Identification of a novel mutation in the ryanodine receptor gene (RYR1) in a malignant hyperthermia Italian family

Malignant hyperthermia (MH) is an inherited autosomal dominant pharmacogenetic disorder and is one of the main causes of death subsequent to anaesthesia. Around 50% of affected families are linked to the ryanodine receptor (RYR1) gene. To date, 19 mutations have been identified in the coding region of this gene and appear to be associated with the MH-susceptible phenotype. Here we report the identification by two independent methods of a novel mutation associated with the MH-susceptible phenotype in the RYR1 gene: the 6488G-->C transversion, resulting in the replacement of the Arg2163 with a proline residue.     

Hemochromatosis (HFE) gene splice site mutation IVS5+1 G/A in North American Vietnamese with and without phenotypic evidence of iron overload

Homozygosity for a novel hemochromatosis (HFE) gene splice site mutation (IVS5+1 G/A) was previously reported in a 48-year-old Vietnamese man residing in Germany who had an elevated serum ferritin (SF) and transferrin saturation (TS) and severe iron overload on liver biopsy. This mutation was not found in 222 controls of central European origin but has been found in Southeast Asians living in Vietnam without evidence of iron overload. Hemochromatosis and iron overload screening (HEIRS) Study is an ongoing, multiethnic, primary care-based study of 101,168 North American adults, including 12,772 Asians, a group that the HEIRS Study found has a significantly higher than expected prevalence of elevated serum TS and SF but very low prevalence of the common C282Y and H63D HFE alleles usually associated with hereditary hemochromatosis. It was hypothesized that the IVS5+1 G/A splice site mutation might explain some elevated biochemical iron measures in North American Asians. Overall, 200 Vietnamese subjects from the Los Angeles Field Center who had TS and SF values greater than the 75th percentile of all HEIRS Study participants after adjusting for covariates and 149 controls randomly selected to represent this Vietnamese population were genotyped. Among cases, 1 homozygous mutant and 7 heterozygotes were found; among controls, 1 homozygous mutant and 4 heterozygotes were found yielding an allele frequency of 2.32% for cases and 2.04% for controls (P>0.5). This finding suggests that the HFE IVS5+1 G/A splice site mutation is not the major explanation for unexpectedly high prevalence of TS and SF in North American Asians.     

Progeroid facial features and lipodystrophy associated with a novel splice site mutation in the final intron of the FBN1 gene

The association of progeroid features and lipodystrophy was very recently described in a female adult with additional manifestations of Marfan syndrome. Mutation analysis of the fibrillin I (FBN1) gene revealed a novel heterozygous frameshift mutation at the 3' end in that patient. Here, we report on a 3.5-year-old girl with progeroid facial signs of neonatal onset, lipodystrophy, large head circumference with corresponding hydrocephaly, and tall stature at the end of infancy. Her facial appearance showed convincing clinical similarities to the above-mentioned case. We identified a novel heterozygous de novo splice site mutation c.8226+1G>T affecting the last intron of FBN1. We suggest a specific clinical entity characterized by progeroid facial features, lipodystrophy, and at least some clinical signs of Marfan syndrome is associated with a subset of mutations located at the 3' end of FBN1. This phenotype which is different from that of classical Marfan syndrome could be caused by a truncated FBN1 protein which could escape nonsense-mediated RNA decay.     

Identification of novel single nucleotide polymorphisms in intron 1B and exon 1C of the human interleukin-1 receptor type I (IL-1RI) gene

We have identified two novel single nucleotide polymorphisms in the 5' region of the human IL-1RI gene: (1) A-->G at position 52 in intron 1B (GenBank accession number AF146426), which creates an Mspl restriction endonuclease site. Allele frequencies in a Caucasian population were 0.1 (A allele) and 0.9 (G allele). (2) A-->T at position 140 in exon 1C (GenBank accession number AF146427). Allele frequencies in a Caucasian population were 0.27 (A allele) and 0.73 (T allele).     

Identification and characterization of a novel splice site mutation in the SERPING1 gene in a family with hereditary angioedema

Hereditary angioedema due to C1-inhibitor deficiency (HAE-C1INH) is a rare autosomal-dominant disease caused by mutations in SERPING1 gene. The main clinical feature of C1INH deficiency is the spontaneous edema of the subcutaneous and submucosal layers. More than 280 different mutations scattering the entire SERPING1 gene have been reported. We identified and characterized a new mutation in SERPING1 gene in a Spanish family with hereditary angioedema. The mutation (c.685 + 2 T > A) disrupts the donor splice site of intron 4 leading to the loss of exon 4 in mutant mRNA. We demonstrated that mutant mRNA is mostly degraded, probably by the surveillance pathway no-go mRNA decay. Bioinformatic analysis showed that the mutant protein, if produced, would be non-functional since the protein lacks a stretch of 45 amino acids affecting the functional RCL loop. Finally, we found a reduction of the wild-type mRNA expression in c.685 + 2 T > A carriers.     

Identification of a novel single base-pair polymorphism in the glutamate dehydrogenase (GLUD1) gene

A novel single base-pair polymorphism, G/A at ntd 955, was identified within the coding region of the glutamate dehydrogenase gene (GLUD1). This polymorphism should prove useful for the study of human disorders with altered ammonia and/or blood glucose levels. Received: February 15, 1999 / Accepted: February 18, 1999