RESUMO
Mice deficient in complement C3 (C3(-/-)) are hematologically normal under steady-state conditions, and yet displayed a significant delay in hematopoietic recovery from either irradiation or transplantation of wild-type (WT) hematopoietic stem/progenitor cells (HSPC). Transplantation of histocompatible WT Sca-1(+) cells into C3(-/-) mice resulted in a (i) decrease in day 12 CFU-S, (ii) 5-7-day delay in platelet and leukocyte recovery, and (iii) reduced number of BM CFU-GM progenitors at day 16 after transplantation. Nevertheless, HSPC from C3(-/-) mice engrafted normally into irradiated WT mice, suggesting that there was a defect in the hematopoietic environment of C3(-/-) mice. Since C3(-/-) mice cannot activate/cleave C3, the C3 fragments C3a, C3a(des-Arg), and iC3b were examined for a role in HSPC engraftment. Liquid-phase C3a and C3a(des-Arg) increased CXCR4 incorporation into membrane lipid rafts (thus potentiating HSPC responses to SDF-1 gradients), whereas iC3b was deposited onto irradiated BM cells and functioned to tether CR3(CD11b/CD18)(+)HSPC to damaged stroma. The activity of C3a(des-Arg) suggested that C3aR(+)HSPC also expressed the C5L2 (receptor for C3a and C3a(des-Arg)) and this was confirmed. In conclusion, a novel mechanism for HSC engraftment was identified, which involves complement activation and specific C3 fragments that promote conditioning for transplantation and enhance HSPC engraftment.
Assuntos
Células da Medula Óssea/fisiologia , Transplante de Medula Óssea , Complemento C3/fisiologia , Animais , Antígenos Ly/metabolismo , Ativação do Complemento , Complemento C3/genética , Fator Estimulador de Colônias de Granulócitos/farmacologia , Humanos , Microdomínios da Membrana/química , Microdomínios da Membrana/metabolismo , Proteínas de Membrana/genética , Proteínas de Membrana/metabolismo , Proteínas de Membrana/fisiologia , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Receptores CXCR4/metabolismo , Receptores de Complemento/genética , Receptores de Complemento/fisiologia , Células Estromais/citologia , Irradiação Corporal TotalRESUMO
GTP cyclohydrolase II catalyzes the first committed step in the biosynthesis of riboflavin. The gene coding for this enzyme in Escherichia coli has been cloned by marker rescue. Sequencing indicated an open reading frame of 588 bp coding for a 21.8-kDa peptide of 196 amino acids. The gene was mapped to a position at 28.2 min on the E. coli chromosome and is identical with ribA. GTP cyclohydrolase II was overexpressed in a recombinant strain carrying a plasmid with the cloned gene. The enzyme was purified to homogeneity from the recombinant strain. The N-terminal sequence determined by Edman degradation was identical to the predicted sequence. The sequence is homologous to the 3' part of the central open reading frame in the riboflavin operon of Bacillus subtilis.
Assuntos
Escherichia coli/genética , GTP Cicloidrolase/genética , Riboflavina/biossíntese , Sequência de Aminoácidos , Sequência de Bases , Clonagem Molecular , Escherichia coli/enzimologia , GTP Cicloidrolase/biossíntese , Dados de Sequência Molecular , Proteínas Recombinantes/biossíntese , Mapeamento por Restrição , Análise de Sequência de DNA , Homologia de Sequência de AminoácidosRESUMO
Clinical histories and physical features of two sisters affected with a previously unreported syndrome are presented with illustrations. The manifestations were profound postnatal growth and psychomotor retardation, hydrocephaly, cleft lip and palate, corneal opacities, central nervous system impairment, and genitourinary anomalies. Four other siblings, two males and two females and the parents of the affected were examined and found to be normal. Infectious, metabolic, and chromosomal etiologies were excluded by appropriate studies. The most likely pattern of inheritance is autosomal recessive.
