the tibia. Full mobility between 0 degrees and 90 degrees is maintained. Physiotherapy started immediately and early weight bearing is allowed with a posterior splint. Olecranisation prevents posterior subluxation of the tibia and gives an anterior tibial subluxation force which is minor in flexion but major in extension. We followed up our patients for 1 to 8 years. The latest testing with radiographs demonstrate posterior drawer but all patients report good results. Early physiotherapy avoids stiffness, amyotrophy, and reflex sympathetic dystrophy. Olecranisation appears to give similar results more quickly and with fewer complications than P. C. L. surgery.

The 1993-94 Généthon human genetic linkage map

In 1992, we described a second-generation genetic linkage map of the human genome. Using 1,267 new microsatellite markers, we now present a new genetic linkage map containing a total of 2,066 (AC)n short tandem repeats, 60% of which show a heterozygosity of over 0.7. Statistical linkage analysis based on the genotyping of eight large CEPH families placed these markers in the 23 linkage groups. The map includes 1,266 intervals and spans a total distance of 3690 centiMorgans (cM). A total of 1,041 markers could be ordered with odds ratios greater than 1000:1. About 56% of this map is at a distance of 1 cM or less from one of its markers.

The genetic locus for free sialic acid storage disease maps to the long arm of chromosome 6

Salla disease (SD), or adult-type free sialic acid storage disease, is an autosomal recessive lysosomal storage disorder characterized by impaired transport of free sialic acid across the lysosomal membrane and severe psychomotor retardation. Random linkage analysis of a sample of 27 Finnish families allowed us to localize the SD locus to the long arm of chromosome 6. The highest lod score of 8.95 was obtained with a microsatellite marker of locus D6S286 at theta = .00. Evidence for linkage disequilibrium was observed between the SD locus and the alleles of three closely linked markers, suggesting that the length of the critical region for the SD locus is in the order of 190 kb.

An index marker map of chromosome 9 provides strong evidence for positive interference

An index marker map of chromosome 9 has been constructed using the Centre d'Etude du Polymorphisme Humain reference pedigrees. The map comprises 26 markers, with a maximum intermarker interval of 13.1 cM and only two intervals > 10 cM. Placement of all but one marker into the map was achieved with > 10,000:1 odds. The sex-equal length is 151 cM, with male length of 121 cM and female length of 185 cM. The map extends to within 2%-3% of physical length at the telomeres, and its coverage therefore is expected to be within 20-30 cM of full map length. The markers are all of the GT/CA repeat type and have average heterozygosity .77, with a range of .60-.89. The map shows both marked contraction of genetic distance relative to physical distance in the pericentromeric region and expansion in the telomeric regions. Genotypic data were carefully examined for errors by using the crossover routine of the program DATAMAN. Five new mutations were observed among 17,316 meiotic events examined. There were two double-crossover events occurring within an interval of 0-10 cM, and another eight were observed within an interval of 10-20 cM. Many of these could be due to additional mutational events in which one parental allele converted to the other by either gene conversion or random strand slippage. When there was no correction for these possible mutational events, the number of crossovers displayed by the maternal and paternal chromosomes was significantly different (P < .001) from that predicted by the Poisson distribution, which would be expected in the absence of interference. In addition, the observed crossover distribution for paternally derived chromosomes was similar to that predicted from cytogenetic chiasma frequency observations. In all, the data strongly support the occurrence of strong positive interference on human chromosome 9 and suggest that flanking markers at an interval of < or = 20 cM are generally sufficient for disease gene inheritance predictions in presymptomatic genetic counseling by linkage analysis.

Localization of Friedreich ataxia phenotype with selective vitamin E deficiency to chromosome 8q by homozygosity mapping

Friedreich ataxia and ataxia with selective vitamin E deficiency (AVED) share very similar clinical phenotypes. We have mapped the AVED locus to proximal 8q with only three large consanguinous Tunisian families, representing to our knowledge the first use of homozygosity mapping for primary linkage analysis. Subsequently, three additional families showed linkage with the same markers. A maximum lod score of 17.9 was obtained at theta = 0 for the haplotype D8S260-D8S510, consisting of the two closest markers. With only 6 families, the AVED locus is therefore mapped precisely as illustrated by the lod-1 confidence interval of 2.4 cM on either side of D8S260-D8S510. Isolation of a yeast artificial chromosome contig > 800 kilobases (kb) showed that D8S260 and D8S510 are less than 400 kb apart.

A second-generation linkage map of the human genome

A linkage map of the human genome has been constructed based on the segregation analysis of 814 newly characterized polymorphic loci containing short tracts of (C-A)n repeats in a panel of DNAs from eight large families. Statistical linkage analysis placed 813 of the markers into 23 linkage groups corresponding to the 22 autosomes and the X chromosome; 605 show a heterozygosity above 0.7 and 553 could be ordered with odds ratios above 1,000:1. The distance spanned corresponds to approximately 90% of the estimated length of the human genome.