Gel retardation at low pH resolves trp repressor-DNA complexes for quantitative study

The affinity and stoichiometry of DNA binding by Escherichia coli trp repressor were studied by electrophoresis in nondenaturing gels. The ability of trp repressor to retard the electrophoretic mobility of an operator DNA fragment depends on the pH of the gel system. Above the pI of the protein, little retardation of DNA is observed, although complex formation can be detected by other assays. As the pH of the gel is lowered, retardation is enhanced. The apparent dissociation constant for the interaction between trp repressor and trpEDCBA operator fragments is 0.5 nM under the conditions used here. Nonspecific binding occurs with only about 200-fold weaker affinity. The stoichiometries of specific and nonspecific complexes were determined directly by using trp repressor labeled in vivo. High-affinity operator binding requires a single dimer of trp repressor. DNase I-protection analysis ("footprinting") was used to confirm the dissociation constants and to locate the binding site.

Genetic analysis of NF1: identification of close flanking markers on chromosome 17

The gene causing von Recklinghausen neurofibromatosis, or NF1, has been more precisely localized in the pericentromeric region of chromosome 17. Narrowing of the location for the disease became possible through the identification of eight new DNA probe genetic markers in the centromeric region. Markers that closely flank the centromere also closely flank the NF1 gene. Although there was evidence against this localization in one recombinant, a review of the clinical records revealed a borderline diagnosis of NF1. Significant sex differences in recombination were observed in the pericentric region, and odds for different orders were less discriminating when sex differences were considered in multilocus analyses. The location of the NF1 gene with respect to the centromere could not be determined because recombinants between NF1 and the centromere were not detected in the set of families tested.

Tightly linked markers for the neurofibromatosis type 1 gene

Relationships among genetic markers in the region of the neurofibromatosis type 1 (NF1) gene on chromosome 17 were investigated by linkage studies in a large sample set of affected families and in a panel of 58 normal families. A new marker, pHHH202 (D17S33), was included along with two markers known to be closely linked to NF. The maximum likelihood estimate of the recombination rate between the pHHH202 and NF1 loci was found to be O. Multilocus analysis suggested the following marker order: pA10-41-(p3-6, pHHH202); the NF1 gene fell with equal likelihood between either pA10-41-p3-6 or p3-6-pHHH202. The odds against NF1 being outside this cluster of tightly linked markers were greater than 15:1.

A genomic search for linkage of neurofibromatosis to RFLPs

Our initial attempt to map NF was directed towards chromosomes 4 and 19, both of which had provided positive evidence for linkage in previous reports. This analysis showed no evidence in support of either hypothesis. Our second attempt at mapping NF was a general search of the genome, analysing a set of markers selected according to their degree of polymorphism, chromosomal location, ease of use, and availability. Data for linkage analysis were obtained from 17 multiplex families which are segregating a gene for NF. Linkage analyses were performed using PAP. Of note is the lod score of +1.17 at a recombination fraction of 0.1 between NF and the centromere of chromosome 17.

Isochromosome 12p mosaicism (Pallister mosaic aneuploidy or Pallister-Killian syndrome): report of 11 cases

We report on 11 cases of isochromosome 12p mosaicism (or Pallister mosaic aneuploidy syndrome) in which the isochromosome is usually absent in cultured lymphocytes but present in fibroblasts. The patients range in age from a 22-week-gestation fetus to a 45-year-old man. They have a distinct pattern of anomalies which enables one to make a diagnosis based on clinical manifestations alone. Craniofacial manifestations include "coarse" face with prominent forehead, sparsity of scalp hair, hypertelorism, epicanthal folds, flat bridge of nose, and highly arched palate. Affected newborn infants are profoundly hypotonic with sparsity of scalp hair especially bitemporally and a prominent forehead. Most have accessory nipples. Birthweight and growth parameters are usually normal; however, some newborn infants are unusually large. In infancy, the facial appearance becomes "coarse," hypotonia persists, and seizures may occur. As adults, growth may be normal, scalp hair is thicker and the mandible becomes prominent. Most have a generalized pigmentary dysplasia which may be evident with a Wood's lamp only. All cases have been sporadic and there is no consistent pattern of advanced parental age.

Gene for von Recklinghausen neurofibromatosis is in the pericentromeric region of chromosome 17

Linkage analysis of 15 Utah kindreds demonstrated that a gene responsible for von Recklinghausen neurofibromatosis (NF) is located near the centromere on chromosome 17. The families also gave no evidence for heterogeneity, indicating that a significant proportion of NF cases are due to mutations at a single locus. Further genetic analysis can now refine this localization and may lead to the eventual identification and cloning of the defective gene responsible for this disorder.

Dominantly inherited renal adysplasia

We are reporting on 7 families with both unilateral and bilateral renal agenesis (or severe dysplasia). This condition, termed hereditary renal adysplasia (HRA) [Buchta et al, 1973], is an autosomal dominant trait with incomplete penetrance and variable expression. Review of the literature on familial renal agenesis suggests that HRA is more common than previously supposed and may account for most recurrences of bilateral renal agenesis (BRA), even when the parents are normal. There are no consistent phenotypic differences between sporadic and familial renal agenesis. Associated non-urogenital anomalies, although more frequent in sporadic cases, have been reported in HRA. Use of several approaches, including the Weinberg Proband Method, segregation analysis, and empiric risk estimation, leads to the conclusion that autosomal dominant inheritance is the most likely pattern of transmission for most cases of renal agenesis. Penetrance is between 50% and 90%. Ultrasound study of the kidneys of parents, sibs, and other relatives is recommended in all families in which there is an individual with unilateral or bilateral renal agenesis. The empiric risk for recurrence of BRA in sibs has been estimated at 3.5% [Carter, et al, 1979] but in the offspring of affected or obligate heterozygotes for HRA, the empiric risk of bilateral severe renal adysplasia is 15-20%.

Detection of transcription-pausing in vivo in the trp operon leader region

To determine whether RNA polymerase pauses during transcription in vivo, we have examined transcripts of the trp operon leader regions of Serratia marcescens and Escherichia coli. Labeled RNAs synthesized in E. coli strains containing plasmids bearing wild-type or mutant trp leader regions of S. marcescens or E. coli were isolated by hybridization and analyzed by polyacrylamide gel electrophoresis. The labeled RNAs synthesized in vivo on the S. marcescens wild-type and deletion mutant plasmids were the same size as the in vitro pause and leader transcripts. Hybridization of the presumed in vivo pause RNAs, and control in vitro pause RNAs, to M13 phage DNA containing a trp leader region deletion followed by treatment with S1 nuclease produced identical protected RNA species, proving that the in vitro and in vivo RNAs were identical. The amount of labeled pause RNAs relative to leader RNAs decreased following a chase with unlabeled uridine. E. coli RNAs identical to the previously characterized in vitro pause and leader transcripts were demonstrated by electrophoretic band position and fingerprint analysis. The finding that transcription pausing occurs in vivo is consistent with the view that transcription pausing and ribosome release of paused transcription complexes are responsible for the coupling of translation with transcription that is crucial to attenuation.

Further linkage data on Norrie disease

We obtained a LOD score of +1.61 using DNA marker L1.28 in 5 generations of a family with Norrie disease, raising the total LOD score to +5.42. There have been no recombinations between the 2 loci in any family to date, making the marker useful for genetic counseling.

A three year follow up of patients allocated to placebo, or oral or injectable gold therapy for rheumatoid arthritis

Ninety patients randomly allocated to receive auranofin, matching placebo, or sodium aurothiomalate have been followed up for three years. Inefficacy led to cessation of treatment in 14 patients receiving auranofin, 27 receiving placebo, and one receiving sodium aurothiomalate. Twenty seven of the patients receiving placebo were reallocated within the study and 16 continued therapy at three years. This group showed similar statistically significant improvement in clinical and laboratory parameters at one, two, and three years to those on an active drug from the outset. Patients who discontinued auranofin because of inefficacy were offered sodium aurothiomalate therapy--eight patients in this group completed three years of treatment on sodium aurothiomalate and showed significant improvement in some but not all parameters. A hand radiograph erosion score showed a deterioration in 80% of patients remaining on auranofin, 75% of those on sodium aurothiomalate, and 80% of the original placebo group who continued an active drug for three years. Although more patients discontinued auranofin over the study period because of inefficacy, no difference could be shown between the degree of improvement in the subgroup who remained on auranofin and those receiving sodium aurothiomalate. No disadvantage in outcome could be shown for patients originally assigned to placebo.

Association of amyoplasia with gastroschisis, bowel atresia, and defects of the muscular layer of the trunk

We reviewed 225 cases of amyoplasia, and the association of amyoplasia with gastroschisis and with monozygotic twinning was confirmed. In addition, an apparently increased association of bowel atresia and defects in the muscular layer of the trunk wall with amyoplasia was observed. The association of amyoplasia, monozygotic twinning, and these trunk wall defects strongly suggests that the pathogenesis of amyoplasia is linked to some type of vascular compromise.

Large neurons in the primate neostriatum examined with the combined Golgi-electron microscopic method

Large neurons in the monkey neostriatum were examined in the electron microscope in tissue treated with the rapid-Golgi impregnation method followed by the gold-toning procedure. Two types of large neurons were investigated: an aspiny neuron (aspiny type II; N = 5) with numerous varicose dendrites and a spiny cell (spiny type II; N = 1) with few sparsely spined dendrites. The large aspiny neurons had variably shaped somata, an eccentric highly invaginated nucleus, and a cytoplasm rich in organelles. Mitochondria were distributed unevenly in dendrites and were localized primarily in varicosities. Some mitochondria exhibited dense bodies 80-300 nm in size. Most synapses (84%) onto large aspiny neurons occurred 20 micron or more from the cell body and contacted dendritic varicosities (63%). A smaller proportion of boutons (21%) contacted constricted portions of varicose segments. A low incidence of synaptic boutons was observed on smooth primary and secondary dendrites (11%), cell bodies (3%), and branch points (2%). Seven percent of the axons that synapsed with large aspiny neurons also contacted nearby dendrites or spines of medium-sized spiny neurons. At least eight morphologically distinct types of axons making synapses with large aspiny neurons were identified and included both symmetric and asymmetric types. The large spiny neuron was different from the large aspiny neuron in its subcellular characteristics. Synapses were found on all portions of the cell, including the axon initial segment, but fewer types of axonal inputs were identified. These findings confirm that the two types of large neurons identified in Golgi impregnations of the primate neostriatum are also different at the ultrastructural level, both in their cytological features and in their synaptic organization. The large aspiny neuron integrates synaptic inputs that innervate a relatively large area of caudate neuropil and appear to arise from a variety of extrinsic and intrinsic sources. The high density of synaptic inputs to dendritic varicosities suggests that they have an important functional role.