Cytogenetic and molecular analysis of a de novo tandem duplication of chromosome 21

Summary We have characterised by cytogenetic and molecular analysis a de novo tandem duplication of chromosome 21. High resolution chromosome examination of lymphocytes revealed the following karyotype in 90% of the cells: 46,XY,dir dup (21)(pterq22.300::q11.205 qter). Of these cells, 10% showed a normal karyotype. Gene dosage of chromosome 21 sequences by a slot blot method indicated that the duplication extends from D21S16 to D21S55. In situ hybridization with probes close to the borders of the duplicated segment confirmed the gene dosage data and gave results consistent with a true tandem duplication of chromosome 21. Pulsed field gel electrophoresis of the patient's DNA showed an abnormal restriction band common to D21S55 and D21S16, confirming that the junction point between the two homologous parts of the tandem chromosome brings these two sequences into proximity. Restriction fragment length polymorphism analysis indicated that the abnormal chromosome was maternal in origin and that the rearrangement of chromosome 21 could not have occurred at a post-zygotic stage of development but resulted from a recombination event during maternal gametogenesis. The possible mechanisms of formation of the abnormal chromosome are discussed, as is the presence of cells with normal chromosomes 21, in the patient.     

Implications for the cis-requirements for Ds transposition based on the sequence of the wxB4 Ds element

Summary The nucleotide sequence of the 1494 by wxB4 Ds element is presented. A comparison with previously characterized Ds elements reveals several novel features. This element has less Ac terminal sequence than other Ac-like Ds elements. The left terminus contains 398 by of Ac sequence interrupted by a transposon-like DNA insertion, leaving only 317 by of contiguous Ac sequence. The right terminus has 259 by of Ac terminal sequence. The interior of the element contains sequences not found in other cloned members of the Ac/Ds family. We suggest that the role of this non-Ac DNA is to separate the Ac termini by a minimum distance and may be a cis requirement for Ds transposition in maize.Abbreviations Ac activator - Adh1 alcohol dehydrogenase 1 - Ds dissociation - RFLP restriction fragment length polymorphism - Spm suppressor mutator - Wx waxy     

No significant effect of monosomy for distal 21q22.3 on the Down syndrome phenotype in “Mirror” duplications of chromosome 21

Three Down syndrome patients for whom karyotypic analysis showed a "mirror" (reverse tandem) duplication of chromosome 21 were studied by phenotypic, cytogenetic, and molecular methods. On high-resolution R-banding analysis performed in two cases, the size of the fusion 21q22.3 band was apparently less than twice the size of the normal 21q22.3, suggesting a partial deletion of distal 21q. The evaluation of eight chromosome 21 single-copy sequences of the 21q22 region--namely, SOD1, D21S15, D21S42, CRYA1, PFKL, CD18, COL6A1, and S100B--by a slot blot method showed in all three cases a partial deletion of 21q22.3 and partial monosomy. The translocation breakpoints were different in each patient, and in two cases the rearranged chromosome was found to be asymmetrical. The molecular definition of the monosomy 21 in each patient was, respectively, COL6A1-S100B, CD18-S100B, and PFKL-S100B. DNA polymorphism analysis indicated in all cases a homozygosity of the duplicated material. The duplicated region was maternal in two patients and paternal in one patient. These data suggest that the reverse tandem chromosomes did not result from a telomeric fusion between chromosomes 21 but from a translocation between sister chromatids. The phenotypes of these patients did not differ significantly from that of individuals with full trisomy 21, except in one case with large ears with an unfolded helix. The fact that monosomy of distal 21q22.3 in these patients resulted in a phenotype very similar to Down syndrome suggests that the duplication of the genes located in this part of chromosome 21 is not necessary for the pathogenesis of the Down syndrome features observed in these patients, including most of the facial and hand features, muscular hypotonia, cardiopathy of the Fallot tetralogy type, and part of the mental retardation.     

Cytologie Comparée de l'espèce Parthénogénétique Luffia ferchaultella Steph. et de L'espèce bisexuée L. Lapidella goeze (Lepidoptera,Psychidae)

Summary The cytology of two species of Luffia has been studied. The first one, L. lapidella, is bisexual, the second one, L. ferchaultella, parthenogenetic and derived from the first. In both species the females have a diploid number of 61 chromosomes. The male of lapidella has 62 chromosomes.The development of the fertilized egg of L. lapidella does not show any noticeable peculiarity other than the slow rate of the first meiotic division.The meiotic divisions of the parthenogenetic egg of L. ferchaultella begin normally as in lapidella but are interrupted either at the end of anaphase I or at metaphase II or anywhere between these two stages. Through various procedures the two haploid plates reunite to form a new metaphase spindle, which carries out a normal though diploid second meiotic division. The restoration of the diploid number happens therefore by means of the fusion of the first polar body with the nucleus of the oocyte II. The different procedures which lead to it have been studied and their variability examined in connection with the environment, the morphological types of the females and the geographical distribution of the species.

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Cytologie Comparée de l'espèce Parthénogénétique Luffia ferchaultella Steph. et de L'espèce bisexuée L. Lapidella goeze (Lepidoptera, Psychidae)

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Travail subventionné par le Fonds National Suisse de la Recherche Scientifique.     

The association between birth weight and visceral fat in middle-age adults

Objective: Low birth weight, a proxy for fetal underdevelopment, is associated with increased risk of developing type 2 diabetes during adulthood. Low birth weight is also associated with central obesity, but little is known about the association between birth weight and visceral adiposity. The purpose of this study is to test the hypothesis that lower birth weight is associated with increased amounts of visceral fat in middle‐age adults. Research Methods and Procedures: This is an observational study of 91 adults (58 men and 33 women) 40 ± 6 years of age (mean ± standard deviation). Ethnicity was either Japanese American (79%) or non‐Hispanic white (21%). Birth weight was obtained from State Departments of Health. Measurements included smoking status, BMI, and visceral (intra‐abdominal) fat measured by computed tomography. Results: Visceral fat was not associated with birth weight after adjustment for age, sex, ethnicity, BMI, or smoking status (p = 0.76). There was no evidence that the association between birth weight and visceral fat varied by age, sex, or ethnicity. Discussion: We found no evidence that low birth weight is associated with increased visceral fat in middle‐age adults     

Are powerful females powerful enough? Acceleration in gravid green iguanas (Iguana iguana)

One demand placed exclusively on the musculoskeletal systemof females is maintaining locomotor performance with an increasingload over the reproductive cycle. Here, we examine whether gravid(i.e., "pregnant") iguanas can increase their force and powerproduction to support, stabilize, and accelerate the additionalmass of a clutch of eggs. At any acceleration, gravid iguanasproduced very high mechanical power (average total power = 673w/kg; total peak power = 1175 w/kg). While the increase in totalpower was partly a result of greater propulsive power (averagepropulsive power = 25% higher, peak propulsive power = 38% higher),increased vertical power (roughly 200% increase) was the maincontributor. Gravid iguanas were also able to increase peakforces (propulsive = 23%, mediolateral = 44%, vertical = 42%),and step duration (44%) resulting in greater impulses (i.e.,the sum of force produced during a step) to accelerate, balance,and support their increased mass. The increase in step durationand smaller increase in peak propulsive force suggests thatgravid iguanas may be force-limited in the direction of motion.We discuss how biomechanical constraints due to females’reproductive role may influence the evolution of the femalemusculoskeletal systems and contribute to the evolution andmaintenance of ecological dimorphism in lizards.     

Structure of a novel enzyme that catalyzes acyl transfer to alcohols in aqueous conditions

The unusual architecture of the enzyme (MsAcT) isolated from Mycobacterium smegmatis forms the mechanistic basis for favoring alcoholysis over hydrolysis in water. Unlike hydrolases that perform alcoholysis only under anhydrous conditions, MsAcT demonstrates alcoholysis in substantially aqueous media and, in the presence of hydrogen peroxide, has a perhydrolysis:hydrolysis ratio 50-fold greater than that of the best lipase tested. The crystal structures of the apoenzyme and an inhibitor-bound form have been determined to 1.5 A resolution. MsAcT is an octamer in the asymmetric unit and forms a tightly associated aggregate in solution. Relative to other structurally similar monomers, MsAcT contains several insertions that contribute to the oligomerization and greatly restrict the shape of the active site, thereby limiting its accessibility. These properties create an environment by which MsAcT can catalyze transesterification reactions in an aqueous medium and suggests how a serine hydrolase can be engineered to be an efficient acyltransferase.     

A novel in vitro three-dimensional skeletal muscle model

A novel three-dimensional (3D) skeletal muscle model composed of C2C12 mouse myoblasts is described. This model was generated by cultivating myoblasts in suspension using the rotary cell culture system (RCCS), a unique culture environment. Single-cell suspensions of myoblasts were seeded at 5 × 10⁵/ml in growth medium without exogenous support structures or substrates. Cell aggregation occurred in both RCCS and suspension control (SC) conditions within 12 h but occurred more rapidly in the SC at all time intervals examined. RCCS-cultured myoblasts fused and differentiated into a 3D construct without serum deprivation or alterations. Syncitia were quantified at 3 and 6+ d in stained thin sections. A significantly greater number of syncitia was found at 6+ d in the RCCS cultures compared to the SC. The majority of syncitia were localized to the periphery of the cell constructs for all treatments. The expression of sarcomeric myosin heavy chain (MHC) was localized at or near the periphery of the 3D construct. The majority of MHC was associated with the large cells (syncitia) of the 6+-d aggregates. These results show, for the first time, that myoblasts form syncitia and express MHC in the presence of growth factors and without the use of exogenous supports or substrates. This model test system is useful for investigating initial cell binding, myoblast fusion and syncitia formation, and differentiation processes.