21－羟化酶CYP21B基因Ile~（172）→Asn错义突变

为了解先天性肾上腺皮质增生症患者的２１－羟化酶ＣＹＰ２１Ｂ基因中Ｉｌｅ~（１７２）→Ａｓｎ错义突变的发生率，根据放大受阻突变体系（Ａｍｐｌｉｆｉｃａｔｉｏｎｒｅｆｒａｃｔｏｒｙｍｕｔａｔｉｏｎｓｙｓｔｅｍ，ＡＲＭＳ）的要求，设计了３种引物：５＇ｄ（ＴＴＧＧＧＡＧＡＣＴＡＣＴＣＣＣＴＧＣＴＣＴ）３＇（共同引物）、５＇ｄ（ＡＧＧＴＧＡＧＧＴＡＡＣＡＧＡ）３＇（正常引物）、５＇ｄ（ＡＧＧＴＧＡＧＧＴＡＡＣＡＧＴ）３＇（突变引物），在７例患儿中进行了检测，发现具有本突变者３例。对其中一例进行的家系分析，结果提示：这组引物有快速、简便的优点，不需使用同位素就能对具有Ｉｌｅ~（１７２）→Ａｓｎ变异的高危家庭成员作产前诊断。     

Brief Communication: Role of Nuclear Background and in vivo Environment in Variable Segregation Behavior of the Aging-Dependent T414G Mutation at Critical Control Site for Human Fibroblast mtDNA Replication

Previous work had shown a large accumulation (up to 50% of mtDNA) of a noninherited T414G transversion at a critical control site for mtDNA replication in skin fibroblasts from the majority of human subjects above 65 years old, and its absence in younger individuals. In the present studies, long-term in vitro culture of several fibroblasts populations carrying the heteroplasmic T414G mutation revealed an outgrowth of the mutant cells by wild-type cells. This observation supported the previous conclusion that the mutation accumulation is an in vivo phenomenon, while, at the same time, indicating intrinsic physiological differences between mutant and wild-type cells. Furthermore, subcloning experiments revealed a striking mosaic distribution of the mutation in the original fibroblasts populations, as shown by its presence, in heteroplasmic or homoplasmic form, in a fraction (18–32%) of the fibroblasts, and its absence in the others. In other investigations, transfer of mitochondria from mutation-carrying fibroblasts into mtDNA-less 143B.TK^–0 206 cells revealed the persistence of the mosaic distribution of the mutation, however, with a near-complete shift to homoplasmy. The generality of the latter phenomenon would exclude a founder effect by one or few mitochondria in the transformation experiments, and would rather point to the important role of the nuclear background in the in vitro behavior of the T414G mutation. The stability of the homoplasmic mutation in ⁰ cell transformants provides a powerful tool for analyzing its biochemical effects.     

Haplotype analysis in gelsoiin-related amyloidosis reveals independent origin of identical mutation (G654A) of gelsolin in Finland and Japan

Familial amyloidosis, Finnish type (FAF) (gelsolin-related amyloidosis) is an autosomal dominant form of systemic amyloidosis characterized by corneal lattice dystrophy and peripheral polyneuropathy. The accumulating protein in FAF consists of fragments of gelsolin, an actin-modulating protein. The gelsolin mutation G654A has been found in both Finnish and Japanese patients. To study the origin of the gelsolin mutation in these patients we performed haplotype analysis in 10 Finnish and 2 Japanese FAF families. Poymorphic DNA markers GSN, D9S103, AFMa061xd9, and AFMa139xb9 revealed a uniform disease haplotype in all the disease-associated chromosomes of the Finnish FAF families, which was different from the one observed in the Japanese families. The present results and the previously detected gelsolin mutation G654T in Czech and Danish FAF patients suggest that nucle otide 654 may represent a mutation hot spot in the gelsolin gene. The DNA markers studied here will be useful in future genealogical analyses of FAF. © 1995 Wiley-Liss, Inc.     

Fetal anticonvulsant syndrome and mutation in the maternal MTHFR gene

Around 6% of infants born to mothers taking anticonvulsants have malformations, including neural tube defects, and a further proportion show developmental delay in later childhood. Three commonly used anticonvulsants, carbamazepine, phenytoin and sodium valproate, interfere with folic acid metabolism. We investigated the common 677 C>T mutation in the methylenetetrahydrofolate reductase (MTHFR) gene in samples from 57 patients and their parents and 152 controls to determine its contribution to the risk of fetal anticonvulsant syndrome. The 677 C>T mutation frequency was significantly higher in the mothers than in the controls, but there was no significant difference in 677 C>T frequency in the patients or in the fathers. Genotype frequencies in the mothers were significantly different from controls, there being an excess of 677 C>T homozygotes. Amongst the patients, there was an apparent excess of heterozygotes (not statistically significant), and the fathers were not significantly different from controls. Mutation in the MTHFR gene in a mother taking sodium valproate, phenytoin or carbamazepine during pregnancy is associated with fetal anticonvulsant syndrome in her offspring. The skewed distribution of genotypes in the affected children probably reflects the association of fetal anticonvulsant syndrome with the maternal genotype.     

Allelic association with SNPs: metrics, populations, and the linkage disequilibrium map

Comparison of different metrics, using three large samples of haplotypes from different populations, demonstrates that rho is the most efficient measure of association between pairs of single nucleotide polymorphisms (SNPs). Pairwise data can be modeled, using composite likelihood, to describe the decline in linkage disequilibrium with distance (the Malecot model). The evidence from more isolated populations (Finland, Sardinia) suggests that linkage disequilibrium extends to 427-893 kb but, even in samples representative of large heterogeneous populations, such as CEPH, the extent is 385 kb or greater. This suggests that isolated populations are not essential for linkage disequilibrium mapping of common diseases with SNPs. The in parameter of the Malecot model (recombination and time), evaluated at each SNP, indicates regions of the genome with extensive and less extensive disequilibrium (low and high values of in respectively). When plotted against the physical map, the regions with extensive and less extensive linkage disequilibrium may correspond to recombination cold and hot spots. This is discussed in relation to the Xq25 cytogenetic band and the HFE gene region.     

Mutagenicity of gamma-radiation,mitomycin C,and etoposide in the Hprt and Tk genes of Tk(+/-) mice

The recently developed Tk(+/-) mouse detects in vivo somatic cell mutation in the endogenous, autosomal Tk gene. To evaluate the sensitivity of this model, we have treated Tk(+/-) mice with three agents that induce DNA damage by different mechanisms, and determined spleen lymphocyte mutant frequencies (MFs) in the autosomal Tk gene and in the X-linked Hprt gene. gamma-Radiation, which produces single- and double-strand breaks by nonspecific oxidative stress, efficiently increased Hprt MF, but not Tk MF. Mitomycin C, which produces bulky DNA monoadducts and crosslinks, was mutagenic in both the Hprt and Tk genes, but the response was greater in the Tk gene. An inhibitor of the ligase function of DNA topoisomerase II, etoposide, did not increase Hprt MF, and induced a small, but nonsignificant increase in Tk MF. Combined with previous data, the results indicate that the two genes are differentially sensitive to many agents, and that the Tk gene is more sensitive than the Hprt gene to some, but not all types of DNA damage.     

Retrospective analysis of antiretroviral HIV treatment success based on medical history or guided by the reverse hybridisation LiPA HIV genotyping system

The changes in viral load and CD4(+) count at 3 and 6 months in a group of 166 HIV-infected patients was evaluated. The new therapy was chosen based on the medical history procedures for 70 patients, and in 96 patients it was guided by the partial or complete result of the line probe assay (LiPA) HIV RT and Protease resistance tests. The absolute difference from the baseline of the log viral load at 3 and 6 months was significantly different between the two groups when adjusted for baseline viral load (P < 0.0001) and stayed significant when intention-to-treat analysis was carried out (P < 0.001). The absolute difference of the CD4(+) count was not significantly different when adjusted for baseline CD4(+) (P = 0.854, 3 months; P = 0.06, 6 months). The proportion of patients with a viral load 相似文献   

Molecular and serological evaluation of surface antigen negative hepatitis B virus infection in blood donors from Venezuela

Surface antigen negative hepatitis B virus (HBV) infection was evaluated in Venezuela, by molecular characterization of blood samples positive for antibodies to core antigen (anti-HBc) and negative for surface antigen (HBsAg) in blood donors (residual infections). HBV DNA was found in 11/258 samples (4.3%), and was significantly associated with high levels of anti-HBc antibodies (>25 UI/ml, P < 0.05), while no correlation was found between the presence of HBV DNA and the levels of anti-HBs. Synonymous and non-synonymous mutations were found in the HBV surface region (but not vaccine escape mutants) and in the precore/core region (precore mutants in 2/7 samples and 33-45 bp deletions near the N-terminal core region in 4/19 samples). While HBV genotype F prevails among HBsAg positive samples from blood donors in Venezuela, residual infection isolates were mainly genotypes A and D. Phylogenetic analysis of viral surface and core region revealed discrepancies in genotype designation in 6/9 samples, suggesting the presence of mixed infection or recombination. In conclusion, HBV residual infection in Venezuela does not seem to be frequently observed in HBV genotype F. This type of infection is frequently associated with variants exhibiting mutations in the surface gene that might be affecting the correct recognition by commercial tests, with precore mutants and with core internal deletions. These variants do not seem to cause severe liver disease, and on the contrary, were found circulating at low viremia.     

Clinical,immunological, and molecular analysis in a large cohort of patients with X-linked agammaglobulinemia: an Italian multicenter study

A questionnaire-based retrospective clinical and immunological survey was conducted in 73 males with a definite diagnosis of X-linked agammaglobulinemia based on BTK sequence analysis. Forty-four were sporadic and 29 familial cases. At December 2000, the patients' ages ranged from 2 to 33 years; mean age at diagnosis and mean duration of follow-up were 3.5 and 10 years respectively. After the mid-1980s all but 2 were on intravenous immunoglobulin (IVIG) substitution therapy, with residual IgG >500 mg/dl in 94% of the patients at the time of enrollment. Respiratory infections were the most frequent manifestation both prior to diagnosis and over follow-up. Chronic lung disease (CLD) was present in 24 patients, in 15 already at diagnosis and in 9 more by 2000. The cumulative risk to present at diagnosis with CLD increased from 0.17 to 0.40 and 0.78 when the diagnosis was made at the ages of 5, 10, and 15 years respectively. For the 9 patients who developed CLD during follow-up, the duration of follow-up, rather than age at diagnosis; previous administration of intramuscular immunoglobulin; and residual IgG levels had a significant effect on the development of CLD. Chronic sinusitis was present in 35 patients (48%), in 15 already at diagnosis and in 20 by 2000. Sistemic infections such as sepsis and meningitis/meningoencephalitis decreased over follow-up, probably due to optimal protection provided by high circulating IgG levels reached with IVIG.     

Cystic fibrosis mutations and immotile cilia syndrome

The immotile cilia syndrome (ICS) presents with autosomal recessive inheritance and is a chronic respiratory disease supposed to be caused by different genetic determinants. The hypothesis that cystic fibrosis (CF) heterozygotes may have a predisposition to develop bronchial or respiratory diseases other than CF prompted us to look for CF mutations in patients with ICS. Five patients, as well as the parents and two healthy brothers of one patient were tested for 12 CF mutations, for the polymorphic GATT repeat in intron 6a and for the CF gene flanking markers XV-2c, KM19, MP6d-9, J3.11. None of the 12 mutations at the CF locus have been detected in the ICS patients and no linkage was found between ICS and the polymorphic markers. Thus, based on our data, ICS and CF seem to be two different clinical entities.