Porcine malignant hyperthermia carrier detection and chromosomal assignment using a linked probe

Genomic organization and analysis of the 5' end of the porcine ryanodine receptor gene (ryr1)

In this study we describe the isolation of genomic clones of the 5' region of the porcine ryanodine receptor gene, a candidate for malignant hyperthermia in pigs and humans. The recombinants were isolated from a porcine liver, genomic DNA library in phage EMBL3A after screening with PCR amplified DNA fragments. The exon/intron structure of the ryanodine receptor gene was determined by DNA sequencing. Based on the sequence data it was possible to develop a simple test for the detection of malignant hyperthermia susceptible and normal pigs.

Cosegregation of porcine malignant hyperthermia and a probable causal mutation in the skeletal muscle ryanodine receptor gene in backcross families

A study of the inheritance of malignant hyperthermia (MH) in the British Landrace breed revealed the same substitution of T for C at nucleotide 1843 in the ryanodine receptor (RYR1) gene that was previously shown to be correlated with MG in five Canadian swine breeds. Cosegregation of the mutation with MH in 338 informative meioses led to a lod score of 101.75 for linkage at Omax = 0.0. The substitution was also associated with a HinPI- BanII+ RsaI- haplotype in this breed, as in the five breeds tested earlier, suggesting its origin in a common founder animal. DNA-based detection of the MH status in 376 MH-susceptible heterozygous (N/n) and homozygous (n/n) pigs was shown to be accurate, eliminating the 5% diagnostic error that is associated with the halothane challenge test and flanking marker haplotyping procedures in current diagnostic use. These results strongly support the view that the substitution of T for C at nucleotide 1843 is the causative mutation in porcine MH and demonstrate the feasibility of rapid, accurate, noninvasive, large-scale testing for porcine MH status using DNA-based tests for the mutation.

Porcine SINEs: characterization and use in species-specific amplification

A porcine repetitive DNA sequence has been isolated from an intron of the glucose phosphate isomerase gene. The copy number of this and related sequences was estimated to be approximately 10(5) copies per genome. The sequence possesses all the characteristics of short interspersed elements (SINEs) described in other mammals: The repeat is 300 bp in length, has an poly(A)stretch, and contains insertion duplication sites. Homology to seven other porcine sequences, which also have the characteristics of SINEs, has been demonstrated. Primer oligonucleotides, based on conserved regions in the SINE sequences, have been synthesized. Using these primers, PCR-mediated specific amplification of porcine sequences was demonstrated from pig x mouse and pig x hamster hybrid cell lines. Cloning and sequencing of some amplified porcine sequences verify that the sites of priming are SINE sequences.

Evidence for linkage of the central core disease locus to the proximal long arm of human chromosome 19

Central core disease of muscle (CCD; MIM 117000) is a rare inheritable myopathy that is frequently found in association with susceptibility to malignant hyperthermia (MHS). This observation has prompted us to perform a linkage study in CCD families using various chromosome 19q probes that are linked to the MHS locus and map close to the ryanodine receptor gene (RYR1), a strong MHS candidate gene. Our genetic linkage data support a location of the CCD gene on proximal 19q13.1 and thus suggest that CCD and MHS may be allelic.

Molecular tools to elucidate problems in excitation-contraction coupling

In this review, constituting the 1990 International Lecture of the Biophysical Society, research is described in two areas in which molecular genetic techniques were used to dissect problems related to sarcoplasmic reticulum proteins: the use of site-directed mutagenesis to gain insight into the mechanism of Ca2+ transport by the Ca2(+)-ATPase; and the use of cloning and genetic linkage analysis to identify the Ca2+ release channel (RYR1) gene as a candidate gene for the predisposition to malignant hyperthermia, a neuromuscular disease of humans and domestic animals.

Assignment of the porcine calcium release channel gene, a candidate for the malignant hyperthermia locus, to the 6p11----q21 segment of chromosome 6

Several studies point to the possibility that malignant hyperthermia (MH) in pigs is caused by a defect in the calcium release channel (CRC) of skeletal muscle sarcoplasmic reticulum. The locus for MH is closely linked to the glucosephosphate isomerase (GPI) locus, near the centromere of chromosome 6. We demonstrate synteny of the genes for CRC and GPI using somatic cell hybrid lines, and assign the CRC gene to chromosome 6p11----q21 by in situ hybridization.

Localization of the PGD and TGF beta-1 loci to pig chromosome 6q

The TGF beta-1 and PGD loci have been localized by in situ hybridization to the C-greater than q2.1 and q2.2 -greater than q2.5 regions of pig chromosome 6. These assignments confirm that the conversation of syntenic groups around GPI and PGD extends to pigs where these two groups are uniquely found to be linked. Our data also support the hypothesis that the porcine and human inherited malignant hyperthermia syndromes are caused by mutations in homologous genes which map to human chromosome 19q, porcine chromosome 6q and murine chromosome 7.

Characterization of the 5' end of the gene for human glucose phosphate isomerase (GPI)

We have isolated the gene coding for human glucose phosphate isomerase, and here we report the characterization of its 5' end including the first two exons. The gene is greater than 50 kb in size and contains a minimum of eight exons. We have no evidence that this gene is part of a multigene family or that there are any pseudogenes. The potential transcription start site has been determined by primer extension analysis and is 52 bp upstream from the translation initiation site of the protein. Sequences 5' to the transcription initiation site and within the first intron are extremely GC rich and form part of a CpG island. Five potential Sp1 sites (GGGCGG) have been located at positions -57, -61, -95, +183, and +575. The most 5' of these (GGGGCGGGGG) is likely to be the main Sp1 binding site, as it conforms precisely to a 10-bp consensus sequence. At position -44 there is a putative TATA box (CATAAA). Thus in common with an increasing number of genes, the putative promoter region of glucose phosphate isomerase shows structural similarities to both housekeeping and facultative gene promoters.

A linkage study of malignant hyperthermia (MH)

Five German families segregating for malignant hyperthermia (MH) were tested for linkage relationships using 35 serological and biochemical markers. Slightly positive lod scores were obtained with MNS, EsD, C3 and P. The relation with the C3 locus on chromosome 19p13.3-13.2 (z = 0.72, theta = 0.11) is of some interest, since genetic linkage of MH with several polymorphic DNA markers from the 19q12-13.2 region has been reported (McCarthy et al. 1989).

Ryanodine receptor gene is a candidate for predisposition to malignant hyperthermia

Malignant hyperthermia (MH) is a potentially lethal condition in which sustained muscle contracture, with attendant hypercatabolic reactions and elevation in body temperature, are triggered by commonly used inhalational anaesthetics and skeletal muscle relaxants. In humans, the trait is usually inherited in an autosomal dominant fashion, but in halothane-sensitive pigs with a similar phenotype, inheritance of the disease is autosomal recessive or co-dominant. A simple and accurate non-invasive test for the gene is not available and predisposition to the disease is currently determined through a halothane- and/or caffeine-induced contracture test on a skeletal muscle biopsy. Because Ca2+ is the chief regulator of muscle contraction and metabolism, the primary defect in MH is believed to lie in Ca2+ regulation. Indeed, several studies indicate a defect in the Ca2+ release channel of the sarcoplasmic reticulum, making it a prime candidate for the altered gene product in predisposed individuals. We have recently cloned complementary DNA and genomic DNA encoding the human ryanodine receptor (the Ca2(+)-release channel of the sarcoplasmic reticulum) and mapped the ryanodine receptor gene (RYR) to region q13.1 of human chromosome 19 (ref. 14), in close proximity to genetic markers that have been shown to map near the MH susceptibility locus in humans and the halothane-sensitive gene in pigs. As a more definitive test of whether the RYR gene is a candidate gene for the human MH phenotype, we have carried out a linkage study with MH families to determine whether the MH phenotype segregates with chromosome 19q markers, including markers in the RYR gene. Co-segregation of MH with RYR markers, resulting in a lod score of 4.20 at a linkage distance of zero centimorgans, indicates that MH is likely to be caused by mutations in the RYR gene.