Phenotypic conversion leads to structural and functional changes of smooth muscle sarcolemma

Continuous changes in the length of smooth muscles require a highly organized sarcolemmal structure. Yet, smooth muscle cells also adapt rapidly to altered environmental cues. Their sarcolemmal plasticity must lead to profound changes which affect transmembrane signal transduction as well as contractility. We have established porcine vascular and human visceral smooth muscle cultures of epithelioid and spindle-shaped morphology and determined their plasma membrane properties. Epithelioid cells from both sources contain a higher ratio of cholesterol to glycerophospholipids, and express a less diverse range of lipid-associated annexins. These findings point to a reduction in efficiency of membrane segregation in epithelioid cells. Moreover, compared to spindle-shaped cells, cholesterol is more readily extracted from epithelioid cells with methyl-beta-cyclodextrin and its synthesis is more susceptible to inhibition with lovastatin. The inability of epithelioid cells to process vasoactive metabolites, such as angiotensin or nucleotides further indicates that contractile properties are impaired. Phenotypic plasticity extends beyond the loss of smooth muscle cell marker genes. The plasma membrane has undergone profound functional changes which are incompatible with cyclic foreshortening, but might be important in the development of vascular disease.

Becker muscular dystrophy with marked divergence between clinical and molecular genetic findings: case series

Both Duchenne muscular dystrophy (DMD) and Becker muscular dystrophy (BMD) are caused by mutations of the X-linked dystrophin gene. BMD patients are less affected clinically than DMD patients. We present five patients with a diagnosis of BMD. First, two identical twins, with a deletion of exon 48 of the dystrophin gene, who experienced prominent muscle cramps from the age of three. The histopathological examination of muscle biopsies of these two twins revealed only very slight muscle fiber alterations. Second, two brothers who displayed marked, unusual intrafamilial variability of the clinical picture as well as showing a new point mutation in the dystrophin gene. And finally, a fifth boy who displayed a new point mutation in the dystrophin gene. Although he was clinically asymptomatic at the age of 15 and muscle biopsy only showed very minor myopathic signs, serum Creatine Kinase (CK) levels had been considerably elevated for years. Taken together, these cases add to the spectrum of marked discrepancies in clinical, histopathological and molecular genetic findings in BMD.

Phenotypic and functional analysis of human fetal liver hematopoietic stem cells in culture

Steady-state hematopoiesis and hematopoietic transplantation rely on the unique potential of stem cells to undergo both self-renewal and multilineage differentiation. Fetal liver (FL) represents a promising alternative source of hematopoietic stem cells (HSCs), but limited by the total cell number obtained in a typical harvest. We reported that human FL nonobese diabetic/severe combined immunodeficient (NOD/SCID) repopulating cells (SRCs) could be expanded under simple stroma-free culture conditions. Here, we sought to further characterize FL HSC/SRCs phenotypically and functionally before and following culture. Unexpanded or cultured FL cell suspensions were separated into various subpopulations. These were tested for long-term culture potential and for in vivo repopulating function following transplantation into NOD/SCID mice. We found that upon culture of human FL cells, a tight association between classical stem cell phenotypes, such as CD34(+) /CD38(-) and/or side population, and NOD/SCID repopulating function was lost, as observed with other sources. Although SRC activity before and following culture consistently correlated with the presence of a CD34(+) cell population, we provide evidence that, contrary to umbilical cord blood and adult sources, stem cells present in both CD34(+) and CD34(-) FL populations can sustain long-term hematopoietic cultures. Furthermore, upon additional culture, CD34-depleted cell suspensions, devoid of SRCs, regenerated a population of CD34(+) cells possessing SRC function. Our studies suggest that compared to neonatal and adult sources, the phenotypical characteristics of putative human FL HSCs may be less strictly defined, and reinforce the accumulated evidence that human FL represents a unique, valuable alternative and highly proliferative source of HSCs for clinical applications.

Gene duplication: a drive for phenotypic diversity and cause of human disease

Gene duplication is one of the key factors driving genetic innovation, i.e., producing novel genetic variants. Although the contribution of whole-genome and segmental duplications to phenotypic diversity across species is widely appreciated, the phenotypic spectrum and potential pathogenicity of small-scale duplications in individual genomes are less well explored. This review discusses the nature of small-scale duplications and the phenotypes produced by such duplications. Phenotypic variation and disease phenotypes induced by duplications are more diverse and widespread than previously anticipated, and duplications are a major class of disease-related genomic variation. Pathogenic duplications particularly involve dosage-sensitive genes with both similar and dissimilar over- and underexpression phenotypes, and genes encoding proteins with a propensity to aggregate. Phenotypes related to human-specific copy number variation in genes regulating environmental responses and immunity are increasingly recognized. Small genomic duplications containing defense-related genes also contribute to complex common phenotypes.

Genotypic and phenotypic characterization of Trypanosoma brucei gambiense isolates from Ibba, South Sudan, an area of high melarsoprol treatment failure rate

Resistance of trypanosomes to melarsoprol is ascribed to reduced uptake of the drug via the P2 nucleoside transporter. The aim of this study was to look for evidence of drug resistance in Trypanosoma brucei gambiense isolates from sleeping sickness patients in Ibba, South Sudan, an area of high melarsoprol failure rate. Eighteen T. b. gambiense stocks were phenotypically and only 10 strains genotypically characterized. In vitro, all isolates were sensitive to melarsoprol, melarsen oxide, and diminazene. Infected mice were cured with a 4 day treatment of 2.5mg/kg bwt melarsoprol, confirming that the isolates were sensitive. The gene that codes for the P2 transporter, TbATI, was amplified by PCR and sequenced. The sequences were almost identical to the TbAT1(sensitive) reference, except for one point mutation, C1384T resulting in the amino acid change proline-462 to serine. None of the described TbAT1(resistant)-type mutations were detected. In a T. b. gambiense sleeping sickness focus where melarsoprol had to be abandoned due to the high incidence of treatment failures, no evidence for drug resistant trypanosomes or for TbAT1(resistant)-type alleles of the P2 transporter could be found. These findings indicate that factors other than drug resistance contribute to melarsoprol treatment failures.

The complement inhibitor low molecular weight dextran sulfate prevents TLR4-induced phenotypic and functional maturation of human dendritic cells

Low molecular weight dextran sulfate (DXS) has been reported to inhibit the classical, alternative pathway as well as the mannan-binding lectin pathway of the complement system. Furthermore, it acts as an endothelial cell protectant inhibiting complement-mediated endothelial cell damage. Endothelial cells are covered with a layer of heparan sulfate (HS), which is rapidly released under conditions of inflammation and tissue injury. Soluble HS induces maturation of dendritic cells (DC) via TLR4. In this study, we show the inhibitory effect of DXS on human DC maturation. DXS significantly prevents phenotypic maturation of monocyte-derived DC and peripheral myeloid DC by inhibiting the up-regulation of CD40, CD80, CD83, CD86, ICAM-1, and HLA-DR and down-regulates DC-SIGN in response to HS or exogenous TLR ligands. DXS also inhibits the functional maturation of DC as demonstrated by reduced T cell proliferation, and strongly impairs secretion of the proinflammatory mediators IL-1beta, IL-6, IL-12p70, and TNF-alpha. Exposure to DXS leads to a reduced production of the complement component C1q and a decreased phagocytic activity, whereas C3 secretion is increased. Moreover, DXS was found to inhibit phosphorylation of IkappaB-alpha and activation of NF-kappaB. These findings suggest that DXS prevents TLR-induced maturation of human DC and may therefore be a useful reagent to impede the link between innate and adaptive immunity.

Phenotypic associations of Crohn's disease with antibodies to flagellins A4-Fla2 and Fla-X, ASCA, p-ANCA, PAB, and NOD2 mutations in a Swiss Cohort

BACKGROUND: Distinct Crohn's disease (CD) phenotypes correlate with antibody reactivity to microbial antigens. We examined the association between antibody response to 2 new flagellins called A4-Fla2 and Fla-X, anti-Saccharomyces cerevisiae antibodies (ASCA), anti-neutrophil cytoplasmic antibodies (p-ANCA), anti-pancreas antibodies (PAB), NOD2 mutations (R702W, G908R, and L1007fsinsC), and clinical CD phenotypes (according to Vienna criteria). METHODS: All the above-mentioned antibodies as well as NOD2 mutations were determined in 252 CD patients, 53 with ulcerative colitis (UC), and 43 healthy controls (HC) and correlated with clinical data. RESULTS: A seroreactivity for A4-Fla2/Fla-X/ASCA/p-ANCA/PAB (in percent) was found in 59/57/62/12/22 of CD patients, 6/6/4/51/0 of UC patients, and 0/2/5/0/0 of healthy controls. CD behavior: 37% B1, 36% B2, and 27% B3. In multivariate logistic regression, antibodies to A4-Fla2, Fla-X, and ASCA were significantly associated with stricturing phenotype (P = 0.027, P = 0.041, P < 0.001), negative associations were found with inflammatory phenotype (P = 0.001, P = 0.005, P < 0.001). Antibodies to A4-Fla2, Fla-X, ASCA, and NOD2 mutations were significantly associated with small bowel disease (P = 0.013, P = 0.01, P < 0.001, P = 0.04), whereas ASCA was correlated with fistulizing disease (P = 0.007), and small bowel surgery (P = 0.009). Multiple antibody responses against microbial antigens were associated with stricturing (P < 0.001), fistulizing disease (P = 0.002), and small bowel surgery (P = 0.002). CONCLUSIONS: Anti-flagellin antibodies and ASCA are strongly associated with complicated CD phenotypes. CD patients with serum reactivity against multiple microbes have the greatest frequency of strictures, perforations, and small bowel surgery. Further prospective longitudinal studies are needed to show that antibody-based risk stratification improves the clinical outcome of CD patients.

Phenotypic novelty in experimental hybrids is predicted by the genetic distance between species of cichlid fish

Background: Transgressive segregation describes the occurrence of novel phenotypes in hybrids with extreme trait values not observed in either parental species. A previously experimentally untested prediction is that the amount of transgression increases with the genetic distance between hybridizing species. This follows from QTL studies suggesting that transgression is most commonly due to complementary gene action or epistasis, which become more frequent at larger genetic distances. This is because the number of QTLs fixed for alleles with opposing signs in different species should increase with time since speciation provided that speciation is not driven by disruptive selection. We measured the amount of transgression occurring in hybrids of cichlid fish bred from species pairs with gradually increasing genetic distances and varying phenotypic similarity. Transgression in multi-trait shape phenotypes was quantified using landmark-based geometric morphometric methods. Results: We found that genetic distance explained 52% and 78% of the variation in transgression frequency in F1 and F2 hybrids, respectively. Confirming theoretical predictions, transgression when measured in F2 hybrids, increased linearly with genetic distance between hybridizing species. Phenotypic similarity of species on the other hand was not related to the amount of transgression. Conclusion: The commonness and ease with which novel phenotypes are produced in cichlid hybrids between unrelated species has important implications for the interaction of hybridization with adaptation and speciation. Hybridization may generate new genotypes with adaptive potential that did not reside as standing genetic variation in either parental population, potentially enhancing a population's responsiveness to selection. Our results make it conceivable that hybridization contributed to the rapid rates of phenotypic evolution in the large and rapid adaptive radiations of haplochromine cichlids.