Blood pressure cosegregates with a microsatellite of angiotensin I converting enzyme (ACE) in F2 generation from a cross between original normotensive Wistar-Kyoto rat (WKY) and stroke-prone spontaneously hypertensive rat (SHRSP).

We investigated the linkage between high blood pressure and the ACE gene in the F2 generation between SHRSP/Izm and WKY/Izm. The male F2 rats were categorized into 3 genotypes according to a microsatellite polymorphism in the ACE gene. Significantly high blood pressure was observed in the SHRSP homozygotes when it was compared to the blood pressure of the heterozygotes. Further, after 2 or 3 months salt-loading, the blood pressure was significantly higher in the SHRSP homozygotes than in the heterozygotes and the WKY homozygotes. The heterozygotes had a blood pressure similar to that in the WKY homozygotes, indicating that the effect of the ACE gene genotype was recessive. Salt appetite was neither correlated with the salt-sensitivity nor cosegregated with the ACE genotype. The results indicate that the locus of ACE gene associates with the development of hypertension, especially salt-sensitive hypertension.     

Pericentric inversion in natural populations of Oligoryzomys nigripes (Rodentia: Sigmodontinae).

We analysed polymorphism for pericentric inversion in chromosome 3 of Oligoryzomys nigripes (Rodentia: Sigmodontinae) in several populations in Brazil and examined the meiotic behaviour of this chromosome in heterozygotes. We observed an orderly pairing of all chromosomes at pachytene in heterozygotes for the inverted chromosome 3. No indication of meiotic arrest and germ-cell death was found. Electron microscopy of synaptonemal complexes and conventional meiotic analysis indicated strictly nonhomologous synapsis and crossing-over suppression in the inverted region in the heterozygotes, which prevent the formation of unbalanced gametes. Thus, the pericentric inversion in chromosome 3 does not apparently result in any selective disadvantages in heterozygous carriers. In the majority of the populations studied, the frequencies of acrocentric homozygotes, metacentric homozygotes, and heterozygotes were in Hardy-Weinberg equilibrium. However, in some populations, we detected an excess of heterozygotes and a deficiency of acrocentric homozygotes.     

Tumour necrosis factor-alpha and heat-shock protein 70-2 gene polymorphisms in a family with rheumatoid arthritis

OBJECTIVES: The aim of this work was to investigate the prevalence of TNF-alpha-308 polymorphism among the 29 members of a family with RA and the association between the MHC-linked biallelic HSP70-2 gene and the TNF-alpha polymorphism. Five of the members with RA were diagnosed by using the revised 1987 ACR criteria, and 1 member suffered from SLE. METHODS: The variations in the TNF-alpha and the HSP70-2 genotypes were analyzed by PCR-RFLP, using NcoI and PstI restriction enzymes. RESULTS: Two of the 29 members were homozygotes for allele A, 18 were heterozygotes (TNF A/G) and 9 of them were homozygotes for allele G. Nineteen of the 29 were heterozygotes for HSP70-2 (A/G), 10 of them were homozygotes for the G allele, and none were homozygotes for allele A. Four of the 5 the RA patients carried the A allele for TNF-alpha all 5 were heterozygotes for HSP70-2 genotypes. CONCLUSION: The carriage of the A allele for TNF-alpha of -308 SNP in 4 of the 5 RA patients, and the high prevalence (68.0%) of TNF A allele carriers in this family confirms the important role of this candidate gene in the pathomechanism of RA, and might be of prognostic value for future clinical observations. Further, to test for association a much larger set of genetically independent patients and controls is needed.     

Early morphological abnormalities in splotch mouse embryos and predisposition to gene- and retinoic acid-induced neural tube defects

Genetic and environmental factors contribute to an individual's neural tube defect liability. In the mouse, the gene mutation Splotch (Sp) causes a pigmentation defect in heterozygotes while homozygotes have spina bifida +/- exencephaly. Splotch homozygotes, heterozygotes, and wild-type embryos were examined for somite number, anterior neuropore closure, and posterior neuropore length. The aim was to distinguish potentially affected homozygotes early in pathogenesis and find a morphological basis for increased teratogen susceptibility in heterozygotes. Posterior neuropore closure as well as anterior neuropore closure was significantly delayed in potentially affected Sp as compared to wild-type litter embryos exceeding the incidence found in day-10-diagnosed homozygotes. Part of this excess was attributed to a transient delay in heterozygotes which in turn might predispose to retinoic acid-induced neural tube defects. This idea was supported by an outcross of Sp heterozygote males by inbred SWV females and wild-type males by SWV where a significant increase in retinoic acid-induced neural tube defects was found in Sp carrier litters.     

Evidence for balancing of KM, but not GM, alleles by heterotic advantage in South Amerinds

Two KM alleles occur in 1075 South Amerinds of 14 tribes in approximately balanced and uniform frequency. However, the number of heterozygotes is 12.7% greater than expected by frequency analysis and 16.5% greater by segregation analysis. This excess is evident in children 0–4 years of age and may reflect either prenatal or early childhood selection. The frequencies of GM haplotypes were different, and quite uniformly so, in diverse tribes. Most GM heterozygotes can only be distinguished from GM 1,2,17 21 homozygotes by DNA or family relationship. No deficit of GM homozygotes was observed in 119 children in whom heterozygosis was determined by family. Thus, the KM polymorphism, like HLA, may be maintained by preferential survival of heterozygotes, but GM probably depends on another mechanism. Received: 5 December 1996 / Accepted: 19 March 1997     

Assessment of chronic gamma radiosensitivity as an in vitro assay for heterozygote identification of ataxia-telangiectasia

Ataxia-telangiectasia (A-T) is a rare human autosomal recessive disorder characterized by, among other symptoms, catastrophic reaction to conventional radiotherapy. A-T heterozygotes are clinically asymptomatic and their fibroblasts are intermediate in radiosensitivity between homozygotes and normals. We have attempted to identify heterozygotes by assaying for cellular hypersensitivity to chronic gamma irradiation. Cultured dermal fibroblast strains from 13 control subjects and 55 members from a large Amish pedigree segregating for A-T were assayed for loss of colony-forming ability (CFA) in response to 137Cs gamma radiation delivered at a dose rate of 0.8 cGy/min. For each strain, multiple dose-response curves were summarized in a composite D10 value (dose, in cGy, reducing colony survival to 10%). The D10's of the clinically normal controls and of those pedigree members with known A-T genotype formed a trimodal distribution, with the seven obligate heterozygotes displaying an average value (516 cGy) intermediate between that of the 10 healthy controls (797 cGy) and that of the two affected patients (154 cGy). The D10's were modeled statistically using Gaussian penetrance functions. The most parsimonious model yielded a significant difference in D10 means for heterozygotes and normal homozygotes, a significant donor age effect, but no sex effect. We compared probabilistic identification of heterozygotes based on D10 values with identification based on linkage data for two markers, THY1 and D11S144, closely linked to the A-T gene. This comparison revealed that the D10 data were appreciably less informative than the linked markers. Indeed, the extensive overlap between D10 values for heterozygotes and normal homozygotes precludes the use of postirradiation CFA for either accurate identification of heterozygotes or chromosomal mapping of the A-T gene.     

Chiasma frequency effects of structural chromosome change

Three structural chromosome changes in the plant Hypochoeris radicata 2n = 8 have been tested for their effects on chiasma formation: (1) centric fission of chromosome 1, (2) a whole arm exchange between chromosomes 1 and 3, and (3) an interchange between the long arm of chromosome 1 and the short arm of 2 which gives an effectively three-armed pachytene multiple. Mean chiasma frequencies were compared between full-sibs in families segregating for the rearrangements. In each family the chiasma frequency was higher in heterozygotes than basic homozygotes. The size of the chiasma increase is dependant on the number of additional potentially-paired segments in the complement at pachytene. Fission heterozygotes and 1/2 interchange heterozygotes, with one extra pairing region, both form about 0.45 more chiasmata per PMC than full-sib basic homozygotes. The 1/3 exchange, with two additional pairing regions, increases chiasma frequency by twice this, about 0.85 per PMC. Individuals homozygous for the centric fission maintain the raised chiasma level. The chiasma increase appears limited to the chromosome(s) affected by structural change with no detectable interchromosomal effect.     

High frequency of spontaneous translocations revealed by FISH in cells from patients with the cancer-prone syndromes ataxia telangiectasia and Nijmegen breakage syndrome.

The application of fluorescence in situ hybridization (FISH) using whole-chromosome paints (WCPs) is proving to be a very powerful technique for revealing chromosomal instability that, for the most part, has gone undetected by conventional cytogenetic analysis. We have analyzed the frequency of translocations in lymphocytes and lymphoblastoid cell lines from ataxia telangiectasia (AT) and Nijmegen breakage syndrome (NBS) homozygotes and heterozygotes using a three-color chromosome-painting technique (WCP 1, 2, 4). With this assay we were able to detect an increased frequency of spontaneous translocations in AT homozygotes (median, 18.47 +/- 10.82 translocations per 1,000 metaphase cells; 10 patients) and AT heterozygotes (median, 7.87 +/- 3.15 translocations per 1,000 cells; 7 patients), in comparison to controls (median, 2.26 +/- 1.75 translocations per 1,000 cells; 10 controls). Analysis of NBS homozygotes (median, 19.05 +/- 11.27 translocations per 1,000 cells; 5 patients) and NBS heterozygotes (median, 6.93 +/- 3.04 translocations per 1,000 cells; 6 patients) also showed an increased frequency of translocations in these patients compared to controls. The presence of such hitherto undetected chromosomal aberrations corroborate previous findings of spontaneous chromosomal instability in AT and NBS patients, as manifested by an increased rate of open breaks and rearrangements involving chromosomes 7 and 14. Moreover, we show that the degree of genomic instability in AT and NBS patients is even higher than previously established and that some AT and NBS heterozygotes evidence spontaneous chromosomal instability as well. These increased levels of nonspecific translocations could be an important risk factor for the development of malignancies in homozygotes and heterozygotes for ATM or NBS1 gene mutations.     

APOB‐associated cholesterol deficiency in Holstein cattle is not a simple recessive disease

In 2015, cholesterol deficiency (CD) was reported for the first time as a new recessive defect in Holstein cattle. After GWAS mapping and identification of a disease‐associated haplotype, a causative loss‐of‐function variant in APOB was identified. CD‐clinically affected APOB homozygotes showed poor development, intermittent diarrhea and hypocholesterolemia and, consequently, a limited life expectation. Herein, we present a collection of 18 cases clinically diagnosed as CD‐affected APOB heterozygotes. CD‐clinically affected heterozygotes show reduced cholesterol and triglyceride blood concentrations. The differences in total blood cholesterol and triglycerides between nine CD‐clinically affected and 36 non‐affected heterozygotes were significant. As only some APOB heterozygotes show the clinical CD phenotype, we assume that the penetrance is reduced in heterozygotes compared to the fully penetrant effect observed in homozygotes. We conclude that APOB‐associated CD represents most likely an incomplete dominant inherited metabolic disease with incomplete penetrance in heterozygotes.     

A primer for predicting risk of disease in HFE-linked hemochromatosis

Since the discovery of the hemochromatosis gene (HFE) in 1996, there has been increasing interest in diagnostic testing for the C282Y and H63D mutations. The high frequency of these two alleles and their incomplete penetrance in homozygotes and compound heterozygotes make genetic counseling for hemochromatosis different from some other autosomal recessive conditions in that parents and children may also be at risk for iron overload, while homozygotes may remain asymptomatic. We provide a guideline for genetic counseling in HFE-linked hemochromatosis based on the genetic probability of inheriting HFE mutations and known information about expression of iron overload in various HFE genotypes. Genetic probabilities were based on allele frequencies derived from large population studies and Hardy-Weinberg equilibrium estimates. Expression of iron overload in those of various genotypes was based on available estimates of serum ferritin from population screening studies. Estimates for the likelihood of clinical iron overload requiring follow-up screening or treatment are provided by gender and genotype. The probability of inheriting HFE mutations and developing iron overload can be estimated in family members of a proband with HFE mutations. Many C282Y homozygotes will not have clinical iron overload. The risk is highest in men and their C282Y homozygous brothers and significantly lower in homozygous women. Iron overload is uncommon in compound heterozygotes and H63D homozygotes.     

Small fitness effects and weak genetic interactions between deleterious mutations in heterozygous loci of the yeast Saccharomyces cerevisiae

Rare, random mutations were induced in budding yeast by ethyl methanesulfonate (EMS). Clones known to bear a single non-neutral mutation were used to obtain mutant heterozygotes and mutant homozygotes that were later compared with wild-type homozygotes. The average homozygous effect of mutation was an approximately 2% decrease in the growth rate. In heterozygotes, the harmful effect of these relatively mild mutations was reduced approximately fivefold. In a test of epistasis, two heterozygous mutant loci were paired at random. Fitness of the double mutants was best explained by multiplicative action of effects at single loci, with little evidence for epistasis and essentially excluding synergism. In other experiments, the same mutations in haploid and heterozygous diploid clones were compared. Regardless of the haploid phenotypes, mildly deleterious or lethal, fitness of the heterozygotes was decreased by less than half a per cent on average. In general, the results presented here suggest that most mutations tend to exhibit small and weakly interacting effects in heterozygous loci regardless of how harmful they are in haploids or homozygotes.     

Heterosis associated with DOPA-oxidase dimorphism in Culex pipiens

1. Isozyme phenotypes were used to deduce genotypes at a dimorphic DOPA-oxidase locus in a laboratory population of Culex pipiens. The frequencies of homozygotes and heterozygotes at the inception and termination of laboratory colonization were compared. 2. Co-dominant alleles F and S condition the fast and slow isozymes (allozymes) respectively at this enzyme locus. 3. The expected and observed ratios of heterozygotes (FS) to homozygotes (FF and SS) were 50:50 and 64:36 respectively for 50 pairs of parents. 4. The observed and statistically significant excess of heterozygotes is taken as evidence of heterosis and the heterotic maintenance of enzyme dimorphism at this locus.     

Serum concentrations of vitamin D-binding protein (Group-specific component) in cystic fibrosis

Summary Vitamin D-binding protein (DBP) concentrations were determined in the sera of 90 cystic fibrosis homozygotes, 57 obligate heterozygotes, and 46 normal controls. Very significantly lower mean concentrations were found in the sera of CF homozygotes compared with both heterozygotes and controls (P<0.01, Wilcoxon Rank Sums Test). Subdivision of the samples by Gc phenotype showed that this relationship held true both in the Gc1 and Gc2-1 phenotypes. The small sample size of the Gc2 genotype makes the significance levels of limited usefulness, but the pattern of variation of DBP levels among CF homozygotes, heterozygotes, and controls was consistent with that observed for the Gc1 and Gc2-1 classes. Haptoglobin levels showed high coefficients of variation when compared among CF homozygotes, obligate heterozygotes, and controls, presumably because of nonspecific elevation in the acute-phase response. Alpha₂-macroglobulin levels were, if anything, slightly elevated in CF homozygotes compared with controls, while albumin levels showed no significant mean differences between these groups. Since the DBP concentration does not vary with age nor with levels of vitamin D and its metabolites, we interpret our results to mean that DBP levels are specifically decreased in cystic fibrosis, perhaps as the result of impaired glycosylation of the protein.A preliminary report of this work appeared in the Proceedings of the 8th International Congress on Cystic Fibrosis.     

Increased hepatic lipase activity and increased direct removal of very-low-density lipoprotein remnants in Watanabe heritable hyperlipidaemic (WHHL) rabbits treated with ethinyl oestradiol.

We studied the effects of ethinyl oestradiol on the serum concentrations and metabolism of very-low- and low-density lipoproteins (VLDL and LDL) in Watanabe heritable hyperlipidaemic (WHHL) homozygous rabbits, an animal model for familial hypercholesterolaemia. The results were compared with those in untreated homozygotes as well as in heterozygotes treated or not with ethinyl oestradiol. The gain in body weight was similar in all groups. Treatment with ethinyl oestradiol resulted in the homozygotes in an approx. 80% decrease in the concentrations of lipids and apoprotein B in the d less than 1.019 lipoprotein fraction; those in the LDL fraction did not change. In the heterozygotes, basal serum lipids and apoprotein B levels in the d less than 1.019 fraction were low; ethinyl oestradiol treatment especially affected the LDL fraction (cholesterol -84%, apoprotein B -64%). Turnover experiments with 125I-labelled VLDL revealed that, on treatment with ethinyl oestradiol, the fractional catabolic rate in homozygous rabbits increased 2-fold. The secretion rates of lipids and protein in the d less than 1.019 fraction as estimated after injection of Triton WR-1339 was not decreased. In homozygotes and heterozygotes increases in post-heparin hepatic lipase activity of 62 and 80% respectively were observed, with no changes in lipoprotein lipase activity. We conclude that ethinyl oestradiol induces in homozygous WHHL rabbits a direct removal of VLDL and VLDL remnants from the plasma, apparently due to an increase in hepatic lipase activity.     

Application of random amplified polymorphic DNA PCR for genomic analysis of HIV-1-infected individuals

Random amplified polymorphic DNA polymerase chain reaction (RAPD-PCR) is a DNA fingerprinting technique used to detect genomic polymorphisms. We employed sixteen different RAPD-PCR 10-mer primers to amplify DNA from the peripheral blood mononuclear cells (PBMC) of 80 HIV-1-infected individuals. These individuals were previously identified as either heterozygotes (+/Δ32) and homozygotes (+/+) for the CCR5 locus by PCR with gene specific primers. Four of the sixteen randomly selected RAPD primers produced distinguishable banding profiles between CCR5 (+/Δ32) heterozygotes and CCR5 (+/+) homozygotes. Direct sequencing of some RAPD-PCR products obtained with one of the four RAPD primers that were tested yielded clearly readable, but limited sequences, which were similar to portions of the previously published sequences for (+/+) homozygotes (98% similarity) and (+/Δ32) heterozygotes (87% similarity) of the CCR5 alleles. Thus, the RAPD-PCR technique may be useful for the identification of human molecular markers that may correlate with susceptibility to HIV-1-infection, or differences in disease progression among HIV-1-infected individuals.     

Phenotypic and Genotypic Analysis of Rats with Cerebellar GABAA Receptors Composed from Mutant and Wild-Type α6 Subunits

Abstract: The alcohol-sensitive (ANT) rat line, developed for high behavioral sensitivity to ethanol, also exhibits enhanced sensitivity to benzodiazepines, such as diazepam. The rat line carries a point mutation in the cerebellum-specific γ-aminobutyric acid type A (GABA_A) receptor subunit α6, making their diazepam-insensitive (DIS) receptors sensitive to diazepam. We now report that phenotypes of individual ANT and alcohol-insensitive rats, classified on diazepam sensitivity of cerebellar [³H]Ro 15-4513 binding, correlated well with homozygous wild-type, homozygous mutant, and heterozygous genotypes, although some heterozygotes were biased toward the parental phenotypes. GABA down-modulated DIS [³H]Ro 15-4513 binding in mutant homozygotes but tended to up-modulate it in heterozygotes and wild-type homozygotes. Slopes for GABA inhibition of cerebellar t-butylbicyclophosphoro[³⁵S]thionate binding were larger in mutant than in wild-type homozygotes, with heterozygotes being intermediate. Diazepam displacement of [³H]Ro 15-4513 binding in heterozygotes revealed three components, with their affinities indistinguishable from those in combined wild-type and mutant homozygotes. This lack of interaction in DIS binding between wild-type and mutant α6 subunits was substantiated by experiments on recombinant receptors. The data suggest that the α6 subunit-containing GABA_A receptors in the heterozygotes are formed from individual mutant and wild-type subunits with their relative expression differing from animal to animal.     

Mouse mammary tumor virus promoter directs high‐level expression of bovine αS1 casein in the milk of transgenic heterozygous and homozygous mice

Abstract

To test the mouse mammary tumor virus (MMTV) promoter as an inducible mammary‐specific promoter, we have produced 3 lines of transgenic mice carrying bovine αS1 casein cDNA under the control of MMTV promoter. The RNA analysis showed that in line 27, heterozygotes expressed 25%, and homozygotes 37% of the endogenous αSI casein mRNA of a mid‐lactation cow. Dexamethasone increased expression by about 3 fold in both heterozygotes and homozygotes. A similar increase in the level of mRNA was observed in both heterozygotes and homozygotes from line 42 with/without induction by dexamethasone. The transgenes were expressed predominantly in the mammary gland with low levels in the salivary gland, spleen, lung, and kidney. Their expression in mammary glands was lactation‐specific. The offspring from lines 27 and 42 expressed a high‐level bovine αS1 casein in their milk. Their expression in milk were 0.21 and 0.11 g/L for heterozygotes, 0.36 and 0.19 g/L for homozygotes, respectively. Dexamethasone further increased the levels of expression by approximately two fold for both heterozygotes and homozygotes.     

Frequency of mutations related to hereditary haemochromatosis in northwestern Poland

Hereditary haemochromatosis has been linked with C282Y and H63D mutations of the HFE gene. In Europe, frequencies of these mutations are the highest in Northern European countries and gradually decrease southwards. We analysed the prevalence of HFE mutations in 1517 DNA samples, including 1000 samples from the general population (subjects registered at general practitioner practices) in northwestern Poland, and 517 samples of cord blood from the same region. We identified 2 (0.13%) homozygotes and 117 (7.8%) heterozygotes for the C282Y mutation. As regards the H63D mutation (1505 DNA samples analysed), 38 (2.5%) samples were homozygotes and 380 (25%) were heterozygotes. Twenty-one (1.4%) compound heterozygotes were found. These results correspond well with data from other Central European countries and seem to confirm the hypothesis of North-South spread of the C282Y mutation.     

见于我国人群的一例MiⅢ血型糖蛋白

在我国人群中筛查出一例血型糖蛋白（ＧＰ）变种。先证者为海南省黎族男青年。家系调查表明，先证者及其父属纯合子，母亲为杂合子。通过免疫印迹与限制性内切酶图谱分析，确证它为见于我国的首例ＭｉＩＩＩＧＰ；属（δ－α－δ）基因杂化体。     

Polymorphisms in the interleukin-4 receptor alpha chain: association with traits of allergy and asthma in an admixed population in Hawaii.

Single nucleotide polymorphisms (SNPs) in the gene encoding the interleukin-4 receptor alpha chain (IL-4R alpha) have been associated with IgE levels or clinical atopy in some populations. Two SNPs that encode S503P and Q576R in the intracytoplasmic domain of the receptor are associated with loss or gain of function, respectively. We investigated the frequency of these SNPs and their association with traits of allergic asthma in 36 unrelated subjects selected from a racially admixed, clinically ascertained study population with family histories of asthma. The frequency of the 1682 T to C substitution that encodes S503P was 0.11 (70 alleles analyzed, from 29 TT homozygotes and 6 TC heterozygotes). The frequency of the 1902 A to G substitution that encodes Q576R was 0.26 (68 alleles analyzed, from 20 AA homozygotes, 10 AG heterozygotes and 4 GG homozygotes). In this atopic admixed sample, no significant association was detected between the variant genotypes and serum IgE levels, percentage of eosinophils, skin test reactivity, diagnosis of asthma or methacholine reactivity. More conclusive findings await clinical characterization of non-atopic, non-asthmatic subjects as well as more efficient and extensive haplotyping.