Atypical Allele Research Articles

Paternal exclusion: allele sharing in microsatellite testing

A paternity disagreement analyzed with 15 autosomal microsatellite markers indicated allele sharing between the mother, questioned child and the alleged father generating an inconclusive paternity result. In total, 15 autosomal and 17 Y tandem repeat loci were analyzed using AmpF/STR Identifiler, AmpF/STR Y-filer kits followed by six microsatellite markers on X chromosome in DNA extracted from peripheral blood samples of the mother, questioned child and alleged father. Microsatellite analysis examined with 15 autosomal short tandem repeats (STRs) indicated at least one allele sharing at 14 loci between the mother, questioned child and alleged father except for the TPOX locus where a paternal-child allele mismatch was observed. Y chromosome investigations using 17 repeat markers signified the case as non-paternity (exclusion). A complete match of the six X chromosome loci in the questioned child with the mother was observed. Our investigations on inconclusive paternity due to atypical allele sharing in autosomal microsatellites were resolved with X- and Y-chromosome STR analyses confirming the case as non-paternity.

The expression of Clostridium perfringens consensus beta2 toxin is associated with bovine enterotoxaemia syndrome

Clostridium perfringens has been implicated in a broad array of enteric infections including the fatal haemorrhagic enteritis/enterotoxaemia syndrome in cattle. The beta2 toxin (CPB2), encoded by cpb2, is suspected to be implicated in this syndrome. However, among C. perfringens isolates from cattle suspected of clostridial disease, an atypical allele was recently found to predominate at the cpb2 locus and atypical corresponding CPB2 proteins were shown to be poorly expressed, thus arguing against a biologically significant role of the beta2 toxin in clostridial diseases in cattle. This study compared genotype and phenotype of the beta2 toxin between C. perfringens isolates from a group of healthy calves ( n = 14, 87 isolates) and from a group of enterotoxaemic calves ( n = 8, 41 isolates). PCR results revealed the exclusive presence of the typical “consensus” cpb2 in the enterotoxaemic group. Western blot analysis demonstrated that the typical variant of CPB2 was often expressed in isolates from enterotoxaemic calves (43.9%) and infrequently in isolates from healthy cattle (6.9%). These data suggest that the typical variant of the CPB2 toxin may play a role in the pathogenesis of cattle enterotoxaemia.

Production of the Butyrylcholinesterase Knockout Mouse

The butyrylcholinesterase (BChE [EC 3.1.1.8]) knockout mouse is a model for BChE deficiency in humans. The existence of genetic variants of human BChE was discovered after a new muscle relaxant, succinylcholine, was introduced into the practice of medicine in the late 1950s. People with the atypical variant were unable to breathe for 2 h after receiving a dose intended to paralyze for 3-5 min (Kalow and Gunn, 1957, 1959). The atypical variant was later found to have a single-amino-acid mutation at Asp-70 (McGuire et al., 1989), which decreased the affinity of BChE for all positively charged compounds. Though the atypical BChE mutant is the one most commonly encountered in cases of succinylcholine apnea, an additional 58 mutations in the BChE coding sequence have been reported. The frequency of BChE mutations in the American population is known (Lockridge, 1990). One person out of 25 carries one atypical allele (D70G), whereas 1 out of 2500 is homozygous for D70G. The most frequent mutation, A539T, is carried by 1 person out of every 4 and is found in homozygous form in 1 person out of 69 (Bartels et al., 1992). The homozygous A539T form is associated with a 33% decrease in plasma BChE activity. Some people have no detectable BChE activity in plasma, owing to a mutation that truncates the protein, or inactivates it. The frequency of silent BChE is 1 out of 160 for carriers, and 1 out of 110,000 for homozygotes. The BChE knockout mice are models for silent BChE in humans. The literature contains no documentation of the health of people with silent BChE, other than to say they are healthy. We know nothing about their life expectancy, fertility, risk of cognitive impairment, risk of heart disease, or susceptibility to toxins. The BChE knockout mouse will allow us to test the hypothesis that the function of BChE is to detoxify poisons and will allow us to test the role of BChE in other physiological functions.

Genetic Polymorphism of Aldehyde Dehydrogenase 2 (ALDH2) in a Chinese Population: Gender, Age, Culture, and Genotypes of ALDH2

Not only is alcoholism one of the world’s major public health problems because of the significant morbidity caused by alcohol abuse disorder but it is also a big social problem. An atypical allele (ALDH2∗487Lys, former name ALDH2∗2) in low Km aldehyde dehydrogenase (ALDH2), which is highly prevalent in Asian populations, is associated with drinking behavior and some alcohol-related diseases (Yoshida, 1994; Yokoyama et al., 2003). There are some differences in its frequency among Asian populations of different geographic areas. In our previous study, the frequency of the ALDH2∗487Lys allele was much lower (12%) in Wuhan Han Chinese and much higher (31%) in Guangdong Han Chinese populations than that reported in other Oriental populations (Chen et al., 1999; Luo et al., 2001; Luo and Zhang, 2004). Recent developments in gene therapy allow a long-term inhibition of gene expression. Garver et al. (2001) asserted that antisense oligonucleotides

Disease-associated Mutations Inactivate AMP-Lysine Hydrolase Activity of Aprataxin

Ataxia-oculomotor apraxia syndrome 1 is an early onset cerebellar ataxia that results from loss of function mutations in the APTX gene, encoding Aprataxin, which contains three conserved domains. The forkhead-associated domain of Aprataxin mediates protein-protein interactions with molecules that respond to DNA damage, but the cellular phenotype of the disease does not appear to be consistent with a major loss in DNA damage responses. Disease-associated mutations in Aprataxin target a histidine triad domain that is similar to Hint, a universally conserved AMP-lysine hydrolase, or truncate the protein NH2-terminal to a zinc finger. With novel fluorigenic substrates, we demonstrate that Aprataxin possesses an active-site-dependent AMP-lysine and GMP-lysine hydrolase activity that depends additionally on the zinc finger for protein stability and on the forkhead associated domain for enzymatic activity. Alleles carrying any of eight recessive mutations associated with ataxia and oculomotor apraxia encode proteins with huge losses in protein stability and enzymatic activity, consistent with a null phenotype. The mild presentation allele, APTX-K197Q, associated with ataxia but not oculomotor apraxia, encodes a protein with a mild defect in stability and activity, while enzyme encoded by the atypical presentation allele, APTX-R199H, retained substantial function, consistent with altered and not loss of activity. The data suggest that the essential function of Aprataxin is reversal of nucleotidylylated protein modifications, that all three domains contribute to formation of a stable enzyme, and that the in vitro behavior of cloned APTX alleles can score disease-associated mutations.

Genetic variants of serum butyrylcholinesterase in Chilean Mapuche Indians

We estimated the frequencies of serum butyrylcholinesterase (BChE) alleles in three tribes of Mapuche Indians from southern Chile, using enzymatic methods, and we estimated the frequency of allele BCHE*K in one tribe using primer reduced restriction analysis (PCR-PIRA). The three tribes have different degrees of European admixture, which is reflected in the observed frequencies of the atypical allele BCHE*A: 1.11% in Huilliches, 0.89% in Cuncos, and 0% in Pehuenches. This result is evidence in favor of the hypothesis that BCHE*A is absent in native Amerindians. The frequencies of BCHE*F were higher than in most reported studies (3.89%, 5.78%, and 4.41%, respectively). These results are probably due to an overestimation of the frequency of allele BCHE*F, since none of the 20 BCHE UF individuals (by the enzymatic test) individuals analyzed showed either of the two DNA base substitutions associated with this allele. Although enzymatic methods rarely detect the presence of allele BCHE*K, PCR-PIRA found the allele in an appreciable frequency (5.76%), although lower than that found in other ethnic groups. Since observed frequencies of unusual alleles correspond to estimated percentages of European admixture, it is likely that none of these unusual alleles were present in Mapuche Indians before the arrival of Europeans.

Distribution of genetic polymorphism of aldehyde dehydrogenase-2 (ALDH2) in Indonesian subjects

Aldehyde dehydrogenase (ALDH) plays a pivotal role in the alcohol metabolism. Decreased activity of ALDH enzyme has more influence on the hypersensitivity to alcohol than of alcohol dehydrogenase. ALDH enzyme exists in several isozymes. Among these isozymes, ALDH2 is a major isozyme that has a very high affinity for acetaldehyde. Recent studies suggested that the deficiency of ALDH2 may be inherited. Functional polymorphism of ALDH2 gene has been observed in a nucleotide of the 487th codon. In the atypical gene, this codon consists of AAA nucleotides for lysine, instead of GAA for glutamic acid in the wild type gene. In this study, we have analyzed the genetic polymorphism of ALDH2 gene among 100 Indonesian students using genomic DNA extracted from hair roots. Polymerase chain reaction (PCR) and restriction fragment length polymorphism (RFLP) methods were performed for this purpose. Three oligonucleotide primers were designed for two steps PCR. The reverse primer R was intentionally constructed not to be 100% complementary to the template strand, to generate a restriction site for Eco RI within the variable nucleotide in the PCR product of ALDH2 gene. This study indicates that 70 subjects (70%) have wild type, 29 (29%) atypical heterozygote and only 1 (1%) atypical homozygote ALDH2 alleles. Conclusively, the atypical ALDH2 allele frequency in Indonesians (31/200) is higher than in Caucasoids (only about 5-10%), but less than in Mongoloids (40-50%). This may be due to the diverse ethnics of Indonesian population. (Med J Indones 2002; 11: 135-42) Keywords: alcohol hypersensitivity, genetic polymorphism, aldehyde dehydrogenase-2 (ALDH2) gene

Markedly Prolonged Paralysis After Mivacurium in a Patient Apparently Heterozygous for the Atypical and Usual Pseudocholinesterase Alleles by Conventional Biochemical Testing

Markedly Prolonged Paralysis After Mivacurium in a Patient Apparently Heterozygous for the Atypical and Usual Pseudocholinesterase Alleles by Conventional Biochemical Testing

Plasma cholinesterase activity and dibucaine number in infants and children

Summary Reference values for plasma cholinesterase in adults are available, but data for paediatric patients are scarce. In this study plasma cholinesterase activity and dibucaine number were measured in 111 healthy infants and children two months to 12 years. There were no significant differences in cholinesterase values between the infants and the older children. The cholinesterase activity of the paediatric population was comparable to that of adults. One infant had markedly decreased cholinesterase activity and was presumed to have an atypical variant of the enzyme. Further analysis of this child and the family, identified that this child had most probably the atypical allele (E1a E1a), whereas his two siblings, his mother and maternal uncle were probably heterozygous. The implications of cholinesterase activity in the paediatric population are discussed.

Distribution of the E1 gene among Norwegian blood donors studied by an automated screening method.

An automated screening method for the atypical cholinesterase gene (E1a) is described. By this method, 97 heterozygotes but no homozygotes for the atypical allele were found in a series of 3,143 Norwegian blood donors (gene frequency 0.0154). The method seems useful in the screening of large series of sera for the atypical enzyme also in samples stored frozen for many years.

Transient respiratory depression of the newborn. Its occurrence after succinylcholine administration to the mother.

A baby born after a cesarean section experienced transient respiratory depression. The mother had a postsuccinylcholine apnea caused by homozygosity for the atypical allele for serum pseudocholinesterase; the baby was heterozygous for this allele and the usual allele for serum pseudocholinesterase. The possible relationship between the genotype of the baby and the respiratory difficulty at birth is raised.

E1k, another quantitative variant at cholinesterase locus 1.

Two families segregating for the atypical (E1a) allele at cholinesterase locus 1 are described. Unusual results for dibucaine inhibition led to the recognition of a new allele (E1k) also segregating in these families. The enzymatic and immunological data are consistent with the hypothesis that E1k causes reduction of 'usual' (E1u) molecules by about 33%. Whether the reduction of E1u caused by E1k is caused by retarded synthesis or accelerated degradation of serum cholinesterase remains to be determined.

The atypical allele Fyx: study of a family

The atypical allele Fyx: study of a family

Sex and population differences in the incidence of a plasma cholinesterase variant.

Accumulating knowledge of polymorphic enzyme systems poses intriguing possibilities of anthropologic genetics. Development of an automated procedure for determination of heterozygosity or homozygosity of the atypical plasma cholinesterase allele (E(1)(a)) permitted screening of 2317 individuals during a national Preschool Nutrition Survey and several smaller population studies. Frequencies of the allele (E(1)(a)) closely parallel those previously reported. Caucasians manifested a heterozygote male preponderance of 1.85: 1.