Refinement of diagnostic assays for a probable causal mutation for porcine and human malignant hyperthermia.

The substitutions of T for C1843 in the porcine ryanodine receptor (RYR1) gene, which deletes a HinPI restriction endonuclease site and creates a HgiAI site, and of T for C1840 in human RYR1, which deletes a RsaI site, lead to Cys for Arg substitutions in the ryanodine receptors and are probable causal mutations for malignant hyperthermia (MH). To improve the restriction endonuclease assay of these sites, thereby providing an accurate, reliable diagnosis for MH, introns flanking the exon containing the mutation were sequenced, permitting identification and PCR amplification of a 659-bp porcine gene sequence that contains both constant and variant HgiAI sites and a 922-bp human gene sequence that contains both constant and variant RsaI sites. As a result, these PCR-amplified sequences contain constant internal controls for the reliable differentiation by restriction endonuclease digestion of normal, heterozygous, and MH genotypes.     

A substitution of cysteine for arginine 614 in the ryanodine receptor is potentially causative of human malignant hyperthermia.

Malignant hyperthermia (MH) is a devastating, potentially lethal response to anesthetics that occurs in genetically predisposed individuals. The skeletal muscle ryanodine receptor (RYR1) gene has been linked to porcine and human MH. Furthermore, a Cys for Arg substitution tightly linked to, and potentially causative of, porcine MH has been identified in the ryanodine receptor. Analysis of 35 human families predisposed to malignant hyperthermia has revealed the presence, and cosegregation with phenotype, of the corresponding substitution in a single family. This substitution, by analogy to the findings in pig, may be causal for predisposition to MH in this family.     

Identification of novel mutations in the ryanodine-receptor gene (RYR1) in malignant hyperthermia: genotype-phenotype correlation.

Malignant hyperthermia (MH) is a pharmacogenetic disorder of skeletal muscle that is triggered in genetically predisposed individuals by common anesthetics and muscle relaxants. The ryanodine receptor (RYR1) is mutated in a number of MH pedigrees, some members of which also have central core disease (CCD), an inherited myopathy closely associated with MH. Mutation screening of 6 kb of the RYR1 gene has identified four adjacent novel mutations, C6487T, G6488A, G6502A, and C6617T, which result in the amino acid alterations Arg2163Cys, Arg2163His, Val2168Met, and Thr2206Met, respectively. Collectively, these mutations account for 11% of MH cases and identify the gene segment 6400-6700 as a mutation hot spot. Correlation analysis of the in vitro contracture-test data available for pedigrees bearing these and other RYR1 mutations showed an exceptionally good correlation between caffeine threshold and tension values, whereas no correlation was observed between halothane threshold and tension values. This finding has important ramifications for assignment of the MH-susceptible phenotype, in genotyping studies, and indicates that assessment of recombinant individuals on the basis of caffeine response is justified, whereas assessment on the basis of halothane response may be problematic. Interestingly, the data suggest a link between the caffeine threshold and tension values and the MH/CCD phenotype.     

Voltage-dependent calcium release in human malignant hyperthermia muscle fibers.

Malignant hyperthermia (MH) results from a defect of calcium release control in skeletal muscle that is often caused by point mutations in the ryanodine receptor gene (RYR1). In malignant hyperthermia-susceptible (MHS) muscle, calcium release responds more sensitively to drugs such as halothane and caffeine. In addition, experiments on the porcine homolog of malignant hyperthermia (mutation Arg615Cys in RYR1) indicated a higher sensitivity to membrane depolarization. Here, we investigated depolarization-dependent calcium release under voltage clamp conditions in human MHS muscle. Segments of muscle fibers dissected from biopsies of the vastus lateralis muscle of MHN (malignant hyperthermia negative) and MHS subjects were voltage-clamped in a double vaseline gap system. Free calcium was determined with the fluorescent indicator fura-2 and converted to an estimate of the rate of SR calcium release. Both MHN and MHS fibers showed an initial peak of the release rate, a subsequent decline, and rapid turn-off after repolarization. Neither the kinetics nor the voltage dependence of calcium release showed significant deviations from controls, but the average maximal peak rate of release was about threefold larger in MHS fibers.     

Co-segregation of the malignant hyperthermia and the Arg615-Cys615 mutation in the skeletal muscle calcium release channel protein in five European Landrace and Pietrain pig breeds

A total of 392 pigs of European Landrace and Pietrain origin segregating for malignant hyperthermia (MH) were genotyped using a polymerase chain reaction (PCR)/restriction endonuclease test for the C—T mutation at nucleotide (nt) 1843 in the skeletal muscle ryanodine receptor (RYR1) gene, earlier identified as the causal mutation for MH. All pigs had been halothane tested and genotyped at linked polymorphic marker loci. There was complete correlation between MH status of the 392 animals, as diagnosed by a combination of the halothane challenge test with S, GPI, H, A1BG, PGD haplotyping, and the DNA-based test. DNA-based detection of the MH status in 238 MH-susceptible heterozygous (N/n) and homozygous (n/n) pigs was shown to be accurate, eliminating the 2% diagnostic error that is associated with the halothane challenge test. The mutation was also associated with an allele of a polymorphic microsatellite (ETH5 001) at the RYR1 locus.     

Discordance, in a Malignant Hyperthermia Pedigree, between in Vitro Contracture-Test Phenotypes and Haplotypes for the MHS1 Region on Chromosome 19q12–13.2, Comprising the C1840T Transition in the RYR1 Gene

A point mutation in the gene encoding the skeletal muscle calcium release channel (RYR1) has been proposed as the probable cause of malignant hyperthermia (MH) in swine, where it segregates with the disease in all MH–prone strains investigated. The same C-to-T exchange in nucleotide position 1840 of the human RYR1 cDNA sequence was found in a few human MH pedigrees. We report a German MH pedigree where in vitro contracture test (IVCT) results and haplotypes of markers for the MHS1/RYR1 region including this base transition have yielded several discrepancies. The MH-susceptible phenotype was defined by IVCT performed according to the European standard protocol. Haplotypes were constructed for markers for the MHS1/RYR1 region on chromosome 19 and include the C1840T base exchange. Discussing the probabilities for a number of hypotheses to explain these data, we suggest that our results may challenge the causative role of this mutation—and possibly the role of the RYR1 gene itself—in human MH susceptibility, at least in some cases.     

Mapping of a Further Malignant Hyperthermia Susceptibility Locus to Chromosome 3q13.1

Malignant hyperthermia (MH) is a potentially lethal pharmacogenetic disease for which MH susceptibility (MHS) is transmitted as an autosomal dominant trait. A potentially life-threatening MH crisis is triggered by exposure to commonly used inhalational anesthetics and depolarizing muscle relaxants. The first malignant hyperthermia susceptibility locus (MHS1) was identified on human chromosome 19q13.1, and evidence has been obtained that defects in the gene for the calcium-release channel of skeletal muscle sarcoplasmic reticulum (ryanodine receptor; RYR1) can cause some forms of MH. However, MH has been shown to be genetically heterogeneous, and additional loci on chromosomes 17q and 7q have been suggested. In a collaborative search of the human genome with polymorphic microsatellite markers, we now found linkage of the MHS phenotype, as assessed by the European in vitro contracture test protocol, to markers defining a 1-cM interval on chromosome 3q13.1. A maximum multipoint lod score of 3.22 was obtained in a single German pedigree with classical MH, and none of the other pedigrees investigated in this study showed linkage to this region. Linkage to both MHS1/RYR1 and putative loci on chromosome 17q and 7q were excluded. This study supports the view that considerable genetic heterogeneity exists in MH.     

Molecular genetic study of autosomal dominant retinitis pigmentosa in Lithuanian patients

Lithuanian patients with visual problems were clinically examined for retinitis pigmentosa (RP). A total of 33 unrelated families with autosomal dominant RP (adRP) were identified. Screening for mutations in the rhodopsin (RHO) and peripherin/RDS (RDS) genes was performed using DNA heteroduplex analysis. Direct DNA sequencing in the cases of heteroduplex formation showed the presence of the following mutations and polymorphisms in 14 adRP patients: RHO gene - Lys248Arg (1 case), and Pro347Leu (2 cases); RDS gene - Glu304Gln (12 cases), Lys310Arg (5 cases), and Gly338Asp (12 cases). The presence of these mutations (except Lys248Arg in the RHO gene) was confirmed by relevant restriction enzyme digestion. The frequency of the RDS gene mutations Glu304Gln and Gly338Asp was estimated to be 36.4%, while mutation Lys310Arg was less frequent (15.2%). These 3 RDS gene mutations appear to be polypeptide polymorphisms not related to adRP.     

Evidence for genetic heterogeneity of malignant hyperthermia susceptibility

A locus for malignant hyperthermia susceptibility (MHS) has been localized on chromosome 19q12-13.2, while at the same time the gene encoding the skeletal muscle ryanodine receptor (RYR1) also has been mapped to this region and has been found to be tightly linked to MHS. RYR1 was consequently postulated as the candidate for the molecular defect causing MHS, and a point mutation in the gene has now been identified and is thought to be the cause of MH in at least some MHS patients. Here we report the results of a linkage study done with 19q12-13.2 markers, including the RYR1 cDNA, in two Bavarian families with MHS. In one of the families, three unambiguous recombination events between MHS and the RYR1 locus were found. In the second family only one informative meiosis was seen with RYR1. However, segregation analysis with markers for D19S75, D19S28, D19S47, CYP2A, BCL3, and APOC2 shows that the crossovers in the first family involve the entire haplotype defined by these markers flanking RYR1 and, furthermore, reveals multiple crossovers between these haplotypes and MHS in the second family. In these families, pairwise and multipoint lod scores below -2 exclude MHS from an interval spanning more than 26 cM and comprising the RYR1 and the previously described MHS locus. Our findings thus strongly suggest genetic heterogeneity of the MHS trait and prompt the search for another MHS locus.     

Single-amino-acid deletion in the RYR1 gene, associated with malignant hyperthermia susceptibility and unusual contraction phenotype

Malignant hyperthermia (MH) is an anesthetic-drug-induced, life-threatening hypermetabolic syndrome caused by abnormal calcium regulation in skeletal muscle. Often inherited as an autosomal dominant trait, MH has linkage to 30 different mutations in the RYR1 gene, which encodes a calcium-release-channel protein found in the sarcoplasmic reticulum membrane in skeletal muscle. All published RYR1 mutations exclusively represent single-nucleotide changes. The present report documents, in exon 44 of RYR1 in two unrelated, MH-susceptible families, a 3-bp deletion that results in deletion of a conserved glutamic acid at position 2347. This is the first deletion, in RYR1, found to be associated with MH susceptibility. MH susceptibility was confirmed among some family members by in vitro diagnostic pharmacological contracture testing of biopsied skeletal muscle. Although a single-amino-acid deletion appears to be a subtle change in the protein, the deletion of Glu2347 from RYR1 produces an unusually large electrically evoked contraction tension in MH-positive individuals, suggesting that this deletion produces an alteration in skeletal-muscle calcium regulation, even in the absence of pharmacological agents.     

Double-strand DNA conformation polymorphisms as a source of highly polymorphic genetic markers

The molecular basis for several apparent restriction fragment length polymorphisms of the porcine growth hormone gene was examined through DNA sequence analysis. Electrophoretic and sequence analysis suggest polymorphisms result from 1–3 base substitutions that affect double-strand DNA conformation and electrophoretic mobility. Two allelic forms of the porcine growth hormone 5'flank and four allelic forms of the second exon/intron region were identified. A marker system was developed which combined conformation polymorphisms with HaeII and DdeI RFLPs. Using this system, nine haplotypes were observed in samples from three US swine breeds. The data presented suggest that double-strand DNA conformation can be exploited in base substitution detection and development of highly polymorphic genetic marker systems.     

Mutations in the RYR1 gene in Italian patients at risk for malignant hyperthermia: evidence for a cluster of novel mutations in the C-terminal region

Mutations in the ryanodine receptor type 1 (RYR1) gene are associated with Malignant Hyperthermia (MH) and Central Core Disease (CCD). We report here on the molecular analysis of the RYR1 gene in Italian families referred as potential cases of MH or in patients with CCD or multicore/minicore myopathy. Of a total of 20 individuals with mutations in the RYR1 gene, 14 were part of a group of 47 MH susceptible (MHS) patients, 4 of 34 individuals diagnosed as MH equivocal (MHE), and 2 were patients diagnosed with minicore myopathy and CCD, respectively. Mutations were found to segregate with the MHS or MHE phenotype within the families of the probands. A discordance between phenotype and genotype was observed in a family where a mutation detected in an MHS proband was also found in the father who had been diagnosed MH normal (MHN) at the IVCT. In addition to known mutations, seven novel mutations were found, five of which occurred in exons encoding the C-terminal region of RYR1. These results indicate that the C-terminal region of RYR1 represents an additional hot spot for mutations in patients with MH, similar to what has been reported for patients with CCD.     

Dantrolene inhibition of ryanodine receptor Ca2+ release channels. Molecular mechanism and isoform selectivity

As an inhibitor of Ca(2+) release through ryanodine receptor (RYR) channels, the skeletal muscle relaxant dantrolene has proven to be both a valuable experimental probe of intracellular Ca(2+) signaling and a lifesaving treatment for the pharmacogenetic disorder malignant hyperthermia. However, the molecular basis and specificity of the actions of dantrolene on RYR channels have remained in question. Here we utilize [(3)H]ryanodine binding to further investigate the actions of dantrolene on the three mammalian RYR isoforms. The inhibition of the pig skeletal muscle RYR1 by dantrolene (10 microm) was associated with a 3-fold increase in the K(d) of [(3)H]ryanodine binding to sarcoplasmic reticulum (SR) vesicles such that dantrolene effectively reversed the 3-fold decrease in the K(d) for [(3)H]ryanodine binding resulting from the malignant hyperthermia RYR1 Arg(615) --> Cys mutation. Dantrolene inhibition of the RYR1 was dependent on the presence of the adenine nucleotide and calmodulin and reflected a selective decrease in the apparent affinity of RYR1 activation sites for Ca(2+) relative to Mg(2+). In contrast to the RYR1 isoform, the cardiac RYR2 isoform was unaffected by dantrolene, both in native cardiac SR vesicles and when heterologously expressed in HEK-293 cells. By comparison, the RYR3 isoform expressed in HEK-293 cells was significantly inhibited by dantrolene, and the extent of RYR3 inhibition was similar to that displayed by the RYR1 in native SR vesicles. Our results thus indicate that both the RYR1 and the RYR3, but not the RYR2, may be targets for dantrolene inhibition in vivo.     

Genetic polymorphisms and haplotype structures of the CYP4A22 gene in a Japanese population

The CYP4A fatty acid monooxygenases oxidize endogenous arachidonic acid to 20-hydroxyeicosatetraenoic acid that acts as a regulator of blood pressure. Among the isoforms of the CYP4A subfamily, the human CYP4A22 was recently identified. In this study, we report the comprehensive investigation of polymorphisms in the CYP4A22 gene. To investigate genetic variation in CYP4A22 in 191 Japanese subjects, we used denaturing HPLC (DHPLC) and direct sequencing. Our investigation has enabled the identification of 13 sequence variations in the CYP4A22 coding region, thereby demonstrating for the first time that this gene is subject to polymorphism. Two of these sequence variations correspond to silent mutations located in exons 8 (His323His) and 9 (Gly390Gly). Nine of these sequence variations correspond to missense mutations located in exons 1 (Arg11Cys), 3 (Arg126Trp), 4 (Gly130Ser and Asn152Tyr), 5 (Val185Phe), 6 (Cys231Arg), 7 (Lys276Thr), 10 (Leu428Pro), and 12 (Leu509Phe). One of these sequence variations corresponds to nonsense mutations located in exon 9 (Gln368stop). The 13th mutation corresponds to a nucleotide deletion (G7067del) that causes a frameshift and consequently results in a stop codon 80 nucleotides downstream. In addition to the wild-type CYP4A22*1 allele, 20 variants, namely CYP4A22*2-15, were characterized by haplotype analysis. Based on these data, we concluded that allelic variants of the human CYP4A22 gene exist and speculated that some of these variants may be functionally relevant.     

Independent origin of identical beta cardiac myosin heavy-chain mutations in hypertrophic cardiomyopathy.

The origins of the beta cardiac myosin heavy-chain (MHC) gene missense mutations that cause familial hypertrophic cardiomyopathy (FHC) in 14 families have been evaluated. Of eight different mutations, four were present in single families, while four occurred in two or more families. To investigate the origins of the four shared mutations, we defined the beta cardiac MHC haplotypes of each of the mutation-bearing chromosomes by determining the alleles present at three intragenic polymorphic loci. Two of the mutations (Arg453Cys and Val606Met) have arisen independently in each of three families, being found on different chromosomal backgrounds. A third mutation (Gly584Arg) is associated with identical haplotypes in two families with Portuguese ancestors, suggesting a founder effect. Haplotype analysis was uninformative for the fourth mutation (Arg403Gln). Thus, FHC-causing mutations have arisen independently in at least 12 of the 14 families studied, suggesting that the majority have arisen relatively recently as new mutations. This finding predicts the prevalence of disease-causing beta cardiac MHC mutations to be comparable in all population groups.     

Polymorphic DNA haplotypes at the human low-density lipoprotein receptor gene locus in Koreans

Many low-density lipoprotein (LDL) receptor mutations have been identified and characterized, demonstrating a high degree of allelic heterogeneity at this locus. The ability to identify mutant LDL-receptor genes for prenatal diagnosis of familial hypercholesterolemia (FH) or to study the role of the LDL-receptor gene in polygenic hypercholesterolemia requires the use of closely linked restriction fragment lenghth polymorphisms (RFLPs). In the present study nine different RFLPs (TaqI, StuI, HincII, BstEII, AvaII, PvuII, MspIA, MspIB, and NcoI) and a sequence variation at Arg450 were used to clarify the characteristics of the LDL-receptor gene in Koreans. A total of 978 LDL-receptor alleles from 244 members of 43 different pedigrees (15 normal and 28 FH pedigrees) and 245 individuals (187 normal and 58 FH) were analyzed. Frequencies of these polymorphisms did not differ significantly between controls and FH patients. Individually, seven sites--TaqI, BstEII, AvaII, MspIA, MspIB, NcoI and Arg450--had heterozygosity indices ranging from 0.3610 to 0.4601, whereas the PvuII site displayed low levels of polymorphism and StuI was monomorphic. Haplotypes were constructed for 215 individuals of 13 normal and 24 FH pedigrees using the nine polymorphisms. Of 512 (= 2(9)) possible combinations for the nine polymorphic sites, 39 unique haplotypes were detected. The frequency distribution of individual haplotypes ranged from 1/155 (0.65%) to 40/155 (25.8%). The four most common haplotypes accounted for 59.4% of those sampled. Statistical analysis of the haplotypes indicated marked linkage disequilibrium for these 10 sites and throughout the region containing the LDL-receptor gene. Owing to the high degree of linkage disequilibrium over the entire locus, not all RFLPs were informative. We rank each RFLP according to its informativeness and present a strategy for the optimal selection of RFLPs for pedigree analysis.     

Analysis of mutations in the p16/CDKN2A gene in sporadic and familial melanoma in the Polish population

Mutations in CDKN2A have been found in sporadic cutaneous malignant (CMM), in familial CMM and in other syndromes associated with melanoma. In this study DNA was obtained from 207 individuals and five cell lines. There were 157 CMM patients and 50 healthy members of melanoma patients families. The CMM group included patients with one or two melanoma cases in the family, families with dysplastic nevus syndrom (DNS) and patients with a spectrum of other types of cancers in the family. PCR-SSCP analysis and sequencing identified: six substitutions in codon 58 CGA/TGA (Arg/Stop), 16 substitutions GAC/GAT in codon 84 (Asp/Asp), six substitutions CGA/TGA in codon 148 (Arg/Thr), 14 substitutions G/C in 3'UTR and 4 double changes (two in codon 84 and 3'UTR; two in codon 148 and 3'UTR). The mutation identified in codon 58 was found in tissue only. Other substitutions were polymorphisms found in DNA from tissue and blood samples. Most of them were identified in sporadic CMM (six in codon 148 Ala/Thr, 12 in codon 84 Asp/Asp and six in 3'UTR). The frequency of the polymorphisms was also high in DNS and CMM/DNS families (four in codon 84 Asp/Asp and six in 3'UTR). No mutations or polymorphisms were found in CMM patients with one or two melanoma cases and CMM patients, with other cancers in family history. The analysis of the CDKN2A gene mutations in the Polish population demonstrated: (i) no germline mutations; (ii) a relatively high number of genetic changes in sporadic melanoma; (iii) a high number of polymorphisms in DNS and CMM/DNS families.     

Conformational effects of the substitution of Arg for Gly 13 in the ras oncogene-encoded P21 protein

The effect of the substitution of Arg for Gly 13 on the structure of the transforming region decapeptide (Leu 6-Gly 15) of the ras oncogene encoded P21 protein has been investigated using conformational energy analysis. A human malignancy has been identified that contains a ras gene with a single mutation in the thirteenth codon such that the encoded protein would have Arg substituted for Gly at this position, and transfection of cells in culture with this gene results in malignant transformation. Conformational analysis demonstrates that the Arg 13 decapeptide adopts a conformation identical to that for other peptides with substitutions at position 13 (Asp 13, Val 13) from transforming proteins that is distinctively different from that for peptides (Gly 13, Ser 13) from normal, nontransforming proteins. This is found to be an indirect effect resulting from changes in the conformation of Gly 12 produced by substitutions at position 13. These results are consistent with recent analysis of crystallographic data of proteins on conformational preferences for glycine in tripeptide sequences.     

Characterization of five new mutants in the carboxyl-terminal domain of human apolipoprotein E: No cosegregation with severe hyperlipidemia

Assessment of the apolipoprotein E (apoE) phenotype by isoelectric focusing of both hyperlipidemic and normolipidemic individuals identified five new variants. All mutations were confined to the downstream part of the APOE gene by using denaturing gradient gel electrophoresis (DGGE). Sequence analysis revealed five new mutations causing unique amino acid substitutions in the carboxyl-terminal part of the protein containing the putative lipid-binding domain. Three hyperlipoproteinemic probands were carriers of the APOE*2(Val236→Glu) allele, the APOE*3(Cys112→Arg; Arg251→Gly) allele, or the APOE*1(Arg158→Cys; Leu252→Glu) allele. DGGE of the region encoding the receptor-binding domain was useful for haplotyping the mutations at codons 112 and 158. Family studies failed to demonstrate cosegregation between the new mutations and severe hyperlipoproteinemia, although a number of carriers for the APOE*3(Cys112→Arg; Arg251→Gly) allele and the APOE*1(Arg158→Cys; Leu252→Glu) allele expressed hypertriglyceridemia and/or hypercholesterolemia. Two other mutant alleles, APOE*4⁻ (Cys112→Arg; Arg274→His) and APOE*4⁺(Ser296→Arg), were found in normolipidemic probands. The lack of cosegregation of these new mutations with severe hyperlipoproteinemia suggests that these mutations do not exert a dominant effect on the functioning of apoE.     

人前列腺癌细胞系PC-3中PTI-1 cDNA的克隆及序列分析

为获取人前列腺癌诱导基因家族新成员 ,以人前列腺癌细胞系PC 3的总RNA为模板 ,用RT PCR方法扩增人前列腺癌诱导基因 1(PTI 1) ,将其亚克隆至克隆载体pUC19,进行测序 .将克隆得到的PTI 1基因片段与国外报道的人PTI 1基因编码区cDNA同源性为 99.3% ,但第 72 6、74 6、116 7、12 70、132 6、144 9、16 94和 16 95位碱基分别由A、A、C、C、A、A、T和C替代了文献中的C、C、G、G、G、C、C和T .其中 6个碱基的不同 ,导致了第 36、183、2 17、2 36、2 77和 35 9位密码子代表的氨基酸分别由Lys替代Gln ,Arg替代Gly ,Ala替代Gly ,Ser替代Gly ,Thr替代Pro和Arg替代Cys .将所获得的基因在GenBank登录 ,登录号为AF3974 0 3.结果提示 ,获得了PTI 1家族新成员 ,并且与EF 1α分子的同源性较已报道的PTI 1高 .