Validity of a screening test for typing serum cholinesterase variants among Greek populations.

A screening method for determining the abnormal phenotypes of human serum cholinesterase variants in a population survey was investigated. The test appeared to be satisfactory in detecting abnormal genotypes, but not assigning them into correct classification. The results of the population survey indicate that there may be a higher frequency of ChU1ChD1 genotype than those reported earlier. Family studies of the suxamethonium-sensitive propositi in this population demonstrate that abnormal genes ChD1, ChF1 and ChS1 are segregating, according to the usual Mendelian type of inheritance pattern. The possibility of a relatively high frequency of these abnormal genotypes among the Greek population has been indicated.     

The G1021A substitution in the RYR1 gene does not cosegregate with malignant hyperthermia susceptibility in a British pedigree.

A single base change in the RYR1 gene encoding the skeletal muscle ryanodine receptor (calcium-sensitive calcium-release channel of the sarcoplasmic reticulum), resulting in the substitution of G1021 by A, has been proposed to underlie malignant-hyperthermia (MH) susceptibility in as many as 10% of cases in the European population. As part of our mutation-screening program in MH-susceptible (MHS) individuals, we have investigated this substitution in individuals from 151 unrelated British MHS families and have detected G1021A heterozygotes in 7 families. This mutation was not found in 156 unrelated MH-negative (MHN) individuals. We also examined eight families with central core disease (CCD): the mutation did not occur in any family members of any disease status (affected or unaffected for CCD, MHS, or MHN). In one large family, the G1021A mutation was found but did not show complete cosegregation with MH susceptibility: it occurred in only 7/12 MHS individuals in the kinship, and susceptibility was inherited from parents who were G1021 homozygotes, as well as from parents who were heterozygotes. On the basis of these findings, it is clearly unreliable at present to offer presymptomatic DNA testing for MH status, even in families in which a mutation has been detected.     

Genetic study of psoriasis in the Kharkov population

By means of genetic analysis of 400 individuals suffering from psoriasis the mendelian inheritance model have been rejected: the segregation frequencies are SFNxN = 0.083 and SFNxA = 0.1474. The heritability of psoriasis in the polygenic model is about 100%. The main gene model with incomplete penetration have been proposed (p = 0.044, [symbol: see text]1 = 6.1%, [symbol: see text]2 = 82.2%). 0.189% residents of Kharkov population are homozygotes and 8.32% heterozygotes on psoriatic gene, 0.155% residents are suffering from psoriasis heterozygotes and 0.508% heterozygotes. Among individuals suffering from psoriasis 23% are homozygotes and 77% heterozygotes.     

The frequency of the C854 mutation in the aspartoacylase gene in Ashkenazi Jews in Israel.

Canavan disease (CD) is an infantile neurodegenerative disease that is transmitted in an autosomal recessive manner and has mainly been reported in Ashkenazi Jewish families. The primary enzymatic defect is aspartoacylase deficiency, and an A-to-C transition at nucleotide 854 of the cDNA has recently been reported. We screened 18 patients with CD and 879 healthy individuals, all Israeli Ashkenazi Jews, for the mutation. All 18 patients were homozygotes for the mutation, and 15 heterozygotes were found among the healthy individuals. The results disclose a carrier rate of 1:59 and suggest that a screening for the mutation is warranted among Ashkenazi Jewish couples.     

Family studies of the E1kE1s genotype for plasma cholinesterase

Six individuals in three families with a history of suxamethonium sensitivity have been found to have genotype E1kE1s. The biochemical data for the recognition of this genotype have been analysed and the mean values compared with similar parameters for the usual phenotype. Individuals with genotype E1kE1s will be sensitive to suxamethonium.     

Mutations associated with variant phenotypes in ataxia-telangiectasia.

We have identified 14 families with ataxia-telangiectasia (A-T) in which mutation of the ATM gene is associated with a less severe clinical and cellular phenotype (approximately 10%-15% of A-T families identified in the United Kingdom). In 10 of these families, all the homozygotes have a 137-bp insertion in their cDNA caused by a point mutation in a sequence resembling a splice-donor site. The second A-T allele has a different mutation in each patient. We show that the less severe phenotype in these patients is caused by some degree of normal splicing, which occurs as an alternative product from the insertion-containing allele. The level of the 137-bp PCR product containing the insertion was lowest in two patients who showed a later onset of cerebellar ataxia. A further four families who do not have this insertion have been identified. Mutations detected in two of four of these are missense mutations, normally rare in A-T patients. The demonstration of mutations giving rise to a slightly milder phenotype in A-T raises the interesting question of what range of phenotypes might occur in individuals in whom both mutations are milder. One possibility might be that individuals who are compound heterozygotes for ATM mutations are more common than we realize.     

Congenital malformations and developmental disabilities in ataxia-telangiectasia, Fanconi anemia, and xeroderma pigmentosum families.

Heterozygous carriers of an ataxia-telangiectasia (A-T), Fanconi anemia (FA), or xeroderma pigmentosum (XP) gene may be predisposed to some of the same congenital malformations or developmental disabilities that are common among homozygotes. To test this hypothesis, medical records, death certificates, and questionnaires from 27 A-T families, 25 FA families, and 31 XP families were reviewed. Eleven XP blood relatives (out of 1,100) were found with moderate or severe unexplained mental retardation, a significant excess compared to the FA and A-T families (3/1,439). There were four microcephalic XP blood relatives and none in the FA or A-T families. In the A-T families, idiopathic scoliosis and vertebral anomalies were in excess, while genitourinary and distal limb malformations were found in the FA families. A-T, FA, or XP heterozygotes may constitute an important proportion of individuals at risk for specific malformations or developmental abnormalities.     

Establishment and characterization of B cell lines from individuals with various types of adenine phosphoribosyltransferase deficiencies

Patients with 2,8-dihydroxyadenine urolithiasis are either completely or partially deficient in adenine phosphoribosyltransferase activities. Patients with partial enzyme deficiencies, all of whom have been found among Japanese, are homozygotes having a unique mutant adenine phosphoribosyltransferase gene (APRT*J) in double dose (Japanese type deficiency). We have established B-cell lines from heterozygotes and homozygotes of complete and Japanese type adenine phosphoribosyltransferase deficiencies as well as normal individuals. Characterization of the cell lines indicated that all homozygous cells were deficient in adenine phosphoribosyltransferase function while all heterozygous and normal cells had functional adenine phosphoribosyltransferase.     

Identification of two novel mutations in the SLC25A13 gene and detection of seven mutations in 102 patients with adult-onset type II citrullinemia

Adult-onset type II citrullinemia (CTLN2) is characterized by a liver-specific deficiency of argininosuccinate synthetase (ASS) protein. We have recently identified the gene responsible for CTLN2, viz., SLC25A13, which encodes a calcium-binding mitochondrial carrier protein, designated citrin, and found five mutations of the SLC25A13 gene in CTLN2 patients. In the present study, we have identified two novel mutations, 1800ins1 and R605X, in SLC25A13 mRNA and the SLC25A13 gene. Diagnostic analysis for the seven mutations in 103 CTLN2 patients diagnosed by biochemical and enzymatic studies has revealed that 102 patients had one or two of the seven mutations and 93 patients were homozygotes or compound heterozygotes. These results indicate that CTLN2 is caused by an abnormality in the SLC25A13 gene, and that our criteria for CTLN2 before DNA diagnosis are correct. Five of 22 patients from consanguineous unions have been shown to be compound heterozygotes, suggesting a high frequency of the mutated genes. The frequency of homozygotes is calculated to be more than 1 in 20,000 from carrier detection (6 in 400 individuals tested) in the Japanese population. We have detected no cross-reactive immune materials in the liver of CTLN2 patients with any of the seven mutations by Western blot analysis with anti-human citrin antibody. From these findings, we hypothesize that CTLN2 is caused by a complete deletion of citrin, although the mechanism of ASS deficiency is still unknown.     

Viable mutant homozygotes at Adh1 locus in sugar beet and their combination ablility

Selection for an increased frequency of mutant semilethal allele Adh1-S of the gene for alcohol dehydrogenase (ADH) was conducted in inbred families of sugar beet. Starting from the fourth generation, viable plants of mutant Adh1-SS homozygotes appeared. In the sixth generation of selection, the combinative ability of mutant homozygotes SS, normal homozygotes FF, and heterozygotes FS was estimated. The hybrids of mutant homozygotes outperformed the hybrids of normal homozygotes in all parameters examined (germinating capacity of seeds, length and weight of 1-week shoots, chlorophyll content in leaves, and root weight). The hybrids of heterozygotes had intermediate values of the parameters. The results obtained are discussed with regard to the mechanisms underlying the recovery of viability of mutant homozygotes and the formation of a compensating gene complex (CGC).     

Recognition of the E1kE1f cholinesterase genotype in a family segregating three rare genes, E1k, E1f and E1a

The first identification of the cholinesterase variant E1kE1f is reported from a family study. The evidence is based on the determination of enzymic activity, dibucaine, fluoride and RO2 numbers. Three individuals appear to have this genotype, and family evidence is not at variance with our conclusions. All three individuals will be sensitive to suxamethonium.     

Haemolytic anaemia in Basenji dogs. 2. Partial deficiency of erythrocyte pyruvate kinase (PK; EC 2.7.1.40) in heterozygous carriers

Congenital nonspherocytic haemolytic anaemia (HA) in dogs of the Basenji breed is inherited as a simple, autosomal recessive trait. Previous results of pyruvate kinase (PK) assays suggest a causal relationship between the anaemia and PK deficiency in erythrocytes. In the present investigation assays of this enzyme have been performed on haemolysates from 45 Basenji dogs, comprising 3 anaemic and 42 non-anaemic individuals of which 13 were known heterozygotes. The PK activity in haemolysates from the 42 non-anaemic dogs exhibited a bimodal distribution corresponding to the genotypic classes: heterozygotes and normal homozygotes. The results indicate that heterozygotes have a partial, detectable enzyme deficiency, not reflected in clinical disease, and thus give evidence of a gene dosage effect in agreement with observations in man. The proposed genotypes PK PK, PK pk and pk pk refer to normal homozygotes, heterozygotes, and anaemic individuals, respectively. The findings strengthen the genetic hypothesis of recessiveness of the anaemia by direct detection of heterozygosity of parents of affected individuals. Moreover, the results are of value in comparative studies and they have practical application in connection with eradication programmes.     

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.     

Pre-adult viability differences of melanic Biston betularia (L.) (Lepidoptera)

Departures from mendelian ratios have been analysed in all published family data for the peppered moth, Biston betularia. No distinction was made between different insularia alleles; thus carbonaria is top dominant while insularia is dominant over typical. Viabilities of five of the six genotypes were calculated by a simple algebraic method; a maximum likelihood method gave viabilities for all six genotypes together with their standard errors. Carbonaria homozygotes (and possibly also insularia homozygotes) have enhanced viability while the viability of insularia/carbonaria heterozygotes is reduced. The significance of these findings is discussed in relation to phenotype frequencies found in the wild.     

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.     

Haemolytic anaemia in Basenji dogs. 2. Partial deficiency of erythrocyte pyruvate kinase (PK; EC 2.7.1.40) in heterozygous carriers1

Congenital nonspherocytic haemolytic anaemia (HA) in dogs of the Basenji breed is inherited as a simple, autosomal recessive trait. Previous results of pyruvate kinase (PK) assays suggest a causal relationship between the anaemia and PK deficiency in erythrocytes. In the present investigation assays of this enzyme have been performed on haemolysates from 45 Basenji dogs, comprising 3 anaemic and 42 non-anaemic individuals of which 13 were known heterozygotes. The PK activity in haemolysates from the 42 non-anaemic dogs exhibited a bimodal distribution corresponding to the genotypic classes: heterozygotes and normal homozygotes. The results indicate that heterozygotes have a partial, detectable enzyme deficiency, not reflected in clinical disease, and thus give evidence of a gene dosage effect in agreement with observations in man. The proposed genotypes PK PK, PK pk and pk pk refer to normal homozygotes, heterozygotes, and anaemic individuals, respectively. The findings strengthen the genetic hypothesis of recessiveness of the anaemia by direct detection of heterozygosity of parents of affected individuals. Moreover, the results are of value in comparative studies and they have practical application in connection with eradication programmes.     

Predicting genotypes at loci for autosomal recessive disorders using linked genetic markers: application to Wilson's disease

Summary Recently, the Wilson's disease locus (WND) has been mapped to the long arm of chromosome 13. We have analyzed segregation of serveral chromosome 13 markers flanking the WND locus and used multipoint linkage analysis to determine the most likely WND genotype of each of 57 unaffected individuals in 5 Wilson's disease families. Approximately 46% of these could be classified as carrier (heterozygote), homozygous normal, or homozygous affected (not yet symptomatic) with a probability of at least 90%, while 77% could be classified with a probability of at least 80%. Our results demonstrate that even though there is a significant decrease on average in serum copper concentration in Wilson's disease heterozygotes compared to normal homozygotes, other sources of variation in serum copper concentration are much greater and preclude use of serum copper to detect heterozygotes for Wilson's disease. Subsequent analyses showed that a familial component, independent of WND genotype, is the major factor accounting for variation in ceruloplasmin levels among unaffected individuals; age is another factor accounting for more variation in copper levels among unaffected individuals than WND genotype.     

ΔF508 testing of the DNA bank of the Royal Manchester Children's Hospital

Summary Details of haplotype and ΔF508 status from various populations represented in the cystic fibrosis (CF) DNA bank of the Royal Manchester Children's Hospital are provided, together with information on the association of genotype and clinical status. Clinical details and DNA analyses from native English in the North-West and South-West of England (Bath), from Lancashire Pakistani families and from Afrikaans Namibian families are compared. A 78.5% incidence of ΔF508 has been found in English families. Compound heterozygotes with CF and only one ΔF508 gene have an increased likelihood of having milder disease, with lessPseudomonas isolated from sputum and relatively more showing either no regular respiratory pathogens or colonisation withStaphylococcus. There is also a relative increase in meconium ileus in these compound heterozygotes. The diagnosis of CF may be in doubt in some subjects negative for ΔF508. Some of the Bath families have unusual haplotypes for an English population and a compound heterozygote ΔF508/ΔI507 has been found. There is evidence from metD analysis of the founder effect in the Afrikaans Namibian families, who have a high ΔF508 incidence.     

European ACP1*C allele has recessive deleterious effects on early life viability

The acid phosphatase locus (ACP1) is a classical polymorphism that has been surveyed in hundreds of human populations worldwide. Among individuals of European ancestry, the ACP1*C allele occurs with an average frequency of approximately 0.05, whereas it is nearly absent in all other human populations. It has been hypothesized that this allele is maintained by overdominant selection among European populations. Here, we analyze ACP1 protein polymorphism data from more than 50,000 individuals previously surveyed in 67 populations across Europe as well as inheritance data from more than 6,000 European parent-offspring pairs to assess the signature of natural selection currently acting on this allele. Although we see a significant excess of ACP1*C heterozygotes relative to Hardy-Weinberg expectations, we find no evidence that natural selection favors ACP1*C heterozygotes. Instead, ACP1*C appears to have a strongly deleterious and recessive fitness effect. We observed only 48.9% of expected homozygous offspring from heterozygous parents and significantly fewer homozygotes than expected within populations. Because parent-offspring pairs indicate a significant deficiency of ACP1*C homozygotes, we infer that viability selection is acting on ACP1*C homozygotes very early in life, perhaps before birth. We estimate that approximately 1.2% of all couples of European ancestry are composed of individuals who both carry the APC1*C allele. As such, selection against ACP1*C homozygotes may represent a nonnegligible contribution to the overall number of spontaneous abortions among women of European ancestry and may cause substantial fertility reductions among some combinations of parental genotypes.