An exonic mutation in the HuP2 paired domain gene causes Waardenburg's syndrome.

Here we report the identification and characterization of a gene defect causing Waardenburg's syndrome with hearing loss in a large Brazilian family. This demonstrates a mutation causing Waardenburg's syndrome as well as a mutation causing a form of congenital deafness. The mutation was found in the HuP2 gene, a member of the paired domain family of proteins that bind DNA and regulate gene expression. The mutation occurred in 100% of the cases with the disease in this family and was absent in a random sample of 50 unrelated control subjects. Identification of the Waardenburg's syndrome gene and future characterization of its gene product is likely to increase our understanding of the pathogenesis of this disorder and may allow prevention of deafness of this type.     

国产盐酸二甲胺四环素对裸鼠体内麻风杆菌的影响

本研究系用麻风裸鼠实验模型，采用动力法投药１０５天，观察了０．０２％二甲胺四环素和０．０４％ＭＩＮＯ的抗麻风杆菌活性，并同０．０２％进口ＭＩＮＯ和已知抗麻风药物０．０２％利福平进行了平行比较，实验结果表明，国产ＭＩＮＯ儿进口ＭＩＮＯ的实验疗效基本一致。而且，随着药物剂量的提高，抑制麻风杆蓖作用增强，在停药早期，以０．０４％ＭＩＮＯ组疗效最佳，显示有部分杀菌活性，显示有部分杀菌活性，但是，随着停药是     

A frame-shift mutation in the cystic fibrosis gene.

Cystic fibrosis (CF) is a common recessive lethal genetic disorder, affecting 1 in 1,600 Caucasians. The disease causes defective regulation of chloride-ion transport in exocrine cells. Although in all CF families the disease is linked to a locus on chromosome 7q31, there is clinical heterogeneity in the severity of the disease and the age at which it is diagnosed. CF is caused by mutations in the CF transmembrane conductance regulator (CFTR) gene. A three-nucleotide deletion (delta F508) causing the loss of a phenylalanine residue in the tenth exon of the CFTR gene has been found on 70% of CF chromosomes. We have now characterized a CF family in which neither parent of the affected individual carries the common mutation, and identified a two-nucleotide insertion in the CF allele of the mother. The mutation introduces a termination codon in exon 13 of the CFTR gene at residue 821, and is predicted to result in the production of a severely truncated nonfunctional protein.     

Effects of an Rb mutation in the mouse.

The retinoblastoma gene is mutated in several types of human cancer and is the best characterized of the tumour-suppressor genes. A mouse strain has been constructed in which one allele of Rb is disrupted. These heterozygous animals are not predisposed to retinoblastoma, but some display pituitary tumours arising from cells in which the wild-type Rb allele is absent. Embryos homozygous for the mutation die between days 14 and 15 of gestation, exhibiting neuronal cell death and defective erythropoiesis.     

六年中裸小鼠繁殖群动物自发性肿瘤发病情况研究

对饲养于ＳＰＦ条件下的４６６只ＮＣ系自育选留的繁殖群小鼠自发性中瘤发病情况进行了６年观察，研究其中包括纯合子雄鼠（ｎｕ／ｎｕ）１６４只，杂合了雄鼠（ｎｕ／＋）３０２只。每只动物的平均观察时间均达７个月以上，淘汰时均详细解剖学检查，检出病变者进行病理组织学及透射电镜观察确诊。多数肿瘤病例结合裸鼠间可移植性鉴定。共检出自发性肿瘤７例，发生于纯合子裸鼠（♂，ｎｕ／ｎｕ）５例，杂合子裸鼠（♂，ｎｕ／＋）２例。本结果表明，在相同饲养环境条件下，裸鼠（♂，ｎｕ、／ｎｕ）的自发性肿瘤发病率（３．０４％）比其同系的有胸腺杂合子裸鼠（♀，ｎｕ／＋）（０．６６％）明显增高，两者发病比较有显著性差异（Ｐ＜０．０５），且前者的平均发瘤鼠龄比后者为短。结果支持了免疫功能缺陷的裸鼠比其同系免疫功能正常鼠有更高的自发性肿瘤发生的观点。且表明了ＮＣ系裸鼠的自发性肿瘤以恶性上皮性肿瘤为主。此外作者针对前人的观察结果，提出了对一裸群体的自发性肿瘤的正确评价，必须是在相同的生存环境条件下，相同的观察时间内与相同品系或相同基因背景的有胸腺小鼠进行比较，并经详细的病理学检查，才能得出较客观可靠的结论这一见解。     

Extrathymic positive selection of alpha beta T-cell precursors in nude mice.

T lymphocytes expressing alpha beta T-cell receptors with sufficient affinity to major histocompatibility complex (MHC) molecules expressed on thymus epithelial cells are positively selected and mature to functional T cells. But several studies have demonstrated that athymic nude mice grafted with MHC-incompatible thymuses developed T cells specific for nude host rather than thymic MHC. We examined this paradox by analysing the specificity of T lymphocytes derived from nude mice. We report here that nude T lymphocyte precursors transferred to allogeneic SCID (severe combined immunodeficiency) mice with a functioning thymus (but lacking T or B cells) generated host MHC-restricted effector T cells but also contained T cells restricted to donor MHC. If nude T cells were depleted from nude lymphohaemopoietic donor cells before or after transfer, only host MHC-specific T cells matured. The results may explain the unusual MHC specificities of nude T lymphocytes described in earlier studies and demonstrate two separate differentiation steps: in nude mice, T cells may be positively selected for self-MHC restriction specificity extrathymically; then a functional thymus is required for efficient T cell maturation.     

Suppression of the nonsense mutation in homozygous beta 0 thalassaemia.

The common form of beta thalassaemia associated with elevated haemoglobin A2 levels can be broadly classified as beta + or beta 0 type according to the presence or absence of beta-globin chain synthesis in the homozygous state. The molecular pathology of each type is heterogeneous. Apart from a subgroup of Indo-Pakistani patients, the beta-globin structural gene is intact in the majority of patients with beta 0 thalassaemia. The amount of beta-globin mRNA present in the reticulocytes of these patients varies: in some it is absent or barely detectable; in others, a substantial amount is present, but it is nonfunctional. We recently demonstrated that the molecular lesion in a Chinese patient with nonfunctional beta-globin mRNA was due to the mutation of the normal lysine codon AAG at amino acid 17 to the amber terminator codon UAG, which prematurely terminates the beta-globin chain. In the present study we demonstrate the first example of a nonsense mutation in humans which can be suppressed in vitro by the suppressor tRNA, as has been found in other eukaryotic cells and viruses.