Rapid mutation screening of phenylketonuria by polymerase chain reaction-linked restriction enzyme assay and direct sequence of the phenylalanine hydroxylase gene: clinical application in northern Japan and northern China

We describe a simple and technically feasible method for mutation screening of the phenylalanine hydroxylase (PAH) gene and its application to Japanese and Chinese patients with hyperphenylalaninemia. The strategy is based on the identification of a nucleotide substitution by restriction enzyme analysis, coupled with PCR and direct sequencing of exon 7 of the PAH gene. Because the detection of various mutations can proceed simultaneously using the same technique, it is quite rapid and reproducible, making it possible to perform effective molecular diagnosis and carrier screening in most laboratories. Using this procedure, we found that the most common molecular defects were R413P in Hokkaido, Japan (35 %) and R243Q in Heilongjiang, China (50%). R111X, IVS4nt-1, and five mutations in exon 7 (R241C, R243Q, R252W, A259T, and S273P) accounted for 55% of phenylketonuria (PKU) alleles in Hokkaido. In Heilongjiang, the R111X, Y356X, and R408W mutations accounted for 35% of PKU alleles. Clinically, homozygotes or compound heterozygotes of null alleles, which express nonfunctional enzyme activity, were all associated with classic PKU. On the other hand, patients heterozygous for the R241C allele had a benign phenotype of mild hyperphenylalaninemia. The DNA diagnosis in early infancy can predict various PKU phenotypes, and can prove useful in decision-making concerning dietary therapy.     

In vitro type II binding of chromosomal DNA to membrane in Bacillus subtilis

DNA-membrane association critical for initiation of DNA replication in Bacillus subtilis can be classified into two types. Type I is salt resistant and dependent on the initiation gene, dnaB, and type II is salt sensitive and independent of the dnaB gene. We found and sequenced two adjacent areas of type II binding within 1% of oriC on the B. subtilis chromosome.     

Clonal sublines of rat neurotumor RT4 and cell differentiation: IV. Cell surface proteins

There are stem cells in RT4 neurotumor that undergo spontaneous differentiation into three distinct cell types in culture (cell type conversion). Stem cells (RT4-AC) and one of the differentiated cell types (RT4-D) are tumorigenic and synthesize glial-specific S100 protein, while the others (RT4-B and RT4-E) are nontumorigenic and demonstrate some neuronal function. Interrelationships between cell surface proteins and differentiation of RT4 cells were analyzed. The surface proteins are radioiodinated by a lactoperoxidase method, separated by gel electrophoresis in two dimensions, visualized by autoradiography, and quantitated according to the relative radioactivity associated with each protein species. Integral surface proteins are compared in the present study which remain associated with plasma membrane after the extraction of radioiodinated cells with 0.1 N NaOH. The extraction also helps to remove serum proteins in the medium which are absorbed on cell surfaces and may be artifactually recognized as surface proteins. All RT4 cell types are complex in cell surface protein composition and nearly 100 integral surface proteins have been identified when all RT4 cell types are combined. Many unique proteins as well as common proteins have been identified. Considerable similarity exists between RT4-AC and RT4-D and between RT4-B and RT4-E. The two cell types of each pair are distinct yet share some common neurological and tumorigenic characteristics. In contrast, little similarity exists in other combinations of the two cell types, e.g., RT4-AC and RT4-E, etc. The results support the notion that the pattern of cell surface protein expression is a stable differentiation property and a characteristic set of proteins corresponds to each stage of differentiation.     

Directional mutation pressure,selective constraints,and genetic equilibria

Summary Rates of substitution mutations in two directions, v [from an A-T or T-A nucleotide pair (AT-pair) to a G-C or C-G nucleotide pair (GC-pair)] and u [from a GC-pair to an AT-pair], are usually not the same. The net effect, v/(u + v), has previously been defined as directional mutation pressure ( _d ), which explains the wide interspecific variation and narrow intragenomic heterogeneity of DNA G+C content in bacteria. In this article, first, a theory of the evolution of DNA G+C content is presented that is based on the equilibrium among three components: directional mutation pressure, DNA G+C content, and selective constraints. According to this theory, consideration of both u and v as well as selective constraints is essential to explain the molecular evolution of the DNA base composition and sequence. Second, the theory of directional mutation pressure is applied to the analysis of the wide intragenomic heterogeneity of DNA G+C content in multicellular eukaryotes. The theory explains the extensive intragenomic heterogeneity of G+C content of higher eukaryotes primarily as the result of the intragenomic differences of directional mutation pressure and selective constraints rather than the result of positive selections for functional advantages of the DNA G+C content itself.     

Temperature-Sensitive DNA Synthesis Mutants of BACILLUS SUBTILIS—APPENDIX: Theory of Density Transfer for Symmetric Chromosome Replication

A simple method for characterizing temperature-sensitive DNA synthesis mutants is described. The method uses density transfer and transformation techniques and is based on expected theoretical behavior of the chromosome population. A direct proof of inhibition of initiation of DNA replication is provided. The mutant dna-1, showing quick inhibition of initiation, is further characterized and mapped. An independent method for mapping genetic markers close to the origin, based on their transfer behavior after inhibition of initiation, is presented.     

Effects of steroid hormones on the level of corticotropin messenger RNA activity in cultured mouse-pituitary-tumor cells.

Studies have been made with the mouse pituitary tumor cell line AtT-20 in culture to determine whether or not the suppression of pituitary corticotropin messenger RNA activity observed upon the administration of glucocorticoids to adrenalectomized rats is due to a direct action of these steroid hormones on the pituitary. The levels of corticotropin messenger RNA activity in AtT-20 cells treated with various steroid hormones were measured with the use of the cell-free protein-synthesizing system derived from wheat germ. The addition of dexamethasone to culture medium reduced the level of corticotropin messenger RNA activity to 30-40% of that in untreated cells. Corticosterone and cortisol exhibited a suppressive effect to a lesser extent. In contrast, nonglucocorticoids such as testosterone and 17beta-estradiol were essentially ineffective. These results indicate that at least part of the glucocorticoid action is exerted directly on the pituitary to suppress corticotropin messenger RNA activity.     

Fetal Calf Spinal Cords as Enriched Source of mRNA Encoding Glial Fibrillary Acidic Protein

Abstract: Total poly(A)⁺ RNA was isolated from fetal calf spinal cord, adult rat spinal cord, and young rat brain, and was translated using the rabbit reticulocyte lysate system. The amount of glial fibrillary acidic protein in the translation products was measured by immunoprecipitation with antiserum against glial fibrillary acidic protein. RNA from fetal calf spinal cord could direct glial fibrillary acidic protein synthesis such that this protein comprised approximately 1.4% of the total products. RNAs from adult rat spinal cord and brain could direct glial fibrillary acidic protein synthesis much less efficiently, with this protein comprising <0.3% of the total products. These results suggest that the gene for glial fibrillary acidic protein is strongly expressed in fetal calf spinal cord and that this tissue is an enriched source of mRNA encoding glial fibrillary acidic protein.     

Clonal sublines of rat neurotumor RT4 and cell differentiation. VI. Chromosome analysis

The RT4 neurotumor cell system consists of clonally derived cell lines where a stem cell type segregates in vitro into three biochemically and morphologically different cell types, one glial and two neuronal types. This process has been termed cell-type conversion (M. Imada and N. Sueoka, 1978, Dev. Biol. 66, 97-108). Detailed cytogenetic analysis of the RT4 cell lines are described. Giemsa-banding analysis of 12 independent clonal isolates of the four different RT4 cell types showed a relatively stable karyotype. The stem cell line, RT4-AC, is diploid and most stable, and it has one 4q+ marker chromosome in place of a normal No. 4. This 4q+ marker was identified in all cell types of the RT4 system and was not observed in other cell lines of BDIX origin. The 4q+, therefore, is a chromosomal marker of the RT4 system. Consistent chromosome rearrangement was not found in any one of the cell-type conversions of the RT4-AC cells into the three derivative cell types. The relative stability of the karyotype of the different clonal isolates gives the RT4 system an advantage in studies of genetic regulation and expression of cell-type conversion in vitro. Also the 4q+ marker can be used to identify RT4 cells in coculture experiments or to distinguish RT4 cells in cases of suspected cell-line contamination.